Gas Mileage

[88red4cyl]

Refresh me.. What's the PCM do again?

[rockfangd]

powertrain control module. left front i think. Get the cat tested

[88red4cyl]

powertrain control module. left front i think. Get the cat tested

 

How do you test the cat?

[88red4cyl]

I posted this is Whatever!, but I figured I'd post it here too for the guys who don't post in that thread:

 

Bit of an update on the LTZ I thought I would throw at you guys.. I was talking to the guy who works on my car at work today, and he told me he had been thinking.. He worked on another guys Dodge pickup yesterday, and decided to hook the scanner up to it for the heck of it.. He saw the the O2 sensors on his truck were constantly fluctuating in value.. On the LTZ, the one was fluctuating, and the other one was reading steady (lean) values, unless you revved the hell out of it, and then it would go up.. Since it was within normal values, we didn't think much of it at the time, but now... Does it sound like the O2 sensor that is reading lean most of the time needs to be replaced, or would that point to the cat being bad?

[CRONER]

shit, that's worse than a H1

[Addicted To Boost]

Does it sound like the O2 sensor that is reading lean most of the time needs to be replaced

Absolutely. If it is reading lean, then it will dump more fuel than is needed into the engine.

[88red4cyl]

Thanks.. I didn't know if it could be a problem since there wasn't a SES light.. Is there a way to tell which one it is, or do I have to just guess?

[pontiacmaniac94]

Thanks.. I didn't know if it could be a problem since there wasn't a SES light.. Is there a way to tell which one it is, or do I have to just guess?

 

 

scan tool should help you out on this as well.

 

 

that thing should solve all your personal problems (atleast it does for me)

[Brian P]

with that kind of fuel being dumped into the engine, that cat must get red hot. Replace the upstream O2's, clean the MAF (or heck, disconnect it for a few days and run off speed density mode)

[Brian P]

 

I haven't been adding any antifreeze to it.. Last time a scan tool was hooked up to it (couple weeks ago) the coolant temp sensor was way off.. It was all corroded so it was cleaned, and then it was working right.. I thought that would fix my problem, but it didn't... Could a bad IAC cause these problems? I have noticed that it is idling a bit higher than it used to..

 

This I'm a little confused on. You removed the sensor and then cleaned it? Was the probe corroded, or the wire pins? That's a big thing, even if there's a loose connection and maybe it fluctuates between connected and disconnected, it will think the coolant temp is like -40 and dump a lot of fuel.

[88red4cyl]

with that kind of fuel being dumped into the engine, that cat must get red hot. Replace the upstream O2's, clean the MAF (or heck, disconnect it for a few days and run off speed density mode)

 

What's speed density mode? The upstream 02 and the MAF are reading within their limits, it's the other 02 that isn't reading right.. And apparently that won't affect my mileage, so it isn't worthy of replacing right now.. So I should be able to look at the cat and it should be glowing red?

 

I haven't been adding any antifreeze to it.. Last time a scan tool was hooked up to it (couple weeks ago) the coolant temp sensor was way off.. It was all corroded so it was cleaned, and then it was working right.. I thought that would fix my problem, but it didn't... Could a bad IAC cause these problems? I have noticed that it is idling a bit higher than it used to..

 

This I'm a little confused on. You removed the sensor and then cleaned it? Was the probe corroded, or the wire pins? That's a big thing, even if there's a loose connection and maybe it fluctuates between connected and disconnected, it will think the coolant temp is like -40 and dump a lot of fuel.

 

I'm not entirely sure.. I didn't physically see the corrosion, I was just told that there was some.. If it makes a difference I can find out.. After cleaning it though, it reads correctly to the ECM now, which it wasn't before the cleaning.. After that, I ran a whole tank through (which doesn't take very long btw), and it helped me about .2 mpg...

[Brian P]

with that kind of fuel being dumped into the engine, that cat must get red hot. Replace the upstream O2's, clean the MAF (or heck, disconnect it for a few days and run off speed density mode)

 

What's speed density mode? The upstream 02 and the MAF are reading within their limits, it's the other 02 that isn't reading right.. And apparently that won't affect my mileage, so it isn't worthy of replacing right now.. So I should be able to look at the cat and it should be glowing red?

 

I haven't been adding any antifreeze to it.. Last time a scan tool was hooked up to it (couple weeks ago) the coolant temp sensor was way off.. It was all corroded so it was cleaned, and then it was working right.. I thought that would fix my problem, but it didn't... Could a bad IAC cause these problems? I have noticed that it is idling a bit higher than it used to..

 

This I'm a little confused on. You removed the sensor and then cleaned it? Was the probe corroded, or the wire pins? That's a big thing, even if there's a loose connection and maybe it fluctuates between connected and disconnected, it will think the coolant temp is like -40 and dump a lot of fuel.

 

I'm not entirely sure.. I didn't physically see the corrosion, I was just told that there was some.. If it makes a difference I can find out.. After cleaning it though, it reads correctly to the ECM now, which it wasn't before the cleaning.. After that, I ran a whole tank through (which doesn't take very long btw), and it helped me about .2 mpg...

 

OH! So it's your downstream that is switching slow? That would be normal, for the most part. That also gives indication that the cat is working good.

 

I'm thinking more along the lines that the temp sensor is on its way out. Like maybe it's reading okay when you scan it, but what about while driving and such?

 

Speed density mode is a fuel management based off the MAP sensor. Basically it's how 2.8/3.1 cars were run, and is sort of a fail safe for if the MAF fails. Since you have access to a scanner, did you catch the fuel trim values? A fuel trim value of zero plus or minus 5 means the fueling is correct for what the PCM is commanding. Higher than 5 means the PCM is adding more fuel (based on what the O2 sensor sees), and less than -5 means it's pulling fuel. This is important to take a look at especially while driving.

 

[88red4cyl]

with that kind of fuel being dumped into the engine, that cat must get red hot. Replace the upstream O2's, clean the MAF (or heck, disconnect it for a few days and run off speed density mode)

 

What's speed density mode? The upstream 02 and the MAF are reading within their limits, it's the other 02 that isn't reading right.. And apparently that won't affect my mileage, so it isn't worthy of replacing right now.. So I should be able to look at the cat and it should be glowing red?

 

I haven't been adding any antifreeze to it.. Last time a scan tool was hooked up to it (couple weeks ago) the coolant temp sensor was way off.. It was all corroded so it was cleaned, and then it was working right.. I thought that would fix my problem, but it didn't... Could a bad IAC cause these problems? I have noticed that it is idling a bit higher than it used to..

 

This I'm a little confused on. You removed the sensor and then cleaned it? Was the probe corroded, or the wire pins? That's a big thing, even if there's a loose connection and maybe it fluctuates between connected and disconnected, it will think the coolant temp is like -40 and dump a lot of fuel.

 

I'm not entirely sure.. I didn't physically see the corrosion, I was just told that there was some.. If it makes a difference I can find out.. After cleaning it though, it reads correctly to the ECM now, which it wasn't before the cleaning.. After that, I ran a whole tank through (which doesn't take very long btw), and it helped me about .2 mpg...

 

OH! So it's your downstream that is switching slow? That would be normal, for the most part. That also gives indication that the cat is working good.

 

I'm thinking more along the lines that the temp sensor is on its way out. Like maybe it's reading okay when you scan it, but what about while driving and such?

 

Speed density mode is a fuel management based off the MAP sensor. Basically it's how 2.8/3.1 cars were run, and is sort of a fail safe for if the MAF fails. Since you have access to a scanner, did you catch the fuel trim values? A fuel trim value of zero plus or minus 5 means the fueling is correct for what the PCM is commanding. Higher than 5 means the PCM is adding more fuel (based on what the O2 sensor sees), and less than -5 means it's pulling fuel. This is important to take a look at especially while driving.

 

 

I will take a look at the trim values , probably next week (my buddy is getting married this weekend so I probably won't have time) around Monday or Tuesday.. The downstream sensor is pretty much reading flat, unless you really get on the gas, and then it will move.. We hooked it up to another vehicle he had sitting around, and both the 02 sensors on it were fluctuating constantly, so we figured that the 02 was bad, but even if it is, then is wouldn't be worth the $70 to replace it since it'll only tell me if the cat is bad or not..

[Brian P]

Yeah I wouldn't be concerned with the downstream. Next time you scan it, reset the PCM too. Might be a little screwed up from the false coolant temp readings.

[88red4cyl]

Is the only way to reset the PCM with the scanner? If it isn't, then I could do it right now and see if it helps..

[Brian P]

supposedly if you unhook the battery for 20 minutes, that does it too, but for me it hasn't worked.

[88red4cyl]

supposedly if you unhook the battery for 20 minutes, that does it too, but for me it hasn't worked.

Thanks. Not even gonna mess with it if it hasn't worked for you.. Reprogramming the HU in that car sucks..

[88red4cyl]

Hmm.. I don't wanna speak too soon, but it may be fixed.. I got the fuel injector service done last week, and I had to fill up the tank because of the additive so it could work properly.. Anyway, I drove for half the tank last time before I replaced the o-ring on the fuel line that was leaking a bit.. I drove from 1/2 to 1/4 with that fixed and had the fuel injector thing done at 1/4 tank.. When I filled up, my average was up from 6.2 (for several tanks in a row) to 11.7, and that was only with it fixed for ~4 gallons of fuel.. I've driven about 20 miles since then, and the needle has barely moved past the F mark...

 

On a side note, there was something else fuel related that has got me puzzled.. The gas gauge on this car used to go past the Full line a bit when you would fill the car up.. Now, you fill it up until it won't take anymore, and it is right on the Full line, maybe a tiny fraction before it.. What happened here??

[88red4cyl]

Hm.. I still have a problem.. The mileage has gone up, about double what it was, but it still sucks.. Where do I go from here?

[EviLette]

Hmm.. I don't wanna speak too soon, but it may be fixed.. I got the fuel injector service done last week, and I had to fill up the tank because of the additive so it could work properly.. Anyway, I drove for half the tank last time before I replaced the o-ring on the fuel line that was leaking a bit.. I drove from 1/2 to 1/4 with that fixed and had the fuel injector thing done at 1/4 tank.. When I filled up, my average was up from 6.2 (for several tanks in a row) to 11.7, and that was only with it fixed for ~4 gallons of fuel.. I've driven about 20 miles since then, and the needle has barely moved past the F mark...

 

On a side note, there was something else fuel related that has got me puzzled.. The gas gauge on this car used to go past the Full line a bit when you would fill the car up.. Now, you fill it up until it won't take anymore, and it is right on the Full line, maybe a tiny fraction before it.. What happened here??

 

The level on my gauge did that when I had fuel pumps changed out a while back. It doesn't move forever above F, then below 1/2 tank it drops pretty quick LOL. I think it has something to do with the ingenius design of the float positioning for the gauge inside the tank.

[Euro]

Do you do a lot of highway or straight road type driving? Using CC seems to help me. Since I can't keep my speed too steady with just my foot, I clicked on the cruise today and got better mileage than usual on the highway

[88red4cyl]

Do you do a lot of highway or straight road type driving? Using CC seems to help me. Since I can't keep my speed too steady with just my foot, I clicked on the cruise today and got better mileage than usual on the highway

 

I haven't really driven this car on the highway since I got the 95.. I've taken it on a couple hour long trips, but all the big trips I use the 95 for now.. That is a good tip on the CC though.

[Brian P]

How many gallons did your last fill-up take?

[88red4cyl]

How many gallons did your last fill-up take?

 

Um.. The last fill up was around 12 or 13 gallons I think.. Last time I put gas in it was around 9 gallons..