03 Gt Woes

Recently got into mustangs...but not to automotive performance.

Recently bought an 03 gt with a leaking intake manifold...

I replaced that with a new frpp manifold.

Before the swap I had a condition where it would stumble at idle a little, then during wot pulls it would act as if it were starving for fuel.

I really figured the leak was soaking a plug or two causing a misfire. I blew the plug bores out with air when I had the Mani off and got some liquid out of a couple.

I put it all back together and everything went smoothly. I replaced the gasket on the IAC simply because the ford store didn't have a valve on the shelf.

Long story short, with the new intake and dry plugs, I've still got a stumble at idle, which according to my live wire, is around 680-710rpm.

Anyone wanna guide me to a starting point? Are these 2v coils known for breaking up?

I have several k$ worth of diagnostic tools, but I don't have an IDS, so I can view most anything, just can't flash.

Any advice is welcomed.

Thanks

Adam

1987stangman said:

Codes? Check for them even if no SES light is on. I would replace the plugs First and test. Then start looking at the cops.

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No codes. No misfire data...no misfires...according to the ecm at least.

Plugs are new.

jcgafford said:

Those 4.6 liters are known for a couple different spots that fray vacuum lines and cause problems like this. Also if the iac is not a fomoco part I bet it is either causing you problems or is about to and it will not throw a code

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It is a fomoco part...how old it is I can't say.

I do have it running pretty good now. The short eBay cai that the po put on it went away and it got a better one from late model...that made a good bit of difference.

Cleaning the maf made the most difference however