1994 XJ 4.0

I have a no idea situation on my XJ, MAP is good, IAC is good but it will not idle. I have good fuel and I can get a rough idle for a few seconds but I have to constantly pump the gas to keep it going for those few seconds. Could this be the TPS bad? The engine hasn't ran in a year I bought it not running as a project. Any ideas?

What I've done
Coil pack
New plugs and wires
CPS
Cam shaft position sensor
Fuel pump
Fuel filter
MAP
IAC

 

what happens when you start the jeep? does it run rough and then die, or runs normal and dies when you stop applying throttle?

in my experience tps won't do that, i had completely removed mine and all it did was not shift out of 1st (again, that's from my experience, maybe there's something else to it but I doubt it)

if it runs rough i would check the downstream o2 sensor

 

It's runs very rough and just for a few seconds for you pump the throttle or hold it down.

 

I replaced the O2 and still the same result, really rough for a couple seconds and no idle

 

Did it get stored for a year because it stopped running, or was it running fine but then wouldn't start after a year of sitting? Verify you have fuel pressure and that the plug wires are hooked up in the right sequence. Maybe an animal made a home in the air box lol

 

Definitely not an animal in the airbox lol, according to the person I bought it from it stopped running. They thought the engine locked up (it was a starter they were not the most intelligent of individuals), I installed a full new ignition system, fuel pump, filter and cleaned the lines. I have good pressure at the rail and I will double check the firing order and I am also going to test the injectors this weekend. I was also going to pull the throttle body and intake and clean them very well it had a bad PCV valve and was letting oil back into the air intake which has made a royal mess of the throttle body.

I will update once I have done all of this and see what happens.

 

It happens..

 

Clean the AIC? How's the battery and cables?

 

AIC/IAC was replaced already, battery and cables are brand new

 

These types of posts tend to get common this time of year as the temperature drops and the ambient moisture increases. Although many things can cause a fire/bad idle situation, the first and easiest thing you should be checking is your electrical connections. Particularly, your ground connections. It sounds like your system is suffering from low voltage during startup. The computer will fire, but the low voltage will cause the computer to do some strange things, and continuing to run only when the gas pedal is depressed is one of them.

 

Thanks! I will check that this weekend, once I have a chance to go through everything I will update.