autobuilder4u

What I have is a 1998 GT bone stock .When I bought the car a couple years ago I noticed a small hiccup if you lugged it down around 1200 rpm in a high gear, no big deal. Over time has gotten worse and worse. NOW anything under 2000 rpm in any gear but 1st it bucks and jumps terrible.Under hard acceleration it surges terrible like 200 rpm up and down, but under a light load 1/4 accellerator or less and above 2000rpm it runs OK . It does it all the time not just when hot or cold.Can some body help me out I need some help PLEASE!
I have pulled the codes they are none.
I have checked the fuel pressure it is 30psi idle to 40 psi under load.
I have changed fuel filter.
I have changed MAF.
I have changed plugs and wires.
I have changed coil packs.
I have checked TPS sensor.
Any Ideas will help me I am out.

Thanks

96mustanggt46

Mine does the exact same thing and so does many people on the forum that i have spoken to.

I have narrowed it down to it will only buck whene my cooling fan is on, I have a switch to turn on my fan and it will start to serge like you said at low rpm's in a high gear and i will turn off the fan and it runs fine.

autobuilder4u

On a suggestion from a co-worker I replaced the plugs again.

It FIXED my problem.

I have came to the conclusion the problem was,(Pick one below)

A. The expensive double platnium plugs I paid $4.00 a piece for was a waste of money

B. The plug gap was to wide since I set the new ones to .035

C. My new plug wires were not completly down all the way on the plugs.

D. Your guess is as good as mine.

E. All of the above. Thanks for the replies.

Green97GT

i ahve the same bucking i think... its like a knocking sound. mine does it when i start the car and in low rpm at higher gear like he said.

Poobs

The gap on the NGK plugs on my 98 is supposed to be .054 ( !! )

Are you sure about .035 ?

BBond007

I just reciently purchased a 96.

It was doing the same thing. Some days it would only do it in 1st around 1200rpm when lugging for the first 5 minutes.

Some days it was more obnoxious.

Eventually it triggred a "Check Engine" Light "Missfire Cyl #3".

I was very worried so I ran a compression test and replaced the plugs in the process.

New plugs fixed it...