MY 97 F250HD HAS A WIERD LOW IDLE-EVERY MORNING I GO START THE TRUCK & LET IT WARM UP FOR@10 MINS.WHEN I GET BACK OUTSIDE THE IDLE DROPS WAY DOWN-ALMOST TO STALL-THEN COMES BACK UP-IT DOES THIS BACK & FORTH UNTIL I BEGIN TOP DRIVE-IT DOESNT DO THIS EVERY DAY-AND IT SEEMS NOT TO BE PROBLEM WHILE I AM DRIVING-IVE HAVENT HAD THE TRUCK FOR A MONTH YET, SO ITS STILL UNDER WARRANTY-IVE BROUGHT IT BACK TO THE DEALER & THEY REPLACED THE TPS THE FIRST TIME-THE 2ND TIME THEY REPLACED THE ENTIRE COMPUTER-STILL NO GOOD-THE C.E. LIGHT ISN'T COMING ON SO I REALLY DONT KNOW WHERE TO START LOOKING

IN CASE THIS HELPS 97(OLD BODY) F250HD 4X4 351 C.I./AUTO @51K ANY HELP WOULD BE GREAT SINCE DEALER HASN'T FIGURED IT OUT YET

 

Sounds like an ignition timing problem. What is causing it i don't know, could be a variety of things. Sounds like the techs are throwing parts at it instead of trying to do a good diagnosis. The good thing is when you bring it back a third time you can threaten with lemon law. That should make them bring in there master techs and regional tech specialists, they should be able to fix it.

-Jon

 

since my last post...no problem i will wait & see if it comes back-thanks for your advice i will not be such a nice customer if i have to go talk to those knuckleheads again

 

I have a 93 5.0 4x4 and it has done the same thing since I bought it. I haven't figured out what it is either, but it doesn't seem to hurt anything. I'd like to know what it is if you find out though.

 

if it comes back i will be back at the dealership...& i will let you know what it is. hopefully it is gone forever-but i think that 's just wishful thinking

 

Mine surges (almost stalls) during warm up only if the defrost(AC clutch) is on.

I think the volt-regulator in the alternator is going bad. So I don't warm it up with defrost on.

I load tested the battery and it didn't surge for 2 weeks...this is what lead me to believe its the alternator. Charging sysytem tested good at the time of test.

Also, AC charge is low. Just a couple of things to think about.

The only bad thing that might be happening is the Cats might be loading up during this cold exhaust situation. Takes a few moments for the computer to figure out the idle, then it mellows out.

 

inski21
its been pretty warm around here the last couple of days-so i havent needed my defroster-& i havent had any problems...the next cold day(if we get another cold day) i will have to do a little experiment & put on the defroster to see if it happens again-i will let you know how it goes-thanks for the suggestions

-nate

 

Sounds like the ecm isn't compensating for the extra load that
the defrost/a/c is putting on the engine kicking on and off.Maybe the idle bypass valve is going bad or is dirty.It's one of those things with speed density does.

 

Sounds like the ISC motor. 9 out 10 times the ISC fixes idles problems when you do NOT have a check enigne light.