bradcox00

my 1998 4.0 cherokee spits, sputters, backfires. its so random and so violent, i have to pull over and let it sit for a minute and it kinda just goes away or is not that bad. changed dist cap plugs wires etc. also ignition coil and tried almost everything.... dont want to send her to jeep heaven just yet, but i just cant figure this one out......there is just to rime or reason behind it, cold, hot, wet, dry its driving me nuts. maybe PCM?

k2keith

This could be a variety of things -

Does it do it constantly or does it run sometimes well and other times poorly?

Have you picked up a time pattern, for instance it runs 20 minutes fine then starts to have issues.

Possible causes include, but are not limited to -
fuel - pump, filter, bad gas, water in the tank, fuel injectors
spark - timing - other?
electrical - sensors, computer, iac
exhaust - clogged cat.

I am sure others will jump in with more specifics

Throttle Jockey

lets not even talk about jeep heaven. the way i see it you have one of two things happening. #1 the ignition system, #2 the fuel system. one of the two is breaking down. i hate to say it but you may just have to drive it until something fails. if all systems are working properly then obviously you can't fix it. if it only does it once in a while then it will be hard to nail down.

Cherryokee

That Spit & Sputter might be PCM as you stated - or it could be worse. From your description, the condition may be related to a sensor where timing is affected by thermal (coolant temp sensor? - not the sender for the temp gauge). Check your Cam and Crank position sensors as well. BTW: Have you run a OBD scan yet? If you don't have access to a scan tool, many auto-part stores have one for customers to use on their premises (be prepared to let them hold your license or credit card while you use it). The scan-tool connector is beneath the driver's side knee panel. Good Luck!

bradcox00

ill try that go a day or 2 and see what happens

CodeXJ

Pull the intake boot and take a look at the throttle body. Is it pretty dirty and gunked up? If so, you may want to remove it, remove the sensors, and spend a few hours cleaning it up. It's not hard to do, a little carb cleaner and a cheap toothbrush go a long way.

You may want to consider Seafoaming the motor, at the very least that'll clean any crap out. Lucas Fuel Injector cleaner is really good for cleaning fuel injectors, as well, I run a tank full through every couple of months.

If it's intermittent, it's not ready for Jeep Heaven. It's just something acting up and should be fixable, probably something fairly cheap honestly. The problem comes with figuring out which fairly cheap item it is that needs replacing. A lot of mechanics just throw parts at the problem until it goes away, which gets expensive.

motorheadmoe

if the check engine lite is on autozone will test it for free. if it reads throttle position sensor and dealer code for your transmission it is your tps i took mine to the dealer and it cost me a small fortune