cruiser54

So, who the hell are we working with now?

Doesn't the title of the thread say Renix?

DFlintstone

Agreed. My Renix ran fine on defaults, with the 02 not grounding the 5 volt ECU feed at all. BUT, I don't know what it would do if that feed from the ECU was grounding somewhere.....

'90Cherokee

One of the replies, guy with a '99 talked about his damaged O2 and thinking it was causing his to bog and suggested that the OP check his.

'90Cherokee

Which is the only thing that lead me to say unlikely the cause instead of just saying that aint it, altho to my knowledge the sensor should still get ignored under heavy load.

95cherokee89

O2 sensor is about 3 weeks old. I checked the fuel pressure, and it seemed alright, somewhere around 30ish psi (Guage is a homemade thing, not that accurate) I'll double check compression, it's possible I have a bad valve seat or something.

DFlintstone

Yes, Renix will ignore it past 70-80% throttle. (and a bunch of other sensors).

Btw, A guy with backfiring into the intake just posted he found a broken valve spring.

DFlintstone

"Unplugged, the Jeep side 02 plug has 12 Volts for the heater (orange on one end). Got the ground down from .9, to .8 ohms by cleaning the ground gang at the dip stick tube. (the ground is in the middle). Then got about 5v on the sensor wire, (other end). All is well. (a note, have the engine running to check the 02 heater wire) "

OK, a thought. You saw a big difference after changing the 02. Maybe try this. Unplug the 02 and meter the feed wire to the ECU for resistance to ground with ign off. From the above you can see that the orange heater wire, (hot with 12v, engine running), is on one end, ground is in the middle, and that ECU wire is on the other end.

With it off and the plug off, check resistance to ground on the Jeep/harness ECU wire while you jiggle the harness all the way up to where it meets the injector harness, and back from there.

My thinking is that when you changed it and nearly doubled your Kilomrage?, you jossled a wire??

https://www.cherokeeforum.com/f2/ren...ce-rms-133153/

And YES! At 307K a set of wet/dry compression numbers is a fine idea.

95cherokee89

compression was good, about 135-140 on all cylinders, only bled down a small amount after a while.

The ground for the 02 is good, I followed the wires up to the c101 connector and then cleaned it up, no change in the fuel economy, that's why I just replaced the sensor (NTK) it went up by about 100k a tank, and seems to have stayed there this time. Did some more tweaking with the map sensor, I had the hose on the nearest port on the manifold. I put it back to the spot on the throttle body and replaced the hose, it seems slightly more responsive now, ill have to drive it more to see.

I'll do a bit more tweaking, but for now, I think i'll just live with it. the misfire is only noticeable at idle, and the sputtering only happens when I just start it up and accelerate when its cold, still has tons of torque, it'll spin the wheels like nothing, top speed is the only thing that seems to have suffered.

At this point, its just an old beat on jeep, I don't drive it often enough to really care about having it working perfectly, just enough.

95cherokee89

just thought I'd update. Turns out my fuel pump was on its way out, it started getting loud, and I started experiencing common failing fuel pump symptoms. Swapped it out and it seems to have much more power, and isn't sputtering on acceleration anymore.

DFlintstone

We coulda shoulda brought up the (free) fuel pressure check sooner! When there is more than one problem It can get tough....Looks like you have it narrowed down, nice job!

67 GMC

Did you adjust the TV cable? Sometimes when you think you're flooring it, you aren't. There's lots of write up on how to do that. The Fuel pump was probably the issue though.

95cherokee89

I'm glad you brought up the tv cable, I never even thought of that. I went to adjust it and found that the plastic clip had actually broken off, so the cable wasn't being used during acceleration. couple of zip ties and it should stay on now, I'll have to see how much of a difference it makes after I drive it for a bit.

67 GMC

Good. Adjusting the TV cable made a big difference for me.

What's the rust like in BC? My '87 was from Newfoundland and apparently they don't use a lot of salt on the roads there so it was pretty good underneath. I picked up an '88 parts Jeep for $350. It's from where I live and they use a ton of salt here and it has the rust cancer bad (basically a Fred Flintstone floor). Best investment though as it's great to be able to swap parts out quick. I see our Jeeps on Kijiji BC quite a bit so maybe pick up another one if you can get one for the right price and you've got space to keep it.

95cherokee89

Rust is pretty bad, floor pans were pretty rusted out, had to replace them. and there's some rust on the bottom of the doors as well. I picked up one for parts for cheap as well, and it was so rusted out it was starting to fall apart structurally.

95cherokee89

The weirdest thing happened yesterday. I had been driving for about an hour, and when I got back home, I let it idle for a while, and it was idling bang on at about 600rpm, the misfire was gone, and I had gotten about 100 km to just over an 1/8th of tank. about 10 minutes after I shut it off, it went back to what it used to do, but it's just weird how it fixed itself for a while.