sputters and hard/no start

I have a little problem with my 89 4.0. It started after I was parked for two days in a snow storm. At first it started right up and I drove 5-6 miles. It sat for 30 min, and then would not start. I finally got it started and had it would not idle. It sputtered. I drove around for 30 minutes, and it got better, and it was ok after the 30 min. It then sat for 3 days and then would not start. Had to tow it home. I cleaned and wiped the distributor cover. Then it started. I drove it at highway speed, and it seems it has normal power. Now it has rough idle and sputters when I open the trottle. I checked the cps it was 210 ohms.

What else could be causing this?

Torfinn

The eratic/intermittent nature of the problem suggests sensor. It sounds like a classic CPS failure. Taking a resistance reading (ohms) alone will not tell you if the CPS is shot. You need to be able to watch the ouput voltage smoothly swing as you rotate the throttle shaft. I just went through this with my daughter's 1990 XJ, and replacing the CPS fixed it. Her jeep needs the new harness that connects the CPS directly to the computer, since I suspect some continuity issues. The harness and CPS are available together at the dealer- some people report the kit cheaper than the CPS alone!

On an 89 you might also want to check that the EGR valve isn't sticking open. When they wear, they can hang up intermittently and cause problems similar to yours. The EGR valve diaphragm is open at the bottom, so you can reach a finger in and push it open then let go. If it has hung up it will often snap shut and restore your idle. If this helps, you can either replace the EGR valve, or cheat and just clamp off its vacuum line. You can run it clamped off forever and your Jeep will not know the difference. Don't disconnect the whole system, because the solenoid that controls it also controls fuel canister purge.

Thank you. I replaced the cps I had bought for a case like this. What a job. Had to use 3 extenders to get to the top bolt. Luckily they were not thightened very hard. I also adjusted the tps, which was a little off spec. The car was also stored indoors for 24 hours in a warm garage. So I guess I never know what cured it. It started up fine and I drove it for 15 minutes. :laugh3:

PS. I also tested the egr valve it seemed to work. It moved when i sucked on the hose.

Torfinn

torfinn said:

Thank you. I replaced the cps I had bought for a case like this. What a job. Had to use 3 extenders to get to the top bolt. Luckily they were not thightened very hard. I also adjusted the tps, which was a little off spec. The car was also stored indoors for 24 hours in a warm garage. So I guess I never know what cured it. It started up fine and I drove it for 15 minutes. :laugh3:

PS. I also tested the egr valve it seemed to work. It moved when i sucked on the hose.

Torfinn

Click to expand...

The EGR is probably fine, but the problem I am describing above is intermittent and independent of the diaphragm - something inside the mechanism wears and prevents it from closing all the way, but not every time. So if the problem recurs keep that in mind.