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88 restore/ rough at low rpm?

baybilly

NAXJA Forum User
i pick this gem up for 250.00 bucs at a yard sale. very clean and getting all the bugs worked out from sitting for 3 yrs. no rust and under side looks good. interior is spotless

88xj11-1.jpg



here is the problem, at idle it will run smooth then get kinda rough and then fine then smooth, rough. it keeps going back and forth. i have replaced just about all the vac lines. i'm restoring this one, new here , i have a few FSJ'S but they have no putter in them so i'm going to need so help on this project. thanks for any help

Dave
 
Your going to have to be more specific, engine? Miles on it? Also do a search for RenX files, it will be very helpful.
 
88 Wagonman said:
Your going to have to be more specific, engine? Miles on it? Also do a search for RenX files, it will be very helpful.

sorry , 4.0 motor was replaced by PO and has 18,000 on it. rig has 182000. i got it because the PO couldnt get it to started one day. and after putting in a new dist/ coil/ putter/ and a wiring harness he gave up. well you know the problem as i did. $30.06 crank sensor from napa and it runs great. well not yet but does run fine up and down the road. chasing oil leaks from sitting. thanks for the heads up on the search.
 
Thats a nice un-molested XJ!

I would start out by cleaning all of the grounds. There is a strap that goes from the back of the head, drivers side to the firewall, clean both ends. At the dipstick tube holdown bolt there are 3 grounds, loosen that up and clean those. I would also remove every connector, one at a time, and clean them with contact cleaner and lube them with di-electric grease.

Another step to take is to upgrade the battery cables and grounds, (5-90) sells a very nice upgrade for that. Jon is one of our NAXJA RENIX gurus.

There are a couple of other tricks to try as well. There is a screw that is very similar to a needle valve on the drivers side of the throttle body at the base of the TB(it has a torx head on it). Make sure that screw is adjusted all the way in. Your butterfly should be just slightly open at idle, it should not go completly shut metal to metal but rather have a very slight gap.

With all of that said, my 90', which is all new, new engine, all new sensors/outputs, upgraded grounds, improved vacuum plumbing, (you name it-its new) and everything adjusted properly, I still have a very low idle, 300-400 rpm in gear. It idles like a John Deere tractor!
 
xjtrailrider said:
Thats a nice un-molested XJ!

I would start out by cleaning all of the grounds. There is a strap that goes from the back of the head, drivers side to the firewall, clean both ends. At the dipstick tube holdown bolt there are 3 grounds, loosen that up and clean those. I would also remove every connector, one at a time, and clean them with contact cleaner and lube them with di-electric grease.

Another step to take is to upgrade the battery cables and grounds, (5-90) sells a very nice upgrade for that. Jon is one of our NAXJA RENIX gurus.

There are a couple of other tricks to try as well. There is a screw that is very similar to a needle valve on the drivers side of the throttle body at the base of the TB(it has a torx head on it). Make sure that screw is adjusted all the way in. Your butterfly should be just slightly open at idle, it should not go completly shut metal to metal but rather have a very slight gap.

With all of that said, my 90', which is all new, new engine, all new sensors/outputs, upgraded grounds, improved vacuum plumbing, (you name it-its new) and everything adjusted properly, I still have a very low idle, 300-400 rpm in gear. It idles like a John Deere tractor!

Thanks for the help, i'll be going over all the grounds today and putting new o-ring in the oil filter adapter leak.
 
rough at low rpm? update

just want to say thanks for the help and you guys were right. i guess who ever installed the new motor forgot a few ground straps. runs fine now. as far as the oil leaks i did the oil filter adapter o-rings and valve cover gasket, then did a search on oil leaks and you guys were right again, found the crank case vent line pulged up solid. i hope that will take care of the rear main seal leak. we will see in time. being new here i just wanted to thank you guys for a great site and all the helpful threads in the tech search.
 
well made the trip to work and back today, 112 miles round trip. ran great. got home and the oil filter adapter was soak again ?? after looking closer could the dist be leaking just above it?? is their a seal or o-ring on it also? the oil sender looks fine. and rear main seal is not as bad as it was but still leaking. i found the rear trans mount wasted from all the leaks over the years, rubber was mush and that was the noise i herd/ like somthing loose/ it was the TC hitting the skid plate when i hit a bump.
 
The small vacuum line from the rear of the valve cover to the intake usually has to be cleaned out. Also check the valve cover and the intake nipple and make sure they aren't plugged. The motor will build pressure if this line gets plugged up and tends to leak worse.
The oil leaking onto the starter may eventually cause grief, it as a way of working it's way into the starter and can cause trouble at the brushes. If your starter begins to act up, cleaning the brushes often does the trick.
Three levels of oil leaks in a 4.0, seep, drip and gush. I ignore the seeps.
 
8Mud said:
The small vacuum line from the rear of the valve cover to the intake usually has to be cleaned out. Also check the valve cover and the intake nipple and make sure they aren't plugged. The motor will build pressure if this line gets plugged up and tends to leak worse.
The oil leaking onto the starter may eventually cause grief, it as a way of working it's way into the starter and can cause trouble at the brushes. If your starter begins to act up, cleaning the brushes often does the trick.
Three levels of oil leaks in a 4.0, seep, drip and gush. I ignore the seeps.

already cleaned out the ccv tube. and ya your right the starter that was in it was oil soaked real bad and would hardly turn it over.i have replaced the starter and don't want to buy another one because of oil leaks!!!!!! remember this rig had sat for a few years after the motor replacment before i grabed it up so i'm going to be chasing dried up seals i'm sure. thanks for the input.
 
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