Stall Question

[Jackpine]

Originally Posted by jconna

The first time I noticed it was backing into my parking spot at work the day after I installed my unit. This was 4 days ago and it's happened in the same scenerio each day since but today to the point of a stall. Not sure what to make of it.

As for idle.....Idle's high on start up 1300 or so and then drops down to around 600. It's habit that I never pull out before the idle down and I can't say I notice much difference now vs. before I installed the programmer. Seems to take about the same timeframe and drops to around the same level. If anything....RPM's may baseline a little higher than before. It used to drop to around 500 before I pulled out. Once warmed up.....It appears to run around 700 now which does seem higher than before. I believe even once warmed up before installing the programmer it would still hang around the 500 mark but I can't promise my memory is serving me correctly on that. Overall in answer to your question....It apears to run a little higher RPM at idle across the board.

The possible issues you are mentioning make sense as to the possible cause of the issue but I don't get why they never occurred before I installed the gryphon. All I can figure is that it modified settings based on the assumption that everything was in good working order when in fact I do have an issue with one of the mentioned. Overall I'm happy....Much better acceleration and shifting....This stalling issue has me a little concerned though. Something that is going to drive me crazy until I figure it out.

I'll try to answer your question here. The "learning" capability of the PCM allows it to cope with gradually changing conditions as the engine ages. It compensates for things like partially clogged throttle bodies and similar issues.

When you load a custom tune though, all that "learning" is wiped out, because the tune is written for a "perfect" system (you couldn't really write the tune any other way - nor would you want to). Now, the PCM can't learn fast enough to compensate for what it sees as a sudden change in component operation and the truck can run badly. I'd take a peek at the throttle body if I were you and probably look at the MAF sensor too. Here's a link to a thread on cleaning the MAF sensor: How to Clean MAF-2005 5.4 - F150online Forums It should be valid for your truck too.

- Jack