Slight studder at start-up

kvoriley · Dec 5, 2014

97 GT PI swap, comp cams, tuned, etc... Everything including the fuel pump and injectors is new. When I drive the car for awhile and it gets close to operating temp, I will shut it off. I get in it an hour or two afterwards, and it almost seems like its not getting fuel for about 30 seconds. Runs funny almost studders if I rev it a little, but then it drives perfectly fine once warmed up a little.
I am thinking fuel pressure regulator? It is the only thing I can think of that would be causing this issue. It has done this before and after the engine swap. But I was also looking at my fuel rail and it looks as if the fuel rail and pressure regulator are all one piece. There is no way to remove the stock regulator, but they sell a motorcraft regulator at O'Reilly's.

Cornbread52 · Dec 5, 2014

Have you checked the fuel pressure when it does this?

Ninety8stang · Dec 8, 2014

Just throwing this out there because maybe it could be a possibility but maybe it could be a faulty IAT sensor. I would just go through and clean up the MAF as well and check your tps and it's voltage. At least this way you know they are in working order and wont have to spend money. Worth a try. Could also be something in the tune.

96blak54 · Dec 8, 2014

Tru ^

kvoriley · Dec 9, 2014

Cornbread52 said:
Have you checked the fuel pressure when it does this?

I've only checked it once, and not at start up when the problem occurs. I'm going to try and catch it soon and see if there is a difference.

kvoriley · Dec 9, 2014

Ninety8stang said:
Just throwing this out there because maybe it could be a possibility but maybe it could be a faulty IAT sensor. I would just go through and clean up the MAF as well and check your tps and it's voltage. At least this way you know they are in working order and wont have to spend money. Worth a try. Could also be something in the tune.

The tune is possible, but I thought I remembered it doing this before the engine swap as well, and MAF is clean, and the only thing that hasn't been replaced is the MAF and IAT , everything else is new. What are symptoms of a bad IAT?