10 MPG with the LQ1

[Nas Escobar]

So I've noticed since I started driving the Cutlass again that the car is giving me a whopping 10 MPG in MIXED driving... I'm almost scared to know what it would do in real downtown city driving.

 

Anyways, I hooked up tunerpro to the car, and I'm not getting any codes. The only thing I do see is the computer actually affirming me that I'm getting 10mpg. That's what the dash on tunerpro says. At times I get lucky and it will jump to 12 or 14 but most of the time it's 10. This is interstate driving, where usually, I would get 18-20MPG. It used to be that when the car was in 4th gear and doing 70, I got 23mpg, but that's no longer the case. No matter the speed, it's giving me 10mpg.

 

I have switched the TPS out thinking it was that, but no avail. No codes set, no vacuum leaks, tried seafoaming it, that didn't help. I'm at a loss.

 

The interesting part is that I do smell a sweet honey like smell after turning the car off. I sometimes do also notice the engine a bit sluggish around the 2000rpm mark, but resolves itself if I floor it to 3000rpm. After that it acts normal but will feel sluggish if I go back to 2000rpm.

 

I do have a datastream from the time I ran it with tunerpro, but don't know how to attach.

 

All help is appreciated.

[RobertISaar]

scent sounds a lot like coolant.

 

to be getting that poor of fuel economy..... have to have at least one of the following:

 

ignition issues causing crappy combustion

fueling issues causing crappy combustion

an O2 sensor that isn't doing its job

significant load to the engine causing huge amounts of air(therefore, fuel) to be required to power through some kind of friction(driveline or breathing)

 

that's about it outside of fuel spilling out of the tank/lines/etc.

 

if you had a weak ignition or were dumping huge amounts of unnecessary fuel into the engine, it would show up in a really obvious way on the spark plugs. that would rule out 3 of 4 possibilities.

[94 olds vert]

I get around 10 MPG in my 94 Cutlass when I stopped driving it 2 years ago. Nothing was wrong with it. I just drove it hard as hell.

[Nas Escobar]

scent sounds a lot like coolant.

 

I don't see leaks nor do I need to add more coolant. I have thought about pressure washing the engine to see if that gets rid of the smell.

 

to be getting that poor of fuel economy..... have to have at least one of the following:

 

ignition issues causing crappy combustion

fueling issues causing crappy combustion

an O2 sensor that isn't doing its job

significant load to the engine causing huge amounts of air(therefore, fuel) to be required to power through some kind of friction(driveline or breathing)

 

that's about it outside of fuel spilling out of the tank/lines/etc.

 

if you had a weak ignition or were dumping huge amounts of unnecessary fuel into the engine, it would show up in a really obvious way on the spark plugs. that would rule out 3 of 4 possibilities.

 

Well I see no leaks whatsoever and I would think they would be apparent when the car is off. The fuel needle doesn't move if I leave it off nor is there puddles or a gas smell.

 

I'm considering it would be the 4th one but I have suspected the FPR as well. I'm probably gonna pull the spark plugs on it though.

 

What intrigues me is that the ECM recognizes the bad mpg when in tunerpro and actually states it as such. I remember before the computer would say 20mpg at 60mph now it barely gets to 14. Idk what else to look at as far as the ecm goes.

 

This is my readout on the Tunerpro dash...

 

IAT: 61

BASE PULSE WIDTH: 11.55

INJECTOR DUTY CYCLE: 21.4

FUEL ECON: 14.4

MAF: 39.39

TPS:8.43

TCC SLIP: 19.00

COOLANT TEMP: 174°

LOOP STATUS: CLOSED

TCC: LOCKED

TRANS AXLE TEMP: 71.9

COMMANDED GEAR: 4

BATTERY VOLTAGE: 13.7

MPH: 60

RPM: 2000

[RobertISaar]

8.4% TPS isn't a lot...... that is about where I would expect to see to maintain 60MPH.

 

40 grams/sec of air should be flowing about 2.72 grams of fuel for the same second. roughly 163.2 grams of fuel flowed in one mile. a gallon of gas can be between 5.9 and 6.4lbs depending on exact composition/temperature. that's 2,676-2,903 grams. 16.4-17.8MPG, going off of calculated MAF values and assuming a 14.7:1 AFR.

 

what are the fuel trims(either short/long term fuel trims or BLM/INT, depending on who wrote the definition)? if they don't show up on the dash, they should at least be in the list view.

 

it seems like you're having to flow a lot of air(and fuel to match) to make enough power to maintain speed. the injectors running at a 21% duty cycle also confirm this.

 

I think if you pull plugs(I would only bother with the front 3 for now), you'll see normal-ish looking plugs, perhaps looking like they're running somewhat on the hot side.

[l67ss]

10mpg.......wow. with the old l67 I never got below 20mpg.....even with bad lim, icm and a dead coilpack.....and me driving it stupid

[Nas Escobar]

Robert, the BLM is at 149 and the INT is a fluctuating value, however it averages out to be around 135ish. It will drop as low as 130 and as high as 155. The BLM's sweet spot is 149.

 

I do feel the engine to be sluggish, as I stated in the 1st post, it's mostly a thing around 2000RPM. I've pondered the fact whether or not the cat is clogged creating excess backpressure thus making it feel as it needs more air and fuel.

 

10mpg.......wow. with the old l67 I never got below 20mpg.....even with bad lim, icm and a dead coilpack.....and me driving it stupid

 

Tell me about it... I'm getting worse MPG than when I only had 3 gears and was driving 75mph at 3500rpm. In that configuration, I got 15mpg at the lowest, 17-18 mpg at the best. Even then, when I had bad LIM gaskets the 1st time around and it would die on me, I actually got 23mpg at one point.

 

The worst I've gotten in my 3800 Camaro is 20, that's me being stupid, flooring it, hitting excess mph, burning out at the stop lights, revving back at ricers, driving it in downtown DC and during rush hour (which is pretty bad here).

[RobertISaar]

a BLM of 149 indicates a long-term trend of adding 16.4% more fuel than what the MAF is indicating is necessary. the INT averaging 135 adds another 5.5%.

 

either your O2 sensor is screwed up or your MAF is(or one hell of a vacuum leak), because that is a LOT of extra fuel.

 

if the cat isn't clogged, it is likely at least damaged from the engine running like this.

 

in reference to the log file, I've been uploading everything via dropbox lately, but I know some people aren't fond of it. http://www.wikifortio.com/ is another I've used with good results.

[Schurkey]

Why is the TCC not engaging?

 

What is the knock sensor doing?

 

How many O2 sensor cross-counts?

 

Why is the coolant at 174 instead of 194?

[Nas Escobar]

a BLM of 149 indicates a long-term trend of adding 16.4% more fuel than what the MAF is indicating is necessary. the INT averaging 135 adds another 5.5%.

 

Well that's not good at all. I guess that explains the gas guzzling status, however the fact that the "MPG" data sometimes will jump to it's normal level baffles me. I wasn't going to mention it at all because I felt that it detracted from the actual issue where 10MPG is the average, but after swapping out the TPS, it gave me 12. In the log file, you'll see that the fuel econ info is all over the place. The INT is also all over the place.

 

either your O2 sensor is screwed up or your MAF is(or one hell of a vacuum leak), because that is a LOT of extra fuel.

 

Wouldn't I hear such a vacuum leak though? I hear no hissing at all and all cracked hard plastics were replaced with rubber lines. I also have replaced most of the couplings on the lines.

 

MAF was swapped out this summer. It's a Reman unit. This car is on its 2nd MAF. However, I may have the original MAF laying around. I can try swapping it if I find it/still have it.

O2 was swapped out late January 2014.

 

if the cat isn't clogged, it is likely at least damaged from the engine running like this.

 

I'll find that out come emission time. If it passes emissions, it stays. If it fails, it gets a high flow cat. If it messes up after passing emissions, it gets replaced with a pipe until it's time for emissions again. That's the game plan on that. I've feared the day that piece is no longer.

 

in reference to the log file, I've been uploading everything via dropbox lately, but I know some people aren't fond of it. http://www.wikifortio.com/ is another I've used with good results.

 

I'll PM you the link once it's uploaded.

 

Why is the TCC not engaging?

 

Actually, the TCC does engage, it wasn't engaged when I took a screen shot. Why? I do not know.

 

What is the knock sensor doing?

 

That one I can't answer for sure, Idk how to see those values. If you want to know how many times it "knocked" then it was 10, but that was during a 45 minute run. The engine does surge when going back to idle before leveling out at 850rpm. That's when it will "knock" but I never figured out why.

 

How many O2 sensor cross-counts?

 

That I can't answer. I'm not very familiar with TunerPro as I would like to be. If someone can assist with that, I can give the info.

 

Why is the coolant at 174 instead of 194?

 

I assume it's because I was driving on the interstate and it's between 28F and 45F in the midatlantic region. When I took the data, it was 35F outside, and driving it at 60mph. Yes I know the engine is not air cooled but the colder air is doing something with the radiator. I haven't seen or heard the fans on since summer left the building. The engine does get hotter than 174 in city driving.

[RobertISaar]

Well that's not good at all. I guess that explains the gas guzzling status, however the fact that the "MPG" data sometimes will jump to it's normal level baffles me. I wasn't going to mention it at all because I felt that it detracted from the actual issue where 10MPG is the average, but after swapping out the TPS, it gave me 12. In the log file, you'll see that the fuel econ info is all over the place. The INT is also all over the place.

 

the fuel economy number is an instant estimated value, it sounds like it is doing what it's supposed to. it's really difficult to do a trip MPG value without sending requests to the PCM to send out the injector flow data that would be sent to the DIC/DIS, I never implemented it because it would slow down logging speed. I also have yet to figure out a way to keep track of the fuel usage value rolling over, which will happen when the collective on-time for the injectors hits 1 second. idling, that takes a while(2mS on-time at a 800RPM idle would take 37.5 seconds, your info of driving at 60MPH at 2000 RPM with an on-time of 11.55mSec would take ~2.6 seconds).

 

INT should move around a bit, that's just how short-term trims work. with the earlier code, there is an ultra-short term trim value that can move many, many "steps" per data frame. I don't know if the 94-95 LQ1 code uses that scheme though.

 

Wouldn't I hear such a vacuum leak though? I hear no hissing at all and all cracked hard plastics were replaced with rubber lines. I also have replaced most of the couplings on the lines.

 

if there were a vacuum leak that bad, the IAC would get pegged down to 0 steps at an idle and still hold an excessively high idle speed, along with running very little spark advance(in an effort to combat excessive idle speed).

 

MAF was swapped out this summer. It's a Reman unit. This car is on its 2nd MAF. However, I may have the original MAF laying around. I can try swapping it if I find it/still have it.

O2 was swapped out late January 2014.

 

newish MAF, newish O2.... perhaps the log will show something telling of either of them. though it is possible neither of them are the base problem.

 

I'll find that out come emission time. If it passes emissions, it stays. If it fails, it gets a high flow cat. If it messes up after passing emissions, it gets replaced with a pipe until it's time for emissions again. That's the game plan on that. I've feared the day that piece is no longer.

 

 

 

I'll PM you the link once it's uploaded.

 

 

 

Actually, the TCC does engage, it wasn't engaged when I took a screen shot. Why? I do not know.

 

locked, with a slip speed of 19 RPM, normal.

 

That one I can't answer for sure, Idk how to see those values. If you want to know how many times it "knocked" then it was 10, but that was during a 45 minute run. The engine does surge when going back to idle before leveling out at 850rpm. That's when it will "knock" but I never figured out why.

 

sounds like you're looking at just the dash view..... the item list view should show more values, just not graphically. there should be both a "knock count" and "knock retard" value, one indicates occurances since key-on(will roll over if it hits 256), the other is how much retard is currently being applied to keep the sensor happy.

 

knocking near idle is..... weird.

 

That I can't answer. I'm not very familiar with TunerPro as I would like to be. If someone can assist with that, I can give the info.

 

the 94-95 LQ1 code should have an O2 sensor cross count in the item list as well. depending on the code, it will show number of O2 cross events(how many times the engine has transitioned between rich and lean) since the last data frame, since the last second or just a rolling total(which will rollover when it gets to 256). I can't remember which scheme this one uses off-hand.

 

I assume it's because I was driving on the interstate and it's between 28F and 45F in the midatlantic region. When I took the data, it was 35F outside, and driving it at 60mph. Yes I know the engine is not air cooled but the colder air is doing something with the radiator. I haven't seen or heard the fans on since summer left the building. The engine does get hotter than 174 in city driving.

 

bold stuff.

[RobertISaar]

log notes:

 

looks like with 94-95 LQ1, O2 cross-counts are transitions in the last second.

 

cylinder 5 is intermittently getting tagged as a bad cylinder. the 94-95 LQ1 code uses the 24X crank sensor to do some basic misfire detection, cylinder 5 is the only one that seems to be getting ID'd as a potential misfire, so it may be weaker than the rest for whatever reason.

 

idling about 8 minutes in: BLM of 135, INT of 132, O2 is transitioning about 13 times/second, MAF is showing 7.3 grams/sec, LV8(easiest way to explain that is that it is an "airmass in cylinder" value) in mid 80s/low 90s, advance is sitting at 20*(I forgot, some calibrations don't attempt to control idle speed with spark changes), coolant temp is kind of low at 184, 37 IAC steps(which seems kind of high, but I'm used to 3.1/3100 idling characteristics).

 

I see knock happen 3 times in the log, none of which were severe knocks(most extreme one required 2.3* to keep the sensor happy).

[Schurkey]

I assume it's because I was driving on the interstate and it's between 28F and 45F in the midatlantic region. When I took the data, it was 35F outside, and driving it at 60mph. Yes I know the engine is not air cooled but the colder air is doing something with the radiator. I haven't seen or heard the fans on since summer left the building. The engine does get hotter than 174 in city driving.

Nope. I drove mine today, -15F, and the dash gauge ends up in the same place it does in the summer. Takes a lot of run-time to get there, though.

Your engine is ~20 degrees under-temperature. In my garage, that thing would get a replacement thermostat. I suspect it's stuck partially-open, or it's the wrong temperature 'stat. Cold engine may be creating a rich-command and therefore affecting fuel economy.

 

Still have my doubts about the O2 sensor and knock sensor/spark retard--but let's start with the thermostat.

[Nas Escobar]

the fuel economy number is an instant estimated value, it sounds like it is doing what it's supposed to. it's really difficult to do a trip MPG value without sending requests to the PCM to send out the injector flow data that would be sent to the DIC/DIS, I never implemented it because it would slow down logging speed. I also have yet to figure out a way to keep track of the fuel usage value rolling over, which will happen when the collective on-time for the injectors hits 1 second. idling, that takes a while(2mS on-time at a 800RPM idle would take 37.5 seconds, your info of driving at 60MPH at 2000 RPM with an on-time of 11.55mSec would take ~2.6 seconds).

 

INT should move around a bit, that's just how short-term trims work. with the earlier code, there is an ultra-short term trim value that can move many, many "steps" per data frame. I don't know if the 94-95 LQ1 code uses that scheme though.

 

Yeah, that's why I didn't want to really mention it. I figured the seesaw was just the programming. I am mostly amazed that the program confirmed bad fuel economy.

 

I thought the INT had something to do with it. Then again, IDK what BLT and INT mean as far as data logging goes. TunerPro is fairly new to me still.

 

if there were a vacuum leak that bad, the IAC would get pegged down to 0 steps at an idle and still hold an excessively high idle speed, along with running very little spark advance(in an effort to combat excessive idle speed).

 

The only time this car has had erratic idle was when I bought it and it had a bad LIM. Since then, the car starts fine, but does cold start at 1000-1300RPM. I've been told that's normal for a car to do in cold weather.

 

newish MAF, newish O2.... perhaps the log will show something telling of either of them. though it is possible neither of them are the base problem.

 

Well the parts do have warranty. Would it be a good idea to swap out the MAF again?

 

sounds like you're looking at just the dash view..... the item list view should show more values, just not graphically. there should be both a "knock count" and "knock retard" value, one indicates occurances since key-on(will roll over if it hits 256), the other is how much retard is currently being applied to keep the sensor happy.

 

I use dash view since I look at the values while driving it. Using list view... requires me to pull over, rendering the program somewhat useless since I can't see the info as it happens.

 

I do know the knock count is in dash view but not the retard value. It does say whether or not it's open/closed and I know the timing advance is by 10 degrees or so on average.

 

the 94-95 LQ1 code should have an O2 sensor cross count in the item list as well. depending on the code, it will show number of O2 cross events(how many times the engine has transitioned between rich and lean) since the last data frame, since the last second or just a rolling total(which will rollover when it gets to 256). I can't remember which scheme this one uses off-hand.

Isn't that the knock counter?

[Nas Escobar]

log notes:

 

looks like with 94-95 LQ1, O2 cross-counts are transitions in the last second.

 

cylinder 5 is intermittently getting tagged as a bad cylinder. the 94-95 LQ1 code uses the 24X crank sensor to do some basic misfire detection, cylinder 5 is the only one that seems to be getting ID'd as a potential misfire, so it may be weaker than the rest for whatever reason.

 

idling about 8 minutes in: BLM of 135, INT of 132, O2 is transitioning about 13 times/second, MAF is showing 7.3 grams/sec, LV8(easiest way to explain that is that it is an "airmass in cylinder" value) in mid 80s/low 90s, advance is sitting at 20*(I forgot, some calibrations don't attempt to control idle speed with spark changes), coolant temp is kind of low at 184, 37 IAC steps(which seems kind of high, but I'm used to 3.1/3100 idling characteristics).

 

I see knock happen 3 times in the log, none of which were severe knocks(most extreme one required 2.3* to keep the sensor happy).

 

weaker cylinder = bad coil pack? The spark plugs are fairly new as are the wires. They haven't gotten more than 15k on them. They were replaced in April 2013. I'll pull plugs once it's sunny out and report back, but what else might cause a misfire in one cylinder?

 

That log wasn't a cold start btw. I can get another longer log if it can help confirm or debunk any possible theories. I'm assuming I should swap out that t-stat based on this and Schurkey's post.

 

Nope. I drove mine today, -15F, and the dash gauge ends up in the same place it does in the summer. Takes a lot of run-time to get there, though.

Your engine is ~20 degrees under-temperature. In my garage, that thing would get a replacement thermostat. I suspect it's stuck partially-open, or it's the wrong temperature 'stat. Cold engine may be creating a rich-command and therefore affecting fuel economy.

 

Still have my doubts about the O2 sensor and knock sensor/spark retard--but let's start with the thermostat.

 

Interesting. Most cars I've driven don't heat up all the way when it's under 25F. I've seen them usually 20 degrees colder than normal. I was always told that was normal by mechanics.

 

I shall replace the thermostat and pull plugs to see if there's any indications of suspect activity. Will have to wait for a sunny day though.

[Nas Escobar]

So here's the official update.

 

13MPG. That's my mileage after today's run. That's mixed driving. Ran it on local roads then a nice run on the interstate.

 

Today, I changed the T-Stat. Now the computer reads 195F as the running temperature. I also checked plugs, no activity to report there there. This is how the 3 look in the front.

 

 

And here's the spark plug for cylinder #5 aka the misfire one.

 

 

I did find a vac line somewhat loose so I fixed that up. That seemed to take away some of the hesitation it had.

 

Other than that, the data is pretty much the same.

 

Here's the worst run. As you can see, BLM and INT is almost the same, as well as the Injector Duty Cycle.

 

 

The most disturbing thing to me is that from a dead stop, if I floor the engine, the car barely moves. It's very sluggish. It takes a a bit for it to move, and even then it doesn't jump. The engine doesn't feel like it has any power until hitting the 3000rpm mark, after that it's normal LQ1 action.

[Schurkey]

13MPG. That's my mileage after today's run. That's mixed driving. Ran it on local roads then a nice run on the interstate.

So I've noticed since I started driving the Cutlass again that the car is giving me a whopping 10 MPG in MIXED driving

An increase of 3 mpg (33%) is not a bad start. Especially since all it's cost you is a thermostat + labor.

 

Today, I changed the T-Stat. Now the computer reads 195F as the running temperature.

Success.

 

I also checked plugs, no activity to report there there. This is how the 3 look in the front.

 

Is it the photo, or am I seeing a shitload of electrode wear and considerable deposit formation? How many miles are on these plugs? I have the impression that it's about 15K, but in quickly reviewing this thread, I don't see confirmation of that.

 

And here's the spark plug for cylinder #5 aka the misfire one.

 

First Guess: Oil. What do the plugs for 1 and 3 look like? I don't see the electrode wear on this plug that I think I see on the photo above it. Makes me wonder how long this plug hasn't been firing!

 

I'd run a compression test on all six, but I'm especially curious about #5. Any cylinders that test low, would get a leakdown test, to see where the compression is going.

 

I did find a vac line somewhat loose so I fixed that up. That seemed to take away some of the hesitation it had.

 

Other than that, the data is pretty much the same.

 

Here's the worst run. As you can see, BLM and INT is almost the same, as well as the Injector Duty Cycle.

 

You go 50 mph, and the TCC isn't being commanded to engage? You're SURE the TCC works?

 

Nice to see reasonable O2 crosscounts (rich/lean transitions) and no knock sensor/spark retard activity.

 

The most disturbing thing to me is that from a dead stop, if I floor the engine, the car barely moves. It's very sluggish. It takes a a bit for it to move, and even then it doesn't jump. The engine doesn't feel like it has any power until hitting the 3000rpm mark, after that it's normal LQ1 action.

Yes, there's still something wrong. At least the engine is up to proper temp, so the heat in the interior should have improved.

 

I want compression test results. If the cranking compression pressure is adequate, that would confirm that the cams are still in time, and the compression is adequate to eliminate engine mechanical problems as a source for misfire.

 

A tailpipe emissions test might narrow down rich/lean or misfire problems at idle/low rpm. A misfiring cylinder will provide false "lean" information via the O2 sensor, driving the fuel trim excessively rich. Seems likely based on the fouled #5 spark plug.

 

Potential non-engine problems that will affect power 'n' fuel economy:

Have you checked for dragging brakes? Low tire pressure? I wonder about the torque converter one-way clutch. A failed (free-wheeling) one-way clutch will kill low-rpm performance, while having no effect on higher-rpm manners.

Edited December 30, 2014 by Schurkey

[Nas Escobar]

An increase of 3 mpg (33%) is not a bad start. Especially since all it's cost you is a thermostat + labor.

 

That's only interstate driving. I drove it in traffic, and it's at 10. Of course, I never measured what traffic driving was before I started this because I usually avoid driving the car in traffic.

 

 

Success.

 

 

Is it the photo, or am I seeing a shitload of electrode wear and considerable deposit formation? How many miles are on these plugs? I have the impression that it's about 15K, but in quickly reviewing this thread, I don't see confirmation of that.

 

The plugs have 30k. I swapped them out at when I first bought the car at 90k. I bought the car with a bad LIM gasket that the previous owner failed to tell me about. I thought the hard starts and screwy idle had to do with the spark plugs and not the LIM. Had I known, I might have walked away. I haven't touched them since March 2013. The plugs are from April 2013 (couldn't find them in store, had to order them online). The only thing that I assume is still from the factory in 94 are the coil packs. I have seen a lot of stuff on the car that's still from factory. The PCV valve was an original AC Rochester. The IAC is an original AC Rochester. I've changed the MAF (swapped it out again today under warranty to rule it out. Just idles better now IMO), o2 sensor Jan. 14, LIM has been done twice in the same year.

 

 

First Guess: Oil. What do the plugs for 1 and 3 look like? I don't see the electrode wear on this plug that I think I see on the photo above it. Makes me wonder how long this plug hasn't been firing!

 

I did not check those 2 plugs. I assumed they looked the same in the front, but I'll check it next chance I get, aka when I get the compression tool to check the compression.

 

I'd run a compression test on all six, but I'm especially curious about #5. Any cylinders that test low, would get a leakdown test, to see where the compression is going.

 

I'll see if I can rent the tool after new years. IDK if I'll manage to do it on new years eve, but it shall get done. I will then ask about leakdown tests if any cylinder is low. There's a lot of engine stuff I'm still new to. This car has shown me a lot in the almost 2 years I've had it.

 

You go 50 mph, and the TCC isn't being commanded to engage? You're SURE the TCC works?

 

I'll check the service manual to test it. I've seen it say it engages on in TunerPro but I can't say for sure. Another thing could be is that these screen shots may be when I let go of the gas. IDK if that has anything to do in that situation.

 

Nice to see reasonable O2 crosscounts (rich/lean transitions) and no knock sensor/spark retard activity.

 

 

Yes, there's still something wrong. At least the engine is up to proper temp, so the heat in the interior should have improved.

 

I want compression test results. If the cranking compression pressure is adequate, that would confirm that the cams are still in time, and the compression is adequate to eliminate engine mechanical problems as a source for misfire.

 

Can any tool work with the LQ1 or is there something DOHC specific? I remember Gnat commenting that he couldn't do a compression test because he needed a DOHC adapter.

 

A tailpipe emissions test might narrow down rich/lean or misfire problems at idle/low rpm. A misfiring cylinder will provide false "lean" information via the O2 sensor, driving the fuel trim excessively rich. Seems likely based on the fouled #5 spark plug.

 

Potential non-engine problems that will affect power 'n' fuel economy:

Have you checked for dragging brakes? Low tire pressure? I wonder about the torque converter one-way clutch. A failed (free-wheeling) one-way clutch will kill low-rpm performance, while having no effect on higher-rpm manners.

 

I do know that sometimes the car has a slight gas smell from the exhaust but that goes away after heating up. I was told that was normal though, but I'm seeing most people take situations as normal that shouldn't be.

 

As far as I see, brakes don't drag and I have the tires inflated at 30, per the manufacturer's specs. I am running factory wheels and they're wrapped around 225/60 tires. (16 inches). I'll double check the rear brakes to make sure but other than that, I know the trans was swapped out due to a 4th gear issue but the trans in it now was tested and true. The loss of power actually showed up when I had the EGR3 code but that hasn't been an issue again. It does have a new EGR valve. I have however thought it was the vacuum modulator.

[Nas Escobar]

OK so I fixed the issue, however it had to get worse before it got better.

 

So I had to drive the car and I did a cold start and drove it after starting. Well that went bad because the car had a noticeable miss if I got it to 2200rpm and would jerk. Once it heated up the jerking disappeared but was still sluggish as always. 10mpg galore again.

 

So it being new years and all I couldn't do much... I did preliminary tests, mostly to say I checked it and was good. Brakes don't drag, front injectors were 12.0 11.9 and 12.0, i didn't check the rear plugs because i had no real reason to believe i had a bad injector or bad FPR. I sprayed all vacuum joints to check for leaks, everything was nice and tight so I was stumped, mostly at the cold start misfire. As I thought about it, I realized the misfire felt like a crossed plug (where it ran but felt weak and couldn't make power past a certain rpm). I then pondered whether or not I had a coil issue...

 

So the parts store was open, I got one, put it on and was surprised at the results. I got my power back.

 

So that took care of the shake. Then I decided to test drive it just to see if it changed the power band. Well the first thing it did way lay some rubber. I floored it after getting out my neighborhood and it was good. I then tried getting to passing speed and no sluggishness there. I saw it wasn't struggling when I needed the power. Drove around just to see what mpg it got. 20mpg, used 2.7 gallons in almost 60 miles. Drove interstate and in light city traffic. Didn't feel forced at all.

 

TLDR: Car had a noticeable misfire when cold, went away when at operating temp, changed a coil pack, issues went away. Runs good now.

[GnatGoSplat]

Nice work!

One handy tool I'd recommend for checking coils is an inductive timing light. Actually bought it to adjust ignition timing on an old '78 AMC I had a loooong time ago, but they're useful on modern cars for checking coils too. Well, anything that uses plug wires anyway.

[Nas Escobar]

Nice work!

One handy tool I'd recommend for checking coils is an inductive timing light. Actually bought it to adjust ignition timing on an old '78 AMC I had a loooong time ago, but they're useful on modern cars for checking coils too. Well, anything that uses plug wires anyway.

 

How much is that tool? I kinda wanna check my other 2 coils to verify good working order.

[l67ss]

How much is that tool? I kinda wanna check my other 2 coils to verify good working order.

 

Just pull one plug wire at a time and start it ......look for a strong blue spark......also listen for differences in running conditions. Make sure to turn it off in between pulling/replugging plug wires

[GnatGoSplat]

How much is that tool? I kinda wanna check my other 2 coils to verify good working order.

 

$42 from Autozone, but that seems way overpriced.

http://www.autozone.com/test-scan-and-specialty-tools/timing-light/actron-inductive-timing-light/718067_0_0/

 

$18 shipped from eBay seems much more reasonable.

http://www.ebay.com/itm/New-Professional-Xenon-Inductive-Timing-Light-Engine-Motor-Automotive-Tune-Up-/400729793043

 

Just pull one plug wire at a time and start it ......look for a strong blue spark......also listen for differences in running conditions. Make sure to turn it off in between pulling/replugging plug wires

 

Running with a plug wire disconnected stresses the coil and generally isn't a good idea. Some people also believe it could potentially damage sensitive electronics like ICM or ECM.

[Galaxie500XL]

I just use one of those old spark testers, does an OK job, and doesn't seem to harm DIS systems.