I have a 97 mustang with the 3.8 engine. What might be the cause of the engine feeling like it surging as I am driving it. The plugs are autolight iridium which are about a year old. The wires are about two years old. I do not hear any missing when I listen to the exhaust to indicate a misfire nor is it showing up on my carchip insert as a code which it normally does if a plug is missing. No engine light light showing. The engine has about 198000 miles on it and the engine has never gone thru an injector cleaning. I changed the gas filter which made no difference. The gas tank just had the donut seal changed on the filler neck. When I let the engine just idle I can see a slight intermitant flicker in the tach needle. Any ideas of what might be the cause?

 

I would check the fuel pressure.Make sure you have between 38-40psi under a load and it doesnt bleed off.I used to replace pumps left and right when i was at Ford.

 

Hey Gary,

Did you ever get your problem figured out? I'm having the same issue with a 94 3.8, but mine only happens when the defrost (front not rear) is on.

 

did you check for a vacuum leak?

 

Yep...I sure did! I think I might have it figured out though. I totally forgot that the a/c compressor kicks in when using the defrost mode. This could be causing an electrical drain which could be causing the surging. I'll know more when I can get the hood up later today.

Thanks