BRB-83-911SC

There is no end yet. Still battling it. The thinking right now is flywheel/clutch pack imbalance. I would love to hear from others how such an issue might present itself to see if it matches up with my symptoms.

I will provide more details on all of the troubleshooting that has taken place since my last post when I get back to a computer - on a mobile device ATM.

Bill Ball

Hmmm... I wonder if one of the accessories is the source of not only the noise but the vibrations as well. Can you run the engine w/o the accessory belts and see what changes?

So, plug 7 has ash? If this was present before and after the injector cleaning, then that probably rules out a bad injector. If a new problem, I would swap the injector and see if the ash moves with it. Could 7 have a bad oil ring or valve stem seal or could this be a sign of poor ignition? I know you replaced wires, etc. Have you checked 7's wire resistance. Something is going on with 7, agreed?

BRB-83-911SC

Thanks Bill for following along. Quick reply to your points; full documentation on what we have tested /concluded forthcoming when I get some time to document.

We did disconnect the accessory belts and engine vibration was still present. The noise was no longer there after reinstalling the belts - suspect it was belt noise due to improper tension.

Yes, something seems to be up with #7. Plug readings the same before and after the following: new Beru wires, cleaned/tested injectors, noid light verification of injector pulse, replaced all valve stem seals, new caps/rotors, new Bosch copper plugs, fully decarbonized when engine was apart last year. So, *I think* #7 is getting oil fouled, although the plug is never oily - just dirtier than the others. What's left other than rings? I do note that there is an oil breather hose entering the plenum right next to the #7 intake tube....could #7 be injesting the majority of the oil vapors from that breather hose?

I have tried to set my idle CO with a Gunson Gastester sniffer, but the readings drift quite a bit (tool or ?). I have it close to 1.5% (airpump diverter valve vacuum line disconnected and plugged), but noticed if I increase RPMs off idle to ~1200-1500, it goes real lean. I'm thinking the misfire is a result of a lean condition.

Also, I think the vibration is a balance issue in the clutch/flywheel assembly. However, it would be ideal to remove the random misfire from the equation.

A few observation points: during cold start/warmup, there is no misfire, yet the vibes are present in the RPM ranges outlined above.

Also, when cruising at speed ~75mph, ~2500rpm, and vibes are present, removing foot from the gas, clutch engaged (idle switch closed, so no fuel input), the vibes are still present. Depressing the clutch and/or taking the car out of gear, the vibes stop immediately as the engine goes to idle speed.

We are plugging away as time permits, which is fairly sporadic lately. I'm not driving the car except for test runs.

Keep the ideas comeing, and thanks!

worf928

I saw a post pop up on a "Vibration" thread and was about to post to it when I noticed that it was Bill's thread and not this one. But, in sympathy I thought I'd post a brief update on this thread.

Brian pulled the clutch assembly and flywheel last weekend. He's going to take the bits to a machine shop.

The DD flywheel is a two piece affair (as many of you know) with the toothed ring gear pressed onto the 'meat' of the flywheel. The last time we had the clutch out I felt something on the flywheel: There was a high-spot on the ring gear - as if the ring gear was eccentric on the flywheel. I measured the run-out at the edge of the flywheel as < 0.001". Then I measured the run-out on the ring gear: 0.009".

I gave the ring gear some careful percussive adjustment and got the run-out to about 0.004". This adjustment had a noticeable effect on the magnitude of the vibration at the 1200-ish RPM nodes as observed with an on-stands static test. However, the on-highway vibration was still irksome.

In the weeks following, as time permitted, Brian and I have chased some other leads. We found an intake gasket leak on the #4 runner. Brian fixed that. CO has been re-tuned. We've had no luck locating the prospective intermittent-but-consistent misfire to a specific cylinder. (I'm hunting a new o'scope in the usual places. The one I have is not up to the job.) Brian swapped-in (and then out) a new CPS on the off chance that it had been damaged during the several clutch R&Rs. No effect. We've checked static fuel pressure: in spec. (But, it really needs to be checked under load with a remote gauge/sender set-up which I have yet to acquire.)

We also did a static idle test of an '85 EuroS and noticed that it too exhibited resonant vibration at 1200-ish rpm nodes. However they were about 1/10th the magnitude of Brian's '84.

Brian did a lot of careful on-highway tests with his '84 and based upon discussion of his observations it seems clear that the vibration - as we have suspected - is at the motor end of the drive shaft: intermediate shaft, clutch, flywheel, and bits forward.

At this point all the data points to the flywheel run-out and/or clutch pack imbalance. So that's what we're chasing.

BRB-83-911SC

UPDATE: At this point, focus for source of vibration has turned to the transaxle. See this thread: https://rennlist.com/forums/showthre...ferrerid=34007

I will update here if these apparent transaxle issues turn out to be the root cause of this vibration nightmare.

EDIT: I guess I never shared the outcome of the clutch/flywheel suspect. I had it checked and balanced at a machine shop, and everything was in spec. He did make some adjustments in balance that would only be felt above 7k RPM (not that I would ever notice). So, clutch/flywheel was reinstalled and crossed off the list. Test run after this revealed an increasing amount of gear whine, directing focus to the transaxle and the above thread....

Pfc. Parts

Brian, any further results on the #7 cylinder tests? I'm having nearly the same problem with my '85 after an intake refresh. How did you rule out injectors?

BRB-83-911SC

Scott - we moved away from the engine as the suspected source of the vibration, and have focused on the transmission. Something did not go together correctly when I had the synchros replaced (a whole other story for another time), and the transmission is now with Greg Brown being put right.

As for chasing my misfire, we concluded that it is not a likely source of the vibes - it is a random miss, just off idle, then no noticeable misfire as RPMs rise. We did check that all injectors are firing using a mechanic's stethescope - you can clearly hear each one clicking. Also removed each injector wire one at a time, and each one caused a change in engine note (meaning it was working).

I think my random misfire is most likely an off idle lean condition - I need to dial in the CO via the MAF adjustment. (note that this misfire is quite minor, and most may not even notice it - the engine runs very strong otherwise).

I would start with a mechanic's stethescope (the one with the long probe for reaching deep into tight spaces) first, to see if you can hear each one clicking. Other than that, I 'm afraid I can't be much more help.

Pfc. Parts

Thanks for the update Brian, I wish you luck with this. In my case I've just completed an intake refresh and I'm getting a vibration like the one you describe but haven't done anything to the transmission. Sounds like we have different problems.

The mechanics stethoscope was a good tip. Dr. Bob suggested using a stethoscope to check my injectors and I have a few, but they're physician's scopes and I couldn't figure out how to get them into position. Amazon carries the mechanic's version for 12 bucks and it has a long thin probe on it that I think will work.

Good luck and thanks for the advice,

Bill Ball

Am I confused about the vibration? You described an RPM related vibration, there despite taking the drivetrain out of the equation. Any tranny-related vibration would be eliminated by just pushing the clutch pedal down.

BRB-83-911SC

I know, this whole saga has been confusing to follow, as we have travelled down several rat holes in the process.

Quick sequence of events:

• Summer of 2012 and since my acquisition in 2009 - car ran great, no significant vibes
• Winter 2012/2013 - pulled transaxle and TT for new 2nd and 3rd synchros (farmed out synchro replacement locally) and Super Bearings
• Spring 2013 - reinstalled transaxle and TT - 1st drive revealed harmonic resonant vibration at certain RPM's under load felt through the chassis. We did nothing that would affect the running condition of the engine.
• Summer 2013 - chased down every possible source of vibration (documented in this thread).

We discovered that the engine does appear to have a very slight harmonic vibration (so slight, most wouldn't notice if not looking for it). The troublesome vibration felt through the chassis was only under load - we thought the engine vibes were getting amplified and resonated in some way. We "tested" another 16V Euro to see if the engine (isolated) exhibited the same slight harmonics, and it did - so we started thinking that it is just a characteristic (the slight engine vibes). However, the amplified vibration (almost a droning) was unique to my car, and only appeared after the Tranny and TT R&R.

So, we switched attention to the only thing we didn't look closely at, and the one system that had received surgery - the tranaxle. I had only driven the car 200 miles all summer, mostly test runs, but there was a definitive gear whine becoming more and more pronounced. Running the car on stands in gear with the half shafts disconnected isolated this noise and accompanying rattle to the transaxle. We had assumed (I know) that the transaxle work was done properly and shouldn't be the cause of the issue.

So, we decide to drop the transaxle again. We took the diff cover off and discovered the oil full of metal shavings (only 200 miles on the oil), and saw what we thought was excessive backlash. We also noticed that one of the drive axle flange shims was mangled and pinched into the case opening.

At that point, we decided to ship the box off the Greg Brown for a thorough going through. He discovered many things wrong inside the box in addition to what Dave and I could see - syncros installed in the wrong gears, mangled engaging teeth, roll pins not in the right locations, worn out LSD friction discs, and bearing damage, presumably from the metal in the gear oil (it should be noted that when I drained the gear oil in the Winter of 2012 in prep for the initial synchro replacement the oil was clean). Greg also noted some "secondary wear patterns" on the R&P.

Dave and I feel that something went very wrong with the reassembly of this transmission and is the cause of the issue we have been chasing. At this point, Greg has the transmission and is rebuilding it. Needless to say, I can't wait to get it back - hopefully that will be the end of this saga.

EDIT: to summarize, if the engine has an inherant harmonic vibration (whether normal, or from some other cause), we did nothing to change the running condition of the engine, and it was not resonating through the chassis before the "synchro job". The theory now is that sloppy reassembly of the transmission caused the R&P setup to be off causing this vibration under load, We will know soon enough.

Pfc. Parts

Great writeup Brian. Thanks for sharing it with everyone. After I find my engine vibration my next project is the transmission, halfshafts and TT. Sounds like you're near the end of your nightmare.

BRB-83-911SC

The saga continues. The rebuilt transmission is in, and performing like new. The gear whine and marbles in a box noise is gone, and it shifts beautifully. Greg found many things wrong inside, some the result of many years of a poorly performing clutch, but mostly issues resulting from 2 prior "rebuild" attempts that failed miserably. It really has transformed the car.

But, alas, the vibration remains, and if anything, is more pronounced than before. RPM dependant, most strong under load, can also be felt when coasting down through the RPM ranges with foot off the gas (presumably in no fueling mode), as well as when reving the engine through the ranges, clutch in.

The RPM ranges where the vibes are felt seem to crescendo at approx 1300 RPM intervals, and you can feel the car shake slightly at idle. If I were encountering these symptoms for the first time, I would immediately think motor mounts - as the vibes seem to resonate through the body of the car, as if something in the drivetrain was making contact - causes the interior trim to buzz.

But, we have checked every potential point of contact, and all is clear. New transmission mounts, new motor mounts (Volvo) last year, engine rocks when revved, nothing touching anywhere,

So, the focus will turn back to the running condition of the engine. While all of the usual suspects are new or newly rebuilt (wires, caps, rotors, plugs, coils swaped with known good, ignition amplifiers swapped with known good, injectors cleaned/tested, MAF rebuilt, intake leak tested, fuel pressure verified in spec, TT rebuilt, clutch/flywheel balanced, etc.), we will revisit some of these, including resetting CO, a compression test, and possibly some diag with an oscilloscope.

Other than the vibes, the car runs very strong and makes very good power - no surges or bogging down - it just rips. However, I don't feel comfortable driving it like this - who knows what kind of damage it could be causing.

You can hear an occasional misfire, especially off idle approaching 1300 RPMs. It's not every revolution, but an occasional, very muffled "pop..pop.........pop..........pop.....pop...." - random misfire - what I would think a lean misfire would sound like.

Since Winter is arriving any day now, there may not be much to report until driving season returns to New England.

Thanks for playing along and offering ideas. Very discouraged at the moment.

G8RB8

I'll go back to my old saw. What did you touch? The torque tube. What could cause a resonance there? The relative positions of the bearings, or just a bad bearing. Sorry Constantine, but it happens.

BRB-83-911SC

Clutch in, TT not spinning, vibes still present.

G8RB8

Missed that, sorry.