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1990 Chevy Corsica stalling issue.


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Ironman
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May 26, 2013, 10:35 PM

Post #1 of 8 (1120 views)
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  post locked   post icon 1990 Chevy Corsica stalling issue.  

I have a 1990 Chevy Corsica with 2.2L, TBI, 176,000 mi.
It had been running fine, I drive it 30 mi. one way to work everyday. One day going in no problems 12 hours later hard to start, extended cranking time, finally started but died immediately. A couple more tries each time long crank time running rough not wanting to Idle. About the 4th try seemed to smooth out fine, started down the road and in less than 1/2 mile it just died going down the road. Next day still not wanting to start, I shot some starting fluid into the throttle body, it fired right up but then died. Found that it would not idle or run at any steady throttle position but would run if I jockey the throttle open/close/open/close/etc. Installed a junkyard IAC valve no help, have verified original and replacement extend at high rpm idle, appear to work fine. I suspected a fuel delivery issue so I replaced fuel filter, no help. Next I installed a new fuel injector, no help. I verified fuel delivery from the pump but replaced it anyway. Cleaned the throttle body and fuel pressure regulator diaphragm and spring. Borrowed a fuel pressure tester holding 12 PSI steady. Checked voltage for TPS .6 volts at closed throttle smooth increase to 4.8 volts at open throttle. I checked for codes on OBD1 no codes present. During troubleshooting I discovered that the car will start and run on it's own if I leave the vacuum line for the MAP disconnected. Checked voltage output from the MAP 4.8 volts with no vacuum applied smooth decrease down to 1.1 volts with 20 inches of mercury applied. With the vacuum line disconnected the car starts and idles but idles faster than normal, also accelerates fine and runs at steady throttle. If I plug the vacuum line the idle slows to normal and the car will still run and accelerate and run at steady throttle. It usually dies after idling for a while but tends to run longer with the vacuum line open. If I disconnect the electrical connector to the MAP the car dies. The car stumbles under load with the vacuum disconnected from the MAP but returns to the original symptoms when the MAP is connected. I've also looked for vacuum leaks but can't find any and applied a vacuum gauge to the Map port from the throttle body and get 18-20 inches of mercury but it does kind of flutter between 18-20 instead of holding steady. It also dies if I apply vacuum to the MAP with a vacuum pump. It seems to actually increase in RPM up to about 5-7 inches of mercury but after that point it will die. think my ECM could be bad? Any help would be greatly appreciated. Thanks. Forgot to add that the spark to all cylinders seems fine as far as I can tell.
Unsure


(This post was edited by Ironman on May 26, 2013, 10:42 PM)


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

May 27, 2013, 8:08 AM

Post #2 of 8 (1091 views)
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  post locked   Re: 1990 Chevy Corsica stalling issue. [In reply to]  

You probably need to look as sensor data, especially the adaptives and see what they are doing. See what the fuel pressure actually is and is it changing when the problem occurs. I would also do a compression test to see if you have any timing chain issues.




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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Ironman
New User

May 27, 2013, 9:57 AM

Post #3 of 8 (1082 views)
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  post locked   Re: 1990 Chevy Corsica stalling issue. [In reply to]  

OK, it will probably be a week or so before I get another chance to work on it but I have another car that I can drive. This is my primary work car and I'd really like to get it going again but it isn't worth much so I prefer not to take it to a shop. I'll get back to you once I do a compression test. I don't have any type of scanner to look at sensor data in real time I was just looking at the CEL flashes with pins 1 & 2 shorted & the key on.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

May 27, 2013, 10:00 AM

Post #4 of 8 (1076 views)
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  post locked   Re: 1990 Chevy Corsica stalling issue. [In reply to]  

There's a lot more information to be had using a scanner than simply codes.




~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Discretesignals
Veteran / Moderator
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May 27, 2013, 11:16 AM

Post #5 of 8 (1070 views)
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  post locked   Re: 1990 Chevy Corsica stalling issue. [In reply to]  

When you disconnected the MAP sensor vacuum, that causes the ECM to injector more fuel because it thinks the engine is under load. Your masking the fuel problem when you disconnect the MAP, so a vacuum leak isn't your problem.

What is the coolant sensor voltage when the engine is cold? ECT plays a huge role on a speed density engine, so you should check that out too.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on May 27, 2013, 11:17 AM)


Ironman
New User

Jun 8, 2013, 9:07 PM

Post #6 of 8 (1000 views)
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  post locked   Re: 1990 Chevy Corsica stalling issue. [In reply to]  

I don't have a scanner just shorting the pins to read codes. Is there a scanner out there that's reasonably cheap and can it display real time data? Remember this is an old car 1990 OBD1.


Ironman
New User

Jun 23, 2013, 3:38 PM

Post #7 of 8 (954 views)
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  post locked   Re: 1990 Chevy Corsica stalling issue. [In reply to]  

Last weekend I went to the salvage yard and got a used ECM. This has solved the problem.Smile


Tom Greenleaf
Ultimate Carjunky / Moderator
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Jun 23, 2013, 3:56 PM

Post #8 of 8 (949 views)
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  post locked   Re: 1990 Chevy Corsica stalling issue. [In reply to]  

No argument with what works. Glad to hear you are up and running.

Let's lock this thread to avoid spammers. Opened at your request,

T
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Long retired now




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