loosing power and stalling with big backfiring

[RCJP]

Hi to all. long time since my las visit..

My ZJ is a 1998 L6 4.0 grand Cherokee, lately i been having problems were my car stops accelerating or loosing power. some times it so bad that the car will stall i have to pull over. and when it doesn't stall it backfires.

looking in some trouble shooting it says that i need to correct valve timing.

any other ideas?

thankyou

 

[MudderChuck]

Doubtful it's the valve timing. I'd say either a fuel problem or sensor problem. When they run way lean they will stall or buck and backfire.
Various sensor or wiring problems can cause this. Instead of playing musical parts it my be a better idea just to pay the money and get a scan. I've heard some of the major parts houses scan for free.
And another word of wisdom, just because a sensor scans bad doesn't mean it is the sensor, it may well be the wiring.
My 96 would stall occasionally, buck or backfire occasionally. Some times near idle, sometimes around 2000 RPM. Turned out to be an O2 senor wire (the rear) cooking on the exhaust. The cable clamp came loose.
Another time it started stalling and restarts got iffy, when it did run it wold sputter and backfire sometimes. Turned out to be a short in the CPS (CPK), that messed with multiple sensors by sucking down the 5 volt reference for voltage multiple sensors.
Right now I'm fighting an IAC problem, mine sticks occasionally. When the throttle closes the IAC opens, if it doesn't it can starve your motor of air. It may stall, miss, buck or just have a way low idle for a second or two (hesitation or near stall).
My anti theft module actually caused many of the same symptoms, it was going bad and the ASD relay function got iffy, sometimes the ASD relay would work, sometimes it wouldn't and sometimes it kind of worked (low voltage).

 

[RCJP]

I have a scaner to get codes but all i get is the EVAP code and another code for the ignition coil. i replaced the coil but i still get the code. checked wiring and everything but still no thing.

thank you

 

[MudderChuck]

I'd hate to send you down the wrong path, but if the sensors seem OK. It may be time to check some of the basics. Are you loosing any coolant? Do you periodically have to add a little though there are no leaks that you know of? May want to look at the plugs, the color can tell a tale. Hopefully you aren't feeling the affects of a leaky head gasket.
A sticky IAC can mess up the fuel air ration and cause stalling and back pop through the TB. The air fuel mix gets momentarily way rich, then what puddles in the intake may ignite causing the pop.
If your year still has the distributor cap ? Clean it out good, crossfire is always a possibility and may be intermittent.
Just a few ideas.
Is the EVAP code for your charcoal canister purge solenoid? If it is, it may need a closer look. Maybe plug the line between the purge solenoid and the intake and see what happens as a test.

 

[Bounty__Hunter]

Could be the CPS or CPS harness without throwing a code.