HELP HELP HELP Vibration and slow as molasses

[groove groce]

My first time here, so bear with me. I've owned 6 E21's over the years and even bought one new in 78' so I'm pretty familiar with them. This car, an 83' 320iS US is BEAUTIFUL all original Henna red paint, 110K orig miles. I bought it 2 yrs ago from original owner and have spent a TON recomissioning after a very long storage. All is done....BUT....I have a subtle vibration I feel through the pedals at RPMs around 2500-3500 PLUS a drone and vibration through exhaust at same RPM. I noticed this after replacing the original 240 Getrag trans with used 245 as original was filled with rust from sitting. I cannot say for sure this is when it definitely started. Since then, I've replaced tranny AGAIN with a different 245 with better synchros, had the flywheel and clutch balanced, replaced both motor mounts and vibration damper and it's still there. Also, this car is SLOW !!. I know they are not particularly fast to begin with but this is the worst I've owned. It seems to lack that little surge that you normally feel around 3 grand. I'm constantly having to down shift for hills and the best 0-60 time I can achieve is 14 seconds. It starts and runs flawlessly other than this. I don't know if the 2 problems are related but ?? I might mention that this is the first AC E21 I've ever owned but can't imagine that could change the performance that much. Could the AC be causing the vibration ? How about the distributer ? I've had 3 so-called experts here try to analyze and the all just say "live with it, it runs good" HELP !!

[Jeroen]

Welcome here! Let's try to analyze this! Issues could be related but for starters I'd like to think that's not the case and try to get a decent understanding of each issue.

Vibrations
Can you feel what its coming from? If its through the pedals (and possibly steering wheel as well then?) you'd say front suspension? Or driveline, where guibo disc or propshaft bearing and balance could very well be the cause. You fitted another gearbox, replaced the guibo? Where did you get it from? Sure the clutch is centered correctly? When does this vibration occurr exactly? Does it look like speed dependant, rev count dependant, gear dependant, under braking, under acceleration? What I understand from your post is that you very much believe it is engine and rev related? But as you did notice this after replacing the gearbox my first guess would be driveline.

Power
You have a Cat fitted I guess? Not clogged up? Did you make an exhaust gas analysis? Especially wondering what your CO is at. Did you check ignition timing? And what about compression?

[groove groce]

First of all, Thank you so much for taking the time to help me resolve this issue. This car is a perfect 100K mi. original survivor in every other respect and it's frustrating not to have it 100%. The vibration is a buzzing feeling through the pedals and stick shift @ 2500-3500 RPM. There is a DRONE sound that occurs through the exhaust while this is happening. None of this is super severe but it's anoying and for me it takes the joy out of driving the car. The car can be sitting still in neutral and will do this. The guibo and drive line came from a donor car when the the first donor Getrag 240 was installed. Those parts had almost 300K on them but had to be used as, apparently, the 240 is a slightly different length than the original Getrag 245 that rusted inside which is specific to 83's only. [learned all of this along the way....even the so-called BMW experts here didn't know this] ] I changed trannys AGAIN with another 240 that was much better [good synchros and silent] but kept the guibo and driveline from the first donor car [300k] as I could'nt get another. That's when I took the pressure plate and flywheel in for balancing. it was slightly off ....not bad. Dumb question, Does the guibo spin when car isn't moving ?....don't think so ....so I think it's engine related vs. driveline but I'm open to any thoughts. It doesn't matter if you're excellerating or not, If you bring up the RPM's to 2500-3500, you feel it and hear the drone. I DID think of the catalyst and when I had that revalation, I hoped all would magically be fixed. I went to an exhaust shop where they performed a pressure check and proclaimed it good....not perfect but well within specs...I was dissapointed ! I'm not sure of the mixture setting although the car now passes local smog test with flying colors which it didn't when I got it. My mechanic tuned it up and like I say, It runs smooth and beautifully cold/hot ...very reliable...just lacking that little surge of power that you normally feel in E21's and it seems to take forever to get to 5500 RPM when you step on it . Again, I REALLY appreciate your advise...It looks like I should have come to this site a long time ago. Interesting note: My 27 yr old daughter who is an RN here has a matching 83' 320is in Henna red.....same cloth Recarro interior and you can't tell the cars apart with the exception of AC in mine. Her E21 is beautiful as well although has had a little re-painting here and there and has 60K more miles . So I have a good comparison car for issues like this. Hers is a JOY to drive ! Thanks !

[Peter V.]

I can say that the AC does kil a lot of power. I have the M20B20 with AC and with the compressor locked up it is much slower. Even the idle RPM drops a few hundred.

So the drone noise is there when the car is standing still and only the revs are up. Indeed the guibo is not turning when the car stand stil. What i had with the AC compressor is that when the magnetic clutch is not powered (AC On) it still makes a wining noise but that starts from idle to max revs.

[groove groce]

Thanks Peter, Yes I can feel power loss when AC is on , that's normal of course, but this is all when it's off. I AM tempted to remove belt just to make sure that the vibration isn't related to compressor even when not engaged. Wonder if that would be a waste of time ?

[Jeroen]

If the engine is cold you could even take both belts off for a minute. You never know. But if I understand correctly the engine runs evenly. Could it be a more external vibration, like from the front crossmember? And for lack of grunt I'd want to check the condition of the cat and if the CO isn't too low.

[groove groce]

Thanks Jeroen, Not sure about the front crossmember. I've had a lot of front end work done including new tie rods, bushings, Bilsteins, etc. I presume all is well there. Car handles wonderfully now. Yes, engine runs evenly. Maybe I WILL take the belts off starting with the AC....couldn't hurt....after that...I just don't know. I'll see if someone can check the CO for me. Any other thoughts are more than welcome....Thanks

[Jeroen]

Its just really weird and not a common issue, and you already had so many things done and checked! Hope someone else has a brainwave as well perhaps!

[nas80]

I'd suggest it could be prop shaft related. Have you replaced the centre bearing and the rubber guibos / flex disk? I would get the prop balanced.

Also you need to get the car tuned up. Sounds like it could be a timing / injection related thing. Have you compression tested the car? Also could 've been a dodgy valave seat or something like that.

[groove groce]

Thanks Nas80, No, this vibration is not drivetrain related. It's a buzzy kind of vibration associated with engine RPM even when the car is sitting still. Car has been tuned and runs quite well, just feels like it's putting out about 85 HP to me . Engine is tight.....using no oil whatsoever and not a trace of smoke. Thanks for the thoughts though....I truly appreciate it !

[nas80]

does your car have a catalytic converter still? try removing it?

maybe its the harmonic damper? Is the fan missing a blade or anything like that?

you have a mechanics stethoscope? Does the noise go away if you open the doors / bonnet? My thinking is that the buzzy noise might not even be the engine but you might have something loose like a panel.

Can you record a vid and put it on youtube so we can hear it?

btw a guibo with 300k on it is likely to perish its made from rubber - id change that as maintenance same with the centre bearing.

[nas80]

i have heard of the innards of the catalytic converter coming loose with age and then rattling about at certain revs, remove the cat and give it a shake, if you hear any kind of movement that's more then likely it you know. it would also explain the lack of power despite engine being tuned fine.

[groove groce]

All good thoughts nas80....As I mentioned earlier, I thought of the cat. I went to an exhaust shop where they performed a "pressure check" and proclaimed it well within specs. I was actually dissapointed with that. It does make me wonder though because as I mentioned earlier there is a drone sound at the same RPM's as the vibration. The heat shield bolted to the cat definitely was rattling when this occured so I made insulators out of gasket material and that stopped. So I wondered, Is it the exhaust causing the buzzy vibration ? Or is the exhaust vibrating and droning from someting in the engine causing a vibration ??? What is the "harmonic damper" ? If it's the engine vibration damper [small shock mounted on left side of engine] I did replace that along with motor mounts. Fan is good.....Again, Thanks for your thoughts.

[pandemonium001]

would a pressure check not just check for leaks??
a flow check or back pressure check between the head and cat would tell you if the cell has collapsed.

But why not remove it any way and replace with a sports cat that will comply with your local smog laws? i think minimum I have seen in UK is 100 cell.

is it an original exhaust? stainless systems can sound buzzy when first installed. until they get lined up with soot.

[groove groce]

Hi Pandemonium, Yes, exhaust is 100% stock with new OEM muffler. I'm weird that way. I also have a 73' 2002 tii that is bone stock down to the hubcaps and I had to fight hard the temptation to lower this E21 when I put in the Bilsteins. Anyway, I watched them perform the "pressure check". They drilled a small hole in the cat and inserted a pressure guage into the hole while someone else runs the RPM up to about 5 grand. The guage should read a certain amount of pressure. Apparently it was well within specs. I think my next plan of attack is to remove the AC belt followed by the alternator belt [for a short period of time of course] If that doesn't do it....I think I WILL look at the cat again and maybe just replace it. I sure appreciate your thoughts....