mrobers

My friend just called for an update; he went to a shop which had a snap-on DRB-II scanner to 'read' the Jeep. It doesn't store codes, but the scanner indicated that every sensor was functioning normally. The guy at the shop suggest a leaking (intake?) valve so my friend is going to do a compression test on the engine tomorrow.

Has anyone heard of a leaking valve? It sounds strange to me...

The grounds were checked and cleaned as described without results. Everything else looks normal so I don't know where to look anymore

cruiser54

Do the ground test described under IMPORTANT NOTE in this instruction sheet for TPSs.

Does your Jeep have a bolted together wire harness connector above the brake booster mounted on the firewall?

cruiser54

Try this while you're at it:

Renix Jeep ICU/Coil contact refreshing
　
　
The contacts between the coil and the ICU on your Renix Jeep can become corroded and loose causing a complete or intermittent no-start condition. I recommend the following procedure as a maintenance precaution to insure this is eliminated as a possible cause now and in the future.
The coil is attached to the ICU by two T20 Torx bolts. Remove these two bolts and lift the coil up off the ICU. You will see 2 pins and 2 sets of contacts. Clean both the pins and springy contact pieces with a good electronics cleaner.
Squeeze the springy contacts closer together with some needlenose pliers. Apply some dielectric grease to the contacts and bolt the coil back on to the ICU.
While you’re right there unplug the connectors from the ICU and inspect the pins in the harness connector. Make sure the pins are not retracted into the connector. Spray out the connector and the receptacle of the ICU with the same good electronics cleaner you used earlier. Apply dielectric grease to the connectors and plug them back in.
I feel this procedure should be performed at least once in the lifetime of a Renix Jeep.
　
Revised 11-29-2011

mrobers

Thanks: I just send him the link tothis topic so he can check all ground related tips you guys gave me. Meanwhile he whatsapped me the results of the compression tests :

1: 130 Psi
2: 127 Psi
3: 145 Psi
4: 150 Psi
5: 135 Psi
6: 140 Psi

All with cold engine. Sounds about right to me...

He is now going to perform a leakdown test but he does't have the right equipment so he is trying to MacGyver something together... ;-)

donkeypunch

Would a leak in the exhaust manifold, or anywhere before the O2 sensor cause your erratic idle? I have similar idle issues but I can smell exhaust in the cabin while I am driving and under hood when parked.

Flash1034

Having the same problem. One min running great, next min rough idle and cyl 1 misfire code.

Flash

truckntractorhick

Check the basics. Pull your injectors out make sure they're cycling properly. See if your spark is getting weaker as the engine gets warmer (maybe bad wire or ignition coil) swap spark plugs. Judging by your compression test I doubt it's a valve problem

Flash1034

Will do tonight and report back tomorrow.

Flash

mrobers

The Jeep is still at the mechanic but it is running ok for several days now.

The problem might be in the #2 cylinder because when he removed the injector-connector, it didn't change idle. Spark was ok. He switched injectors to see the effect, but it still was #2.

He pulled the valve-cover and found that the pivot/bridge on #2 was bent (???). He fixed it (don't know how) and put everything back together. Since then, the Jeep is running fine. He's keeping the Jeep for a few days to see if the problem really is solved.

I don't have enough knowledge about rockers/pivots/bridges, but can something like this cause the rough idle and the miss?

cruiser54

Yes, it most certainly can.

mrobers

Wow, talk about a fast reply (1 minute)

I tried searching for a clear picture of how the rocker/pivot looks, but couldn't find one. He forgot to take pictures

I really hope this has solved the problem!

mrobers

Problem solved thanks to what I described before.