Why does this buck and hesitate?

Robs96 · Aug 30, 2006

I have a '96 GT and for some reason the car runs bad when its in drive. The car will idle fine in park or neutral but when it is in drive, it hesitates at idle at a stoplight, not constantly but about every 5 seconds. The tach barely registers the miss but you can still hear the car cut out. When accelerating it bucks on any amount of throttle but clears out if you punch it and then it runs with just a small miss after reaching cruising speeds. I have already replaced the plugs and coils as this vehicle has 150k on it. Tested the fuel pressure and it puts out 30lbs, and 38lbs with the vacuum removed from the pressure regulator. I also changed the fuel filter. The plug wires have 50k on them but seem fine (at least no arc in the dark anyway). I did get code p1443 which is something to do with the purge flow sensor or solenoid, but Ford said that it wouldn't make it run like this. I cleaned out the IAC and EGR valve with no different results. I don't want to just throw parts at this, so does anyone have any ideas?

Mike97gt · Aug 30, 2006

replace the plugs and check the wires and coil packs. common common problem with these cars.

Robs96 · Aug 30, 2006

I've already changed the plugs and coils but not the wires. I did notice the drivers side plugs, all four were worn on the electrodes as opposed to almost no wear on the passenger bank plugs. Not 100% sure, but I don't believe it is the wires.

Robs96 · Aug 30, 2006

I did already change the plugs and the coils. I'm not 100% sure, but I don't believe it is the wires. I did notice when changing the plugs, the four on the driver side bank had worn electrodes and the four on the passenger bank were fine and still properly gapped. The car is also hard to start after sitting for long periods of time. It will sputter for a few seconds before coming to steady idle and if you try to give it gas to help, a small backfire can be heard from the engine compartment. This is a stock, untouched motor.

stangGT97 · Aug 31, 2006

too much EGR flow can cause those symptoms. Check the DPFE sensor, it could have gone on you...

Kilgore Trout · Aug 31, 2006

My guess is that you have the original fuel filter in it with 150k miles on it

speedfreak98r · Aug 31, 2006

While you're at it, change the PCV valve..That fixed my bucking problem. Only about $2..

Robs96 · Aug 31, 2006

No, I've changed the fuel filter, and pcv. I'm anal about routine maintenance. The DPFE sounds interesting though. I haven't tried checking the vacuum to see if it is within specs. I did remove the egr and clean it. It wasn't really fouled or anything though.

Kilgore Trout · Aug 31, 2006

Robs96 said:
I'm anal about routine maintenance.

Mike97gt · Aug 31, 2006

it is also possible as others have suggested that you could have a egr sticking partially open, but I really would take a good look at your secondary ignition ( plugs,wires)

50k miles is not exactly new wires, a good way to find this would be to use the power balance test on the Ford IDS scan tool and see what cylinder is droping out.. then you can move the wires around and see if the miss moves

since this test is not availible to you it makes this a lot harder. one other way you can do this is to see if you can buy or borrow a spark tester that will work with our ignition wires, since our plugs are in a well it's hard to use the plug in inline testers.

If you can find a tester to use then you can have a friend put the car in gear and load the engine while your stoped and see if you have good spark getting to each plug..

Even if you have good spark to the plug the plug may be fuel fouled.. read this thread there is a lot of info on misfires and fuel fouling.

From my experience on these cars 99-100 times these problems tend to be ignition related, it's gotten to the point that the dispatcher sees these symptoms on a ticket of a modular car or truck and he says " hey mike diag this plug and coil problem" it's become a joke now it's so common.

http://forums.stangnet.com/showthread.php?t=655274

Why does this buck and hesitate?

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