i need help with my cherokee

[b_radley_08]

i just did a head gasket on my 90 jeep cherokee, 4.0, automatic, 4x4. i have doen this before and never had any problems, but this time i got it all back together and it will start but it runs like crap. i have doen a few checks myself and everything is looking good. is there anyone in the spanish fork area that would be willing to help? i can pay you for your time.

 

[DOSS]

what checks have you done? What exactly does it do when it runs like crap? stall, gutless, misfire etc?
make sure that you don't have any vacum leaks anywhere that will cause running like crap

 

[Kiel]

Did you have the head machined? Valves?

 

[b_radley_08]

i have done comprssion test, timing, fuel presure to the fuel rail, i have checked the injectors, map sensor, crank position sensor, i think that is it and they all checked out good. the computer is new and most all of my sensors are less than six months old.

it idles up and down, it back fires, and no throughtle respons

i checked all the vacume lines ten times everything looks good. i even pulled the intak/exhaust manifolds off and redid the gaskets??????

 

[b_radley_08]

no but the head was good i checked. i have good compression. i pulled the valve cover and turned over the engine. all the of the valves are opening and closing fine

 

[DOSS]

I would double check all your vacuum connections.. and then lean towards a CPS .. I know that they can test good and still be crap..

 

[b_radley_08]

what is the chances it would go out if its only four months old?

 

[jet_aj]

Without actually looking and hearing it... backfiring sounds like it could be a timing issue... but if thats been checked and is correct. Its been a couple years since I did a head gasket on a jeep.

NO throttle response? or just sluggish reaction?

I just did a nissan inline 4cyl and had messed up the intake manifold gasket while putting it back together. It had a "loping" idle ran rough (like only running on 3 cylinders) and had poor throttle response, it would rev up, but reacted slowly and erratic. It would occasionally backfire because to get it to run decent enough to stay idling I had to adjust the timing out of spec. Couldn't hear or see the leak, but by spraying some starting fluid around the intake manifold gasket I was able to discover it. Just be very careful if you try that. I know you said you redid the gasket, but in my experience with the gasket on a 4.0 that i did it is very easy to misalign or damage the gasket when installing the manifolds.
I'm kinda too far away to come in and take a look... hope you get it. I fought the nissan for a couple weeks before i got it all solved.

 

[DOSS]

what is the chances it would go out if its only four months old?

yep.. it is possible.. but I would lean towards a vacuum problem or misaligned gasket.. use starting fluid, brake cleaner or even a propane torch (not lit) to check vac connections it should rev if you spray next to a leak.

 

[mbryson]

what is the chances it would go out if its only four months old?

Good to excellent if it's not a dealer item. Even a decent chance if it's a dealer sensor. That's a piece of sh!t sensor. Almost as bad as the F*rd 7.3L one.


Sounds like a vacuum leak to me though.

I don't have experience with the Renix 4.0L, but a '91 will NOT START or run if the timing is off at all.

 

[jet_aj]

I replaced all the vacuum lines on my XJ trying to find an idle issue. They were like ~25 from www.rockauto.com and i figured it was worth replacing to know they were not the problem.
Mine problem ended up being a missing rearmost bolt for the manifold... Got all your bolts?

 

[b_radley_08]

i tried the starting fluid around the intake. so far nothing but i will give it another try. is there anything i can do to know for sure its the cps? i dont really have the extra money to throw parts at it.

 

[b_radley_08]

on the 4.0 its self ajusting timing, so after you get the timing set you cant ajust it. it is all controled by the computer

 

[b_radley_08]

i have changed all my vacume lines too

 

[Milner]

Did you pull the dist. out? If so, could it be a tooth off?
A cracked or wet dist cap can also cause a miss.
X2 on the cps....non dealers ones are POS's. BUT I have never had a renix that would run with a bad cps. When they are bad it will not fire at all.

 

[Kiel]

What is good compression? Also I would check the simple things, plugs, wires, cap, rotor, etc

 

[mbryson]

on the 4.0 its self ajusting timing, so after you get the timing set you cant ajust it. it is all controled by the computer

Sounds like the 4.0L HO. I might reset to TDC and stab the dist. one more time just to make sure, but it sounds like you've got it right. A small block Chev or whatever will run a tooth off, just not even close to right. The 4.0L I had would NOT run a tooth off.

There was no timing adjustment on the dizzy either, it was all done by the computer.

 

[b_radley_08]

four months ago i had a problem with it running like crap. i could still drive it but it would stall and stuff. at that time i worked at a mechanic shop in az. the diagnostics tec worked on it for three days. everything was checking out good. the cps was reading at 8.3v. it is supposed to be 4.5v or around there. he didnt think anything of it. after trying a hundred other things he changed the cps and it fixed it. so i guess you are right i should give it a try.

 

[b_radley_08]

120 psi. i have new wires, plugs, cap and rotor.

 

[mbryson]

four months ago i had a problem with it running like crap. i could still drive it but it would stall and stuff. at that time i worked at a mechanic shop in az. the diagnostics tec worked on it for three days. everything was checking out good. the cps was reading at 8.3v. it is supposed to be 4.5v or around there. he didnt think anything of it. after trying a hundred other things he changed the cps and it fixed it. so i guess you are right i should give it a try.

One of my bad 4.0L CPS would still run, just not well (happened to be an Autozone one).