'99 LeSabre - stalling problems
I have a 1999 Buick LaSabre that began stalling when it was hot and the outside temperature was hot. Now it stalls when cold also and the car seems to want to cut off sometimes when driving. Sometimes it will crank back up on the first cranking attempt and sometimes you must wait up to ten minutes. It will sometimes cut off when I take my foot off the accelerator and come to a stop. I have replaced the crank sensor, MAF sensor, EGR, and fuel filter. Replaced fuel pump about two years ago. I do lots of stop and go driving. What could be the problem? Thank you.
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Best Answers
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Mr_Shiftright
Member Posts: 64,481
Stalling can be difficult to track down. Careful diagnosis is the key here--it's a lot better than guessing.
For one thing you cannot assume anything. Even if the fuel pump was put in last week, you still have to test the fuel pressure and the fuel pressure regulator.
If a car stalls, it has lost something--either fuel or spark in your case. So which is it?
Have you tried to extract any trouble codes? What were they, if you did?
You may need in invest in a cheap spark tester and in a fuel pressure guage, so as to test the car immediately after it stalls, to see what isn't there that should be there.
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Mr_Shiftright
Member Posts: 64,481
Well the codes don't actually tell you what component to replace---it only tells you the system or circuit that is in distress. So the codes you got might still have the hint you need.5
Answers
Does it cut out completely and immediately when it does the stall or stumble? Or does it sort of work its way down to stalling? If you can watch the tach when it's just stalled or is feeling like it's threatening to do so, does the tach go to zero indicating no spark or timing signal from the CPS/spark control module?
Also, I've not verified this but when it won't restart immediately and needs to cool, does the tach show rpm's indicating it's getting a signal from the CPS and spark control module. IF it shows 0 while cranking, that could verify you're losing the spark signals from the CPS or from the spark control module.
Then I'd check the connections and wires for the CPS. Maybe a broken wire or poor connection.
You might hook up a resistance meter to the right two of the three wires on the TPS and operate it to see if you can catch a break in the smooth increase or decrease in the resistance from a worn TPS.
The spark control module might be failing. If you have access to a pick n pull you might get a used one to substitute for yours. If you look on Rockauto for the one fitting your car by AC Delco and click on the blue part number, it will list all the GM cars using the same part. Same for the ACDelco.com parts site. Occasionally people had problems with the connection of the leads at the spark control module. Might take them off and clean.
The test on the ISC that they do at parts stores didn't seem to catch ones that were problematic. Since this sounds like heat soaking might aggravate it, that could be it.
I would have gone first for the CPS based on symptoms, but you've done that already.
You didn't mention spark plugs and wires having been done. But that usually gives a clear code for misfiring.
I hope you find it.
I was lucky that I had two leSabres and I just switched all the spark control module and coils from one to the other to troubleshoot an occasional miss on the 03.
2014 Malibu 2LT, 2015 Cruze 2LT,
Also there are the ground buss connections under the carpet next to the door sill that are wrapped in tape but corrode for some folks over years. One is next to driver and another is on the passenger side.
The multiple grounds from the dash area that are connected to the bar can then give problems. I do not know if anything in the ignition could be grounded through there.
https://forums.edmunds.com/discussion/comment/4066694/#Comment_4066694
http://www.pontiacbonnevilleclub.com/forum/1992/topic35540.html
2014 Malibu 2LT, 2015 Cruze 2LT,
As far as could it be the computer? Yes it can present this symptom. However a lot of other things can cause a symptom like you are describing too, so it's not in your best interest to shot gun another part at this. Someone has to test and prove what is failing.
You're going to have to determine what is missing when it is in one of its won't restart even though it cranks periods. I'd dig out an old spark plus and have one of the front spark plug wires easy to pull off and lay the spark plug attached to the wire on a metal part, not the exhaust manifold, and have someone crank the engine while you check for spark.
If you've got spark, try adding some starting ether while someone cranks the engine to determine if the fuel is missing. Or does the fuel pressure gauge show good fuel line pressure? But are the injectors working when the car won't restart while cranking? People have used the small light bulbs with the wire contacts and plugged those into the end of one of the fuel injector leads and it shows a slight blip of light with each pulse. Or you can feel the pulse with your fingertip held against the injector while cranking.
All it needs is spark, fuel, and air.
Diagnosis wise, one car technician duct taped the fuel pressure gauge to the windshield facing the driver so he could watch and he test drove a misbehaving car.
You may be dealing with a break in a wire to the pump or in a ground from the fuel pump that's cutting out.
I've read a few cases of wear on the ignition switch contacts that would lose contact and cause the engine to cut out with vibrations like your rough roads in H-bodies. Those worn contacts would work but the wear made them let go. This is the switch that's on top of the steering column just below the cluster area--not the igntion lock switch.
Some connectors are plastic and heating up with a high resistance poor contact expands the plastic with the heat causing the contact to physically part.
Have you tried bumping the area of the door sill where the ground buss bar is located. I recall one fellow that found his car that would die started up after bumping that connection with his heel.
It's taking diagnosis to find the problem. If it would act up consistently where a good technician and a Tech II could get it to happen while connected, the savings in time would be worth the cost to me.
2014 Malibu 2LT, 2015 Cruze 2LT,