Urgent Advice Needed. Limp Mode...

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Proby34

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To check for a bent valve just check compression if the timing was off more the 1-2 teeth its almost certain ya bent one. Does it run smooth tho?
How would I know it it is an exhaust or intake valve?
 

Sherman Bird

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I dont even know what you are talking about? explain some more lol
I've seen this code as a "false" or phantom code many times . If you have Coil bleed-over, or inductive interference (EMI), the computer will "see" the inducted current as voltage on whichever affected circuit is involved. This can and will trigger a false code because the computer sees higher voltage as a spike than is programmed into the program parameters, and sees this as a circuit problem.

I have a customer where EMF from ignition coil bleed over from the coil pack on a Ford actually knocked out the PCM! I have another customer with a later model Jeep where this EXACT 344 code set and it turned out that the coil pack was bad and the EMF was crossing to the crankshaft/ camshaft circuit causing this code.

As for cam/ crank correlation, that also requires a scope to definitively diagnose.
 
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Proby34

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I've seen this code as a "false" or phantom code many times . If you have Coil bleed-over, or inductive interference (EMI), the computer will "see" the inducted current as voltage on whichever affected circuit is involved. This can and will trigger a false code because the computer sees higher voltage as a spike than is programmed into the program parameters, and sees this as a circuit problem.

I have a customer where EMF from ignition coil bleed over from the coil pack on a Ford actually knocked out the PCM! I have another customer with a later model Jeep where this EXACT 344 code set and it turned out that the coil pack was bad and the EMF was crossing to the crankshaft/ camshaft circuit causing this code.

As for cam/ crank correlation, that also requires a scope to definitively diagnose.
Thanks, im leaning towards a bent valve and Im gonna load test my battery because i messed up timing once, so that probably bent my valve(s). but imma check battery to ensure it hasnt gone bad at all. Thanks for the input as I will keep it in mind if something doesnt go as planned!
 
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Proby34

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Jut run a compression test if one cylinder is low that head has to come off to see what valve.
Thanks. Does compression vary between each truck, or should I be looking for a baseline number? Obviously is all are the same except for one ill know, but just curious.
 

Sherman Bird

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Jut run a compression test if one cylinder is low that head has to come off to see what valve.
Get in your truck. Floor the accelerator. Crank the engine. It will crank, but not start because, due to it being floored at the time you turn on the ignition and crank it, the computer will "clear flood". This is how one clears a flooded modern DOMESTIC car. Most imports do NOT have this function. While it cranks over, but will NOT start as long as you KEEP the accelerator floored, listen to the "cadence" of the cranking sound. A steady cadence INDICATES normal relative compression across the board. IF the engine has a split second rise in cadence, this indicates a low cylinder due to a mechanically lower compression.
IF YOU LET UP ON THE ACCELERATOR EVEN FOR A SPLIT SECOND DURING CRANKING, THE ENGINE WILL START AND OVER-REV. It is CRUCIAL to make sure the accelerator stays floored!
 
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Proby34

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Get in your truck. Floor the accelerator. Crank the engine. It will crank, but not start because, due to it being floored at the time you turn on the ignition and crank it, the computer will "clear flood". This is how one clears a flooded modern DOMESTIC car. Most imports do NOT have this function. While it cranks over, but will NOT start as long as you KEEP the accelerator floored, listen to the "cadence" of the cranking sound. A steady cadence INDICATES normal relative compression across the board. IF the engine has a split second rise in cadence, this indicates a low cylinder due to a mechanically lower compression.
IF YOU LET UP ON THE ACCELERATOR EVEN FOR A SPLIT SECOND DURING CRANKING, THE ENGINE WILL START AND OVER-REV. It is CRUCIAL to make sure the accelerator stays floored!
I’m just gonna get a compression tester lol. Thanks tho
 
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Proby34

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Battery load test was good, so not that electrical issue. I checked all the wiring and all the sensors. Everything is plugged in and good. Im gonna check continuity in the wires at the cam sensor next as well as the compression test. I started it for the battery test and was feeling it while it ran and you could feel a bit of a miss and a decent shake. Hopefully compression test tells me something.
 
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