Car Running bad - misfiring when holding idle HELP!!!!!!

[Curt]

OK.....My car runs great at wide open throttle, it runs great when I am accelerating in any way. It runs fine when I am decelerating. It misfires when I am holding a steady rpm. If I am crusing and have it a 2K and hold it there without a load it starts to shake. I do not have a check engine light on. I had Hans look at it and he thought it is partially or fully because of the Fuel pressure switch/regulator and the IAC (idle air control motor). I have replaced both, and still have the same problem. The car does run alot smoother now, but still has the same problem. I have also replaced the plugs and fuel filter. If I hold the gas in neutal at 1500K rpm it misfires and will not hold steady. Car is pretty much stock, has no problems under boost. No pending codes. Any body expirence anything like this???? Thanks.


Special thanks to Hans (Deans Performance) for all his time trying to help me with this. Hans went above and beyond for me, and knows these cars in and out. Great Mechanic.

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[rdsnake]

Miles and mods? Could be a coil pack is going out. They are junk.

 

[SecondMustangGT]

Hook it to a scanner and do a mode6 that will tell you what cylinder is missing. Swap two coils and drive it and see if the miss jumps cylinders and if it does you have a bad coil most likely.

 

[Venomblue22]

had the same issue about 3 years ago, it was a bad coil, did not throw a code or nothin, but hooked it to a canner, found it was cylender 6, swaped coils found it moved, problem solved!

 

[Curt]

I had Hans run it on his scanner, but nothing came up. I will call him Tomorrow and see if he did a mode 6 scan or not. I have 40K miles, 2.76 upper, BBK Cold air intake, bbk exhaust, piggyback chip from Bob K.

 

[FuelSlut]

OK.....My car runs great at wide open throttle, it runs great when I am accelerating in any way. It runs fine when I am decelerating. It misfires when I am holding a steady rpm. If I am crusing and have it a 2K and hold it there without a load it starts to shake. I do not have a check engine light on. I had Hans look at it and he thought it is partially or fully because of the Fuel pressure switch/regulator and the IAC (idle air control motor). I have replaced both, and still have the same problem. The car does run alot smoother now, but still has the same problem. I have also replaced the plugs and fuel filter. If I hold the gas in neutal at 1500K rpm it misfires and will not hold steady. Car is pretty much stock, has no problems under boost. No pending codes. Any body expirence anything like this???? Thanks.


Special thanks to Hans (Deans Performance) for all his time trying to help me with this. Hans went above and beyond for me, and knows these cars in and out. Great Mechanic.

Did you recently change your 02 sensors? When I did my LDC cooling mod I accidently criss crossed bank 1&2 when I was reassembling the exhaust and the car ran like crap with no CEL on. I switched them back and the car ran like new. It ran like crap at low rpm but ran fine when at higher RPM's. Its just something to look at because the looms will reach to the opposite banks.

 

[Curt]

Thanks for the tip. The exhaust was on the car when I bought it, so it is possible. I dropped the car at ford a little while ago, I will see what they come up with. Thanks for the tip.

Curt

 

[Curt]

Got car back from Ford today. They admit the car is not running correctly, but can't find anything wrong. They say because it is modfied. Anyone have any advice where to go at this point???

 

[Zack]

Got car back from Ford today. They admit the car is not running correctly, but can't find anything wrong. They say because it is modfied. Anyone have any advice where to go at this point???

Did they stress test the coils?

 

[Curt]

They said they went as deep as the computer would let them. They said because I have a "piggyback" chip that they cant get all the way in the computer. I asked them to run a "mode 6" as someone had said on here and they said they couldn't. I have spent a lot of $ on trying to fix this problem, no luck anywhere.

 

[Curt]

Fixed!!!!!!!!!!!!!!!!!!!!!!!!!

FIXED!!!!!!!!!!!!!!!!!!!!!

Here is the link I found to fix it on google.

http://www.svtsnake.com/tech/

It was the mass meter, needed to be cleaned. K&N oil was making it misfire.