have a 99 class a motor home with the v10. it just started surging at idle. When i step on accelerator it is fine. No CEL was present but gave me a code of 122 or TPS circuit (A) voltage input low. Unhooked battery and changed TPS. Surge still there. Next I changed the IAC thinking it might be a cheap fix. Surge still there. Next day CEL came on with same Code 122 (TPS) Thought maybe I got a bad TPS at Advanced. They swapped it out for me but no difference. I re-set CEL but problem still there.
I checked the infamous PCV hose and that is fine. Checked MAF and appears to be clean. Although I did unplug it and made no difference to engine idle. Surge
still there.
Engine surge is very quick up and down with maybe only 50 to 100 RPM's variation.
Upon cold start it will stall once. Second start is fine
Would weak COP act this way??
PLEASE HELP!
Thanks Build4

 

Weird, hope someone else has some insight. Because of what you already changed...

Bad ground? Maybe check the wiring for the TPS back to the PCM ?

 

A coil problem will usually get worse as you accelerate(under a load). It does not sound like you have a coil going out because you state that it runs fine when you acclerate.

Our new Ford COP’s, the Sultans of Spark(S.O.S.), have
been designed with both durability and performance in mind.
Please see them at:
http://www.performancedistributors.com/soscoils.htm
Quality was the main feature we stressed when we went to the
drawing board on these coils.
By the way, for those of you who only need to replace a defective coil,
our SOS Coils are available separately.

 

Had ford tek at house this afternoon with hi-tek computer laptop and ford diagnostic equipment. (great to have friends at ford garage), Everything checks out within limits except MAF sensor. It was reading 10 -14 HTZ ( think I have that right) lower than it should be.
Tek said he would bet that was the problem and if it was in the shop he would surely change MAF sensor.
Called C.A.P. and will have one at noon tomorrow.
$105.00 compaired to $265.00 at ford garage. (WOW)
Will post results tomorow.
Thanks Guys, great site
P.S. If anyone has any different ideas please let me know.

 

Clean the MAF before putting the new one in. Who knows... maybe something is stuck to it.