I recently (just the last couple days) have a up/down idle on startup. Seems worse when engine is warm. Only lasts about 15 seconds. Weather is cold here all of a sudden, dont know if this matters. (06 -E-350 w 5.4) Any ideas ?

 

Not sure what condition you're describing but if I gather correctly it sounds normal.

When engine first starts the emissions monitors are searching for the conditions in order to make real-time adjustments according to incoming air temps etc etc. Its normal at almost any ambient temp once the engine "catches" it will rev up for a few moments before settling down to its normal idle speed.

I've noticed my '03 5.4 "ramps up" when first started, the viscous fan pretty much locked and running at its full speed. Shortly afterward I hear the fan slow down, RPM's drop slightly and things are okay.

Not sure this is helpful, if your situation is different give us a bit more info please.

 

JWA- Thanks for the quick response - This is something new to my truck. When cold in the morning it has always done the fast idle for about 10 seconds and then idles down. This new thing is happening with eot warm. It will idle up & down 2-3 times within 10 seconds or so then settle down to normal on each startup throughout the day, as I run service calls. Not sure if it is a problem or not but it has never done it , at least this much that I could here it this prevalent.

 

Okay then---that's not 100% normal but if you don't yet have the CEL alerting you to something amiss I'd simply check things like air filter, gently clean the MAF, check vacuum lines especially the PCV assembly as it enters the lower throttle body.

Its also possible the Idle Air Controller is acting up but self-correcting without throwing a code. Intermittent problems or occurrences like this are tough to initially diagnose without a code.

Since this began has there been any other issues? Hard starting, significantly lower MPG's etc etc?

 

No nothing that I am aware of yet, but it just started a few days ago & I really dont check mileage, just fill it when it gets below 1/4 tank. I think I will clean the entire throttle body & maf sensor as u said & see what happens. It has never been serviced since new but only has app. 58k on the clock. Sure it is due for a good cleaning. Thanks for the help. I will post back with results either way, hopefully next week. Reps to u when I can - I,m on lockdown.

 

I am having the same problem with my 1994 ford econoline v8/351. When I start it and just let it sit and idle for a long time the idle goes faster and slower constantly in 10 sec. intervals.


I also noticed a exhaust smell coming from the motor, so I took off the interior dash and console covering the motor to expose it. If I let it run just sitting about every 10 seconds the motor gives off a EXHAUST cloud. I cant really tell what part of the motor it is coming from. Is it okay to drive it with the exhaust leaking like this OR is it some kind of health hazard. It doesn't give off any kind of a exhaust leak noise???