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Hello, I'm having a fit with My Jeep. It's a 2001 JGC Limited with a 4.0 inline 6.
I was pulling away from work about two weeks ago and it sputterd and died. Will restart and idle but cant put in gear and drive of rev up. I got codes, Random missfire, cam and crank sensors, #1 and #3 coils. Replaced the sensors and coil with no luck, checked fuel psi at the rail and it is perfect at 45 psi. Thinking all that was left was the PCM, i ordered on and installed it today and it still won't start up and run. I'm out of idead. Any help would be great.
Thanks,
B.
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First make sure the cam synchronizer hasn't locked up - with the cam sensor removed, does the cup spin when the engine turns? If so, set the cam sensor - line it up on zero TDC (compression, #1) and rotate the cam synchronizer until you can poke a toothpick through the sync housing AND the cup that rotates inside it.
Richard
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Ok, well we set the cam sensor, but all that did was make it start better. It was 5 deg off. I hooked up the MODIS again and have 3 codes PO353, PO351, PO352 all are ignition coil priamary circuit codes. Also was checking readings. At start up it starts and idles perfect! When you start to give it throttle the PCU goes from closed to open loop and starts to spit and sputter. If it dont die it will start to idle like it is only running on a few cylinders. Also will run lean and the injectors are way open at about 7.5 pulse width rather then the 3.5 or so that they are at when it is ideling smooth. Any help would be great.
Thanks,
B.
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What's the fuel pressure?
Richard
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46 psi at the fuel rail.
B.
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If you have a scope function, dual trace the cam and crank sensors - the cam sensor should be making its switch halfway between two of the four tower clusters drawn by the crank sensor.
You need to see what you're losing when it sputters and pops - it's either starving for fuel (injector issues?) or it's firing out of time.
Richard
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What would cause all three coils to throw the same codes though? Thanks for the help.
B.
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Check out the article on my website called "Scan Tools, O-Scopes, and Toothpicks" - I had a Jeep Cherokee throwing me ignition coil codes because of a cam sensor synchronization problem - it would drop companion cylinders and throw ignition coil codes and there was NOTHING wrong with the coils - period. Setting the cam sensor synchronizer with a scope the way I described fixed that one.
Richard
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Just looked at the article again, so was your scan tool showing the synchronizer at 0 and it still ran bad? I put it at 0 today and it still won't throttle up. It was at +5. thanks again.B.*****************************
Read the whole article - the scan tool readings were wrong - and I don't trust a Snap On scanner any more than the one I was using.
Richard
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Just wanted to thank you for all your help and let you know what I found. Well the first thing I checked was the synchronizer cup. It did move a bit at that time but not to the point I thought the gear pin was sheered, so I moved on to everything else. Well I woke up Sat. And figured I would be working all day on the Jeep and maybe find the problem. So I start with the toothpick fix and got no results. Would start and idle great, but step on the gas and it would sputter,, backfire and die.
With the backfire I knew it still had to be a timing problem. I finally decided to pull the synchronizer and physically check the gear and pin. Well I found the problem finally after three weeks of over thinking the whole thing! The pin was not sheared, but was broke to the point that when I would rev it up it could move several degrees out of time. I went to our parts room and FREE roll pin installed it and set timing and boom! Running perfect!
Thanks again for everything.
B.
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