95 GT misfiring pretty badly

[95Grandtouring5.0]

I have a 95 gt with a mild hci set up, it was dyno tuned and put down 281hp and 305rwtq. After I had it dyno tuned it ran the best it ever had, but since about the middle of summer I've had nothing but trouble with the car. Running pig rich and generally just didn't feel as fast as it did. I took it out about a month ago, and decided to get on it a little bit at a stop sign ( During summer my car normally burns the tires in first and second easily, and it was only 20degrees out when I did this). I nailed it in first and it didn't spin at all, then I hit second and it chirped and when I let off i could feel that it was missing when it idled and when you drive it around regularly. However, if you nail it then it doesn't misfire. But if it is idling and regular driving it's pretty bad. Now I know I have a bad IAC on the car, but I don't think it would miss like this. I was almost thinking it was a vacuum problem, but I sprayed some injection cleaner around all my hoses and didn't find any leaks.

Any suggestion would really help I just want this car to run right

 

[CC'S95GT]

clean the maf first, and tune up.
How old is the coil?

 

[95Grandtouring5.0]

Plugs, wires and cap and rotor were put on it during the summer. The coil is probably a few years old. I'm just confused as why the car doesn't miss when you go wot.

 

[castine917]

I have a 95 gt with a mild hci set up, it was dyno tuned and put down 281hp and 305rwtq. After I had it dyno tuned it ran the best it ever had, but since about the middle of summer I've had nothing but trouble with the car. Running pig rich and generally just didn't feel as fast as it did. I took it out about a month ago, and decided to get on it a little bit at a stop sign ( During summer my car normally burns the tires in first and second easily, and it was only 20degrees out when I did this). I nailed it in first and it didn't spin at all, then I hit second and it chirped and when I let off i could feel that it was missing when it idled and when you drive it around regularly. However, if you nail it then it doesn't misfire. But if it is idling and regular driving it's pretty bad. Now I know I have a bad IAC on the car, but I don't think it would miss like this. I was almost thinking it was a vacuum problem, but I sprayed some injection cleaner around all my hoses and didn't find any leaks.

Any suggestion would really help I just want this car to run right

how do you know it's bad? if it's bad, replace it, then re diagnose.

 

[95Grandtouring5.0]

^ Because the car started to have a surging idle, I swapped iac's off of my other mustang and it stopped doing it, then I put it back on the other car. I don't have the other mustang any longer though.

 

[95Grandtouring5.0]

Come on guys, lend a helping hand.

 

[rz5.0]

replace your iac.get vac gauge and measure your vacuum.

 

[red94gt5.0]

is it a stock fuel regulator? the diaphram inside may be shot, also, i know this sounds crazy as hell but for shits and giggles go to your local parts house and get them to test the alternator, a diode can go bad in the alternator and send some crazy signals to the computer (the diode is supposed to keep current flowing one way) this happened on my brothers 04 gt and it was doing EXACTLY what you described. took us MONTHS to figure it out and turns out its the gd alternator!

 

[95Grandtouring5.0]

is it a stock fuel regulator? the diaphram inside may be shot, also, i know this sounds crazy as hell but for shits and giggles go to your local parts house and get them to test the alternator, a diode can go bad in the alternator and send some crazy signals to the computer (the diode is supposed to keep current flowing one way) this happened on my brothers 04 gt and it was doing EXACTLY what you described. took us MONTHS to figure it out and turns out its the gd alternator!

It has a bbk adjustable fpr. Would a place like advance auto or autozone test it? And if so do they charge for it?

 

[rz5.0]

get a fuel pressure gauge and you will be able to tell if its working. a cheap one from autoparts store about 30 dollars

 

[red94gt5.0]

Yes and free

 

[95Grandtouring5.0]

get a fuel pressure gauge and you will be able to tell if its working. a cheap one from autoparts store about 30 dollars

With the bbk manifold I have its not so easy to do.

 

[Billy50H]

Idk if you've fixed theproblem but I had a similar problem. Spent allll last summer trying to fix it and it ended up being the pick up coil wire. There was still a small miss due to the little thing(forgot what its called) that the pick up coil reads. Replace the distributor and everything is fine. btw the pick up coil wire is fairly cheap but you have to disassemble the distributor.