Question , 05 F-250 , Stalls on decel.

38ryr88 · June 20, 2008

I have an 05 F-250 that cust. states stalls on decel. I was only able to duplicate the problem twice, Once cold (EOT approx 110) And once with EOT approx 150. Both times was on decel. Tried to make a recording with ids to monitor IPR % but could not duplicate problem again. Was unable to see if IPR was ramping up or not. The vech starts up again with good icp voltage and pressure. Both times on re-start all pids were good. B+, FICM L and V PWR at 12.7 volts. ICP Approx 1.7 volts and over 1000 psi. Torque Converter working properly. Contacted Hotline thinking I may have a FICM sync issue or wiring problem and was told that its most likely the STC fitting. My question is Why would the vech only stall on decel ? Should'nt I have a long crank or no start concern when warm ? I am sure I am looking past something here but just not quite sure what, Thank You for any help.

Keith Browning · June 20, 2008

I am guessing the lack of any mention of DTC's means there were none to point you in a direction. Does your shop own an VDR? IF it were me I would install our VDR and drive it, have someone else drive it while I continue to work or send the customer off with it and instructions on it's use.

Obviously my answer to you is to attempt to record some data. Not so sure I would agree that a STC fitting is the cause because stalling on decel is not something you hear as being associated with fitting failures, but it is possible. The few I have seen over the years were caused by sticking IPR valves ohhhhhhh and maybe one or two biased ICP's.

mchan68 · June 20, 2008

I had an '05 F-350 about two years ago, that took two visits for me to verify and identify the symptom and the cause. The complaint and symptom was exactly as you describe. And just like yours, it was very intermittent in nature, leaving no DTCs to look at and very difficult to recreate. After some wiggle testing, I finally found it at the FICM harness. I guess the harness was shorting out on one of the intake bolts. Replacing the 9D930 injector harness fixed it. Like Keith, I highly doubt an STC fitting failure would cause what you describe. Shows how little hotline knows. Hope this helps.

38ryr88 · June 21, 2008

I finally got a recording this morning when the engine stalled. Sure enough, The icp starts dropping off as the rpms drop and then the IPR ramps up to about 84% . I found the stc fitting still attached, But barely. It practically fell off when I removed the pump. Dont know if the motor was flexing foward on decel causing the fitting to seperate from the pump or not. I guess we will all have to form our own opnions on this one. Thanks again for the the help gentlemen !

Keith Browning · June 21, 2008

I guess we will all have to form our own opinions on this one.

Live and learn - that is why we are here - no? I still say it is unusual for an STC fitting but now we know better. /forums/images/%%GRAEMLIN_URL%%/wink.gif

Mekanik · June 21, 2008

I'm suprised that the truck started back up after stalling with a STC fitting as bad as your describing. I would have guessed that your losing sync. Maybe rust build up beetween the cam or crank sensor and the block or maybe a bad IPR. But, its fixed. Thats the important thing.

Jim Warman · June 21, 2008

I am surprised that a tech would say "I am surprised about <this>". We live in a world of absolutes.... they can be strange... they can be gnarly... they can be extremely hard to isolate... but it will always be "cause and effect".

Back when I was 20something, I knew everything there was to know... Now? I am old and STUPID.... I can usually be heard to utter "show me"....

A guess is a guess (and this includes guesses that EXCLUDE things)... A guess with evidence is an assumption.... I hope we are all familiar with the ass/u/me conumdrum. An assumption with evidence is a diagnosis....

We have a LOT of hours into a late build... What I am seeing currently defies description.... I'll post more when I have the empirical evidence I desparately need....

Back to topic.... never, EVER discount any possibility... While we didn't take journalism in school, we still ask who, what, where, when and why an awful lot....

BrunoWilimek · June 23, 2008

Back when I was 20something, I knew everything there was to know... Now? I am old and STUPID.... I can usually be heard to utter "show me"....

Back to topic.... never, EVER discount any possibility... While we didn't take journalism in school, we still ask who, what, where, when and why an awful lot....

This hold true especially for the 6.0. It seems to be able to learn new random tricks on a continuing basis.

Tony302600 · June 26, 2008

Hotline told us how to diagnose a bad STC fitting when stalling hot. Brake torque the truck and quickly release the throttle, if it stall's the fitting is more then likely bad. In essence that is kind of what might be happening when the guy is decelling. /forums/images/%%GRAEMLIN_URL%%/2cents.gif