Westy661

Hi,

I just rebuilt my 4.0 thats in my 89 XJ. Its a new jeep to me with 260k miles on it. I had the pressure bottle fail on me on a road trip towing my boat, needless to say I goofed up not purging the system and overheated a few more times before the head gasket blew.

It has a real low idle and is rough. That doesn't seem like a big suprise after searching through this forum. Also, it seems like I am not getting the horsepower out of the motor like I should. I drove the Jeep around and it seems fine for the most part, but when I hooked my boat up it acted like I hooked up a Geo Metro to pull it. I suspect I have a timing isssue but since this ins't adjustable I was looking for some information on how and what controls this and what should the timing be at idle. I measure 12 BCD. That seems like too much. I have tried to rotate the distributor one toother CC and one tooth CCW and that didn't do it. The weird thing is that in all those positions, the timing still should near 12 degrees. I would have suspected a big change. I was thinking about items that retard the iginition. If i have a faulty or shorted Knock Sensor, would this do it? I have searched and searched, but haven't found a source of what timing should be at idle. I am guessing it should be closer to 4 degrees?

So to cover some of the potential questions here is a little break down of what i did and try.

- Fully pulled motor and tranny.
- Tore it down completely - hone cyclinders but replaced with standard rings, bearings and etc. The motor was in really good shape.
- I "think" i have got all the vaccumm lines for the EGR, map sensor and etc all back to where it should be. I read 15-17 psi of vacuum.
- New timing chain - I counted pins when I put it in and rotated it around several times to make sure the dots come back to pointing at eachother. (if i rotated the motor the wrong way and counted the side that should be the slack side of the chain, would this be a big issue? I am just second guessing myself at this point)
- I don't have a fuel pressure gauge but i pulled the fuel rail off and let the injectors spray, they seem to have a great powerfull spray.
- New plugs, dist cap, rotor, and wires. I get spark on all.

Cheers,

Westy

Westy661

27 views and no replies? Either I have stumped the forum or everyone is tired of Timing questions?

NewXJaddict

Wish I could help but I am new at all of this myself.

dirts4racin2

I just had the same problem, totaly rebuilt my 4.0 put it in , fired it and it ran horiable so i went through everything and found nothing. I pulled the engine back out, and noticed the cps was beat up a little bit. So i got a new one put the engine back in yesterday, fired it this morning now it runs great.

Westy661

Since that CPS is such a pain in the $#@&# to get to, I put a brand new one in before dropping the motor back in. I did a Ohm meter test that the Haynes book descripes on the plug and it seems OK.

were_a_work_in_progress

try your pcv valve i had the same problem thought it was timing and i found out while going through vacum lines that my pcv valver was clogged put in a new one and it runs like a champ now