Some background info: I have a 2006 Mustang GT Automatic with 126,000 miles on it. Simple engine mods on the car are K&N Intake with Brenspeed Tune, Borla Mufflers, Ford Racing Shorty Headers. Recently got the car back from a transmission rebuild from a reputable transmission shop backed with a 2 year/24,000 mile warrenty. The mechanic mentioned something about a slight stumble in the engine after test driving it.

The Problem: The car shakes slighty (stumbling) during idle (sometimes intermittenly). The car is idling @750rpm. Also, WOP acceleration feels really rough. The power is definitely missing. The car has no problem starting up, nor does it stall during idle.

The only codes that have popped up so far is Evap P0455 and P0451. I have not seen any DTC's for misfires.

I have already replaced the fuel filter, did an oil change, change the oil filter, cleaned the MAF sensor, but still no improvement. I still need to check the spark plugs, coil packs, and clean the throttle body. I'm thinking a vacuum leak could also be the culprit? I will check for that also.

My question is, would codes P0455 and P0451 have anything to do with the engine's performance the way I described it?

 

Some background info: I have a 2006 Mustang GT Automatic with 126,000 miles on it. Simple engine mods on the car are K&N Intake with Brenspeed Tune, Borla Mufflers, Ford Racing Shorty Headers. Recently got the car back from a transmission rebuild from a reputable transmission shop backed with a 2 year/24,000 mile warrenty. The mechanic mentioned something about a slight stumble in the engine after test driving it.

The Problem: The car shakes slighty (stumbling) during idle (sometimes intermittenly). The car is idling @750rpm. Also, WOP acceleration feels really rough. The power is definitely missing. The car has no problem starting up, nor does it stall during idle.

The only codes that have popped up so far is Evap P0455 and P0451. I have not seen any DTC's for misfires.

I have already replaced the fuel filter, did an oil change, change the oil filter, cleaned the MAF sensor, but still no improvement. I still need to check the spark plugs, coil packs, and clean the throttle body. I'm thinking a vacuum leak could also be the culprit? I will check for that also.

My question is, would codes P0455 and P0451 have anything to do with the engine's performance the way I described it?


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P0455 is a possibility, have you checked your fuel filler cap making sure its closing properly? If you havent changed spark plugs yet then theyre due for a change.

 

I've checked the gas cap to make sure its closed properly. I've changed the sparkplugs @ 100,000 miles. Used Champion Spark Plugs

 

http://engine-codes.com/p0451_ford.html

 

I just finished cleaning the throttle body and turns out it was really dirty. The tb gasket also had some dirt around it. One thing I noticed is that the idle during park is @750rpm and around 500rpm when I put it in drive.

Any recommendations?

 

Idle is higher in Park than drive on every vehicle I've never been in.

 

How many threads are you going to start?

 

It's normal for the idle speed to drop when you put the shifter into D and the engine becomes coupled with the transmission.

 

I didnt know you were the thread police