Strange vibration, any ideas? - PeachParts Mercedes-Benz Forum

Hatterasguy · #1 08-18-2006, 05:22 PM

I'm a bit perplexed by this. Today I drove the SDL to the office and didn't notice anything. Got out of work and did a few earands. Got the front wheels balanced at my usual spot then I noticed it. At idle there is a strange vibration and sound. Its hard to explain almost like a 4 cylinder gas car with weak engine mounts. It is engine related, in N its still there, when in gear I can feel it more. It goes away over 1k rpm.

It almost feels like a collasped engine mount. The drivers side looks fine, now that the car has cooled off a bit I need to look at that pass one. I don't see anything out of sorts. It almost feels like the engine isn't firing right at idle, something is off and I can't put my finger on it. Bad fuel maybe? I'm down to a 1/4 tank. Still I drained the tank a few years ago and the fuel is always clean. I have never had fuel problems with this car, I always buy it from the same high volume place, but still.

Any ideas?

rrgrassi · #2 08-18-2006, 05:27 PM

Could be a mount getting weak. How are the engine shocks, if it has them? Is any of the hard lines sucking air? I just bought a purolator primary filter, and the danged thing cracked open on the 2nd day. Talk about vibration from fuel starvation! Any way it's fixed now. I have a 617, and do not know aboutt he 603.

Brian Carlton · #3 08-18-2006, 06:33 PM

Too vague to diagnose over the wires...........a million possibilities.

But, I can tell you what a 603 feels like when it runs on five.

I started the '86 after it has been in the garage for two months. Started fine.........one second crank, as usual. Smooth idle.

Then, after about 10 seconds, it drops one cylinder.

Sat and shook for about 10 more seconds........seemed like an eternity........until I said "WTF". Then it was gone..........

The entire vehicle shakes and the fact that the engine is wildly unhappy is unmistakeable.

This does not sound like your problem, however.

Hatterasguy · #4 08-18-2006, 07:27 PM

Yeah this is one of those problems you have to feel to track down.

Well I did some tracking. I removed the belt thinking that maybe an accessory had a bad bearing, nothing everything is fine. Thinking a bad batch of fuel and since I was getting down I filled it up, 16 gallons with a large load of power service, no change.

Everything is in order, I think one of the engine mounts is getting weak. Thats the only thing that can be doing this. They are only 2 years old but maybe I got a bad one or something like that.

It certainly isn't a miss fire, way to smooth for that.

Anyway I'll order a pair of engine mounts and see where that gets me.

Brian Carlton · #5 08-18-2006, 07:46 PM

Quote:

Originally Posted by Hatterasguy

I'm a bit perplexed by this. Today I drove the SDL to the office and didn't notice anything. Got out of work and did a few earands. Got the front wheels balanced at my usual spot then I noticed it.

Quote:

Originally Posted by Hatterasguy

Everything is in order, I think one of the engine mounts is getting weak.

You seem to have noticed it instantly. An engine mount failure is usually a gradual degradation.........so.........unless you've been sleeping while driving

over the past two months, the engine mount is not likely the culprit.

ched454 · #6 08-19-2006, 10:56 PM

Quote:

Originally Posted by Brian Carlton

Too vague to diagnose over the wires...........a million possibilities.

But, I can tell you what a 603 feels like when it runs on five.

I started the '86 after it has been in the garage for two months. Started fine.........one second crank, as usual. Smooth idle.

Then, after about 10 seconds, it drops one cylinder.

Sat and shook for about 10 more seconds........seemed like an eternity........until I said "WTF". Then it was gone..........

The entire vehicle shakes and the fact that the engine is wildly unhappy is unmistakeable.

This does not sound like your problem, however.

yesterday morning when starting it cold. First time ever and disappeared after I increased the RPMs to about 1200. For the rest of the day after it was warm, no problems.

Do you have a guess what it may be? Almost feels like an injector problem.

Hatterasguy · #7 08-19-2006, 11:07 PM

No this is recent, I am very sensitive to what this car does if something is off I know it real fast.

Could it be a sudden exhaust leak maybe? Its a strange resonance, with the windows up you really feel it and hear it.

Off on a 400 mile trip tomorrow, nothing seems out of sorts so I'm not worried.

Brian Carlton · #8 08-19-2006, 11:26 PM

Quote:

Originally Posted by ched454

Do you have a guess what it may be? Almost feels like an injector problem.

.......it's either an injector.........or the IP.

Hatterasguy · #9 08-20-2006, 10:18 PM

Well I just got back from the 400 mile trip, the engine runs fine, other than this vibration issue. But the mileage seems off a bit, I'll figure it out when I fill it up tomarrow.

I ordered a set of engine mounts. Its about due for an oil change so Friday, I'll change the oil, rotate the tires, and change the engine mounts. This will give me a chance to inspect everything further.

Don't say IP, I was thinking IP today actualy. This certainly isn't one cylinder, I know what they run like on 5. If my mileage is way off...hmmm maybe its time to remove the IP for a bench test.

But first things first, engine mounts are cheap!