Once again a problem with the olds...

[wilpetty]

Okay so this one is strange. I am cruising about 80 down the highway and the motor just cuts off. The car just turns over...I figure maybe it is the alternator. I get towed to autozone as I am very far from home. Alternator and battery are both good. Car now starts up and drives just like it did before but will die very shortly, OR start up and have a very low and fluctuating rpm and die almost immediately. Please lead me in the right direction to fixing this guy. As usual I will try anything you guys recommend

 

[paratrooper307]

Check your fuel and spark. Sometimes these intermittent problems can occur when a fuse, spark plug, wire or other component is cracked or compromised, and the change in temperature from warming up exposes the defect. Had a similar problem on my 90 Olds 98, turned out the clip for the crank sensor wire had cracked and the wire was making intermittent contact with the sensor.

Try to see what you can eliminate. Check your plugs, wires, and ignition modules. Hook up a fuel pressure guage and see if you are getting consistent pressure at the rail. Is it throwing any codes? This sounds like it could be a sensor problem. TPS and MAP/MAF sensors can cause running and idling problems, and it won't run with a bad crank sensor, although I think I remember you said you replaced that?

 

[wilpetty]

I will have to get back to you to see what I can eliminate

 

[dyeager535]

When it dies can you get it to crank without starting? 1990 right? Fuel and spark, the ignition modules and pickup coils can cause all sorts of grief, but in my experience (which is fairly limited) when one of those goes, it seems to fail pretty quickly and catastrophically. A bit of warning, then nothing.

 

[wilpetty]

It either will start right up or won't start and just turn over. Only 1 time I started it and it ran rough

 

[wilpetty]

yes it is a 1990

 

[diesel4me]

I've seen a 90's cutlass with similar symptoms and after a lot of parts were replaced with zero impovement,my friend decided to ask a tech at a dealership who had a reputation for being able to fix even "unfixable" cars what he'd look for,and he said to take the passenger side kick panel off where the ECM is,and check the grounds,there are several wires that are grounded there and the car often leaks and rusts there..you could be driving along just fine,and it'd quit like the key had been turned off,other times just raising the power windows or turning the lights on caused it to act up ,buck,stall,or lose power momentarily...

We looked there and sure enough,the wires looked to be gangrene and in tough shape and it was pretty rusty where they were grounded..my friend decided to cut all the ground wires off and crimp all of them together into a ring terminal,then drilled a "fresh" hole and sanded it shiny before screwing them down...so far the car hasn't come back,that was over a year ago..

Another Olds omega he fixed had a 2.5 four cylinder,one fuel injector was found to be shorting out intermittently and killing the fuel delivery to all of them...just about every part from the fuel pump,to module,etc,had been replaced and it did run good for some time,then would do the same dam thing...finally a guy told him to unplug one injector at a time and see if it'd start after it died,and sure enough,one was faulty..hard to pin down because it would always start the next day after letting it sit awhile,and might run a week,or 5 minutes,before it would act up again...

Today a friend was trying to fix a V8 Dodge Daktoa that shuts off after 5 minutes of run time..tried swapping a known good computer from an identical truck into it,no change...then replaced the crank sensor,pick up coil,one at a time,and it still dies after it warms up..--sometimes it lost just the sprk,or just the fuel injector pulse,then both !.....
---then I came by and he had me crank it over while he wiggled various wiring harnesses and it fired uo when he lifted one that was routed behind the A/C pump...we took ALL the tape and wrapping off the harness,inspected all of the BUNDLE of wires very closely for worn insulation,and sopts that felt like the wire inside was "missing",etc..nope,no defects were apparent(must be 50 thin wires in that harness and about 150 total going to the ECM!)...if we left the harness up on the intake it would start and run OK,so he decided to tape the harness back up...after it ran 7 minutes,it again stalled,but restarted right away,and then ran a half hour without stalling again...

Is it "fixed"??...who knows!...

Its problems like these that make me like points even more as I get older.....and trust new cars less and less the older I get..

 

[dyeager535]

So when it will crank and not start, do you have spark? How about injector pulse?

 

[wilpetty]

I will have to check and see if I have spark when it just cranks. Past 5 times I've started it it fired right up though, it just wont go far. It dies like if you were driving and just turned the key off. I want to say I have power steering while this happens, but no power brakes. That is probably irrelevant but worth putting it out there

 

[FAB454]

Im with diesel4me. The computers on those cars crap out in funny ways. Check codes, post if you get n e. The other rhing to try: when the caris running ok, bang the pcm, see if it quits.

 

[diesel4me]

Actually I haven't seen that many EMC's "fail",it usually turns out to be a wiring defect or sensor problem in the end,often someone blames the computer right away,replaces it,then finds out despite the vehicle firing up and running and they think its "fixed",it turns out to be some other trouble,and the car quits again!...then the mechanics must really dig deep to find the actual cause..usually its bad wires or connections..

I bet many ECMs get thrown away when there was nothing wrong with them...but some do get corroded inside or get sensitive to temparature changes,my friend suspected the computer in that Dakota because he'd seen others just like it fail to start when cold,but if you put a heat gun on it for a few minutes it'd start right up--or lose spark when they get hot--this truck had a known good one from an identical truck the owner has swapped in it,so we figured it'd be pretty rare to have two computers fail the same exact way..since dodge mounted them on the inner fender,a place prone to high temparature swings and moisture,they dont always live long in those trucks,he decided to try the computer first..
He told the owner it will likely need a new wiring harness,even that may not fix it though.

I've seen more than one later model car have fuse box troubles,and they will run fine one minute,then crap out--and then restart after some time passes like nothing happened...corrosion or damage inside where the fuses go often is the culprit,sometimes one fuse will get hot enough to melt the plastic around it on the fuse box,but not actually blow the fuse,when the wires get hot where it meets the fuse holder...the resulting intermittent connection that makes and breaks as it heats up and cools will drive a tech insane in short order...
I'd take it off and really look closely at the underside,my friend finds many that have no power going to one side of a fuse that should have power,or none,and further inspection determines the fuse box is defective internally..