I am having engine stalling issues with my 89 Bonneville. Will only stall at an idle otherwise runs great. When I back off on the gas to a coast engine may stall or when sitting at a stop. Checked Codes and nothing came up.

I would start by checking the TPS and making sure it is ok. Then a good TB cleaning and paying attention to the IAC port when doing so. Useful links can be found here: http://www.pontiacbonnevilleclub.com/forum/viewforum.php?f=48

Thankyou, all really good info. If sensors were the source of my problems wouldn't I get a Code reading. I am using a GM Code reader by Innova Equus that produces signals by way of the dash 'Check Engine' light ( cheap). I had a similar issue with my 89 ford P/U and it turned out to be failure of the ECM. Could the ECM produce intermittant engine stall?

This is no Ford and there are a lot of other things to rule out before the ECM. Does your reader read only the codes or data also. If it does data, see what it shows for the IAC% and the throttle position.

Try reading the codes using this method: http://www.pontiacbonnevilleclub.com/forum/viewtopic.php?f=51&t=8689&sid=27c66ce2fc716f27173a49a75dd2ac07

Had the same prob check the mass air flow sensor thats what it was for my 88

Finally had it fault again. This time I got the following codes:
13 - Oxygen Sensor
22 - Throttle Position Sensor
23 - Intake Air Temp. Sensor
29 - Gear Switch Diagnosis ( 4th gear )

This seems weird to get so many codes. Any ideas before I start replacing everything???

I would start here and follow this proceedure for testing and replacing (if needed) the TPS:

http://www.pontiacbonnevilleclub.com/forum/viewtopic.php?f=48&t=9098

If you have no idea how old the O2 sensor is, you should change it also. Check the harness and make sure it is not touching the exhaust manifold or the spark plug wires.

The IAT is in the bottom of the stock airbox, make sure it is plugged in and the harness is not damaged. May need a new sensor.

After doing this, disconnect the battery for atleast 15 minutes to clear all the codes. Take it for a drive and read the codes again.

I'm having the same trouble with my '87 Olds 88 Royale. It started today after not being used for a couple of months.

I shall follow all suggestions posted. When you find and fix your problem can you post up what you found please Stephen?.
I may have the same problem as you.

Roger.

Everthing checked out, but I did replace the O2 sensor. Problem still exists and has become more frequent, would stall while running. Sometime codes would come up and others no codes. I did notice when the stall was happening and even though the vehicle was still moving the speedo went to 0. I ran in to a mechanic and when I explained what was happening he immediately pointed to the coil pack ( apparently these vehicles have a history of coil pack failure). However, the coil pack primary and secondry windings all tested to spec. Can coil packs fail intermittantly and still test OK?

I have changed the coil pack, but have only made one trip, without failure.

my 88 sse did same thing. start the car, once its running unplug the mass air flow sensor and see if it runs worse or better and if ot stalls or not.


also how old is your fuel filter. ? have you ever changed it ?

Help. The new coil pack did not solve the problem. Car stalls and will also accelerate all on its own. I've also changed the O2 sensor. Air inlet temp, TPS and Mass air flow all check out fine.
Steve

Could a faulty Idle Air Control valve cause the vehicle to speed up on its own? Does anyone have a check for an IAC, my Haynes book does'nt cover it?

Does the service engine light come on ever while driving? That has to be fixed first. No SES light basically means the computer recognizes thats it's getting signal from the sensors

Faulty IAC = idle stuck, usually too low to idle cold. Pull the IAC and make sure it is not broken, and that the valve doesn't flop open & close.

The common cause for the high idle/car accelerating on its own would be the TPS not in proper adjustment. What is the TPS reading with throttle closed? On the older cars it must be below .5v, so set it to .45v. If you don't have a volt meter, loosen the TPS and turn it back and forth and notice where the rpm just starts to rise off idle, and turn it back to a point just below that and set it.

As for the stalling;
Disconnect the MAS and drive around like usual. If it still stalls out then it's not the MAS.
Check fuel pressure while driving. If it stalls out (safely) immediately turn the key to off and make sure you still have full pressure.
Also, check that the cam and crank sensor wiring to the ICM are not shorting and have continuity. Visually inspect for bare wires, etc.

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Got under the hood of my Olds today, and the engine ran fine, no stalling or rough idling.
I disconnected the IAC and refitted it, then noticed the "service engine soon" light was on. I switched off the engine and restarted, the light went out when it started and didn't come back on.

I don't think I've cured the fault, I'll have to wait until it occurs again.

Roger.

sounds like very typical FPR Symptoms to me pull the vac line on the FPR if you see or smell gas replace it.

_________________
1998 Bonneville SLE 32 mpg
1965 Falcon Futura HT 325hp
1989 Bonnevile SSE
1995 LeSabre LTD
1998 GMC Sierra 4x4
others

You ever find out a solution? Mine is dieing at idle to not as abruptly as yours though.

I'm having the same problem as you just not as severe. Mine is a no start if it gets hot. I'm gonna change the cps and I'll let you know what I find out tommorrow night