Why is my 1999 ford mustang gt hesitating and stumbling when i am accelerating

Richard S

New member
Your not going to like my suggestion, but here goes any way. Fuel injectors are prone to failure and they are hard to diagnosis. Your explanation really fits the injector that is failing. If you have a mechanics stethoscope, you can listen to each injector and hear the injector working or the intermittent miss. Because yours is a load problem, some of the scanners have the ability to fire each injector upon demand. I suggest you pull the fuel rail and the injectors then go to the demand section of the scanner menu. This will allow you to perform a functional test of each injector. Your looking for a conical or cone type spray from each injector. Dripping is a sign of pending failure. This test can also be performed with out pulling the rail and injectors but it is a little less effective because you can not see the spray pattern. This way you still use the scanner, but you monitor the fuel pressure for a drop that indicates that the injector fired. Hope this helps.
 
Get yourself a long handled screwdriver and with the tip of the
screwdriver on the fuel injector, and the handle end against your
ear, listen to the fuel injector. Listen to the others as well and
compare sounds. ( It's an easy quick test )

This sounds like it may very well be your culprit.

Just a thought here

Good Luck to you
 
Your not going to like my suggestion, but here goes any way. Fuel injectors are prone to failure and they are hard to diagnosis. Your explanation really fits the injector that is failing. If you have a mechanics stethoscope, you can listen to each injector and hear the injector working or the intermittent miss. Because yours is a load problem, some of the scanners have the ability to fire each injector upon demand. I suggest you pull the fuel rail and the injectors then go to the demand section of the scanner menu. This will allow you to perform a functional test of each injector. Your looking for a conical or cone type spray from each injector. Dripping is a sign of pending failure. This test can also be performed with out pulling the rail and injectors but it is a little less effective because you can not see the spray pattern. This way you still use the scanner, but you monitor the fuel pressure for a drop that indicates that the injector fired. Hope this helps.
 
in higher gears? I have a 99 ford mustang 4.6l manual 5 speed which is hesitating and stumbling when i press on the gas/accelerate in higher gears most of the time. the problem seems to come and go. i replaced my spark plugs and intention coils. please be aware the car uses the coil on plug configuration thus there are no spark plug wires or a distributor. i have tried using the fuel injector cleaner you can buy at any auto store. the ignition coil wire packs are in tack and just fine. i have had problems with cylinder 8 misfiring in the past and i resolved that problem by replacing the coil in cylinder 8 which worked. i replaced the coil again when i replaced my coils and spark plugs. please advise. this problem does remind me of a slight misfire and it occurs most of the time when i try to accelerate especially in higher gears. the car has about 100,000 miles on it.
 
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