pro306

I need help. I have an 03 Grand Cherokee 4.0L. When cold it runs good but once it worms up it lean backfires through the intake and skips badly. I checked the codes it has misfire codes for all cyl. IAC and 1 trans code.
I did a manual fuel press check when cold the press creaps up to 65psi once it starts skipping it has dropped as low as 15psi. I already installed a new IAC, fuel pump and filter/regulator From Jeep. Also any time you rev the engine the fuel press drops like the pump can't keep up. Any help will be greatly appriciated.

Thanks the newbe, Eddie.

tsconver

did you use a mopar fuel pump or an aftermarket one? Might have gotten a bad pump?

pro306

Everything new from Mopar

tsconver

try to get tehm to replace it, I had a horrible fuel problem on a NEON a fwe years back and it ended up being the ground strap from the tank to the boby. Make sure you have good ground, maybe even run a jumper wire to bypass teh body straight to the battery and see if that fixes it.

pro306

I did some manual tests of voltage and ground. Everything is ok. Just installed another new pump and PROBLEM FIXED
Thanks for everyones help this is a great info forum.