byrdman454

I have been slowly fixing all of my vacuum leaks on my '84 Euro. I need some help tracing down a vibration I have picked up. The vibration starts at about 1200 rpm through 1400. It then goes away until about 3000 rpm. The car is a 5-speed and the vibration is still present when in neutral (not moving), clutch pressed, etc.) This should eliminate, the clutch, transmission, and drivetrain, right? I was thinking motor mounts, but I have changed them over a year ago with Anchors. I could have a premature failure, so I still need to check. Is there a chance my vibration damper is starting to fail? This vibration can be felt through the fenders if you are leaning on the car, so it is a pretty big vibration. The vibration also can be felt through the 5-speed stick. Need more ideas. Please let me know what you guys are thinking...

SharkSkin

The motor mounts are a seprate issue, good or bad. It shouldn't be vibrating like that.

Start with the basics. Inspect the plug wires, run the car with the hood open in the dark and look for arcs on the plug wires. Pull the cap(s) and inspect, looking for dust tracks from arcing, corroded contacts etc. Pull the plugs and look for any sign that one cylinder is running differently. Get a piece of hose and listen to all of the injectors to see if they are firing. Make sure you don't have an air leak on one of the runner-to-plenum boots.

If you don't find anything, check the harmonic balancer, but as you take each accessory belt off run the car again to see if the vibration changes. To take the fan belt off just unbolt the fan.

If you still don't find anything run a compression check, preferably with the engine warm.

If the vibration is there with the clutch disengaged, you have eliminated the clutch disks(but not the intermediate plate or pressure plate), the stub shaft, TT, etc. As a last resort you might check the torque on the pressure plate.

John Speake

I had a similar problem with my 86 Euro. It turned out to be an injector not flowing well. I had then ultrasonically cleaned and that fixed the problem.

Mrmerlin

Add a can of techron to the fuel system do lots of short rides so it has time to work

byrdman454

When I got the car a couple years ago, the POs shop had replaced the injectors with US injectors. they burned up the LH computer. Since then, I bought a set of used Euro injectors from 928 INTL and sent them off to Cruzin Perofrmance for cleaning and flow testing. They came back good. Do you still think I have one causing trouble even though it has only been a couple years? There has probably not been 10000 miles put on the car yet.

John Speake

Seems unlikely that itis an injector problem.........

When you drive the car through that vibration period, does it feel like a misfire ? Or just vibration ?

byrdman454

When you drive the car and holding the RPM steady above 3K, the shifter vibrates like crazy. It vibrates so much that it would put your hand to sleep if you help on to it long enough. The car runs great, does not seem to be a misfire. As I stated earlier, the vibration does occur just sitting there. Not at idle, but if you add some throttle between 1200-1400 rpm there is vibration. It goes away above 1400 and returns at 3000. Since this is happening, it should be something with the engine right, since the TT is not turning.

John Speake

It does sound like from the engine.....if it still does it with cllutch depressed, at rest.

herman maire

I dont know if it has been mentioned yet but check the compression.... I had vibrations on 2 bmw's in the past. They both had low compression in 1 cylinder. The first engine had a burnt valve, 90psi vs 190psi what its supposed to be. The second engine had bad compression rings on 1 cylinder 120psi vs 190psi what it supposed to be.

I hope its nothing that serious but you really should check the compression.

Good luck.

Mrmerlin

what was the last thing you fixed??
Recheck the firing order and routing of the plug wires

mark kibort

I had one like this that was an exhuast muffler hitting and vibrating on the chassis. not likely if you have a stock suspended exhaust system.
mine was a little higher on the rpm scale though. (more like 3-5k). I thought it was a torque tube issue, but found that the problem went away with changing the muffler out in the mid section.

SharkSkin

You're not going to get a definitive answer without going through a process of elimination. Try to rule out the possible causes mentioned above.

byrdman454

Finally got around to checking some of these things. I pulled the plugs. They all looked pretty much the same. I also ran a compression test cold. All cylinders were within 10 percent (150-175 range). I checked for arcing on the plug wires and did not see anything. The plug wires were changed less than 2 years ago. The car has a X-pipe with the stock midpipe and muffler attached. I did not notice anything vibrating or touching the body.

The last thing I was working on was the vacuum leaks. I had several big ones. I am not sure if this vibration was always there and my other problems covered it up, or if my last fixes caused this.

I guess the next thing to try is to start pulling accessories until I reach the vibration balancer unless anyone else has some suggestions first.

byrdman454

bump

jpitman2

Recently changed anything doesnt prove squat. I once had wires less than a month old go bad on me, took a long time to find because they were discounted as near new. Do a systematic check of everything regardless of age. Pull plug leads one at a time to see if any are not contributing ,ie noteand revs dont change when plug is disconnected.
jp 83 Euro S AT 52k