ctartm

I have a 1998 Grand Cherokee that runs bad mainly when cold. I replaced the TPS & coolant sensor, installed a new fuel pump & flushed the injectors....it doesnt act up all the time....and when it does it feels like it is running out of gas....it backfires through the air filter.....if you put the pedal almost at the floor it takes off and seems to run good....I hooked up a scanner but no codes....I also had it hooked up while driving....when it seemed like it was going to act up the values didnt move and then after a minutes all the values went to N/A.....so when I went to work in the morning I hooked it up again and just when I went to leave the screen went blank and said "collecting data" then values popped up....went to leave and did it the same....but then when I got on the road it ran fine and scanner worked ok....I think there is a ground issue or computor issue....this has me stumped, but want to fix it for the lady...anyone have any ideas?

MrCotija

Not 100% sure, but in cases like this one, it sounds like you may have a bad ecu. Mostly because you have a "newish" vehicle with obd2 that's NOT throwing codes.

I haven't looked up how to troubleshoot a bad ecu, but if you have a friend that has a spare, throw it in there and see if it takes care of the problem.

rayharris46

See if you can get some one to run a fuel pressure test..
and check out the injectors, fuel rail and fuel pump.

ctartm

Put a new fuel pump in, flushed injectors.