NEWBIE with a BAD SHAKE!

[justinmanges05]

I bought an 02 Mustang GT about a week ago. It had a bad synchronizer, so I took it to my mechanic to get it looked at. He confirmed my theory, and let me take the car back so I could drive it while the parts where getting here.

On the way home, everything was normal. I'd get on it a bit in 1st, and go straight to 3rd. But then, I put it in cruise in 5th gear, and noticed it started mildly jerking. I figured it was because I was at a low RPM going up a hill.

Later, I came to a light, and when I took off I went from 1 to 3 again, and it started jerking in 3 too. Then 4. It does it worst at 1500-2500 rpm. What I first thought was that the problem was misfire/fuel or something electrical, but the SES never came on. Then when I got home, I took the car out of gear, and it revved up just fine. No jerk at all when out of gear. This all happened and worsened in about a 35 mile trip. by the time I got home, it was almost not driveable. It jerks even if you are driving it hard, making sure the shifts keep you out of low RPM. It always cleans up after a few seconds.

I guess the first time I really noticed it, was going up the hill in 5th. The gas pedal went to the floor cause I had the cruise on. Thats the way it is now too. If you put it in 3rd and put it to the floor, it acts like a misfire. Any suggestions??

Justin

 

[trombonedemon]

I had the same problem before I got t boned in a collision, under 2000 rpm's, my car would buck very badly, I thought it was just the nature of the car, anyway, I took it to the stealership, to replace my rear end, problem solved, I was told it had something to do with my spider gears in the rear in. It dosn't do that anymore. Just food for thought!

 

[justinmanges05]

Im hoping U joint lol

 

[trombonedemon]

If it was the U joint, wouldn't it be consistant through out the entire RPM range? I say you need a rear-end rebuild, unless you have a press to press the bearings from the pinion gear you might want to take it to pro or the dealership; the dealership b/c they would more than likely get the pinion depth correct, heard more than my share of horror stories of people taking there rearends to mechanics and the pinion depth is wrong, to much, it whines, to little it clunks.

 

[Dragstr05]

If it was the U joint, wouldn't it be consistant through out the entire RPM range? I say you need a rear-end rebuild

Don't you think its a little overkill to tell someone they need a rear diff rebuild over this type of concern being diagnosed over the internet? Seriously, c'mon man.

Is the car stock? 5th gear is the most load inducing gear. Chances are a misfire under load will occur under heavy acceleration or 5th gear first and work its way down. A couple months ago I had a misfire that sent me through loops. First it was intermittent, then started happening consistently in higher gears and under heavy load, then light load, etc. Finally figured out it was a coil. Wouldn't throw a code for the longest time and even when it did it was hard to get it to trip a CEL.

I'm not saying it IS a coil. First it would be ideal to isolate the problem to drivetrain or engine if you are able to do so and go from there.

 

[justinmanges05]

I tell you what man, I keep hearin coil. 3 different mechanics have said the same thing (none have actually seen it yet) but I can't remember how to test the little bastards with a voltmeter.

And yeah, it refuses to trip the SES light, and it started in high gear. I certainly hope its a coil vs. the rear end for obvoius reasons lol. I tried to isolate it like you said by taking it out of gear, but now I'm hearin from these guys sometimes the coil will only misfire under a load.

Thanks for all your help, guys. Any further info would help too.

 

[TOOLOW91]

i just did a coil on mine yesterday it was intermittent then it started happening constant yesterday... i would look into that first ..

 

[justinmanges05]

This car was a bank repo. The dealership I work at bought it for me. I bet you the bank detailed the engine bay before selling it to us. How do you check the COP's?

 

[trombonedemon]

Don't you think its a little overkill to tell someone they need a rear diff rebuild over this type of concern being diagnosed over the internet? Seriously, c'mon man.

Is the car stock? 5th gear is the most load inducing gear. Chances are a misfire under load will occur under heavy acceleration or 5th gear first and work its way down. A couple months ago I had a misfire that sent me through loops. First it was intermittent, then started happening consistently in higher gears and under heavy load, then light load, etc. Finally figured out it was a coil. Wouldn't throw a code for the longest time and even when it did it was hard to get it to trip a CEL.

I'm not saying it IS a coil. First it would be ideal to isolate the problem to drivetrain or engine if you are able to do so and go from there.

Funny, its not like hes paying for my advice, Seriously. I don't know about the rest of society, I want the worst case scenerio first. In fact he dos'nt have to listen to me, I'm just saying my COPs are good w/fresh spark plugs, before the accident I had every symptom he had, after they replace my rearend the symptoms went away. I am very aware that some problems can show the same syptoms, its just free advice and his money, lighten up.
Exactly how is 5th gear the most load inducing gear since it dosn't show as higher RPM's as the rest of the gears and obviously its not the largest gear.
Get a mechanic to scope your COPs to rule out them being the problem, the only thing is, it requires you to pierce throught wire to get what I am thinking an analog reading or digital, can't remember which is on our cars. To real car enthusiasts the scope is a must buy, but expensive. I hope its the COP, try putting dielectric grease on your spark plug. Best wishes.
Keep us posted if you get a new symptom.

 

[trombonedemon]

YouTube - Coil on plug lab scope test This is informative!