87 "stalls" when warm

Hi all, I've got an 87 XJ 4.0 AW4. The guy that had it before me swapped a long block and head from an HO and kept all the renix electronics. I've been playing with this thing for a while and got it to pass emissions and run pretty good. So far I've checked and ok'ed the TPS, MAP for sure, and have replaced the TPS and the 02 sensors. I've cleaned out the IAC and swapped fuel injectors around. Now, when the motor is cold, it runs great. When it warms up most of the time it runs good, but sometimes when I slow down to turn or stop at a light and then try to go, the jeep will just stall out....then it's hard to crank. I have to go to WOT to cut the injectors off to get it to start. It almost sounds like it's vapor locking but I don't know what to do about it. And it does it completely randomly. I've tried searching and reading but havn't seen anything quite like this. Any help would be great.

Thanks
Dane

Hallo. I would check the Fuelrail pressure with a testgauge.:wave1:

I did, Guess I could have said that. I got 39 key on, motor off and 41 with motor running. Thanks

Dane

OK When hot, an ignitioncoil can also give problems.:flamemad:

OK. When hot an ignitioncoil can also be a problem.:eeks1:

interesting.... I'll see if I can get a hold of one to swap. Thanks!!!

Dane

sounds like a bad crankshaft position sensor to me, i had the same problem, replaced that, runs great.

:doh:

Hey all,

I ran by the Wal-mart and got a fuel filter, swapped it out, and so far no more problems, I guess that fixed it!?!?! Thanks for the suggestions!!!!!:sunshine:

Dane

I just recently fixed a similar problem by replaceing the relay for the fuel pump. Read that relays can go bad causing intermittent function, this particular one kills the whole show if it turns off. Acts a lot like a bad cps, but mine's pretty new so it had to be something else. Ahhhh... the joys of a 20 year old vehicle...:roll:

db10bo said:

Hey all,

I ran by the Wal-mart and got a fuel filter, swapped it out, and so far no more problems, I guess that fixed it!?!?! Thanks for the suggestions!!!!!:sunshine:

Dane

Click to expand...

Glad to hear you got it fixed :roll:

I hear ya tvc....the only thing worse is working on a 40 year old vehicle, I've got a 67 mustang that I'm still working bugs out on. Thanks again all!

Dane

db10bo said:

I did, Guess I could have said that. I got 39 key on, motor off and 41 with motor running. Thanks

Dane

Click to expand...

It should be 31 psi on that year, 87-90. There is a spring loaded diaphragm fuel pressure regulator at the end of the fuel rail, with a vacuum hose on it. With the vacuum hose off at idle it should be 39 psi, and vacuum hose on at idle it drops to 31 psi. Under load, decel, accel it varies with the engine vacuum! The diaphragms go bad and leak fuel into the vacuum, flooding the engine if it gets bad enough. Pull the vacuum hose and check for gasoline smell, and recheck vac on/off pressures.