Missing and Bucking under load?

[GTU89]

Okay, the GTU misses and bucks under load when warmed up. Doesn't do it when cold and doesn't do it in neutral or park. Only does it when its warm and under load.

Any ideas?

[Koots]

Is the Check Engine Light (CEL) Illuminated?

Whether it is or not, check for stored codes that didn't set off the light.

When was the last time that a tune-up was performed on the car?

Most importantly, the spark plugs, wires and coils.

[3X00-Modified]

if it's when warm start with ignition parts... those fail the most with heat... Crank position sensor in the back of the block is one, and then yes the ICM and coils which are located directly under the front exhaust manifold.

[Koots]

I'm not sure if it's the same for the 60* V6's, but the OBD-I V8's would run awful with a bad CTS (Coolant Temperature Sensor, not the gauge sender).

The sign of a failing one was usually driveability issues once it reaches operating temperatures and terrible mileage.

[GTU89]

I've replaced the plugs, wires, temp sensor (CTS), o2 sensor, IAC and PCV recently.

No CEL or stored codes. My neighbor thought it was the TPS, worth looking into or not?

Ignition is what I was sorta thinking. Anything to start with?

[woody90gtz]

Given the location of ICM on the MPFI cars, that would be my first guess. I've seen them go bad a few times.

[3X00-Modified]

ICM and CPS still left as options

[GTU89]

Any idea of which one is more likely? I know it's hard to diagnose without physically being there to see what it is doing.

[berettaboi]

i have been through that before, and as 3x00 modified has stated 2x... coil packs and/or ICM sitting under them. easy to find in many newer cars also at the junkyard for cheap. i recall the ICM is the same, just the mounting/heat sink is different.

[GTU89]

i have been through that before, and as 3x00 modified has stated 2x... coil packs and/or ICM sitting under them. easy to find in many newer cars also at the junkyard for cheap. i recall the ICM is the same, just the mounting/heat sink is different.

I know that he stated it two times, I was wondering which one was more likely to be the culprit.

Do they regularly go wrong or would searching the junkyard be worth while? (ICM new is $100 and CPS is around ~$25)

I'll try to test the coils tomorrow.

[3X00-Modified]

ICM is easiest to get to as far as testing... the CPS is very common though, but that will typically give hard starting or not start condition when hot... so if you don't have that I'd try to find a spare ICM to swap in to see if it clears up. It's hard to test them since the bench testers don't get them anywhere near as hot as the location of them. And as you know you don't have the issue when cold.

[GTU89]

Just figured I'd bump this instead of making a new thread.

Problem is sorta back, except much worse. Now it is missing and running rich at all times, cold or hot, neutral or not. Smells extremely strongly like gasoline (enough to make you feel like coughing) and puffs black smoke when you rev it from idle. Not drivable at all, dangerously slow now actually.

Right now replacing the fuel pressure regulator is what I'm thinking. Does that sound right?

[DTMAce]

That or fuel injectors. Might want to check the fuel pressure first though.

[GTU89]

Forgot to mention, although this goes with the extremely rich part, quarter-ish throttle shows about 3mpg, no gas at all coasting at around 30mph shows 30mpg (whereas it would shoot to 99.9 iirc before) And it doesn't want to accelerate past about 35mph, full throttle even (takes a relatively long time to get there as well).

I'll probably be hitting a junkyard up to get the part(s) since I can't afford to throw $100 dollar parts at it at the moment.

[berettaboi]

have you tried anything to fix it yet? i know it's likely one of 2 things already stated here a few times...