Vibration in gas pedal

[Raub]

This thing is driving me crazy. My '93 900S has a buzz in the gas pedal from 2500-3000rpm. It fades after 3200rpm. It's definitely engine/RPM related. I've checked all the belt-driven stuff and it seems fine. Bearings were smooth and play was minimal. Replaced belts and alternator mount bushings. Replaced R/H and front engine mounts. Replaced exhaust from header pipe back and made sure it was not touching the body. What am I missing? Engine runs fine too, no abnormal noises or anything. Any suggestions?

[euromobile900]

So it's just a vibration, not a noise? Did you check the gas pedal itself? Does it do it while just sitting there and revving the engine, or only under load? If so, I would have someone watch the engine and ancillaries while you rev it in the driveway.

[Raub]

Yes, just a vibration. Like an electric massager. It will vibrate when it's not under load, and I have had someone rev while I look, but I didn't see anything. Guess I'll give it another go.

[euromobile900]

Though I've never heard of this issue, a blind guess is that it could just be the gas pedal pivot or throttle cable. I really can't think of anything else that would cause a noiseless vibration in only the gas pedal.

[jlrSAAB]

it could be a crack bracket exhaust, not broken, fissure.

[Raub]

It is a 2.1L N/A. It doesn't have the brackets that the turbos have. Or do you mean something different?

[euromobile900]

Hmm, there are rubber hangers for the mid muffler and rear pipe, but other than that no brackets all the way to the headers themselves. I'd say if you've checked it, it's likely not exhaust.

Another thing I thought of checking today is your A/C idler pulley. You know, the one on the tensioner arm. It's worth a try, anyway, as long as you've gone through your alternator and all belts. Often the bearings go on these, so they make noise or vibrate.

[Raub]

I removed the idler pulley and bracket completely. I also removed all the belts today and ran it. The vibration was still there. I'm going to take the A/C pulley off the crank pulley. Then I guess next step is to remove the crank pulley again and inspect it.

I really hope it's not something in the bottom end of the engine.

[jlrSAAB]

once at the end you will find the culprit...

-put special attention to all the bolts and nuts of the brackets pulleys, AC compressor, alternator... so on.
also move with your hand the end pipe exhaust to see if you to simulate a noise or vibration.
check for fissures in all metal tubes from the out engine to exhaust...

good luck

[Raub]

My exhaust is brand new from the header pipe back. The header pipe and manifold are secure. I have eliminated the exhaust.

I took all the belts off and the vibration is still there. I am eliminating the alternator, power steering pump and water pump.

The right and front engine mounts are brand new.

I did run across something that puzzled me. The thru bolt for the left engine mount...my car has a brace that goes from the thru bolt to the drive tunnel. The 15mm bolt at the bottom of the brace was barely threaded in. I don't recall this brace and don't know how it is supposed to be properly installed. Do I tighten the bolt? It seems counter-intuitive, like it would transmit vibrations worse if it was tight.