re-assembled engine... now dies at part throttle

[PTAaron]

Finally got my engine (3.1L '94 Cutlass Supreme) back together after replacing the head gasket this past weekend - I posted this problem in the thread where I've been detailing that fun experience, but I thought I might get more answers if I posted a separate thread for the new problem.

Car starts and idles very nicely. Goosing the throttle revs the engine up just fine. Tapping the throttle slightly and holding it makes the car start to stumble, then stall out.

 

Here is a video clip - I gave it part throttle, went back to idle, then gave it a little bit of throttle again and held it - then it dies:

[video=youtube;Elq_q26-Yu4]

 

I'm not really sure where to even start looking - aside from "Something I took off the engine then put back on it isn't doing its job correctly" ... but that doesn't narrow it down much.

 

Any thoughts?

 

My brain jumps to Throttle Position Sensor, MAP sensor, or something else tied to fuel delivery from my experience with other cars - would this be a logical place to start?

Edited March 28, 2014 by PTAaron

[PTAaron]

Crap - I did it again: 3.1L V6 - '94 Cutlass Supreme. I'm used to cars that only had one engine

[Schurkey]

Two words: Scan Tool.

 

Not a code-reader, or a consumer-grade piece-of-shit scan tool. Find a real one, connect it, and start looking at the data stream.

[PTAaron]

Two words: Scan Tool.

 

Not a code-reader, or a consumer-grade piece-of-shit scan tool. Find a real one, connect it, and start looking at the data stream.

Would love to do that, but there are 2 big problems: I don't have $300-600 to spend on something I will only use once, and I wouldn't know what I'm looking at unless it is spelled out in really simple terms.

 

 

We're to the point where if it is going to cost more than $100 to get the car running again, it is just going to be donated to charity and I will buy something made in this decade.

[Mach 5]

it started right after the head gasket replacement? is it possible either a vac line is pinched or mixed up? cel on? need data

[Schurkey]

We're to the point where if it is going to cost more than $100 to get the car running again, it is just going to be donated to charity and I will buy something made in this decade.

Excellent plan. Give up just after spending a bunch of money and time on the project.

[nitehawkjcb]

Check the vacuum lines, and yes fuel delivery could be an issue also

[RobertISaar]

Excellent plan. Give up just after spending a bunch of money and time on the project.

 

that's the first thought that came to mind as well.... followed by "whoever picks it up won't have to put nearly any money into it".

[PTAaron]

Excellent plan. Give up just after spending a bunch of money and time on the project.

Point taken, sarcasm acknowledged and appreciated. I am just at a point of extreme frustration in getting this car on the road, and I am weighing the benefit of spending more money on repairing this car vs saving the money for a down payment on something new. I simply cannot go out and buy a professional grade scan tool and learn to interpret the data stream information - I'm a physical therapist, not a mechanic so I can't justify spending that kind of money on something that will be used only once or twice.

What I was hoping to get here was a few items to add to the differential diagnosis list so that I can check them out this weekend and hopefully get to the bottom of this mess without needlessly spending money. Currently I am stuck sharing a car with my wife, which is not a situation either of us enjoy.

 

Check the vacuum lines, and yes fuel delivery could be an issue also

Thank you, I checked the vacuum lines attached to the intake - I did crack the "hard" vacuum line when I was removing them at the start of the project, but I created a patch for it using some small gauge soft vacuum line.

 

that's the first thought that came to mind as well.... followed by "whoever picks it up won't have to put nearly any money into it".

You're right.

Previous post was written from a point of massive frustration. It is hard to keep dumping money into this car - it was free, but has cost me at least $1000 in repairs since I got it, not to mention time. I want to keep the car - my goal was to keep it going to at least 200,000 miles or the body rusts the rest of the way off whichever came first.

If you have any suggestions as to what direction I should go, I would greatly appreciate them. Thank you for your immense helpfulness thus far (sincerely).

Edited March 28, 2014 by PTAaron

[PTAaron]

it started right after the head gasket replacement? is it possible either a vac line is pinched or mixed up? cel on? need data

CEL did not come on during the 15 minutes the car was idling, I did not restart it after it stalled out in the video to see if a light came on.

It is possible that something is pinched - I will double check that. Vac lines are the one thing I was certain I didn't mix up... although I briefly had the wrong wire plugged into the ignition coils - but that was corrected before the battery was reconnected. Somehow we got the under hood light plug to fit into the socket for the crank position sensor...

 

I should note that prior to replacement I had a distinct lack of power/bogging down when I attempted to accelerate and the RPMs went above 2000. The car started to stumble/stall just like it is doing now at part throttle (I'm just remembering this now as I type it).

Edited March 28, 2014 by PTAaron

[rich_e777]

First off SHIT HAPPENS. Dig it!

 

Second there is a drive cycle the electronics have to go through before everything is re-learned. I`d go start the fucker back up and take it for a spin in a direction you could potentially leave it overnight should shit go wrong. Let it get to operating temperature then see if you have any indicators like puddles on the ground, a hissing noise coming from a certain area or a midget randomly unplugging and replugging things when you aren't paying attention. All possible scenarios. (Fix the "hard" vacuum line with a replacement not a patch, assuming you are referring to the brake booster line.) Also check all the connection to the fuel system, its easy to forget to plug something back in.

 

When I did my head gaskets I forgot to torque down ONE umm forgot the gawddamn name but it involves the pushrods under the valve covers, and it made the engine run like shit with a wicked lope in the idle, well at 8:30 that Friday evening after spending all week working on it a grabbing parts as needed I wasn't to thrilled either. You did remember the additional torque on your head bolts right? If you forgot you are FUCKED and will need a new set.

 

Being a physical therapist is no excuse in lack of mechanic skills, technically you are rubbing down the car the same way you rub down your clients. Except that metal and muscles are two totally different things and the client pay you for it or however that prostitution racket works. Sorry, I bit mean when on the goldschlager.

[PTAaron]

LOL!

okay, yeah... Physical Therapy and massage therapy aren't the same thing, so don't get your hopes up

My point however was not that I being a PT affects my "mechanic skills" just that I won't be buying a $600 piece of testing equipment that I will never use again. If I were a mechanic it would make more sense to own that because it might get used. I've worked on cars for the past 20 years as a hobby - so I'm fairly comfortable doing it.

I had it at operating temp for quite a while and didn't hear any hisses and there were no drips. I did forgot to check for midgets though... they are a problem around here.

I will take the car out for a drive around the subdivision and test that theory - hope that works!

 

The "hard" vacuum line I was talking about is very small hard plastic line that runs to the passenger/alternator side of the upper intake manifold. The "patch" is just a piece of hose that I slipped both ends of the broken line into with roughly the same ID as the original hard line.

 

I definitely did the extra torque to the head bolts - but that would REALLY suck to forget.

Thanks for the thoughts!

Edited March 29, 2014 by PTAaron

[tornado_735]

Don't worry about Schurkey. Though his advice it sound, he comes off as a huge dickhead. As to whether or not he is in real life? Who knows.

 

Really the only thing you can do is double check EVERYTHING.

 

If you're poor like me, and everything checks out (plugs pressed all the way in, vacuum lines all connected, etc) the only other thing you can do is to eliminate the potential causes. Start it, unplug the Throttle Position Sensor, see if it still happens. If it runs better or will actually rev with the TPS unplugged, try swapping in a new one. If there is no improvement, unplug the MAP sensor. There is no Mass Airflow Sensor on this engine. If the MAP does not improve things, check fuel pressure with a gauge you can rent from the parts store.

 

Sure, a scan tool with tell you exactly what the engine is doing at any given time. But there are ways to hunt down the problem without it...it just takes longer.

[PTAaron]

Don't worry about Schurkey. Though his advice it sound, he comes off as a huge dickhead. As to whether or not he is in real life? Who knows.

 

Really the only thing you can do is double check EVERYTHING.

 

If you're poor like me, and everything checks out (plugs pressed all the way in, vacuum lines all connected, etc) the only other thing you can do is to eliminate the potential causes. Start it, unplug the Throttle Position Sensor, see if it still happens. If it runs better or will actually rev with the TPS unplugged, try swapping in a new one. If there is no improvement, unplug the MAP sensor. There is no Mass Airflow Sensor on this engine. If the MAP does not improve things, check fuel pressure with a gauge you can rent from the parts store.

 

Sure, a scan tool with tell you exactly what the engine is doing at any given time. But there are ways to hunt down the problem without it...it just takes longer.

 

Great, thank you!

 

The plan for tomorrow morning is going to be:

1) Test car with engine cold and see if it does the same thing it did when it was warm (engine was warm when I had the problem - I was so happy it started that I didn't mess with it when it was still cold)

2) double check every connector that I can see again - remove and reconnect them to make sure they have good contact.

3) check all vacuum lines again.

4) replace O2 sensor - I was getting a CEL before the overheating/head gasket issues that I suspect was O2 sensor

5) test TPS voltage readings, replace if necessary

6) clean IAC

7) test out MAP sensor

 

Hopefully at some point along the testing path I will stumble onto the solution.

Edited March 29, 2014 by PTAaron

[Schurkey]

Don't worry about Schurkey. Though his advice it sound, he comes off as a huge dickhead. As to whether or not he is in real life? Who knows.

See signature line

[Imp558]

You really need to think about what changed from the time it ran well till now also:

1) Everything got wet, is the o2 sensor damaged?

2) Did a sensor get damaged during the work that was performed? That happens.

3) Are all the electrical connectors sound or could a wire have pulled off one while unplugging it?

4) Could a plug have gotten crud in it when it was unplugged?

5) Could a pin on a sender have decided to bend instead of seating in the plug?

6) Could your pimp have sabatoged it to keep you under his control? (Dude, I'm sooo sorry, just couldn't help it after reading Rich's post)

 

You get the idea though, just a very good visual inspection on top of what the other guys said here. You may find that there are several small faults all being tiny ass sores and adding up to one giant ass sore.

[rich_e777]

Don't worry about Schurkey. Though his advice it sound, he comes off as a huge dickhead. As to whether or not he is in real life? Who knows.

 

Really the only thing you can do is double check EVERYTHING.

 

If you're poor like me, and everything checks out (plugs pressed all the way in, vacuum lines all connected, etc) the only other thing you can do is to eliminate the potential causes. Start it, unplug the Throttle Position Sensor, see if it still happens. If it runs better or will actually rev with the TPS unplugged, try swapping in a new one. If there is no improvement, unplug the MAP sensor. There is no Mass Airflow Sensor on this engine. If the MAP does not improve things, check fuel pressure with a gauge you can rent from the parts store.

 

Sure, a scan tool with tell you exactly what the engine is doing at any given time. But there are ways to hunt down the problem without it...it just takes longer.

 

Sometimes that's just how grown ass men talk to each other, we aren't a bunch of women worried about damaging feelings:lol:

But hey the damn thing started didn't it? You can chalk that up as a win. 1/2 win maybe.

[PTAaron]

You really need to think about what changed from the time it ran well till now also:

1) Everything got wet, is the o2 sensor damaged?

2) Did a sensor get damaged during the work that was performed? That happens.

3) Are all the electrical connectors sound or could a wire have pulled off one while unplugging it?

4) Could a plug have gotten crud in it when it was unplugged?

5) Could a pin on a sender have decided to bend instead of seating in the plug?

6) Could your pimp have sabatoged it to keep you under his control? (Dude, I'm sooo sorry, just couldn't help it after reading Rich's post)

 

You get the idea though, just a very good visual inspection on top of what the other guys said here. You may find that there are several small faults all being tiny ass sores and adding up to one giant ass sore.

Let's get one thing straight... I'm my own pimp now, I don't care what MackDaddy P is telling people!

[PTAaron]

Sometimes that's just how grown ass men talk to each other, we aren't a bunch of women worried about damaging feelings:lol:

But hey the damn thing started didn't it? You can chalk that up as a win. 1/2 win maybe.

Haha! Yeah, the fact that it started and idled smoothly had me calling it a win for sure.

[PTAaron]

Update:

Replaced the O2 sensor - which was practically welded in place, and did some testing. TPS tested out with .5V with the throttle closed, and had a nice even sweep up to just under 5V at WOT. The IAC looked clean when I took it off, and when we disconnected it while the car was running and warm it made it run poorly - same as when the TPS was disconnected while the car was running.

Double checked vacuum lines and connectors - all looked OK.

The MAP sensor was not giving .5V in key on engine off as it should - it was reading .1-.2. We did not test it with the engine running.

 

Good news is now with the new O2 sensor in place the car is drivable. At start up the idle is rough, then it picks up to around 1500RPM for a while and stays there until you put it in gear. When you go back to park/neutral it will drop to 900-1000.

While driving at part throttle (25%) it accelerates really smoothly. If you push it further than that it bogs down and almost stalls out, then runs rough for a few seconds.

 

Not sure where this leaves us - MAP sensor seems like a likely culprit, so I may be picking one up to try that out.

 

Also - still no engine codes, the light popped on for a second after startup then quickly went out. Did not come back on during 10 minutes of driving around the neighborhood and to the store.

Edited March 30, 2014 by PTAaron

[RobertISaar]

MAP should be showing very close to 5 volts with the engine not running.

[PTAaron]

MAP should be showing very close to 5 volts with the engine not running.

The testing procedure I was reading said 5V on the grey reference wire (which tested out fine) and "approximately 0.5 volts" on the sensor wire with the engine off - was that correct?

 

I replaced the MAP sensor a few minutes ago, and took the car out for a drive - took a while to start because we tried starting it up without the sensor connected first to see what would happen and that ended up (apparently) dumping a lot of extra fuel in.

Idle initially was much smoother than the previous times we started the car today. Drove it around my sub with light/moderate acceleration and it felt really good. Got out of my sub and under part throttle acceleration it was strong, but flooring the pedal made it stumble but it did not start to stall out like it did before. I went back and forth a few times and found that if I kept the pedal down it got past the stumble and would accelerate like normal.

Still no codes showing up - no check engine lights.

 

So... the car is definitely drivable as long as I don't need to mash on the gas for some reason. It seemed to idle even better when I got back from the drive - if that trend continues we'll be in good shape

It is cold out, and it is dark, so I'm done test driving because I don't want to end up stuck somewhere that I'll have to walk home from

 

I would say that it is about 80% better than it was yesterday.

Edited March 30, 2014 by PTAaron

[PTAaron]

My father in-law and I both were saying "It feels like the timing advance is off" - but on this car that is not something that can be adjusted, right?

I'm used to cars with distributors

[RobertISaar]

The testing procedure I was reading said 5V on the grey reference wire (which tested out fine) and "approximately 0.5 volts" on the sensor wire with the engine off - was that correct?

 

with the engine off, the MAP signal should be at atmospheric pressure, which depending on elevation, would be near 5 volts. i don't know where you saw that procedure at or how exactly it was done.... i can see you reading low voltage IF you had one of the meter probes on the 5V reference circuit instead of ground, in which case the voltage shown on the meter would be inverted(4.5 volt sensor reading would show up as .5 volts, for instance).

 

do you have new plugs, wires, coils or ICM since all of this started happening?

 

My father in-law and I both were saying "It feels like the timing advance is off" - but on this car that is not something that can be adjusted, right?

I'm used to cars with distributors

 

timing is non-adjustable, the PCM and ICM takes care of all of that. if actual timing were different than commanded timing...... then something has gone seriously wrong.

[PTAaron]

with the engine off, the MAP signal should be at atmospheric pressure, which depending on elevation, would be near 5 volts. i don't know where you saw that procedure at or how exactly it was done.... i can see you reading low voltage IF you had one of the meter probes on the 5V reference circuit instead of ground, in which case the voltage shown on the meter would be inverted(4.5 volt sensor reading would show up as .5 volts, for instance).

 

do you have new plugs, wires, coils or ICM since all of this started happening?

 

 

 

timing is non-adjustable, the PCM and ICM takes care of all of that. if actual timing were different than commanded timing...... then something has gone seriously wrong.

 

Got the testing procedure from the online manuals on the Autozone website: http://www.autozone.com/autozone/repairinfo/repairguide/repairGuideContent.jsp?pageId=0900c15280067e2d

 

Either way - the number we got was .1 to .2, so it was low regardless.

 

Plug wires were replaced during the head gasket replacement. Plugs are about 6 months old, and were re-gapped during this process. No changes to coils or any other ignition components.

 

I figured as much on the timing - I don't think there is an actual issue with it, but the problem the car was having FELT like a car with the timing off a few degrees.

If it was the MAP sensor that was bad - based on the description of it controlling fuel and timing, it seems like it would cause that symptom.