1994 Bonneville Stalling at sudden Low RPMS

[eappiah]

My 1994 Bonneville has been stalling at lower RPM especially when I coming to a stop or slowing down suddenly. I was trying to decide which of the fuel delivery system part to replace:

1. Fuel Regulator
2. Fuel Injectors

And Catalytic convertor:

However, a scan at my local Murrays show the following codes:

PO300 - Misfire signal
PO171 - Fuel Trim signal lean.

Can LMP or someone help?

[randman1]

You are actually describing an Idle Air Controller problem. These usually don't go bad but the throttle body becomes all gunked up and hinders the movement of the IAC pintle. How many miles on the car? If you're over 100K then that is probably your problem... or at least part of it.

Grab a can of STP Throttle body & Intake cleaner and a new TB gasket. Remove the TB from the motor. Remove the MAF sensor, TPS and IAC from the TB. Clean the heck out of the inside of the TB with the STP cleaner and remove all of the gunk. Clean the IAC pintle as well. Reassemble and reinstall.

This will cost about $15 and is at least good maintenance. It has a good chance of solving your problem too.

Were those codes pulled "history" codes or current ones?

[Bronco2]

Question about the codes you had pulled- a 94 should be a OBD-1 car, PO codes are usually 96 up,but in may be a cross year .It would also help to know what engine you have in the car. Cleaning the IAC valve,etc. won't hurt anything,but a fuel pressure check and the position (steps) of the IAC could be the indicatiion of a vacuum leak.Codes give you problem the system is in,not the part to replace.

[eappiah]

To Randman1 and Bronco2,
My car has 140K. The car is is a crossover of OBD1 and OBD2. I can only use OBD1 with OBD2 connector. The codes are not history since I cleared stored codes before reading the error code. My car has 3.8L EFI

[randman1]

After 140K miles, I'll bet that there is quite a build-up of gunk in the TB. Here's what mine looked like after 146K:



After clean-up:





In the first pic, you can see the back side of the TB and IAC spring all gunked up. The gunk prevents the IAC from moving according to the ECM commands causing it to stumble and sometimes stall. It can also produce a sticky throttle plate.

Before you go spending $60 or more on injectors or other parts, I encourage you to spend the $15 or so and clean up the TB first.

Note: Make sure you carefully remove the 3 components on the TB before using the STP cleaner. The MAF can easily be damaged and is a pricey part.

[eappiah]

Done, cleaned the throttle body as advised but still stalling.
Any help?

[kalafre]

My '98 had very similar problems - never had any codes though. It turns out that there was a recall on my car due to a faulty Fuel Pressure Regulator. Once that was replaced it ran like a champ.