NTY

Hi guys, my 91 3.3 turbo has developed a vibration during acceleration. The symptoms are follow:

1) The vibration gets worse on higher gear. Little on 2nd gear and worst on 5th.

2) No vibration on constant speed, coasting or deceleration. Just on acceleration or under load.

3) Begins at around 1,500 to 2,000 rpm to about 3,000 to 4,000rpm

3) Clutch slipping is smooth. No rattling noise. Had a new clutch 6000 miles ago.

It feels like a misfiring, but my mechanic test drove it and says it could be dual mass flywheel which I'm not very convinced. Does a bad DMF cause shuddering like that? I don't know where to start looking. Any one had same experience to share?

PorschePhD

Check your CV joints. If they are dry then it will cause a vibration under acceleration and certainly worse at higher speeds.

NTY

Thanks. I will do a check CV joints and drive shaft.

But it's more sensitive to engine load. Eg: There will be more vibration on 5th gear and least on 3rd gear accelerating from same speed say 35mph. The higher the load on engine, the worse the vibration.

PorschePhD

That wouldn't be uncommon. The joints are sensitive to load as the bearings move (or don't move) around in the carrier. There is a list of things that could also cause it such as flywheel, engine mounts, tranny mount etc. Start here and then get back to me and we can keep walking through the process. I like to start with the most common issue first and work from there.

Metal Guru

I concur with Steve. This issue is driveline related.
Bad CV joints vibrate under torque load. Rotational speed plays a role in what you feel too.
If it were a wheel bearing, it would rumble under all conditions and get really loud under a cornering load.
If your DMFW went bad, you might or might not hear a high-frequency in 1st gear under acceleration but you would feel it in the gear lever.

NTY

Thanks Stephen and Paul. I would start looking at drive shafts first. I was listing down all the possible causes and got frightened. There are just too many possibilities and I don't know where to begin. From ignition and fuel supply caused misfiring to drive train issues

PorschePhD

You know what they say about how you eat an elephant, right? One bite at a time. Our minds are our own worst enemy which is why you pick one thing (most common and simplest) and work from there. I can't tell you how many people go after the biggest job first only to find out it was the simple thing no one thought of. If I had a dollar for every person that ever called me and asked what would cause their car to stop running I would be rich! The first question I asked was is it out of gas. LOL. You would be surprised the percentage of people that answered yes to that question.

Anyhoo check those and if thats not it we will find it. My bet is it looks like gorilla diarrhea in those boots!

ralt

how old are spring plates??

NTY

I have no idea since there were a few owners before me. But they look really old so I believe they are the original spring plates

ralt

PS how many miles on car? My original clutch went at about 95k. Also have you checked motor mounts. All this stuff wears out over time.

Metal Guru

The stock mounts are oil filled and Ralt is correct, they give up around 20 years +.

NTY

The engine mounts are less than a year old.

The current clutch is about 4,000 miles.

Update:

I refurbished my drive shafts and the vibration is still there. I suspect it could be an engine misfiring. Just ordered new spark plugs, ignition lead and ignition coil

Metal Guru

Test the coil before you replace it. They are not cheap.
It won't hurt to replace the plugs and leads as if they are original they are most likely shot (mine were).
I had a misfire at idle that I traced to a bad coil.
A misfire under acceleration usually is a bad plug lead. Sometimes you can see arcing of bad plug leads at idle with the engine running and the lights off.
You ought to replace the cap and rotor while your at it.

bweSteve

Can't wait to hear whether that's reeealy what NTY sees when looking under those boots. Good one Steve. LMAO

=Steve

blackbull

IMHO that isn't a bad way to start mods...as long as the bank account can withstand it!!!!

LOL