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Jeep missfiring and fire out of the exhaust!! Please HELP!!

8

89cherokee89

NAXJA Forum User
Location
Valdosta, GA
Well, I finally finished the AW4 transmission swap. Got it all hooked up... and then had ignition problems. Tried a few different things and it ended up being the Jeep had fouled almost all of the spark plugs. (these are fairly new plugs...)

I changed the plugs out and it fired right up with a REALLY rough idle. Any time I pushed the gas, it sounded as if it were going to die and the RPMs did not seem to go up at all. It back fired a LOT and fire was shooting out the tailpipe when I attempted to rev it.

I drove it around the parking lot for a bit at idle when the guys I was working on it with yelled at me to stop... the catalytic converter was glowing bright RED. We all figured that it was clogged up so badly that it was restricting air flow so we took it off and tried again.

Still the same problem... just a lot louder now without any muffler or cat. We tried changing the spark plug wires, the distributer rotor, the distributer cap, checked the fuel pressure... everything we could think of. Any ideas?
Please help... I miss OFF ROAD!!!
 
Plug wires in the right place? When you did the tranny swap, did you use the correct flex plate for that year/ecm? Renix and HO used different tooth patterns and aren't exchangeable. Hope that's not the problem as I doubt you want to pull the tranny back out. CPS sensor get damaged?
 
When did the HO start? My jeep is a 1989 and the tranny/flexplate is out of a 1990. Just lengthened the CPS sensor wire... hope the sensor isnt damaged...
 
Blaine B. said:
Probably something with the sensor, did any wires get swapped when you lengthened the harness?
Click to expand...

I sure hope not! I had a friend up at O'reilly auto parts offer to do it for me. He knows what he's doing, so I trust him... but I could always double check. Would that cause the symptoms described? I didn't think it would even start if the CPS wasn't plugged in properly...
 
I have no idea, I do not believe it will run with it disconnected. But I'm not sure about which wires, if crossed, would still make it able to run, but incorrectly.

I mean it is the only thing you messed with really, right?
 
like I said in your other thread and with everyone else Im still leaning towards CPS. Why did you lengthen the cps wire? My renix ran just like that, back fired, wouldnt rev and kept dieing. My CPS wasnt installed correctly, did you re-align it properly? there is some adjustment in the mounting I think. Mine wouldnt run if it wasnt picking up a signal, but the book tells me it should just guess what cylinder if it cant read the CPS. It would also back fire and miss if I held the CPS in my hand and waved it over a peice of metal, if it does have the wrong flexplate it would run like that. atleast if you do need to rip it all apart then you could check your pilot bearing anyway.

you did put in a new TPS didnt you? I dont remember your other thread but the AW$ has a different TPS that goes to the transmission also, unless your running a AWSift kit from Brent?
 
in2fords said:
like I said in your other thread and with everyone else Im still leaning towards CPS. Why did you lengthen the cps wire? My renix ran just like that, back fired, wouldnt rev and kept dieing. My CPS wasnt installed correctly, did you re-align it properly? there is some adjustment in the mounting I think. Mine wouldnt run if it wasnt picking up a signal, but the book tells me it should just guess what cylinder if it cant read the CPS. It would also back fire and miss if I held the CPS in my hand and waved it over a peice of metal, if it does have the wrong flexplate it would run like that. atleast if you do need to rip it all apart then you could check your pilot bearing anyway.

you did put in a new TPS didnt you? I dont remember your other thread but the AW$ has a different TPS that goes to the transmission also, unless your running a AWSift kit from Brent?
Click to expand...

Yessir I am indeed running that beautiful piece of equipment from Brett. There are only 3 wires going directly to the transmission with Brett's setup and those are for the three solenoids. I'm pretty sure I have the right flexplate as it came off of a 1990 XJ, the same one as the transmission.
 
Hey I know this one well, I had to reindex the dist. to solve it. Long story short I bought a dead 87. Some mechanic wanna be had removed the bracket that holds the distributor in place. They made their own custom aluminum one that was set to the correct position if you were at the front of the rig looking back not at the pass side looking to the drivers side. check this out and I would also reccomend this:

http://www.lunghd.com/On_Site_Tech.htm

http://www.naxja.org/forum/showthread.php?t=925824&highlight=stihl029

http://www.naxja.org/forum/showthread.php?t=905849&highlight=renix+files

Hope this helps, mine was a project that is now a daily driver so I had some time to work on it and work the kinks out, I have had to go through many items since it was dead when I got it, Good luck though.
 
Sorry to bring back an old thread... but I've been away for awhile. Bought a new CPS sensor and installed it today. It started... and sounded to not idle as rough, but then it would just die... only would stay started for about 10 seconds at MOST... I am so confused on what to do... could it be the flexplate? The Jeep I got the flexplate from was a 90 1/2, could it possibly be they already started putting the new flexplate on it?
 
recheck connections and distributor, fire out the tail pipe is unburrned fuel or the valve being open while the plug is firing. (timing issue)timing is controled by the CPS and flexplate matching the computer settings. I recomend putting the flex plate that was on the truck to start with back. I did the same thing but did not get any spark at all. it was frustrating and alot of work but the differance in flex plates was the whole problem.
 
Kevinma255 said:
recheck connections and distributor, fire out the tail pipe is unburrned fuel or the valve being open while the plug is firing. (timing issue)timing is controled by the CPS and flexplate matching the computer settings. I recomend putting the flex plate that was on the truck to start with back. I did the same thing but did not get any spark at all. it was frustrating and alot of work but the differance in flex plates was the whole problem.
Click to expand...

I wish I could just put the old one back on... but I just did a manual to automatic transmission swap. So I don't believe the flywheel from the manual would fit in the automatic transmission. (Please correct me, if I'm wrong) So I would have to buy a 1988/1989 flexplate.

Man, I want to get her running again!!!! It's KILLING me not to be able to drive her...
 
89cherokee89 said:
I wish I could just put the old one back on... but I just did a manual to automatic transmission swap. So I don't believe the flywheel from the manual would fit in the automatic transmission. (Please correct me, if I'm wrong) So I would have to buy a 1988/1989 flexplate.

Man, I want to get her running again!!!! It's KILLING me not to be able to drive her...
Click to expand...
To me it really sounds like your problem is CPS related. I had one of these do the same thing in my 90 because the magneto (piece on the end of the CPS) had gotten nicked off. If I revved above 1000 rpms it would shoot a flame out of the tailpipe. Check all connections again, make sure you have the CPS seated right and that it didn't break off that magneto. I really don't think that the flexplate is your problem.
 
Okay, thanks for your advice. It means more than you know! How do I know if the CPS is adjusted correctly? Basically, I just screw it on until it's tight. How do I adjust it to where it needs to be? Thanks again, everything is MUCH appreciated!
 
How do I know if the CPS is adjusted correctly? Basically, I just screw it on until it's tight. How do I adjust it to where it needs to be? Thanks again, everything is MUCH appreciated!
 
Are you allowed to lengthen the wires to the CPS? I know in the aviation business that there are several components that you cannot do that to due to changing the resistance of the wire, which changes the signal that the component puts out or receives. I would start there. If the exhaust is glowing red then your EGT is too high, lean condition (timing due to the CPS being off). Sorta contradicts the fouled plugs though. Maybe they are loading up due to the cranking without firing giving you a false indication of what’s going on.
When you got the new tranny, did you get the black plastic shield that goes around the CPS? When I did my CPS and didnt out it back on it didnt seat correctly, replaced it and it worked. Hope this helps.
 
redneck said:
Are you allowed to lengthen the wires to the CPS? I know in the aviation business that there are several components that you cannot do that to due to changing the resistance of the wire, which changes the signal that the component puts out or receives. I would start there. If the exhaust is glowing red then your EGT is too high, lean condition (timing due to the CPS being off). Sorta contradicts the fouled plugs though. Maybe they are loading up due to the cranking without firing giving you a false indication of what’s going on.
When you got the new tranny, did you get the black plastic shield that goes around the CPS? When I did my CPS and didnt out it back on it didnt seat correctly, replaced it and it worked. Hope this helps.
Click to expand...

Unfortunately, I did not get the black plastic shield that goes around the CPS... Does it go under it and allow the CPS to physically sit up higher? How does it change the position of the CPS? Also, does anyone have a part number for this piece and could this really be the problem that is causing all of this?? Thanks again!
 
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