Rough running 4.0

[Knucklehead97]

This is what my fuel trim says while idling and warm.

[Ωhm]

Using the 88 Electrical Manual which shows O2 Heater being fed (B+) from the IGN SW (I1). Your voltage measurements show O2 Heater voltage is following the actions of the Fuel Pump Relay. Sorry if I misled you on my requested voltage measurements and sent you on a wild goose chase. I will keep this information in mind and now suspect the wiring schematic as incorrect. The most important thing here is you got B+ on the O2 Heater (which you might have already had) with engine running.

 

Your photo on distributor indexing looks "spot on".

 

REM readings look good, well within the ECU range of authority. Give REM (keep driving it) time to see if LTFT changes.
 

[Knucklehead97]

That wild goose chase made me find a lot of issues I needed to sort out, so I didn't mind it at all!  I have been doing some reading on the subject and am now curious about my spark plugs and wires. Lots of people reporting that the Renix 4.0 will have a weird idle with spark plug wires that are not "low resistance". Once I have money again I plan to replace my wires with the recommended type from one of the threads and see if that changes anything. How can I test my fuel injectors/the signal going to each injector?

[JustEmptyEveryPocket]

For the signal, use a noid light. For the actual spray of the injector, not sure.

[Knucklehead97]

I may of found part of the issue. This is the tune up kit I got when I bought the Jeep 3 years ago (can't believe it's been so long...) The resistance on the wires are 3000 OHMs according to the spreadsheet. From what I can tell our Renix wires are supposed to be around 1000 OHMs.

[RustyRodder]

I used that same kit- I'm curious if it makes a difference now!

[Knucklehead97]

Been awhile since I posted on this. Done a lot of work on the MJ! Added a new exhaust manifold from an HO and a newer downpipe. This allowed me to completely delete the EGR and while I had easy access I advanced the timing on my CPS. The 4.0 is A LOT peppier now. And the exhaust sounds better since it has no leaks before the muffler! The spark plug wires and rotor/cap did a lot for how the engine runs, but I'm still having basically the same issue. Now, the engine will sometimes run perfectly and idle at 750-850, but most of the time will still idle low and rough at around 600. If you put it in gear, even with it idling at 750-850 in park, it will drop down to about 550 and idle rough. If it's in gear, headlights on, and fan on, then it idles very rough. I've checked everything and it's all within spec. The only thing I can think of now is either the ECM is acting up, or I found yesterday that even though a couple months ago I adjusted my TPS to spec (.83)  it was out of spec yesterday (.71). I adjusted it back, but it made no change to the way the engine was running.

 

 

 

Any thoughts?