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1987 Cherokee Renix 4.0 - rough Idle/misfire

thanasi85 said:
Run just like an 88 I have in my driveway that needs a new motor because of blowby caused by a worn motor. That filter that was added looks like it was added to keep oil form getting into the air box which is what happens when you have blowby. Take the oil cap off with it running and see if you feel air buffing out the valve cover.
Click to expand...

This^^ could be easily solved by performing Tip 25 in my signature below.
 
Well I lost spark! Gone for a day or two. Drove me nuts and it all happened when I tried a known working distributor... Sure enough I tested everything that has to do with the dist, cps and so forth... All checked out! Finally I thought about the ground and sure enough one of the ground wires cracked off the block! Replaced it and redid all the ground wires, even added another from the block to the firewall bolt and it started right up. Still misfires but phew... It started back up!

So once I got it running I noted a leak in the Injector where I had tried a new Injector, sure enough the o ring ripped slightly and started leaking. I went to the junk yard and got a couple spare injectors and put the Injector back in. No more fuel leaking but still misfiring.

I am going to go grab a noid light tomorrow but I am now noticing that cyl 5 and 6 are not firing... Which were that way forever but when pulling wires I thought I had started at 5 but must have started at 1 and went counter clockwise around the dist cap and stopped at 3... Too many beers that night. Haha

So... I've done everything you guys have suggested minus looking for chaffing on the wire harness coming from the injectors but will do that tomorrow.

I have a different Injector in 6, and it didn't help. Really need to check the Injector harness to see if 5 and 6 are getting pulses. I know they are getting spark and I know they have compression... So either they aren't getting a pulse ( because I have tried multiple injectors) or the intake is completely blocked off at 5 and 6... I can't imagine anything else that could be wrong...

Thanks again everyone. I know I am just another guy with Renix issues... But I appreciate it and I'm learning a ton... Maybe one day I will fix someone else's problem on this forum.
 
Check for power and ground to each injector.

Check ground using an ohmeter with the engine off. Black wires on injectors.

Check power with a test light on the colored injector wires with the engine running.
 
What I did was pull the connector for the ecm and found the corresponding injector pins and checked resistance there with it still connected to the injector and wiggled the connector and wiring vigorously to make sure that the ohms never dropped out. My problem was very very intermittent and strange. It didn't make since that only one injector wouldn't be getting a pulse intermittently. One of the guys on here had suggested a weak/failing injector driver in the ecm. I tested everything and was only left with the Ecm being the issue.
 
cruiser54 said:
This^^ could be easily solved by performing Tip 25 in my signature below.
Click to expand...
I have your tips printed out and they have come in handy over the years. Already did tip 25 on the jeep in question when I did a head gasket on it. It did help but a few cylinder walls looked pretty worn when I was in there and now a year later it has got to the point where I have no compression in one cylinder now and its just missing real bad with lots of blowby.
 
So I rented noid lights to see if the injectors were getting the pulses and sure enough, they all are including 6. I did run through the distributor again because I was really shocked that 5 and 6 were out and I found that the distributor was advanced by 1 tooth. I set that correctly and I found that 5 was working normally again but 6 was still misfiring.
Since I have again narrowed it down to cyl 6, I had to go through everything one more time to make sure I didn't make a stupid mistake. I checked spark (has spark), checked compression (has 150 psi), checked Injector pule and it was pulsing and speeding up with rpm, I have tried 3 different injectors including the Injector from 5 and it didn't make a difference. What am I missing? Maybe a valve clearance issue? I am at a loss now... I was always under the impression that if u have fuel, spark and compression u would have fire? Not in the RENIX world. Haha.
 
Godenades said:
So I rented noid lights to see if the injectors were getting the pulses and sure enough, they all are including 6. I did run through the distributor again because I was really shocked that 5 and 6 were out and I found that the distributor was advanced by 1 tooth. I set that correctly and I found that 5 was working normally again but 6 was still misfiring.
Since I have again narrowed it down to cyl 6, I had to go through everything one more time to make sure I didn't make a stupid mistake. I checked spark (has spark), checked compression (has 150 psi), checked Injector pule and it was pulsing and speeding up with rpm, I have tried 3 different injectors including the Injector from 5 and it didn't make a difference. What am I missing? Maybe a valve clearance issue? I am at a loss now... I was always under the impression that if u have fuel, spark and compression u would have fire? Not in the RENIX world. Haha.
Click to expand...

Renix or not, a clogged injector will cause this problem.
 
Tried 3, possibly 4 different injectors in slot 6 and no change at all... Hard for me to believe it's an Injector...

I noticed something interesting today, when I hold a rev, a high rev, a heavy tick develops right around that 6th cylinder. Would a video of this help? With 150 compression, is it possible a valve is stuck closed or a spring is weak? Anyone have any experience with that type of symptom?
 
the plug looked a bit brown. It certainly was used so there is some sort of a fire, or intermittent fire going on I would think. It was not white and it was not oily... which is strange.
 
I think I may be onto something here... since I have been searching other forums for a couple weeks now, i finally have come accross one that seems identical to what I am experiencing:

http://www.cherokeeforum.com/f2/1-cylinder-no-fire-hole-137751/index3/

Cruiser, you were working with him on there too! You seem to be everywhere my friend, great work.

So I did take off the valve cover last week and i looked at all of the push rods and they all were in the correct place, which is different than his issue, but everything else sounds identical. What else would cause this then? Maybe a bent valve? I suppose I should remove the valve cover again and take off the rockers to investigate further. To me, i would have to think this all comes down to my intake valve. it would explain a lot!

Basically, if my intake valve is stuck closed, then the following items could be happening while I still have this issue:

-I have 150 psi compression
-the sound i hear when i turn over the engine (swooshing) would be the exhaust valve sucking in for intake slightly?
-spark checks out
-injector checks out
-cylinder is still firing but very slightly as it doesn't have the Oxygen needed and is pulling its fresh air in from the exhaust manifold

What do you guys think? Sounds like a possible culprit as I have gone through every thing else I think and it checks out...
 
So here is a video of the rockers, do you see what I see? Exhaust valve rocker isn't moving as much as the intake valve rocker...

There is a point where I am on the passenger side looking at the back of the rockers and you can see that the back of the rocker seems to be consistently as high as the intake rocker ever gets, which means it doesn't look to be sagging which would mean the cam lobe is likely OK... Correct me if I'm wrong.

So this could either be a weak spring causing an overtightened rocker arm and all the tightening is going to the spring side, or maybe a lifter?

What are your thoughts?

https://youtu.be/wXAT-TfRvsw
 
So I backed off the rocker bolt slightly and voila... I no longer have a misfire! Good news right? Now I just need to figure out which part is the issue... I have a heavy ticj and I'm not sure I like that too much.

So what is most likely of the following in your experience?
Weak spring
Bent rocker
Sticking lifter
Other?

Pretty exciting fellas! Big day! Not through the tunnel yet but I see a twinkle of light. :)

https://youtu.be/UritL_ZGsUY
 
Sounds like a lifter to me. I'm glad you've tracked down a problem thought!
 
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