Car stalls at normal operating temperature when stopping or slowing down

MS5550

MEMBER
1995 OLDSMOBILE 88
3.8L
6 CYL
2WD
AUTOMATIC
117,000 MILES

The car stalls occasionally when slowing down or coming to a stop, but only once it is at operating temperature. No check engine light. Also occurs when coasting at lower speeds without touching the gas pedal. The belt squeal gets a bit louder (possibly RPM's dropping?), Until it stalls, all dash lights come on, and I lose power steering and all acceleration. It starts right back up.

All spark plugs and ignition coils recently replaced, but did nothing. Fuel filter pretty new.

Is there something else that can cause this?

9 Replies

ASEMASTER6371

MECHANIC
52,797 POSTS

Good evening,

The first thing I would do is to clean the throttle body. carbon build up will cause this issue.

https://www.2carpros.com/articles/throttle-actuator-service

https://www.2carpros.com/articles/how-a-throttle-body-works

If it still does it then it may be the idle air control motor as it is what controls the idle speed.

https://www.2carpros.com/articles/stall-at-idle

Beyond that the only other thing I can think of is the EGR valve not closing fast enough and it stalls from it being open

Roy

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Monday, December 3rd, 2018 AT 4:54 PM

MS5550

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5 POSTS

Thanks for replying. I've finally had a chance to check it and fix a few things since.

Throttle body is cleaned, new IAC, and I was finally able to read an old CEL code, which GM doesn't make it easy with this OBD "1.5" (the CEL comes on very infrequently but then stays off). The code was P0406, relating to the EGR. So I bought a new EGR valve, and still the issue persists. Hoping it isn't compression loss.

Although I have noticed that I can tell by the belt squeaking sound when it's about to stall. If I turn the wheel it time it starts to lock up but then doesn't stall. I don't understand it.

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Friday, December 14th, 2018 AT 8:00 AM

ASEMASTER6371

MECHANIC
52,797 POSTS

1995 is OBD1. The code lists are two digit codes.

Where did you get the 406 code? Do you have a OBD2 connector?

Roy

Invalid Diagnostic Trouble Code

This vehicle does not generate this trouble code.

Alldata Editor Note: There is one in particular after market Scan-tool that still has not been updated and generates these and other Invalid DTC codes.

We've talked with numerous Alldata users, and they've told us that the work-around is to use the DTC description, and find a code that matches it. A number of our users have used Code P1406 (close match to P406) when the description matches an EGR Pintle Problem.

Our suggestion is:
1. If you have a second Scan-tool in the shop from a different manufacturer, it will probably read the Data-stream correctly and generate a proper code.
If you don't have access to a second Scan-tool,

2. Call you Scan-tool manufacturer and let them advise you on a proper course of action.

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Friday, December 14th, 2018 AT 8:07 AM

MS5550

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5 POSTS

I have edited my last post (accidentally submitted it before I was done).

I'm using the Actron CP9145, since it's one of the few that can read this OBD "1.5" ( OBD1 computer with OBD2 port).

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Friday, December 14th, 2018 AT 8:14 AM

ASEMASTER6371

MECHANIC
52,797 POSTS

If you have the OBD2 connector, you have OBD2 system.

Is the EGR valve electronic?

If it is, did you run the car without the valve mounted? You should do this and listen for an exhaust leak and a loud hissing noise from a gross vacuum leak. You need those two for the valve to work.

Once you confirm this then we can go to other checks. You can turn the valve on and off in your scan tool.

Roy