Vibration under load

[ShadowFist]

I did a basic search for this, but didn't find anything that was relevant (i think) so I will post this here while i comb through the search feature again...

25MPH, I felt a slight 'bump' like you just ran over something small on the road (like a branch or cardboard). Speed limit increased to 35, and when i added a little gas, the car started to shake pretty good (feels like hesitation). I let out the clutch and revved the engine, and it revs fine. Put it back in gear, and add some gas and it starts vibrating again. Tried it in 5th gear (at 35) and it shook bad enough that I was tempted to pull over and just walk home (5 minute walk). The shifter was vibrating a good 3 inches back and forth in 5th gear. I left it in gear and just idled my way home. Turned car off and on again, and problem is still there in all the gears. No error codes yet.

Any ideas?

<heads back into the archives>

 

[ShadowFist]

My car is a 99 cobra. I just took it out for a spin again to see if it was the tranny mounts, and the car behaved fine! So i took it out to some back roads to run some tests. 1st-2nd light and heavy accel, no problems. 3rd, no problems. 4th, no problem. Put it in 5th at 35mph, and I got the vibrations again. Started testing gears at low rpms, and the problem started to appear again in the other gears (except 1st). Started load testing the gears by braking and applying light to heavy throttle, and problem wasnt readily apparent in the lower gears, moderate in 4th, and a lot in 5th. Any ideas?

*EDIT: Took it out again this morning, and problem disappeared until the car warmed up. Could it have something to do with low transmission fluid?

 

[ShadowFist]

Had someone else take a look at it and it looks to be a low rpm miss when the engine is fully warmed up. The problem is not there when the engine is cold and runs fine. I'll keep posting here before i take it to a shop to have them look at it.

Does anyone have a data logger that I could possibly borrow to diagnose the problem?

 

[wythors]

Hey Chris, I talked to Neil (guy in the club that is a tech) on our Nanaimo trip and, after describing your problem, he suggested you check the fuel pressure. Maybe a bad filter, regulator or even a pump. Your description of it doing it under load at low RPM's but not doing it with the clutch in sounded like a lack of fuel to him.

 

[ShadowFist]

How would I check fuel pressure?

*runs off to the archives*

 

[ShadowFist]

Fixed!

Turns out that there was a bunch of water in one of the spark plug shafts, and clearing that out and replacing the spark plugs fixed the problem!

 

[adoggs4valve]

Give your local dealer a call. When I bought my 03, I contacted a buddy of mine that works for Ford. He gave me a heads up on several TSB's out for the driveline on the Cobra's. You may have an issue that Ford knows about. None were a recall, but there were a few small issues.

 

[wythors]

Give your local dealer a call. When I bought my 03, I contacted a buddy of mine that works for Ford. He gave me a heads up on several TSB's out for the driveline on the Cobra's. You may have an issue that Ford knows about. None were a recall, but there were a few small issues.

Apparently, noone actually reads the threads before responding.

 

[ShadowFist]

Be nice now

Thanks for the suggestion, but the spark plugs fixed the problem!