Guess what?? another renix low rough idle.

[Ecomike]

Once you have the injectors properly, run some seafoam (or equal) through the intake to clean the injector heads and valves. Then change the oil as it may be diluted with traces of unburned gas. I was thinking of suggesting the injector wires be checked. Congrats on finding one of the issues. Those spring washers are a MUST!!!

 

[AKghandi]

I'm pretty close to oil change time again so I'm going wait till some more leaks out and put some MMO in and run it for a while.

I haven't seafoamed it in a few months so I may do that too.

It'll be good to have the egr system back in order. not really sure its going to help with my idle but who knows maybe it functions in some strange way I don't know of. I read that it only functions at cruising, but I have also read it opens at idle??

I'm going to put everything back to stock and hope an issue pops out. maybe my manifold is cracked and i didnt know about it or maybe its withcraft.

I was reading through another thread where his misfire was caused by a lifter issue, I know I have a lifter on its way out. sounds almost like a rod knock but it clattered and then got quiet one morning so I think lifter. I was planning on putting in a cam anyways but that will have to wait till taxes.

going to swap in the other eventually motor just to be safe. mine has had a hard life.. and I might just have to turn it into a stroker at some point

 

[AKghandi]

Put about a half quart of MMO in the oild and the rest in the tank. No real difference. Yet.

Also gas mileage seems to be again improving. But that may be because i switch to shell gas. There was a noticable difference.

my friend has a 90 cherokee with nearly identical symptoms. Low idle with slight misfire and his even stalls occasionally.

And i noticed my other cherokee thats also a 90 has a bit of a low idle. Its been shop maintained with an easy life.. no.misfires and it runs great but the idle is a bit low.

 

[blondejoncherokee]

ill be watching this thread to see what fixes it. good luck.

 

[AKghandi]

the only issue i know of so far is low voltage to the o2 heater. im going to run a new wire from the relay to the O2 heater.

I dont think its going to fix it. but who knows.

The only thing i can think is the ECM not being able to regulate the idle or timing.

 

[blondejoncherokee]

the only issue i know of so far is low voltage to the o2 heater. im going to run a new wire from the relay to the O2 heater.

I dont think its going to fix it. but who knows.

The only thing i can think is the ECM not being able to regulate the idle or timing.

interesting. I need to test my o2 next . Ill have to reread the thread to see how to route that wire and what not.

 

[AKghandi]

Things keep getting weirder and weirder...

I decided to pull the relays back up and see if I could see anything obvious. which I did, but thats not the issue, I dont think it is anyways.

this is the diagram showing what relay is what. there is another that shows the ac and o2 relays switched but i tested them and this shows the ac relay in the correct spot.

here is a pic of my relays.

the relay that is missing is the one that when pulled stopped supplying voltage to the O2 heater. exactly 5v. key on not running.

as you can see there is a bit of insulation damage to the large wire. in the middle

according to that diagram, that would be the power latch relay.

also the far left relay the one the diagram shows as the O2 heater only gets 10.5v out of 12.3 the other relays are getting 11.6-12

but to me that looks like a fuel pump relay as it has the largest wires.

I am so confused right now. :banghead:

I am reviewing the FSM now

 

[AKghandi]

so after some mindnumbing research turns out that according to that diagram my power latch and O2 heater relays are backward of eachother. fuel pump and ac are correct.. wow jeep good quality control.

 

[AKghandi]

More discoverys. i am getting 14v (engine running) at every pin on the O2 heater relay. one of them should be ground.

And yet, i am getting 14v to d2 pin 9.

 

[cruiser54]

Got a pinched harness somewhere?

 

[AKghandi]

Well just for giggles I hooked a wire from the d2#9 connector straight to the O2 heater.. still getting 9v... hmmm so I ran a new ground to the O2 sensor. bingo 14v running. where does the O2 ground? at the dipstick with the others? either way I think I'll leave this new ground.

the other day I got an NTK O2 and took back the Bosch.(theres a seller on amazon with the NTKs for $24)


Now here's the strange part. truck spit and coughed and popped through the intake 3 times, then smoothed out. seems to be running better. will find out when I run through this tank of gas.

however, the idle still dips down and has a misfire. the miss doesn't seem as bad but its still there.... I'm getting tired of this.

installed an autostart today. strangely when its running with the autostart the idle goes way down to nearly stalling then comes back up every once and a while. but it doesn't do it if I just start the truck normally.

 

[blondejoncherokee]

I figured mine out. I had my throttle body bored out a while back, and the idle bypass screw was epoxied off and bypassed, guy adjusted the new throttle plate, but it must have been off. well , i cleared out the epoxy and cut down the screw and adjusted it, now it idles perfectly at 750 all the time. I also jumped the ground wires at the MAP sensor, (already did the tps). I also put in an accel cap and rotor and a some 8.2mm plug wires. also added a ton of MMO to the oil and a some BG44k to the gas, which also might have helped . rig idles great all the time now, even in the snow.

 

[AKghandi]

So new development.

it is now idling down to near stalling and then catching itself. with the IAC UNHOOKED!

how????? what could cause this??

this started after i hot wired the O2 so I unhooked the positive wire from the d2#9 to the large wire on O2. left the new ground tied into old ground.

getting 14v running at O2 heater.

My thought is maybe the ground for the heater/sensor is crossed with another wire somewhere but then this would be constant right?
but it is not constant, it varies. I went for a drive and came back and then it idled at 1100. then it dropped to 950.

it would have to be timing or fuel right? I can hear the pump sound change when it idles down but that may just be from lower voltage due to not spinning the alternator fast enough.

the pump is only 5 months old and the ballast resistor is bypassed.

that leaves timing. no knock sensor, distributor indexed, new ICM and coil.

heres a short video https://www.youtube.com/watch?v=ftVDM408wWk

 

[Ecomike]

First off the computer still has fuel injection flow rate control and ignition timing control that can change the idle speed. The MAT temp sensor can send the ECM on a wild goose chase with the idle speed wandering. The IAC valve is not the only control of idle speed. I had a dying ICM do that until I got no starts and finally a complete no start. So a random weak spark, bad plug wires, bad rotor at cap leaking spark to ground randomly will do that. Variable fuel pressure or a variable vacuum leak will cause these issues. Problems with the O2 sensor or its circuit can also cause issues like that. The O2 sensor has a 14 volt and a 5 volt power source and only one ground!!!! Check all three. The O2 sensor may be going bad, as in the resistance heater inside the O2 sensor may be failing?

Your disconnected IAC test confirms the IAC is not the droid you are looking for!!! Try that same trick with the O2 sensor!!! Disconnect it and see if the idle is stable!! But this will not work on the ICM, LMAO!!

 

[cruiser54]

You have or have not indexed your distributor?

 

[Ecomike]

You have or have not indexed your distributor?

Watching the video it does not look like a distributor issue?

 

[cruiser54]

Just asking for clarification

 

[AKghandi]

The distributor has been indexed. Though it never seemed to make much difference.

O2 sensor is NTK and only about 4 days old.
14v,5v,and ground are all good.

Icm is only about 3 months old.

Cap rotor wires and plugs are only about a month old.


Problem persists with every sensor unhooked save the crank pos sensor.

MAT is clean and tested good.

 

[Ecomike]

The use a volt meter under the hood to watch for voltage drop points when the idle drops. Check the O2 sensor wires for a bad insulation spot where the wires rubbed on the drive shaft, steering shaft or exhaust manifold and randomly ground out for a moment. Check the battery and alternator too. Look for a vacuum leak that randomly closes off dropping the idle. And give the injector connections a wiggle to see if they are loose and cause an idle change on wiggling. Does it have good power at higher rpms, if not check the cat converter for a bust cat section that moves around and chokes off the exhaust randomly....lots of gremlin hiding spots.

 

[AKghandi]

Well i drove the truck for about an hour tonight and after its warmed up completely, it idles smooth-ish, though very low

I hooked the IAC back up.

according to the volt gauge the volts stay around 14. unless it idles really low for a while with the accessories on then it dips but doesn't seem to affect the idle when warmed

I read through the FSM and turns out the O2 heater turns off when the ecm senses it can stay warm enough on its own.

But, what i cant understand is what is causing this issue.

I'm about to buy a whole new engine harness and just switch it.

battery and alternator are new


Has great power under part and full throttle, though randomly it seems to have a flat spot just off idle. but its very slight and very random