88XJ coughs backfires and won't get over 1000rpm when cold.

[pacrat]

Ok I have a problem with my 88xj. It started yesterday. I pulled up to stop sign 150ft from the drive way when it stalled. When restarted again it was backfireing, both out the exhaust and through the throutle body. and would not get over 1000rpm. The tach was also jumping wildly. After 5-10 minutes it cleared up and ran fine. This morning the same thing but right from start up. I shut it off disconnectet the battery, the cps and anyother other plug I could find. Reconnected everyhing, still the same problem. I left it Idle while I went back to the garage to get tools when I came back all is fine again. Again it was starting to warm up. Please I need some suggestions. All the usual tricks I have learned for this didn't work. Also about a month ago while coming back from a trip the jeep started to miss and stall out on the freeway, only this time the tach would jump with every burp. After 20 or so miles this cleared up. The jeep was running 210 degs and had been running straight fro almost 4 hours when it started. Thanks for your help.
:confused:

[XJTripp]

I can only tell you that on another type of vehicle, the tach jumping around with a very poorly running engine was symptomatic of a very bad coil to distributor secondary wire. The core was very bad with about one or two strands of fiberglass left. It would not get off idle. Maybe you should check your sparkplug wires. Heat would increase resistance and make the ignition voltage leak more pronounced. The only thing that doesn't fit is this latest missfiring only when cold. This may be coincidental.

[Matthew Currie]

I don't know about the Jeep, but on some vehicles, the tach jumping is symptomatic of either a bad connection to the ignition primary, or a bad ignition module. One of the first things I would check is the connections and terminals to the distributor and coil, and make sure there isn't a short or chafe in any of the wiring.

Old Volvos were notorious for losing ignition when the fuses corroded, and one of the first symptoms here would be the tach dropping to zero and flapping wildly.

[Hawaiian Style]

Before you start with the distributer, you may want to check the threads on the CPS (Crankshaft Position Sensor).

[seanR]

Fly wheel or CPS same thing happened with my 88

[Hawaiian Style]

Oops... just to clarify my post. I mean the NAXJ message board threads.:D

[pacrat]

When the cps went out last time It wouldn't run at all. and when it was sputering the tach didn't jump around. I tested the cps and it checked ok as per book and thread posted here. I even unplugged the cps for 5 min or so and no change until engine warmed up. I'm thinking maybe ign mod?

[Danwa]

I have the same problem with my 88 xj. My problem is a bad EGR valve. Try disconnecting the vacuum line to the EGR. Problem solved for me until I get a new valve.

[pacrat]

Problem solved. The wireing harness for the CPS was against the exhaust manifold and has burned through. Causeing the intermintant short. It seams to be running great now. Thanks for all the help and input. Dave