6.0 No Idle, Runs all day when held above 900 rpm

Moremph · Jul 2, 2013

We have been tinkering with a truck off and on for a while now, Its been to three other places and nobody has a clue (or the only recomendation so far was the tone ring on the cam gear is off/bad)

The thing will sit and run all day long as long as you hold the RPM above 900 rpm, The moment it drops below 900 it shuts down, we have checked and tried about everything we can think of with no real help, It seems to me that it has to be an electrical issue breaking down somewhere when it dies the FICM sync goes to No at the same time with my VCM2.

I found one other thread on the nation about a similar issue truck would run when held above idle but die, That poster never posted the final answer and was a one post wonder.

If you program the ECM with a SCT and set the idle to 925 will start and run all day long,

Tried new ficm, throttle pedal, checked most wiring easily reached for chaffing tried starting with each injector unplugged individualy. All the sensors appear to be in spec and not crazy out.

I am sure someone else has seen this before

Thanks Travis

ghohouston · Jul 2, 2013

Check fuel pressure? Ive never quite experienced this on a stroke, but have seen big truck get a hole in a fuel feed line and did the same thing. You may check crank and cam sensors are in sync... also, have ylu checked ficm voltage?

Gary · Jul 2, 2013

Ok, so when it drop below 900 rpm sync switches to No, I'd say that means your loosing CMP or CKP, I know CMP specs says 800-1000 ohms, I once had a no-start and the CMP was 830 ohms so it was with in specs but that was the problem. What are your ohm readings on the CMP and CKP?, I'd check them at the sensor and PCM.
I think loosing the sync is your problem, the engine has to have both signals so it knows where its at in the firing order - because 720 of crank=360* of cam rotation, IDK if that makes sense to you??? basically its compairing the position of the cam to the crank so it can tell if a cylinder is on compression or exhaust stroke.
Hmmm... But it has to see sync when cranking to start and you have that or it wont start..

Vozar · Jul 2, 2013

what year truck travis?

Big Angry Hillbilly · Jul 2, 2013

Pull cam sensor. Check mounting flange for flatness. (On the sensor). Make sure mounting surface on block is rust free. Look in bore for sensor. If there is rust in bore remove cam sensor o rings and reinstall sensor and see if it runs.

Sounds like the cam sensor is being pushed away from the cam. Higher rpm signals are what's keeping it running.

04stroker · Jul 2, 2013

Whs^^^ check the cam sensor for all those things and wouldn't hurt to check the crank sensor too. Also if/when testing those circuits I would recommend load testing them.

Moremph · Jul 3, 2013

truck is a 2006. new cam and crank sensor from ford. pulled harness and stripped back all the way from ecm to cam and crank sensors. made new wiring from ecm directly to the cam sensor. watched tone wheel with bore scope, all good there. during cranking cam/crank sync is hit or miss but once running it stays in sync. if watching cam/crank sync and ficm sync with ids during running both stay in sync until the rm drops below 900. then ficm sync falls off but cam/crank sync stays. not sure if thats because its happening so fast or not.....
Thanks, Travis

DieselDave · Jul 3, 2013

change your IDS from YES/NO to Graph form and you can slow in down on recording. once is dies does it Start RIGHT back up? Also monitor you RPM. See if its erratic.. Aside from the SENOR or WIRING concern almost sounds like a Low or High Pressure Oil concern....

Any Codes AT ALL?

Moremph · Jul 3, 2013

Will Start back up immediatly, hot cold dont matter, makes desired psi, I believe we have pressure checked this truck already as well

Thanks for the idea on the ids ill try that
Travis

Big Angry Hillbilly · Jul 4, 2013

Look up the bore for the cam sensor for corrosion. It will push on the lower o ring and cause the air gap to increase.

sergio · Nov 20, 2023

Moremph said:
truck is a 2006. new cam and crank sensor from ford. pulled harness and stripped back all the way from ecm to cam and crank sensors. made new wiring from ecm directly to the cam sensor. watched tone wheel with bore scope, all good there. during cranking cam/crank sync is hit or miss but once running it stays in sync. if watching cam/crank sync and ficm sync with ids during running both stay in sync until the rm drops below 900. then ficm sync falls off but cam/crank sync stays. not sure if thats because its happening so fast or not.....
Thanks, Travis

I have the same problem .. did you fix it ??