yorkkars

i havea 97 grand cherokee limitied. it has 119k and has been well looked after its life. I recently bought it with the thoughts the crank sensor was the issue. It was replaced with a OEM part and issue still there.

It will start right up and idle great run pefect when cold. after a few miles it will buck and stumble when you accelorate. you can feather the pedal to get it up to speed, but it will buck as soon as you push on the pedal. I have given it a double dose of techron to rule out any injector issues. no noticable difference.

all other igition parts seem to have replaced as needed and look in good shape. I took out one plug and it was whitish tan, in nice shape. since it runs perfect for thefirst few miles, i assume it they are in at least decent shape.

I know there have been many recalls on this model, maybe something there?

I have also tried to heat up the PCM for a while (20minutes)them run it to see if it could be a chip issue on the board, no difference

The check engine light came one when I was giving it an "italian tune-up" I have not ran the codes yet. looking for direction here first before i go to the dealer

the cat does not seemed plugged with no odors or feel of backup.

any help would be greatly appreciated!!

Thanks in advance! We're all in this together!

Gee oh Dee

What is an "Italian tune-up"?

Did you replace the coil?

It honestly sounds like a fuel pump. Put a fuel pressure gauge on the schrader valve and verify you have good pressure.

yorkkars

fuel pump was replaced with a factory unit by previous owner 9 months ago. I will check the pressure. But why would it run great cold?

an Italian tune up is taking it out and revving the **** out of it to blow out any crap.

Gee oh Dee

Sounds kinda like a slant towards Italians, but I'm not Italian so I'll leave it be for now.


As for running well while cold, electronics such as fuel pumps and ignitions coils can be fine when cold, but as things heat up solder can expand and come loose, tons of issues. I have no idea if either of these would solve your problem, however these things could cause similar issues, if not the same. I'm just trying to fire off ideas to help narrow down your problem.

It could also have to do with your coolant temp sensor, or o2 sensor, although o2 isn't likely. The ECU changes things when your truck gets to running temp, something in that system may have failed.

Again, I'm not an expert, I'm just shooting ideas out trying to help.