Whisper

Before I redid my GSL-SE, I had this violent vibration that I attributed to the engine, as it was in sync with the RPM in any gear, out of gear, and in neutral, clutch in and out.

I didn't bother with it much, the engine was old and I wanted to race the car, so I figured I'm gonna replace everything under the hood anyway, so it'll probably be gone when I'm done.

I was sooo wrong! Half a year and a ton of parts later it's back, stronger than ever (probably due to the polyurethane engine mount amplifying the hell out of it).

To save time, it would be easier to just list the things I did not replace/service:


Transmission (but have new seals and front cover)
AFM
Distributor (but have new cap and rotor)
Ignitors
Eccentric shaft pulley
Trailing coil (using FC coil for leading)
Throttle body (but cleaned and adjusted)
TPS
Solenoids
BAC (but cleaned and tested)
Starter


Umm, yeah, that's about it, I think...

I want to break my new engine in before the track season starts, so I am kind of in a hurry to solve this.

A bit more on vibration. This is purely by feel I got from the gearshift and steering wheel. It's slightly different when on the throttle and when off the throttle. Off the throttle it feels kind of loose and wobbly, but if I apply any amount of throttle, it tightens, if that makes sense. Same frequency, but smaller amplitude. Overall it's pretty harsh, you know, the kind of vibration that loosens bolts and makes things fall off of your car.

For some reason the distributor is my prime suspect. When I set the timing, the mark is kind of jittery. Transmission is my second, even though I don't even know how that would be possible.

It'd driving me nuts. Please help me out. All opinions welcome.

Thanks.

1BADSP

iTrader: (4)

i have had a bent input shaft cause a vibration.

Whisper

With clutch pedal in?

Zackqw

ok well.. i dont believe its your dizzy...(distributor) timing wouldn't make that kind of vib.. more of run like crap.. take for example a d15b(Honda motor 4 cyc) the piston bent would create a pretty good vib with also a hollow sound.. if its a vibration it MIGHT have something to do with the rotor.... tighten down all of your motor mounts really well along with the tranny mount.. if the vibration goes away mostly then it might be inside your motor.. dont rule out your tranny.. if your useing the same tranny it could be that also... might need to get a better tranny or take yours out and open it up to make sure everythings tight.. best i can think of for the moment.. hope it helps

Whisper

Yeah, distributor is unlikely, however if the bearing is worn, maybe it shakes and creates uneven distribution of signal, making lumpy spark, so the combustion is uneven, throwing the rotors off balance... Can that happen?

Transmission does seem like a possible culprit. It's a 12A tranny on a 13B, but I don't think that would make a difference. And with transmission disengaged (clutch in) I think it still vibrates the same. I'm gonna double check just to be absolutely sure, but I still suspect it's engine related.

2GSLSE

iTrader: (6)

I don't know what you call violent but it sounds like a bad trans mount causing the vibrations,.
Has the vibration always been there or have you or anyone else changed anything (excluding any recent work)

DivinDriver

iTrader: (15)

You didn't get the wrong flywheel on the engine by any chance, did you?

installer67

iTrader: (18)

+1 on^^^^ internals unbalanced will do exactly that, till seals wear or bearing goes. Then bye bye.

j9fd3s

iTrader: (3)

alternator/water pump/air pump? any of these can cause vibration, especially the water pump. the factory water pumps can have like 1" of play at the bearing not leak water and vibrate the hell out of everything.... take the belt off, you'll know within 15 seconds if you fixed it or not

a loose fan with do that too

as will the wrong flywheel

Whisper

Flywheel? Maybe... It's the aluminum 13B flywheel, 225 mm. Flywheel itself wouldn't unbalance anything, since it's perfectly round, but wrong counterweight, on the other hand, probably will. Since Rob put the parts together for the engine, including the counterweight and flywheel, I strongly doubt he messed up the balancing, but I will check with him, and I'll also try to measure the counterweight to see which one it is. The reason I doubt the balance is off is that I had this vibration on my old stock 13B engine with stock flywheel and counterweight. Two different engines and flywheel setups - same problem...

@ 2GSLSE
I have replaced the transmission mount about a year ago, because of the vibration. Old one was shot, but the new one didn't make much difference. I also inspected it before reinstalling after recent work and it still looked good. New driveshaft as well, in case that's the next question.

Zackqw

i think its the tranny.. try to find a different tranny to bolt in there just to see if it still has the problem.. this is truly stumping me... i will do more research!!

DivinDriver

iTrader: (15)

If the vibration is RPM dependent & still happens when you are not moving, clutch depressed, trans in gear, brakes held.... your problem must be somewhere from the pilot bearing/input shaft mating point forward. Under these conditions, the input shaft is not rotating (being held by the gear train), so the pilot bearing is hard at work spinning around the input shaft tip.

Only exceptions would be the trans and engine not aligned axially, or the input shaft being bent, or the clutch or flywheel being out of balance somehow.

Is the clutch maybe off-center? Same clutch or different clutch from the other engine?

Whisper

Different clutch and PP. I used the clutch alignment tool when installing it. Is it possible the clutch still isn't fully centered somehow? It's sitting on the input shaft, aligned by the splines, so if the input shaft is bent, clutch would be out of balance.

One thing I kind of remember from test runs back with the old engine, is that vibration would not always be as strong. One time I would drive the car, it would be barely noticeable, and another time it would be horribly harsh. Some days I'd be like "Wow, it's unusually smooth" and other days I'd be like "Holy crap what is wrong!" I don't know if it still does that, I haven't driven the car enough times yet to make that kind of observation.

Input shaft is an interesting theory. Maybe I'll pick up another tranny next week and try it out.

Whisper

Oh, and quick question. What other tests can I try to determine whether the vibration is transmission/input shaft related or if it's the engine? I'd hate to spend time and money on getting a different transmission and putting it in just for the sake of an experiment.

Like revving at a standstill in gear and clutch in. Or shutting the engine down at speed with clutch in. Any of those would tell me anything?

DivinDriver

iTrader: (15)

Those would mainly tell you if it's restricted to times when the car is moving or still... basically could eliminate suspension & drivetrain from the input shaft back.

Whisper

I think I just want to test a condition where the engine is running, but the input shaft and clutch aren't spinning. If it doesn't vibrate under those conditions, then I'll know it's not the input shaft or clutch. And vise-versa, test when the engine isn't spinning, but the input shaft and clutch are, if it doesn't vibrate then, I'll know it's the the tranny that's at fault. If that makes sense...

j9fd3s

iTrader: (3)

to stop the input shaft push clutch, put trans in any gear with the car not moving.

to stop the engine but keep the trans moving, its the opposite, move car stop engine with the trans in gear

Whisper

Alright, pretty much what I thought. Thanks. Will play around with that.

FbDrift

you mean out of gear...

blwfly

iTrader: (4)

get a stepthascope and prode the engine i had somthing alomst similar.
i had over reved my engine and welded the rotor bearing to the shaft.

just a idea not saying it could be your issue.

Whisper

No, he means in gear. With clutch pedal all the way in, obviously. As I understand having transmission in gear ensures that the input shaft is spinning. Clutch out just means the engine doesn't spin with it.


@blwfly
Will check, thanks. I haven't revved this engine past 4000 yet, but never hurts to make sure.

mazdaverx713b

iTrader: (91)

you did the obvious and checked engine mounts and the trans mount correct?

Whisper

Results of the test:

Parked, in gear, clutch pedal all the way in - no effect on vibration.

Driving down the road when vibration is most pronounced, push clutch all the way in while still in gear and let the engine drop down to 800 RPM - even though still driving at the same speed vibration frequency goes down with the engine to exactly where it would be at idle. It was pretty obvious even without shutting the engine down.

So now, with those test results, everything points to the vibration source being forward of the flywheel.

I don't think it's a balancing issue, either. I highly doubt Pineapple screwed up the counterweights. And one thing I observed when warming up today, is it shook pretty good at idle at one point, but after I gave it some gas, and let it drop back to idle it smoothed out - roughly the same RPM and everything.

It's almost as if my sensors are sending a bunch of rubbish to the ECU, and so my mixture is all messed up, causing the engine to fire rough. I suspect TPS or one of the temperature sensors, because in the middle of a warm-up it'll suddenly start to cycle up and down, between maybe 700 and 1100 RPM, shaking violently every time it drops to 700 and smoothing out as it revs, but then a minute later it'll suddenly stop and idle steadily again. Sometimes it'll repeat the process a minute or so later, before it finally evens out for good.

I checked resistance on the TPS according to the FSM, and fully extended it maxes out at about 4.16K instead of the ~5k suggested by the FSM. But at "idle" position it's pretty close to the 1K suggested by the FSM. Maybe it is going bad?

I don't even know anymore. I feel like it vibrates due to crap, uneven combustion, maybe because of the mixture, maybe because of bad spark, maybe because of I-don't-freakin-know-what.

blwfly

iTrader: (4)

check for vaccum leaks and maybe your injectors are dirty stab in the wind
when i swapped a t2 in my repu it ran kinda vilonetly until i had those issues sorted

Whisper

I was kind of hoping for a vacuum leak that I missed, so I had a shop smoke machine it a few days ago, but unfortunately couldn't see anything leaking.

Injectors were cleaned and flow-tested couple years ago. Maybe I'll pull them out to see if they got clogged again, but I doubt it.