Hick-up!!!!!!!!

I have an 87' xj 4dr 4wd with a 4.0 6cyl, auto trans and a 231 transfer case. It runs really well except that it gets what i would call a hickup. Basically it is a slight hesitation for just a half second and then continues on as normal. It happens with the A/C on or off. It does it when accelerating, decelerating or just cruising. The engine is a rebuild that was put in about a year ago with 8-10k miles on it. After reading some of the strings I think it might be a CPS problem but would like some other opinions. I want to get all the engine bugs and driveline issues worked out before I put the 4" lift on. ANy ideas or suggestions would be greatly appreciated.

Ed

P.S I found this site a couple of weeks ago and have been addicted ever since. It says alot about the good people that are involved with this ....uh.....addiction. I really have pulledsome valuable info form here and I really appreciate it.

CPS is a good place to start, but also look at the TPS. Clean the throttle body with a good cleaner. I use the Moper stuff from the Dealer to clean it. That helped me the last time I had that problem. But the TPS could really be off. So have it looked at. Juice

First I'll say it not a transmission problem. I had a similar problem a while back. I'd be going along at 65 or 70, legal speeds in this state, and get a hick-up. If I slowed down it did not do it.

I took it in to the dealer mechanic who understands Renix XJs (87-90). He figured out it was a bad/sticking ERG valve. He replaced it and the problem never came back.

If it turns out to be the EGR then I HIGHLY RECOMMEND you have the throttle body cleaned at the same time. The EGR stuff made my ERG dirty and gave me a poor running vehicle for a year. I nearly dumped my XJ because of the poor running. I then took it back because it was die when only a mile or two from home and it was a dirty throttle body.

Use a mechanic you trust and who knows our style XJs and you will be fine.

difficulty level

So I am going to check TPS first then CPS and clean the throttle body and check the EGR. Is this all stuff that I can do myself? I am fairly handy with the wrench and would like to do this for the experience if nothing else. Im pretty sure I get the Jest of the the CPS and TPS checks at least according to Haynes Manual. Thanks for your input it is much appreciated.

Ed

If it does happen to be the EGR valve, you can use one for an '89 and it will cost a lot less than the one for the '87. Also, it seems to be a dealer only item.

Might also want to check MAP / change O2 sensor.... The problem you describe can sometimes be caused by the a lean condition. A lean condition is many times created by mixing many performance parts, or by worn electronics such as MAP and O2.

update

I changed out the o2 sensor and the problem seems to be solved. Thanks for all the good advice guys.

Ed::cheers

The sensor seemed to fix the problem but the problem has returned. I have cleaned the throddle body, TPS, ISM. Should I check my MAP? Could a CPS cause this. Any help would be appreciated.

Ed

Just for the heck of it, try twisting your rotor with the distributor cap off. Try pulling the distributor shaft up. Loose drive gears and/or worn shaft, will cause harmonics at certain speeds and loads. I don´t know the allowable play in the gears and/or thrust in the shaft. But have seen XJ´s with obviously loose distributor shafts, have a harmonic stutter at certain RPM´s (2000 is common) and under low vacumn conditions.

PaulJ said:

If it does happen to be the EGR valve, you can use one for an '89 and it will cost a lot less than the one for the '87. Also, it seems to be a dealer only item.

Click to expand...

The EGR for the 89 is not a dealer only part. standard makes it but no one ever carrys it in stock and it generaly takes a week to get. also its pretty pricy, around $120

I have found a sensor that is ccracked at the spot where the wiring goes into it. It is screwed into the drivers side of the block just above the oil pan. It has a wire wrapped in a foil(thermal shield?). Can anyone tell me what this is and if it could be the cause of the problem. I have checked the distributor by the way.

Thanks Ed

That's the knock sensor. I wouldn't think it would cause your problem. The ECU uses it to determine timing advance/retard.

I have a stutter in my 88, that bugs me, that has seemed to get better, as I fiddle with the ignition.
It usually happens at a certain RPM (around 2000), with the throttle body mostly open. Not full throttle but, half throttle or better, usually under load and/or low vacume conditions. Moderate acceleration, coasting or driving uphill (moderate). Full open throttle seems to cure it, keeping the torque converter unlocked, also seems to help.
What you are experienceing could be the same or related?
My wiring harness got a little sindged on the exhaust manifild, in the same area as the knock sensor.
I somewhat think it is a combination of things, probably, that combined, try to make the computer function for a few seconds, out of parameters or conflicting signals.
I haven´t changed out the cable harness for the, knock sensor, 02 sensor and temp, sensor yet. Have a new harness, waitng for warmer weather.
I did re index my distributor, which seemed to help some (50% or better).
My motor has always run on the lean side. Which may be a factor,

What really helps and I don´t have clue as to why, is when I run through a puddle and the engine gets wet, the problem seems to disappear.

Ground?.

Most of my EGR valve experiences, showed up as stalling at stops or slow turns.
If you figure something out, please let me know, what you´ve found.

I´ve also got some intake work scheduled. A good cleaning, new gaskets and probably some exaust manifold work. Don´t think it´s my EGR because it almost always happens, at the same RPM/vacume conditions.

Good luck.