leon Posted October 28, 2008 Share Posted October 28, 2008 I have a 04 f250 that when starting sometimes, the engine rpm's slowly go up to idle speed. other times when it stars "normally" rps ramp up and then go down to idle speed, (I hope that makes sense). There are no cmdtc's or on demand codes, engine seems to run normally and this may happen warm or cold, when monitoring pids found that ipr commanded when this happens is less than 40% during crank mode. when it starts normally it goes over 75%. monitored ficm synch, rpm, icp, ipr vpwr, vref, and cannot come to any conclusion, changed to 10/30 rotunda still does it, any ideas? this is one I havent seenbefor it has 70k on odometer and looks pretty well taken care of. Quote Link to comment Share on other sites More sharing options...
Alex Bruene Posted October 28, 2008 Share Posted October 28, 2008 Is it an early or late build? What is the ICP doing during the concern? Quote Link to comment Share on other sites More sharing options...
leon Posted October 28, 2008 Author Share Posted October 28, 2008 icp stars at .24v and goes to 1.06 when this happens (800psi) builds within 1.5 seconds Quote Link to comment Share on other sites More sharing options...
leon Posted October 28, 2008 Author Share Posted October 28, 2008 it is a late build (icp and connector have been changed also ipr valve, (hotline recommended) Quote Link to comment Share on other sites More sharing options...
leon Posted November 10, 2008 Author Share Posted November 10, 2008 ok same truck, when this happens it runs on 3-4 cyls, really struggles to keep idling, cannot perform power balance test when this happens, also found a very strange pid condition, synch pid will read no but ficm synch will read yes, wtf? have swapped pcm and ficm and it still occurs, ficm voltages are normal when this occurs. this one is starting to get to my head!! Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted November 10, 2008 Share Posted November 10, 2008 Leon, if you think you have a SYNC problem print out this diagnostic sheet: sync.pdf We beat the hell out of this topic last year... Quote Link to comment Share on other sites More sharing options...
leon Posted November 10, 2008 Author Share Posted November 10, 2008 thank you, it seems like I am always running into something a little different on these things. I am ready for some straight forward repairs for a while at least. Quote Link to comment Share on other sites More sharing options...
leon Posted December 2, 2008 Author Share Posted December 2, 2008 ok, I feel compelled to let anyone interested know what fixed this one. first off, late build 04 with a 6speed 4x4, at times at start it will run verrry slow (150-300 rpm's) when this happens synch pid goes to no ficm synch yes, and yes it is still running, do not loose cam or crank sensor to pcm I swapped both cam and crank sensors with another truck no difference, overlayed wiring from both sensors to pcm again no difference, attempted to move crank trigger wheel...no movement tried a different pcm and ficm..does anyone see the desperation in this yet? thank goodness for a donor truck that was available during this trucks 4week stay. multiple calls to hotline and fse visited for one day all of us were still scratching our noggins. then...one time while it was doing this I was playing with the ignition witch and the starter engaged for a moment while it was running, and BAM! it came out of its fit. I was able to do this every time. this truck had a dual mass flywheel and at times on start it would do some sort of crazy resonance shit to the crank and cause it to loose sync a single mass flywheel and clutch fixed it... that should have been my first thought, what a moron! Quote Link to comment Share on other sites More sharing options...
mchan68 Posted December 2, 2008 Share Posted December 2, 2008 this truck had a dual mass flywheel and at times on start it would do some sort of crazy resonance shit to the crank and cause it to loose sync a single mass flywheel and clutch fixed it... that should have been my first thought, what a moron!AAAHHHHH the old dual mass flywheel. Reminds me of the pre-'99 F-series trucks equipped with manual transmissions. I used to change A LOT of those before Ford went to the single mass flywheel when the '99 to '03 trucks were introduced. I actually miss those days. I wonder why in the hell they would go back to the dual mass flywheel setup when the 6.0L was introduced. Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted December 3, 2008 Share Posted December 3, 2008 Glad to hear you figured it out even if it did kick your ass. We've all been there. I actually had a customer tell me I was an idiot when I diagnosed his rough idle as a bad flywheel. That is a symptom I doubt I will ever forget. Quote Link to comment Share on other sites More sharing options...
leon Posted December 3, 2008 Author Share Posted December 3, 2008 keith, I too have had a few 7.3l with a rough idle caused by sloppy d.m. flywheel but this one was nothing I mean nothing at all similar to those. Also how does the engine run with the sync pid at no? Thanks for your input Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted December 3, 2008 Share Posted December 3, 2008 That is a good question and I don't know the answer. I might assume that if the engine starts and then loses SYNC then it may continue running with an inferred value... maybe? Kinda like the gas engines with EDIS that if the cam sensor signal was missing the PCM would guess and you had a 50/50 chance of it starting? I have yet to see a 6.0L with a stick shift. All I can do is make comparisons to what I have seen. Maybe someone else here knows. I do know I have had trucks run poorly and trucks stall when losing SYNC. If I recall the one with the rusted block pushing the CMP sensor was one of them. When cold the engine had no SYNC at cranking speed but when started with "an alternate fuel source" it would start, lose SYNC but continue to run with the MIL on. Once that truck warmed up it started and ran, with a lack of power, but it ran. That was a case of a weak signal caused by too large of a sensor. In this case, the flywheel was causing erratic crankshaft variations which created a wacky signal. We often see one or both of the CMP or CKP signals when an engine has a serious misfire, low RPM's or stalling. It's when we see these codes with no other DTC's that things get interesting. We had quite a few topics on diagnosing this with the oscilloscope. Quote Link to comment Share on other sites More sharing options...
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