1990 jeep cherokee
has an 87 4.0L AW4
3 inch lift 33 Inch tires
dual exhaust from cat back no mufflers just the cat

First what its doing-

2-3 second cranking times (I know somewhat normal)

Very light acceleration itll drive fine

Pedal 1/3 of the way itll fall on its face spitting and sputtering like a misfire and backfiring until I let my foot off the throttle or floor it and itll even out once I get to speed and itll cruise unless I lift my foot a little and itll do it again.

It doesnt matter if shes completly warmed up or cold does the same thing no matter what. Only difference I can tell is if I drive it somewere say ten minutes and I shut it off come back ten minutes later it cranks over a lot longer than when she hasnt been run and it might kinda chug for a couple seconds and even out

What ive done-

Cps
Tps
Refreshened all geounds
(0 ohms at tps ground)
4 gauge cable ground rear head
Sparkplugs
Coil
Fuel filter
Fuel pressure 31 psi 39 with vac off
Cap and rotor
Cleaned egr valve
Light seafoam treatment through TB (crank times went from 5-7 seconds to 2-3 now)


Would an o2 sensor cause all this? I dont know how to test this?

Dirty or leaking fuel Injectors? I suppose I could take em out and check em?

What do yall think?

 

One more thing I forgot to mention it shoots some nasty black sooty liquid out the back its watery and the back of my white xj will have lots of black specks from it all over it. Tail pipe looks super sooty? I took the the plugs with about 500 miles on them looked all about the same a little whitish around all the electrodes no oil or any signs of it.

Please help I love my renix

 

No plug wires?

O2 sensor generally just causes a floating idle.

Check the integrity of the hose from MAP to throttle body. Also the connector on the MAP.

Have you snugged up your intake manifold bolts?

Done 3 and 4 in my Tips?

 

I did 3 and 4 the only connector I found that was bad was my headlight harness connector its pretty ****.

The hose to my map has been repaired with super glue and shrink see wrap. Seems to be really sturdy. I only put tiny drops of the glue on it so it wouldnt clog.

 

I havnt snugged up the bolts I will do that today.

I forgot new plug wires also

The way this thing drives is very consistant. If im light on the foot and drive slow I can pretty much make It not do it but if I try and drive like a normal person it it acts like it doeant know what to do I wish o had a tach instead of the giant fuel gauge.

 

Tightened all intake bolts didnt change although a couple were a little loose and it looked like on 2 at the bottom underneath looked like oil leaking slightly

I might just order a new map line just incase

 

2 things. Make sure that hose from the throttle body to MAP flows freely and is not clogged or cracked. Take it off and blow through it. While it's off, make sure there isn't anything clogging the vacuum nipple on the MAP.

Post 13 in my Tips addresses an issue with distributor indexing. You might check that out after the hose and intake bolts.

 

They're no longer available.

 

Not to distract from Cruiser, have you tried floor-boarding it while it's doing that? Past 70-80% throttle Renix will ignore a bunch of sensors. Mine had similar symptoms when the wires to my lower sensors under the manifold were messed up, grounding. It would start, go easy or go full out, but mess up at mid throttle. One of these days I'll un-tape that harness and see which it was that was grounding.

 

Actually flintstone if I do just about floor it, it will pretty much clear up and roar down the road as if nothing was wrong even with 33's shes pretty fast. Im gonna test and re test all the sensors on the manifold.

I did forget to mention 1 thing when im cruising down the highway it does seem to shift back and forth from 3rd to 4th until I put my foot back into it.

 

I know this is neither here nor there, but I want to clarify. The gang/harness off the injector harness to my lower sensors, (CTS, 02 and knock), is what was grounding on the heat shield, (were mis-routed), causing exactly your symptoms.

It fired the mouse nest in the air cleaner out the front grille, I drove through the confetti! No sign of the mouse.

 

Haha nice... ill take a good look at those wires tomorrow. Whats a good way to test them? Im sure ill be looking it up tonight anyway but tips always help! This is my first jeep and of course im hooked!

 

Well, between the three sensors there are at least 8 wires. With the left front wheel hanging you have better access. I'd just poke around look good for anything that might be melted, chewed, or rubbed through on anything. Even the "easy" CTS is a booger to test...the 02, testing it's 12 heater feed and ground is fun as well. (on and the third is the 5v feed from the ECU). The knock sensor....I gather you just "knock" near it with a screwdriver handle and listen for a change in the engine. I haven't tried that. Anyway just look for something messed up! Here is some sensor stuff. > http://www.lunghd.com/Tech_Articles/...iagnostics.htm

 

Awesome good stuff. It just got done raining so once she dries up a little ill get out there. Thanks for all the help

 

I noticed this, this morning when I first start it up it runs a little bit roygh and blows some gray smoke out the tailpipe for anout 20 seconds or so and and clear up and idle fine but still has a slight idle surge every say 30 seconds to a minute. Just tryin to get all the info I can out here I start school in a couple months I just need her in tip top shape