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95 impala stalls while driving

8K views 16 replies 10 participants last post by  ahoora 
#1 ·
hi i have a 95 impala it has a new msd opti maybe 5k miles on it, new icm , new coil, new oem temp senor ,new acdelco fuel pump,pcm for less ecu . the car shuts down while im driving randomly. and doesnt start right away i have to let it sit for 3-4 minutes and it starts up like nothing was wrong . if any 1 has any suggestions i will be happy to hear anything im ready to pull my hair out . the oil level light pops up but i have it bypassed with a paper clip but the light still pops up :confused::confused::mad:
 
#3 ·
I noticed that you also have seen the oil level light flash once very quickly as the car decides to take a crap and die out.

I have simply cut and spliced the oil level sending unit wires and mine still did that.

I believe its the key-on engine-off light test, I originally thought it had something to do with the opti losing the low-resolution signal, but if you think about it, how often do you ever have the engine die out with the key left on in these cars? It seems abnormal, but where you rarely have this scenario happen, it just looks odd to see the warning lights come on like that.
 
#4 ·
When the ICM was replaced, was thermal grease/paste applied to the backside before installing? It sounds like the ICM is overheating, so the ignition is killed, then after it cools off the car will start.
 
#5 ·
Sorry to revive this thread but my car is having a very similar problem. I have been blaming the fuel pump but decided to change the pcm and the problem went away...for a few days. Now it's back and I've got no codes to check.

Did you solve this issue?
 
#6 · (Edited)
Vets can chim in if Im wrong but once it dies again try to narrow down what it might be. I doubt its fuel related becuase when the fp is dead its dead.

Try this once it dies with out warning, remove the plug from the opti thats connected to the coil. So its should be connected to the coil. Have it dangle next to something metal, the Water pump should work. Attempt to crank you should hear sparking.

If it checks out good, plug back to the opti, now remove a wire from a sparkplug let it dangle close to something metal listen for spark. If no spark you have an Opti issue more than likely.

If you didnt get spark at the coilwire connection it could be either the coil or ICM.

Good luck.

Also doesnt hurt to check all elec connections related to ICM Coil and Opti.
 
#7 ·
Thanks. I will try those techniques.

Just to clarify, the car dies intermittently while driving after it's been warmed up (no amount of throttle can even attempt to keep it alive). It does not restart right away and usually takes a few minutes before it does. A lot of threads have pointed to the ICM overheating. My fuel pressure reads fine during this time but when trying to restart, I do not hear the fuel pump prime. After a few minutes I will hear the prime of the fp and it starts just fine.

If it weren't for that stupid fuel pump not priming, I would feel more confident about spending the $175 on a new ICM.
 
#9 ·
ICM typically dont go bad that often....never changed one on my 96 9c1 and it had over 250k on the clock...100k I put on myself....Now I will tell you that this sounds like a electrical fuel issue however. I had the same problem in a 96 ss I had at one time and the guy before me spend hundreds and hundreds of dollars trying to solve this issue 4 optis, fuel pump, ECMs, Plugs/wires. Turns out it was the fuel pump harness inside the tank. The wires will get "burnt" after a while and cause similar issues. Sometimes its good then other times it makes bad connections cause some of the connectors are corroded and wires are a little loose/burnt.

Not saying this is the problem, and its a PITA to drop the tank, but it is a fairly common problem....once I swapped em the car never ran so good in its life.
 
#10 ·
Thanks, I'm trying to avoid dropping the tank as I just installed a Racetronix Pump in August of 2012
 
#11 ·
On my RMW I had intermittent stalls with no restart that seemed temperature related in the underhood relay center on the passenger side. Eventually traced it to a corroded power post behind the relay center that would overheat. Found it by grabbing and wiggling the power cable after it cut out. It would come back on its own if I waited.

You can also check for fuel pump relay issues by using the hot jumper on the passenger side to force the pump circuit to be energized. You can check your chassis wiring for high resistance by checking the voltage drops by back probing the tank harness connector with the pump running. Move and wiggle the underhood and chassis wiring to try to replicate the fault. If you are getting consistently good voltage to the pump and a good ground (i.e., a good voltage drop across the pump supply and ground while running) but have low pump output you will have to drop the tank (assuming no fuel supply issues: filter, etc.).

Did you do a wiring upgrade with the Racetronix pump?

Hope this helps!
 
#15 ·
You can check your chassis wiring for high resistance by checking the voltage drops by back probing the tank harness connector with the pump running. Move and wiggle the underhood and chassis wiring to try to replicate the fault. If you are getting consistently good voltage to the pump and a good ground (i.e., a good voltage drop across the pump supply and ground while running) but have low pump output you will have to drop the tank (assuming no fuel supply issues: filter, etc.).

Did you do a wiring upgrade with the Racetronix pump?

Hope this helps!
Check the ground's on the stud by the ICM on the drivers side head, known break & cause intermittent issues. IIRC there are 3 wires going to one o-ring connector, give that a good wiggle while running, you'll know real fast if that is the issue.
 
#12 · (Edited)
Thanks! I did upgrade the wiring harness. So oddly enough, my battery and alternator were bad, (both new and both checked last week). I replaced them both but was getting the same shut off problem.

I had been checking the new harness's relay but neglected the one under the hood. When I started the car again, I banged on the relay while it was running and could not get the car to repeat the shut off problem again even though it had just been doing it, (worse than ever before). I replaced the relay and took the car out for about 45 minutes and there was no problem.

The real problem is that I cannot get the car to stay consistent with this problem. Any time I want to test something, the car runs perfect:mad:

I'll fiddle around with the wiring like you mentioned tomorrow while the car is running.
 
#13 ·
I had same problem and mine was primary fan was bad,

car was fine till it warmed up, and then randomly,stalled

turn the car off for few minute and it was fine again,for another few minute

fan was turninig, but not fast enough,so make sure it turns,and turns really fast,like your secondary fan, with ac on
 
#14 ·
Other than runnuing hot, the fans are not going to cause an engine to stall. Oh, the primary fan run's with the A/C on...that would be the pass. side fan, dr. side is secondary.
 
#16 ·
I'll check the grounds and even run a few more grounds from motor to chassis to body to battery.

As of last night and today, the car is running fine after replacing the relay. Hopefully this $13 fix does the trick.
 
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