94 SE randomly stalls.

[tjctransport]

3 weeks ago i picked up a 94 Bonneville SE for my niece because she liked the way it looked.
clean 120,000 mile car, from the second owner. never crashed, and it looks like a new car inside and out.
i am not very well versed on these gm cars, seeing as i am a diesel mechanic specializing in Ford diesels..

when we got it it had an EGR valve code, which i cleared and has not come back on. the guy i got it from changed the egr valve but never cleared the code.
in the past 3 weeks, the CEL has come on 3 times, and each time it was from the juice jocky not putting the gas cap on tight.

the only problems i have is on random occasions when the gas gauge is around 1/2 tank, the car will just shut off. it will start rite back up and drive fine until the brakes are applied, then it shuts off again. if you keep it above 1/2 tank(tank full) it is fine.
i am thinking it is a cracked pickup in the tank, but do not know if that is a common problem in these cars like it is in the old ford pickups.

another problem i am having is every now and then it will decide to raise the idle to 2000-2500 rpm. not in gear, just in neutral or park. when it revs high like this, you shut it off and start it back up and it is fine again.

i am thinking throttle position sensor, but am not sure if these GM cars have them or not.

[95se]

The idling high problem sounds like a fault with the idle air circuit, and for the fuel tank i cant help you out on that one

[myfirstbonnie]

I would start with TECHINFO. http://www.pontiacbonnevilleclub.com/fo ... nsors-etc/

Clean the TB, make sure the TPS is good and adjusted properly. How old is the plugs wires and O2 sensor?

As for the stalling and restarting, could be either the CPS or ICM when they get warm.

[tjctransport]

tune up was done when we got it.
my version of a tune up on gas engines also includes removing and cleaning the throttle body, mass airflow sensor, and IAC, and putting new gaskets on when re installing.

i doubt the stalling is from a sensor because it only does it if it is below 1/2 tank of gas.
over 1/2 tank it will never stall.

is the procedure for testing the TPS the same as for fords?
.5 volt at idle and linear rise to around 5 volts at full throttle?
edit: never mind on this, after reading the tech thread i see it is around the same, just a little lower on the voltage readings.

also, i do not get a TPS code, the only stored code was EGR circuit.
it had a new egr valve and gasket put on it before we got it, and the code was not cleared.
the guy we got it from was under the impression that disconnecting the battery for 5 minutes would clear the stored codes.
i cleared codes when we got it and after passing road-ability, it passed New Jersey emissions inspection.

[reb]

I'm thinking faulty fuel sending unit and or fuel pump inside gas tank. Tank has to be dropped to get to it.

[tjctransport]

I'm thinking faulty fuel sending unit and or fuel pump inside gas tank. Tank has to be dropped to get to it.

yea, i ain't looking forward to that. i told her to just keep the gas tank over 1/2 full. so far no problems.











as long as she remembers to put gas in it.

[tjctransport]

well, i have been keeping an eye on it for the past few weeks and it seems to be random now.
the TPS tests fine, and then 20 minutes later she calls and says it is revving at 3,000 rpm again. shut it off and restart, and it is rite at 600rpm like it should be. put the computer on it and no codes show.
then today i put the computer on it while it is revving, and i get a "vehicle not communicating" message.
tried 5 times over 3 hours, and no communication.
finally it starts and idles properly, and the computer talks to the scanner and no codes.

so at this point i am thinking the computer is screwed up.

[e8r23i80c]

question...when the cars stalls do the power windows and locks not work as well?

[tjctransport]

that i do not know, never tried either of them. when it stalls, it starts rite back up instantly though.

[e8r23i80c]

mine would do that as well...stall and then start right back up. It would run fine for 2 days...then randomly stall here and there. Sometimes would start right back up...and other times it would take a few minutes. I was only asking because under the carpet next to the drivers seat is a blue connector that I guess acts as a common ground. These are notorious for shorting out. Of the 8 or so wires on them there is one that controls fuel pump pw and pl. So next time the car stalls...try rolling down your windows and/or locking the doors. If neither work but then start working again when the car starts...thats your issue. Good luck

[tjctransport]

sounds good. i will let her know to try that.

[tjctransport]

well, it was not the plug under the seat.
it got worse the past week, stalling every few miles on in town runs. but not out on the highway.
hooked the computer up and realized it would not work because i was using the wrong OBD-II plug. put the proper plug on and got an EGR code, replaced the EGR valve with new gasket and it seems to be running a lot better.
TPS voltage is .42 volts at idle, and rises to around 1.7 volts at 50% throttle.
i am going to give it a week and see if the EGR fixed it. if not i will throw a TPS on it and see if that fixes it.

[motopsyco]

just to throw this out there about the stalling at below half tank questions you have. I have a similar problem and also it starvesfor fuel during right hand turns only when a little under half tank. Turns out its a common problem with these cars, there are plastic baffles in the gas tank that tend to break loose over time and slosh around in there. When you get at a certain level a baffle is probably in psotion of the pickup and blocking it off, which is why it does it on stopping, sudden loss of steady fuel flow. Mine does the same thing, so I just keep it over a half tank and never have issues with it. So if you have access to another gas tank try swapping them out and see if it goes away. The high idling though I cant help you with, I've always been a ford guy, but just love bonnevilles and pontiacs as well, so I would guess the iac, but I dont think these cars have that. also I did have an issues siliar to that on a mustang before turned out to be the o2 sensor wires got shorted, it would rev up and down after warming up, and sometimes die suddenly, then start right back up and run fine for a little bit.

[tjctransport]

it has not stalled since i replaced the EGR valve.
the throttle is still erratic. i picked up a new TPS for it, but then got stung multiple times in the neck/shoulders by a white faced hornet.
so until the swelling in my neck and back goes down, she is going to have to live with it. hopefully by saturday or sunday i will be able to change it.

[motopsyco]

well maybe I should try that and see if it has anything to do with my problem as well of the dieis or sputtering on turns with less than half tank in it.

[tjctransport]

dying was not any rythem or rhyme.
it would die whenever it felt like it. coming to a stop, or driving down the road at 40 mph.
but after changing the EGR, it has not died and no more codes besides low TPS voltage.

[tjctransport]

success!!!

after changing the TPS, i took it on a nice 1/2 hour drive, highway speeds and under 20 MPH. purrs like a kitten, and no more erratic throttle.

so it appears the problem was 2 fold, a bad EGR valve causing the stalling, and a bad TPS causing the erratic high/low idle..

[motopsyco]

good, glad you got it all figured out, and its also helpful information for others who might have the same problems

[tjctransport]

i hate have a vehicle get the better of me, but i also do not like throwing parts at a problem to fix it if i am not sure the part is bad.
i probably could have solved all these problems 2 months ago if i just did the cheapo store "replace all the sensors and that should fix it" route.

i like to diagnose the problem so i know what i replace is bad before i spend the money on it.

next project is to reprogram 2 remotes i got off ebay so she can open the doors and trunk without the key.

[tjctransport]

just as an update, the car is still purring like a swiss army knife. c