big sam

I have a 1998 4.0L Jeep xj country witch I just got a week ago. The problem that I am having is: When you start the Jeep it runs smooth, when you drive it, it start to back fire thru the intake and you smell a lot of fuel (Like if the timing is out). Then while you drive you turn the engine off and on very quickly it runs fine for a while and then stats to do the same thing over again. Where do I start to look for this problem? Help please?

Killabrew

Is check engine light on? If so get your codes read and go from there!!

tjwalker

Backfiring almost always indicates an imbalance in fuel/air mixture.

As mentioned, if you have any codes, they are invaluable in helping you figure this out.

If you have no codes, the first thing I would do if this were my vehicle would be to test fuel pressure. Easily done with a fuel pressure gauge installed on the schrader valve on the fuel rail. For a 98, you should have 49 psi, plus or minus 5 psi.

Good luck and check back with us to let us know what you find!

big sam

Hi thanks will check for error codes.

big sam

Hi I have found that the distributor shaft has a lot of play on it, can this maby be the problem?

no rdplz

It could as the spark timing could be off allowing a build up of fuel in the cylinder chamber(s). When it does detonate, the fuel/air mix is incorrect, resulting in a rough running vehicle with the smell of fuel coming from the excess burn off, resulting in the engine backfiring.

greengoblin

you might have a injector stuck open or slightly open

VTJeep

Popping at the intake generally means its running lean. Does it start sucking for air hard when issue occurs? If so it could be running dead lean. This would indicate that the fuel delivery is limited. Drop the tank and inspect the pump/filter. If there is debris and/or a bad filter then you will know it. Also, I think you said you put it on a code reader, but was it just a reader or a real diagnostic computer that lets you look at things like throttle position and other specifics? Your o2 sensors my be shot. Could be TPS. Or the PCM..

Edit- ok in looking you said you it needs to put on a reader still.. Even if cel isn't on, that doesn't mean there aren't codes stored in there that will give you a direction. Other things to check are pressure at the rail (when jeep is exhibiting symptoms). But start cheap and easy! Like I said a good diagnostic tool can tell you a lot.

big sam

Editing - I have a 1998 4.0L Jeep xj country. The problem that I am having is: When you start the Jeep it runs smooth, when you drive it, it starts to run very rough and back fire thru the intake (Like if the timing is out). Then while you drive you turn the engine off and on very quickly it runs fine for a while and then stats to do the same thing over again. Another thing that I have notice it seems as if the gearbox don't know what it wants to do - then it changes nice, then it don't what to change gears and then it don't know in what gear it wants to be in. This starts at the same time the engine starts to run rough. I can also see on the trip computer that my fuel consumption go's up to 44L/100KM
The engine light does not come on.
Thing I have tried
1) I found that the distributor had a lot of ply and got it fixed but no joy.
2) I cleaned the MAF sensor and the throttle body but no joy.

To do
I am performing a fuel pressure test tonight.

Where do I start to look for this problem? Help please?