88 Renix Cherokee 4.0 running crazy (long)

[RastMR]

This jeep came to me with a destroyed engine, it was half disassembled but only 100K on the clock. NEW engine now and I'm having some issues. After initial startup it was running absolutely pig-rich which was apparently due to to some bad knock-off injectors and a bad map sensor. I managed to do the cam break in, but then got new map and tps sensors, tps has been adjusted correctly and have reinstalled the old, original injectors and seems to have mostly cured the rich condition. I've checked for vacuum leaks at the manifold, seems fine and to make absolutely sure I've got zero vacuum leaks I've got all manifold vac ports capped off with only FPR connected. Also, egr is gone but holes are capped no leaks, have about 18lbs of manifold vacuum. I put a new bosch O2 sensor in it, engine "runs" now but doesn't want to idle well. Idle is low, 500rpm or less, "hunts" and will die, also will die if you let go of the accelerator quickly. The new plugs turned pretty dark from an hour or so from running so rich (yes changed the oil), will the deposits burn off or do I need to replaced the plugs again? The thing I thought was "weird", is when I tried to start it without the O2 sensor disconnected, it ran at 3000 rpm and would not come down at all, but sounded fine otherwise? I plugged the O2 sensor back in and returned to the former described state, low hunting idle. Is that even remotely normal reaction to unplugging the O2 sensor? All I can think of is that my old injectors are in bad shape and need to be replaced and have NO idea about that O2 sensor reaction but have heard jeeps don't like bosch o2 sensors but running at 3k when disconnected is a bit extreme, maybe the ecu needs to be reset? Apologies for the long winded description, any ideas appreciated.

 

[RCP Phx]

I definitely would start with Cruiser54's web site, he's kind of the Renix guru around here. http://cruiser54.com/

 

[cruiser54]

Did you get the 3 or 4 ground wires attached at a clean and shiny spot on the dipstick tube stud? Ground strap from firewall to head?

 

[RastMR]

Hi, yes sir I did. After removing paint and shining them up I'm measuring about 1 ohm back to neg post, has two braided wires up front and don't have the infamous "connector". If 1 ohm is not good enough, maybe I need to do those ground splices and/or replace my ground battery cable. I'm very curious why my engine would run at 3k without the o2 sensor.

 

[cruiser54]

I don't get the O2 sensor deal either.
Do you have power to the orange wire and a good ground at the black wire?

 

[RastMR]

I'll check that Cruiser, but am suspicious that someone "adjusted" the throttle stop. Will report back in a few.

 

[cruiser54]

You know how to deal with that, right? I'd just make sure it's correct.
It was Uncle Bob....

 

[RastMR]

You know how to deal with that, right? I'd just make sure it's correct.
It was Uncle Bob....

p

Yeah, throttle was very much opened up, I guess that would explain the 3k rpms. I had another unmolested throttle body so gave it a good cleaning, installed my IAC and TPS. Mixed verdict, will idle now but low and lumpy but generally runs better, almost "good" but... I think I've screwed up my spark plugs and O2 sensor with soot so badly that at this point I don't think there's any way it could run properly. Again, it wanted to run hella rich but disconnected the O2 sensor and this time it would idle (no more 3k) and I don't think it was running "soot dumping" rich with the O2 disconnected. Still haven't measured electrical at the O2 but have to ventilate the place for a bit so I won't keel over (good grief what a pain).

 

[RastMR]

Well well, I seem to recall some smart man told me to check for certain electrical parameters on my O2 sensor, think it might have been Cruiser54, yeah pretty sure it was. I did, and golly guess what, I have ZERO volts on my heater wire, 5V on the signal and 4 ohms on the ground (but that was a dirty frame).

 

[RastMR]

Conflicting info, does the engine needs to be running to test for +V to the O2 heater wire? Also tested my brown/white ground wire on my TPS to -, got .9 ohms there.

 

[RastMR]

Ok 14V on orange wire with engine running, 5v and good ground to battery. Started it again with o2 disconnected and it's running pretty good, idle a bit shaky and still rich but not terrible. Going to put new plugs in it and another o2 sensor (not bosch) and this thing should run! Fingers crossed :looney:

 

[RastMR]

Will get my original injectors cleaned at the Bosch service place too, quick turn around.

 

[RastMR]

Wow, same exact thing. Runs good with o2 disconnected stinky rich when connected. My grounds show as about .9 ohm, but guess I'll do the splices, new batt and firewall cables, and clean the ECU connections. Also have a spare ecu from a 90. Anything else I should be doing please advise. Thank you.

 

[RastMR]

Btw only runs bad with o2, in closed loop. Open loop seems fine.

 

[cruiser54]

chuck the 90 ECU in it when you refresh the connector.

 

[RastMR]

chuck the 90 ECU in it when you refresh the connector.

I thought I had found the culprit when I pulled a cardone reman ecu out of it, but my spare is doing the same, again. I did find something tho, you gonna crack me over my virtual head, but tho my TPS brown/white wire tests ok and block grounds too, found the grounds on the terminals on the 4 relays are all bad, best one is 5 ohms on the fuel pump socket. Also the ground on my o2 is flakey, wobbles around. I swear I wiggled the harness and it didn't wobble there, but obviously I have ground issues, surprise eh.

 

[RastMR]

Just finished soldering the brown/white wires, new 2ga batt cable, soldered new eyelets onto the two block grounds, new ground on the firewall, cleaned everything again. My sensor grounds are all in the .6 area, including the o2 ground. What's confusing me is all the relay sockets, i've so far not been able to figure out which ones are supposed to be the ground, or even if they all have a ground. They do not test as good as the sensor grounds, about 1.6 is the best ohm resistance reading I get on any of pins and that's only one of them. I have the electrical schematics for a 90 (mines an 89) but so far it's not helping much, still studying it. Haven't tried to run it yet, would like to make sure my relay connections are ok first and I suspect they're not.

 

[cruiser54]

90 diagram should be fine.

Work on the relays and receptacles.

 

[RastMR]

90 diagram should be fine.

Work on the relays and receptacles.

Not really sure where to even begin on that, I can clean the sockets, would it be worthwhile to start checking continuity of individual wires with their sockets? Thanks

 

[cruiser54]

at this point, probably not. Sockets and relays first.