06 engine misfire, speedo and tachometer dropping

tr21triton

tr21triton

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Blue Ridge, Ga
my brother bought a 06 6 speed with 91k miles rubi yesterday and on the way home it started skipping and the speedo was dropping off. he got it here and I checked the wiring behind the valve cover and the harness had a bridge that keeps it way away from the studs. i took it for a drive and couldn't make it act up in 30 miles. this morning he left for home and it started cutting out . he says it seems to do it when accelerating hard heading uphill, the cel flashes but wont leave a code. i did unplug all the connectors to the pcm and plug them back a few times thinking it would improve a dirty connection if that was the problem ...no change .
 
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@tr21triton Do yiu have anything hooked up aftermarket? Check all powers and grounds. How old is the battery? If it is over a year or you don’t know it’s history, change it. Wranglers are very temperamental on voltage and sometimes it’s easier to find Waldo than a wiring issue on Jeeps.

Pcm failure in 05/06 TJ’s are:

Autos:

Hard shift from 1st to 2nd when cold, o2 sensors showing bad when good, high transmission temperatures and 1600 codes.

Manuals:

Stalling while driving, o2 sensors and loss of guages (usually fuel tank.) you can also tap on a manual pcm with a screwdriver handle and it will die.

Ask your brother to call the seller to confirm if any of the above symptoms were present. Hopefully he will be honest and then let me know what he finds out.

Thanks,

Mark
 
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Wranglerfix said:
@tr21triton Do yiu have anything hooked up aftermarket? Check all powers and grounds. How old is the battery? If it is over a year or you don’t know it’s history, change it. Wranglers are very temperamental on voltage and sometimes it’s easier to find Waldo than a wiring issue on Jeeps.

Pcm failure in 05/06 TJ’s are:

Autos:

Hard shift from 1st to 2nd when cold, o2 sensors showing bad when good, high transmission temperatures and 1600 codes.

Manuals:

Stalling while driving, o2 sensors and loss of guages (usually fuel tank.) you can also tap on a manual pcm with a screwdriver handle and it will die.

Ask your brother to call the seller to confirm if any of the above symptoms were present. Hopefully he will be honest and then let me know what he finds out.

Thanks,

Mark
Click to expand...

had red top battery tested yesterday and they said it was 85% and the alt. was going bad. we changed the alt. last night .. i did notice the volt meter was slightly below 14 but just a hair below... thanks for your fast reply...
 
tr21triton said:
would that also cause the speedo and tach to act the way it does in the video ?
Click to expand...

I reread what you posted above and while the misfire could be O2 sensors related; I am leaning more towards the PCM and wiring.
I read that you disconnected the wiring harness connectors from the PCM and reinserted several times.
Disconnect them again and do a thorough inspection for oxidation or loose wiring gong into the PCM.
The problem that is causing the tach and speedo needle drop (perceived to be a misfire) is related to the loss of PCM signal.
As @Wranglerfix posted above; the 05 & 06 PCMs are know to have problems with the circuit board and terminals.
 
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the battery is 3 1/2 yrs old so he is going now to get a new one. i told him to check/clean the frame grounds before installing it. will keep ya posted if that helps ! thanks
 
Well it threw 2 codes.

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first thing Monday morning I called mark at @Wranglerfix . we came to the conclusion it was the PCM. he said he would send me one . by coincidence I saw on another thread the rebates on the xp985 plugs and told my brother to stop on his way home Sunday and get a set and he did. Guy's I cannot praise Mark enough within a hour of talking to him i had a tracking # and it's on the way :D HOLY JESUS THATS SERVICE !!!!!! Mark thank you so much for your knowledge and outstanding service . so my brother gets home after work monday and changes the plugs and they were the originals :eek: forgot to say he took it for a ride before work and it also threw a P0305 cyl. #5 misfire. so after swapping the plugs he took it for a ride and all systems for a emission test showed ready :D he runs it to the testing place and it passes, THANK GOD, EMERGENCY BY GOD SITUATION DIVERTED and he can get his tag ! :cool: I've told him to keep that PCM because I'm fairly sure that problem is going to return and the PCM's for manual trans are getting rare and he will have this vehicle until he dies ! but once again I can't praise Mark and his business enough !!!!!!!

35752.jpeg
 
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