Stall/Miss When Cold - 2000-3500 RPM Idle When Hot

[1987 GMC Jimmy]

Stall/Miss When Cold - 3000-3500 RPM Idle When Hot

Sorry to keep asking follow up after follow up on these same issues, but I can't seem to iron them out. It's an E4ME Quadrajet. When it hasn't ran for a while, it does pretty decent and can sit there and run fine all day. I drove it to town and I got almost there and noticed it'd stay the same driving speed when I let go of the gas pedal. I stopped it as soon as I could much to the lament of my brakes, and it almost sounded like a run away diesel. It was really high. About 3000 RPM sitting in park maybe more. No binding in the throttle linkage, dashpot pintle was retracted, and the butterfly plate was all the way open. The carb looked good, but I turned it off and it dieseled for almost a minute. The exhaust smelled suuuper lean also. After that little voyage, it struggles to stay running when it's cold: rough running, missing, rich smelling. Exact same problem I've been having with it. It only runs decent when I've let it sit. Otherwise, it'll do all kinds of weird stuff. I'm guessing it's an air problem, but I'd be open to a fuel problem. I'm gonna do my best to check for an intake leak, but that's all it could be vacuum wise, and I was wondering if there were any suggestions out there. My AFR is basically all over the place also courtesy of my SES light.

 

[Rusty Nail]

Is there raw fuel in the regulator vacuum hose? Any at all?
Low vacuum or no vacuum results in high pressure.

 

[1987 GMC Jimmy]

Is there raw fuel in the regulator vacuum hose? Any at all?

I'll repost the emissions diagram because I'm not sure which part you're talking about, buddy. I'll get 19 inches manifold when it's running correctly, but it decreases complementarily to the engine issues.

 

[Rusty Nail]

Lol .
Is this the one we were just talking about the charcoal canister filter, yes?

I'm not hip to the history of this problem, but I assume they are related and somewhere lies the root of it all.
Ever replaced the TPS under the airhorn? It'll throw a hard code and you can test it. Speaking of, what ya got for codes?

 

[1987 GMC Jimmy]

Lol .
Is this the one we were just talking about the charcoal canister filter, yes?

I'm not hip to the history of this problem, but I assume they are related and somewhere lies the root of it all.
Ever replaced the TPS under the airhorn? It'll throw a hard code and you can test it. Speaking of, what ya got for codes?

Yeah, I just replaced the canister filter (per your suggestion) and the O2 sensor. The TPS is ten months old. I'm not getting any hard codes. I'll just get a back and forth 44 and 45 that come and go.

 

[Rusty Nail]

Code 44 is set when the O2 sensor signal voltage remains below .3 volts for 50 seconds or more and the system is operating in "closed loop".
.
The O2 sensor varies the voltage within a range of about one volt, if the exhaust is rich, down thru about .10 volt, if exhaust is lean.

The sensor is like an open circuit and produces no voltage, when it is below about 360 degrees C, 600 degreeF. An open sensor circuit, or a cold sensor, causes Open Loop operation.

Test description:

1.) Code 45 is set when the O2 sensor signal voltage remains above .7 volts for 30 seconds or more and in "closed loop".

HEI shielding - an open ground ckt 453 may result in EMI, will result in induced electrical "noise". The ECM looks at this noise as reference pulses. The additional pulses result in a higher than actual engine speed signal. The ECM then delivers too much fuel, causing the system to go rich. The engine tachometer will, also, show higher than actual engine speed, which can help in diagnosing this problem.
..
...
That's a great way to spend 2 dollars, btw.

MAP sensor - an output that causes the ECM to sense a higher than normal manifold pressure (low vacuum) can cause the system to go rich. Disconnecting the MAP sensor will allow the ECM to set a fixed value for the MAP sensor. Replace the sensor if the rich condition goes away when the sensor is disconnected.
Hmm.

TPS - an intermittent TPS output will cause the system to go rich, due to a false indication of the engine accelerating.

Hmm!

We're gonna fix it.

Duplicate the symptom and unplug the map sensor, as described to blame or eliminate it.
If it gets eliminated, I'm back at the TPS or the HEI short to ground that I don't think is likely. But you DID just tune it up, right? Problem started after that?
What brand did you install btw? Remind me one day and I'll tell you the story about how I became an O'Reilly customer.

Is the engine speed shown higher than actual? That question needs answered.

 

[1987 GMC Jimmy]

Code 44 is set when the O2 sensor signal voltage remains below .3 volts for 50 seconds or more and the system is operating in "closed loop".
.
The O2 sensor varies the voltage within a range of about one volt, if the exhaust is rich, down thru about .10 volt, if exhaust is lean.

The sensor is like an open circuit and produces no voltage, when it is below about 360 degrees C, 600 degreeF. An open sensor circuit, or a cold sensor, causes Open Loop operation.

Test description:

1.) Code 45 is set when the O2 sensor signal voltage remains above .7 volts for 30 seconds or more and in "closed loop".

HEI shielding - an open ground ckt 453 may result in EMI, will result in induced electrical "noise". The ECM looks at this noise as reference pulses. The additional pulses result in a higher than actual engine speed signal. The ECM then delivers too much fuel, causing the system to go rich. The engine tachometer will, also, show higher than actual engine speed, which can help in diagnosing this problem.
..
...
That's a great way to spend 2 dollars, btw.

MAP sensor - an output that causes the ECM to sense a higher than normal manifold pressure (low vacuum) can cause the system to go rich. Disconnecting the MAP sensor will allow the ECM to set a fixed value for the MAP sensor. Replace the sensor if the rich condition goes away when the sensor is disconnected.
Hmm.

TPS - an intermittent TPS output will cause the system to go rich, due to a false indication of the engine accelerating.

Hmm!

We're gonna fix it.

Duplicate the symptom and unplug the map sensor, as described to blame or eliminate it.
If it gets eliminated, I'm back at the TPS or the HEI short to ground that I don't think is likely. But you DID just tune it up, right? Problem started after that?
What brand did you install btw? Remind me one day and I'll tell you the story about how I became an O'Reilly customer.

Is the engine speed shown higher than actual? That question needs answered.

I'll try the MAP sensor! I tuned it all up about ten months ago also. Plugs, wires, cap, rotor, and HEI coil then, but I also replaced the Ignition Control Module (twice) about a month and a half ago. Everything's Delco except the HEI coil, which is a Borg Warner Development. I just ran it. The warm idle was about 800 (as you know, just a guess by auditory comparison), but it'd go up and down a little. I was starting and restarting to see if I'd get anything different on the vacuum gauge, and I restarted twice and got 15 and after a couple minutes, it went back up to 18-19. It was just the other day that it was sitting in the parking lot screaming. It sounded almost as bad as those runaway diesel videos on YouTube. I had to stop at a stop light while it was doing that, and when I let go of the brakes, it launched without touching the pedal! It was also cruising at like 65 without me touching the pedal. And again, the linkage was all perfect. The most recent thing that I replaced before this started was the two way vacuum check valve that comes off the back of the intake. After I did that, the car makes a really high pitched spool down sound, whenever I turn it off, that lasts a few seconds. I'll also add that my super high idle speed/runaway engine happened after I was using the cruise control for a few minutes, which I just got working recently. But again, it was still doing all that in park with no influence from the cruise control.

 

[Rusty Nail]

Engine speed is NOT higher than actual, correct?
This sounds terribly freaking dangerous, we better get it fixed pronto. Is it your daily?

I lean away from TPS.

What is significant about 10 months ago?

TEN MONTHS?

That check valve is one way, are you certain it is installed correctly?
The MAP sensor is awfully cheap man... Unplug it and see if it runs better.

Verify the CEL lights up and retrieve that new code. Check that hard line and wires while your at it . There is a hard 90° if I'm not mistaken.
Best bet is a bad MAP or leak in that hard line. Manifold absolute pressure is the OPPOSITE of vacuum.... When manifold pressure is high..., vacuum is low. The rubber insert at the plug is color coded. Should be green? Lol.
Why can't you replace the hard line with hose? I bet it's split (at the 90°)

Borrow the hose off your hood from the windshield washer real quick.

This is my favorite band/album.

If you continue to throw parts at a computer controlled vehicle, you choose to remain enslaved. Think about it!
[yt]pdzPph7Qxg8[/yt]

 

[1987 GMC Jimmy]

I duplicated the symptoms, and unplugging the MAP sensor made it worse. Same with the TPS but not as noticeable. I said two way check valve because that's what the part that I bought was called. It goes to the vacuum storage ball and one of the HVAC vacuum lines. I noticed that the vacuum takes a sharp turn downward whenever it starts to act up. It stumbled down to 8-9 before I said enough. The cranking vacuum pulsates around 2-3. I've also had to hold the pedal down most of the way when it's cold to start it. Before, a pump or two would be ample to ensure a good start. It wouldn't attach... Here's the link. It's a one way check valve that goes two ways, I guess. http://m.advanceautoparts.com/p/dorman-help-two-way-check-valve-47150/17190329-P

 

[Rusty Nail]

Haha! That's pritty funny!That's called a one way valve because it only passes vacuum one way, man that's funny!
but that's not related.
HOW, exactly, were you able to duplicate the trouble so easily?
After reading the latest post, I was thinking "this sounds like EGR problems but it's not. Does the EGR work okay? If you manually operate the diaphragm from the bottom of the valve, will it kill the engine? Sometimes it's difficult to manipulate with your fingers, if so use a q-tip.

 

[1987 GMC Jimmy]

Haha! That's pritty funny!That's called a one way valve because it only passes vacuum one way, man that's funny!
but that's not related.
HOW, exactly, were you able to duplicate the trouble so easily?
After reading the latest post, I was thinking "this sounds like EGR problems but it's not. Does the EGR work okay? If you manually operate the diaphragm from the bottom of the valve, will it kill the engine? Sometimes it's difficult to manipulate with your fingers, if so use a q-tip.

The EGR holds vacuum, I've tested it for that, but does that mean that it's alright? I've taken it off twice to remove the valve cover and cleaned the caked carbon off the pintle. I don't do anything specifically to duplicate symptoms. They just start happening more than they don't.

 

[1987 GMC Jimmy]

I tightened the carburetor down. I don't know why or how it had gotten loose. I don't have a torque wrench so I do get scared of over tightening that thing. I did get it back on there pretty snug, and I forgot to reconnect the MCS. It ran very strong at 19 inches of vacuum. I went back and plugged the solenoid up, and it ran like garbage and died a few seconds after. I tried to start it back up, and it didn't want to so I unplugged it again, and it started perfect. It ran rich but better than it has in a while. I'll also note that whenever I jump the A and B pins on the ALDL to pull codes, the MCS clicks a lot faster, and I got a fault code for it once (Code 54). With the key on, engine off, it always clicks like it should, though.

 

[Rusty Nail]

There is a proper sequence for tightening the air horn, might be good to check those too.

 

[1987 GMC Jimmy]

I woke up and smelled what I was shoveling with this and bought a new timing light. I had timed it right when I first got it, but I asked my brother to tighten the distributor while I did something else. Well, I got my distributor wrench out, and the bolt was fairly loose already. I checked my base timing in park, and it was 4* ATDC. I don't know if the nine degree weather we had affected something with it for a bunch of **** to be loose that wasn't loose before, but I readjusted my base timing to about 9* BTDC, and it's a lot better. I don't know if I'll get any ping at that level so I'll take it down a couple notches if I do, but hopefully that and the carburetor tightening helps. Did the air horn, too. Scared of messing up carb, but they had a little bit of reasonable tightening left in them.

 

[Rusty Nail]

.....

The hard part will be not popping the hood for say, three days to see if the "fix" worked.
Try not to mess with ANYTHING until you find confidence. In the world of automotive repair, if there are no issues after three key starts, it's fixed.