Hi all I am a Ford man from way back. Irace a 1974 Mustang ll.Here is my problem I recently bought a 1975 Mav 4 door 250 6 cyl automatic. I did a complete tuneup,oil change,and trans filter change. I have gone through the carb 2 times, my Dad has gone through it once and the NAPA shop has gone through it and I still have a horrific hesitation.It starts hard but does run real good (except hesitation) It's so bad you have to drive with one foot on the gas and one on the brake.I'm ready to buy a nrw carb , but I thought I would see what you fellows think. Thanks Big John
Not being real familiar with the 250 and how its set up, I'd guess a vacuum leak would be the culprit. There are some ways to find leaks, most effectively is carb cleaner. Spray it near where you think there might be a leak, and if the engine revs or starts to settle down some (any change in rpm basically), you found the leak.
Mavman Thanks But I've already checked vacuum with no problems.Plus I've checked fuel lines for leaks,cracks,etc. and still found nothing. Thanks again Big John
Put a timing lite on the engine and watch the timing. Jazz the engine into the hesitation and see if the timing is going quite retarded. If so that is a great part of it. The 77 year has a lot of funny controls to satisfy emmissions and the carb has a reverse idle system that may also be very lean.
Sorry about calling it a 77. There are a number of valves and switches and a 3 way solinoid valve involved, controlling vacuum to the distributor. See the volume 6 shop manuel pages 36 thur 40. The ignition timing may not be advancing. The EGR valve could even be involved.
