Backfire out exhaust just past idle on a 1998 xj

[85xjwoody]

This one has me kindof stumped. 1998 Jeep Cherokee 4.0/aw4/231. I picked this jeep up a week ago and have replace quite a few parts and finally got around to trying to fire up the engine. After about 15 long tries it finally started and idled around 800rpm and stays there, but when I go to give it a little throttle I can only get up to around 1800rpm before it backfires pretty good out the exhaust. It starts a little hard but once started it idles pretty good but can do squat but backfire when I try to do anything else.

Parts that I have replaced brand new in the last week which could affect this include:

O2 sensors
cat converter
cap, rotor, plugs, wires


From some reading I have done today it seems like it could be a number of things and I don't want to just start tossing anymore things at this if I don't have to. I have unplugged, cleaned, and plugged back in the CPS, TPS, IAC, and CAM sensors and no change. I have no check engine lights on currently either. Any ideas out there as from what I have been reading it could be the CPS, TPS, CAM, o2 sensor fuse, a simple tuneup which I have done already, injector o-rings, and timing chain. I have a new TPS on the shelf I am going to go and try at the moment but any thoughts or ideas as to what a solution is or what your fix was is greatly appreciated. Thanks.

Kim

 

[philagony94xj]

I might be stating a simple check here but how do the engine grounds look? Battery terminal connections?

 

[WB9YZU]

What are the stored codes?
What is the timing at idle?

 

[85xjwoody]

Grounds are fresh and battery connections are tight and clean. I tried a different PCM from a simular jeep with no changes and am now trying a new ignition coil I had on the shelf.

 

[old_man]

Double check correct spark plug wire order.

 

[85xjwoody]

Just tried a different ignition coil and still the same. I have checked the wiring four different times even comparing things with the 98 and 97 in my driveway. Everything is in place as far as I can see upon comparison. The previous owner had his mechanic tell him the timing was off so he did not know what to do. I checked timing and it is all good. It looks like he might of messed with the distributor as the nut holding down the retainer for the distributor shaft looks like it has had a socket or wrench on it. Hmmm. Could the timing be off by a tooth?

 

[85xjwoody]

I do not have a way of checking codes today. Ron do you mean I actually have to pull out a timing light?

 

[Dano4.0]

my wifes jeep did the same thing when I had the distributor in a tooth off.
when properly installed the rotor is actually past the number one wire.
oil pump slot at 11 o'clock , rotor at 5 o'clock , should fall right in .

 

[85xjwoody]

Hmmm, I am going to take the distributor apart and see what's up, can't go anywhere but up from here.

 

[85xjwoody]

Don't know if this pertains to my problem but when I try to start it it is somewhat hard to start and usually won't start unless I catch it on a good "hickup" I let off the key and it will all of a sudden start.

 

[85xjwoody]

And a new TPS did not change a thing. At least I didn't have to pay for that part.

 

[IllianaXJ]

Definitely sounds like it is a tooth off on the dist.

 

[85xjwoody]

So guess what it was?








Give up?







Well it was the distributor being off one tooth. This thing runs like a raped ape!!!! Now off to the exhaust shop and then for sale.

Thanks to all for the help it was greatly appreciated!!!

Kim

 

[WB9YZU]

Good job Kim!

 

[88trailcrawler]

This thing runs like a raped ape!!!!

Hmmm. I don't know if that's good or bad. :dunno:

 

[85xjwoody]

Well this time it is a good thing!! LOL