1990 Lesabre Stalls While Driving, Also High Idle

I have a 1990 Buick Lesabre with a 3800 motor and about 180,000 miles. This is a problem that has occured before, but with my grandmother and she cant remember the solution. She thinks the dealership replaced the computer but cant totally remember. The car will stall while driving and shut down as if you were to totally unplug the battery. After waiting a while the motor will turn over and start again. Will only drive a few miles and die. The engine also has a very high idle and will clunk while shifting into gear. It will stay at a high idle and you have to apply brake to keep under 35. Also the speedometer and fuel gage will malfuction and stay at different spots. The car sat all last winter and recently started it up for summer driving. Replaced the brake lines and master cylinder prior to problems. Also cut speaker wires to rear speakers due to a crackling noise. Have cleaned the mass air flow sensor with cleaner and tried a working ICM, both with no change in performance. I've checked for codes, but nothing has come up. Pretty confused and looking for help. I am considering replacing the crankshaft position sensor or possiblly the ECM.

Is this mainly a warm engine issue or at all times?

When the engine stalls it is normally due to warm weather and not until the engine has warmed up. But the high idle is something that is happening as soon as you start the car. I'm curious as to why the car would stall, the engine would idle high, and the speedometer and fuel gage would fail all within the same time frame. The engine stalling is totally intermittent, and hasn't stalled out in about a week. But its been somewhat cool here aswell.

Cold engines usually idle high (maybe 1100-1200 RPM) until they warm up a bit. The should gradually reduce RPM to around 800 or so, depending on the model. A warm engine should idle at around 700-800 RPM immediately when it starts.

Intermittent gauges in the instrument panel imply an electrical problem, possibly a common ground.

When it stalls, how long before you get a reliable restart?

Will it crank immediately after it stalls, or does it have to wait a bit before the engine will crank.

If it cranks, but does not start, do you have a spark?

No matter how long you let the car warm up it will still idle high. You can be driving and have to apply brake just to stay under 35 no matter how long you've been driving. Once the car stalls it will take about 5 min to restart. Today when it was started it would have an idle where it would shake the car as if it were missing. If you shut it off and let it sit a few min it would start and run smoother, but still with a high idle. Once it stalls it will crank, but wont fire for a while. Not sure if its getting spark or not. It wont completely stall out when you want it to. Do you think that a failing ECM could be causing the idle problem, stalling problem, and the fuel gage and speedometer problems.

I think it is more likely a temperature related electrical problem. But that could cover a multitude of issues, from a bad connector to failed sensor. I doubt that the ECM is bad if it runs OK some times, but I could be wrong (that happens on occasion)..

On some cars, a failed engine coolant temperature sensor can cause high idle and hard starting while the engine is hot because it makes the ECM think the engine is cold, but I do not know details about your model, and the stalling is a concern.

Some cars have an issue with a crank position sensor. If it is failing or has a bad connection the result can be no spark.

If yo can find the wirign diagram for the car you may be able to assess if the problematic component wiring shares a ground or connector as a possibility.

You may be able to contact the dealer or GM and find out what work has been performed on the car, including ECM replacement.

Wish I could be of more assistance.

Thanks for al your help. I'm going to check into that and see if there is a ground wire that is getting a bad connection. If i figure anything out I'll be sure to post what the problem was.

Thanks for al your help. I'm going to check into that and see if there is a ground wire that is getting a bad connection. If i figure anything out I'll be sure to post what the problem was.

High idle speed might be the sensors mentioned but I've read a few people just have a hose leaking vacuum. At 185K hoses are hardened and brittle and crack in spots you can't find. And intake manifolds can develop leaks with warping. I suggest removing the IAC and cleaning it; it may be sticking.

If it won't crank after stalling, that would be a start issue or battery cables issue. If it has more than one cable on the positive like later 3800s do, cut those back iin the plastic to look for corrosion. Check both ends for fresh metal contacts. If it won't crank, I assume you've checked for start and solenoid issues.