Metrogtiguy
New Member
- Joined
- September 5, 2011
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Well,I've been trying to help my fiancee's parents with their 2003 Mountaineer, V8, for a while now, but they kept bringing it to their mechanic buddy. $800 later, it was still stalling. I finally convinced them to let me change out their IAC, and now, it doesn't stall, but a new problem came up. When I start the truck, it sits at about 1600rpm for 7-8 seconds, and then drops down to 800 or so. I can put it in gear, and idle just fine. But the moment you take it over 15mph, the idle surges, and it will continue to hold 1200-1500rpm. When you hit the brakes, the idle stays up, and it fights you(wants to accelerate) until you get to about 5mph, and then the idle will suddenly drop to normal, and you come to an abrupt stop, because you had to push the brakes so hard to fight the engine.
So far, the MAF and IAC have been changed, new plugs, air filter, fuel filter, I've propane'd any and all hoses and gasket surfaces I can find, and have found no vacuum leaks, I've cleaned the PCV, and the TB, and checked for codes. No codes on the scan tool, and no CEL. I left the neg terminal off of the battery today for 2 hours, hoping that the computer just needed a reset, but it went back to it's misbehavior right away. Without taking into the dealer, I'm stumped on what is causing the idle to surge so bad. It's like the IAC is staying wide open, until you come to a stop.
So far, the MAF and IAC have been changed, new plugs, air filter, fuel filter, I've propane'd any and all hoses and gasket surfaces I can find, and have found no vacuum leaks, I've cleaned the PCV, and the TB, and checked for codes. No codes on the scan tool, and no CEL. I left the neg terminal off of the battery today for 2 hours, hoping that the computer just needed a reset, but it went back to it's misbehavior right away. Without taking into the dealer, I'm stumped on what is causing the idle to surge so bad. It's like the IAC is staying wide open, until you come to a stop.
I'm 100% sure it's the operation of the IAC though. I tried unplugging the IAC, and the idle drops normally. The moment I plug it in, it surges for 5-7 seconds, and then drops 
