XJ TRYS TO DIE BUT WONT....PCM?? HELP!

Hey guys
So my 98 xj 4.0 starts fine
Its when i drive it about a 100 feet it wants to die and looses power in my gas pedal, for a couple seconds it does that then it will work fine
That has been going on for a couple days now
Some people have been telling me that its doing that because
"its cold and i need to warm it up more"
"Bad fuel"
"Something stuck in my air intake"
"Injectors and Plugs are loose"
So i checked all of that and found nothing
So i believed the " bad fuel" and was just waiting it out in tell i could put more fuel in it
But this morning it did the same thing but at every stop light and every time i took my foot off the gas
It wanted to die
and shake and it really felt like it was being starved of gas
So i thought it was the fuel filter
but now i feel like its the PCM acting up...

If anyone out there can help me that would be awesome!
Thanks

Could be various things. One place to start is with the IAC. Dirt and sticky stuff is the usual culprit.
Then a charging system check, charging/battery/voltage issues can cause the IAC to do weird stuff.
I've also had the CPS do this, operation gets marginal and it can be an on again, off again, type thing.

PCM wouldn't be high on my list of probable causes.

Fuel pump have okay pressure? Doesn't take a lot to check it on a gauge.

dirty iac and throttle plate, or failing TPS

Upstream O2S is defective.

Some good advice above. This is not likely to be a computer problem.

1. Load test your battery. A marginal battery can give the engine management sensor fits. I've seen marginal batteries start the engine okay, but takes a little bit before the alternator gets juice rolling back into the battery. Any parts store will load test your battery for free. Not saying this is your problem, but you should rule it out. Simple stuff first. Always.

2. Fuel pressure test. Get a fuel pressure gauge on and monitor it with a cold start. Compare what you are seeing to factory spec of 49 psi for your 98.

3. Clean your idle air control. Never a bad idea, especially if it hasn't been done before. More on that below.
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The Idle Air Control (IAC) is mounted on the back of the throttle body. (front for 87-90) The valve controls the idle speed of the engine by controlling the amount of air flowing through the air control passage. It consists of a stepper motor that moves a pintle shaped plunger in and out of the air control passage. When the valve plunger is moved in, the air control passage flows more air which raises the idle speed. When the valve plunger is moved out, the air control passage flows less air which lowers the idle speed. Over time and miles, the IAC can get carboned up which can have an adverse affect on idle quality. Cleaning the IAC may restore proper function and is an easy procedure to perform and good preventive maintenance so it is never a bad idea.

CLEANING THE JEEP 4.0 IDLE AIR CONTROL

Remove the air filter cover, associated hoses and the rubber boot that goes from the air filter cover to the throttle body. Remove the IAC with a torx driver (2 bolts; one can be kind of hard to get to)

“Gently” wiggle out the IAC from the throttle body. Gasket on the IAC can be re-used if it is not damaged

Clean the IAC with a spray can of throttle body cleaner; inexpensive and available at any place that sells auto parts. Throttle body cleaner is recommended rather than carburetor cleaner as it is less harsh, safe for throttle body coatings and is best for this task. Use cleaner, a rag and a toothbrush and or Q-Tips. Be gentle; don’t twist or pull on the pintle that protrudes from the IAC as it is fragile and you could damage it.

Thoroughly spray clean and flush where the IAC seats in the throttle body with the same spray cleaner

It is also a good idea to clean the entire throttle body itself, the butterfly valve inside of the throttle body and all associated linkage as long as you have things disassembled

Reinstall IAC and check idle quality

Sidewinder CC said:

Upstream O2S is defective.

Click to expand...

Yep it was my O2 Sensor
Thank you to everyone who wrote back!
Appreciate it!!