eddie jr

Ok, I am in need of some serious help here cuz I am stumped with this engine vibration (85 2.8) that I think has been there for quite a while. The vibration is apparent all across the rpm band but it expecially doesn't sound good when revving past 3000. You can even notice a distinguished shake to the car at idle (really noticeable in the dash pad, shifter and seat).

I recently noticed that the harmonic balancer was screwed as you could see it wobble so I thought that has to be it! NOpe......even though the rubber ring was half way out and the outer ring was definitely shifted off centre, not a bit of difference in the vibration The balancer wasn't new (from wreckers) but it looks great and now when spinning is completely true.

I checked the timing tonight and it was at about 20* (not sure how since I set it at 10 last fall) so I shifted it back to 10 and it ran even worse! There was a bad throttle delay and choking which made it hard to get it into 1st. So I put it back to where it was for now since it runs better.

Now I am stumped, what are some other problems that could lead to this vibration???? I am going to check compression, spark and vacuum tonight and will post what I find to see if that helps any. I have been told that V6's naturally have vibration but this just doesn't seem right to me I have put so much time into this car and now it is treating me like ****.

Can anyone help point me in the right direction?

greatly appreciated.

CaliCamaroRS

Have you replaced your timing chain recently? If not, it may have stretched. If your car runs like $hit at 10* base timing but not at 20* base, you have problems. I'd replace the timing chain and do a FULL rebuild of the distributor if you haven't already.


My chain stretched so badly( around 140,000 miles) that it started slapping the idler/tensioner. It slapped it until the idler broke. The engine shook like crazy off idle cause the timing was ****ed. This could explain how your timing changed.

Doward

Check the timing chain, yes... have you replaced the flywheel/flexplate at all lately? (Just curious)

60º V6 should NOT have any vibration - IIRC, it's a naturally balanced motor (as in, EXTREMELY smooth)

eddie jr

Sorry, forgot to mention, just did the timing chain this past week at the same time I put the second balancer on.

Flywheel (T5) has not been replaced since I have had the car. I did the clutch last fall and had it machined but it has never been replaced. I originally kind of thought the vibration may have showed up after the clutch job but I think it was more paranoia than anything else......one of those cases where you question was that really there before or not? It probably was.

Could this potentially be a fuel or ignition system problem?? Could maybe 1 cylinder not be firing?? I did check 3 plugs so far (all on drivers side) and they had a bit of white on them which I have never seen before. Any idea what that would signify? (I will try to post a picture shortly).

Also, on the balancer, I noticed 3 grooves. Which one do you use, the big wide one or one of the other 2 narrower ones?

V6sucker

did you unhook the EST when you set the timing?
Have you checked your motor mounts?
Have you checked your trans mounts?
How old are the above components?

eddie jr

Doh, in all thefrustration I forgot to unplug that However, after putting the timing back to what it was it is probably very close since it was set only last fall and the mark on the old balancer didn't seem to have shifted. I shall check again today though! Thanks for figuring out my stupidity . WHat about the timing marks though? WHich of the 3 do you use?

Tranny mount is new but motor mounts may be original...who knows. I got under and looked at them and they do have tiny heat cracks on the surface only but otherwise don't seem too bad. THere is no clunking.

eddie jr

Forgot to mention, when I did check the timing yesterday the timing mark was anything but steady. It shifted around rapidly by about 2 degrees Is this characteristic of something?

edit: Also noticed that there is a small exhaust leak on the passenger side where the manifold meets the block (at least I think that is what the sound is). Could an exhaust leak at the manifold cause rough running?

V6sucker

Not like you discribe.
On the balancer there should should only be 1 mark. TDC.
On the tab, there shold be a few marks. The top being 10* PTDC Past top dead center) center is TDC, bottom 10* BTDC. My old tab had the actual markings that had 10* and BTDC/TDC/PTDC and a few more.
You are after 10-13*BTDC.

If the engine idles smoothly and there is still a vibration. Is is a rotating part, or a mount.

SSC

The timing jumping can be caused by a few things. You could either have, bad cap/rotor, bad plug wires or too much play in the distributor could even be all of the above. Make sure the wires are seperated as much as possibile when you check timing.

Plugged injectors can cause the engine problem you describe.

A small exhuast leak wont cause this problem unless its right at the O2 sensor.

dream02transam

well now this is probally not the case with your car but I have heard of motor where the harmonic balencer got to be as bad as yours was and left undectected for a lenth of time that it messed up the crank and main bearings. As for your balence I have 3 marks on mine as well. I think its the wide mark that is TDC. If your doing timing it should be the only one that shows up in the timing light if you have it on the #1 plug wire. If the timing was so far advanced or retarded that the other ones showed it should really even run it would be like 120* out. If the wide line is the only wide line then thats TDC if the narrow line is the only narrow line then that one was TDC.... I cant remember I just remember that it was the only one that size. Another way to figure it out for yourself is take the #1 spark plug out and put your finger over the hole until you feel a little compression then watch with a bright flashlight to see when the piston gets to TDC of the compression stroke.... then the correct timing mark SHOULD be right on 0*

TomP

Dream02 is right; use the widest one. The v-belt'd 82-86 2.8's used balancers with three grooves. It was designed for a magnetic pickup timing gun; on your timing indicator you'll see a small tube; that's where the pickup went for the special timing gun. The MPFI 85-86 2.8's have three grooves, one of which is the widest, and means top dead center of #1.

The 82-84's have three grooves that are all the same size... so you have to manually find TDC of #1 (front passenger side cylinder), and whatever mark on the balancer lines up with 0 degrees, that's the one you'd mark w/chalk.

camaro_junkie

You talk about the small exhaust leak on the passenger side. That might not be an exhaust leak, it may be the bypass for the smog pump; it gives kind of an exhaust sound (it took me a long time to figure that out).

Also, check your universal joints on the driveshaft. My mom's car once had a serious vibration problem and when we took one of the u-joints apart, the bearings inside were no longer little pieces of rod, they were dust.

As far as the three marks on the balancer... mine's an '86, but I don't ever recall seeing more that one.

eddie jr

hmmmmm, interesting. is that bypass not at or near the pump though? This sound definitely is coming from the back of the passenger side near cylinder #5.

Reset the timing yesterday with the bypass DISCONNECTED (can't believe I forgot that ) and it is now at 10 although it still bounces around. You can actually see the engine shaking at idle. Gonna change the wires today and see if that makes a difference cuz I put 1 or 2 old ones on and the timing mark got steadier.


So how would one go about figuring out if this is the problem?

When I pulled all the plugs yesterday the electrodes and what not looked to be in decent shaped still but all 6 plugs had a bit of white on them. They had the nice brown as well but all had varying degrees of a thin white powdery coating (not built up deposits). The white would esily wipe off with your finger. ANy idea what this could signify? I am correct in assuming that white is not normal, right?

camaro_junkie

The bypass is right below the exhaust manifold at the #3 cylinder. It could be your "leak" problem because it does sound like it's coming from the manifold. Try taking off the smog pump belt and see if it goes away.

eddie jr

ok, new plug wires on now cuz a on a couple the metal thing was not on the spark plug in the boot, just touching. TIming mark is a bit smoother but still lots of shake at idle and vibration when revving (most noticable between 1500 and 2000 and then over 3000 sound ****ty)

So plugs and cap/rotor only have about 10,000km on them and I even sanded down the terminals last night (still have little dark spots on them but got rid of the corrosion). The pickup coil (or whatever the thing with the poles below the rotor is) looks super ugly cuz of rust/corrosion. The distributor shaft also has some play up and down (not sure how much play is good or bad?)

Did a compression test last night and came up with the following:

cylinder 1 : 172 psi
cylinder 2 : 175 psi
cylinder 3 : 110 psi
cylinder 4 : 175 psi
cylinder 5 : 172 psi
cylinder 6 : 145 psi

Pretty strong except for #3. What do you guys think of these #'s and do you think that would be enough to cause these vibes/shaking???

camaro_junkie

This is going to sound like a very stupid question, but are you ABSOLUTELY SURE that all the spark plug wires are correctly ordered at the distributor?

V6sucker

More and more that sounds like a question in my mind too. remember that #1 is on passanger side, not drivers.

camaro_junkie

It seems like a stupid question, but I did just that last time I did a tune-up. Of course I realized it as soon as I started it up.

eddie jr

haha, no not really stupid cuz it is an easy mistake to make.......but I am sure that they are right......firing order 1,2,3,4,5,6 with 1 on passenger side front of engine and passenger side front of cap as well.....6 on driver's side front of cap........rotation of rotor is clockwise.

dream02transam

If your pickup coil is that corroded I would go aheah and change it. my 89 had that problem. It would run ok then out of nowhere it would stall and then it would get worse to the point that it wouldnt stay running when warmed up unless you held the gas down then wouldnt start at all. It could be the cause of your timing jumping around like that. I bought one at auto zone for less then $10 The only problem is you have to take out your distibutor, knock out the roll pin holding your dist. gear in and slide the shaft out to change it, while your there change out your dist. o-ring seal too. I put mine back in and it started leaking. There is a test of your pick up coil with a Ohm meater in both the chiltons and the factory helms manual, check it out. I know your cap and rotor only have 10,000 on them but that doesnt mean much, I had a cheap NAPA cap and in less than a year it was bad already, It had already had a little corrision and the tower where the coil wire went in I could spin with my hand. I guess something inside had a little mosre resistance because of that. Let us know how you make out.

eddie jr

Checked out the resistance and the coil checks out ok. Also checked out the ignition coil as well. Also checked the resistance of the fuel injectors and they were all dead on 16 ohms.

Any other ideas? I am still stumped as to what is causing this shake and vibration.

Does anyone have comments on the compression numbers? Could that cause something like this??

thanks for all the suggestions so far, keep them coming

eddie jr

checked the timing again and now (with the new wires and after the timing chain) the timing mark no longer appears to bounce around. It seems to be rock steady. So I assume that this would indicate that the performance of the engine (ignition, fuel etc) is all ok then....if it were missing the mark would bounce wouldn't it??

So now I would guess the vibes must be a mechanical balance issue then, would you guys agree? I just called a shop and confirmed again that it doesn't matter which way the pressure pate goes on (there were no dowel pins), so that is ruled out. And there is a new balancer on there.

What could it be???? I am running out of ideas here...

V6sucker

#3 could be a culprit. being it is THAT low.
definatley time for rings.

But even then, it should not cause a major vibration. I still say it is in the mounts, or the suspension.
I say suspension cause where do you think the vibration goes when it hits the frame?

also, if the mounts were just replaced were they rubber or poly? Poly has a habit of transmitting alot of vibration. Part of the whole rigitity thing it has going on.

CaliCamaroRS

That #3 cylinder is way too low. I think the spec is lowest cyl should be at least 70% of the highest cyl.

You can do a power balance test to see if infact #3 is weak. I take short pieces of vacuum hose and put them in between the dist cap and all 6 plug wires. Then, with a test light to ground, you can effectively short out each cylinder individually by grounding the spark from the cap. Each time you short a cylinder you should hear a noticable RPM drop. If the RPM doesn't change then you've got a weak or dead hole. Do it with the IAC disconnected too.

eddie jr

When I pulled the wires at the cap a while ago there was a rpm drop for all 6. Also the plugs were all consistent colour and the timing is now steady. WOuldn't that mean that that cylinder is still doing allright even though the lower compression? I'm not sure, just asking, trying to learn

Well, it shouldn't be in the suspension since you get the vibes anytime (while revving the engine too). THe mounts are rubber but only the tranny mount is new. THe motor mounts don't clunk and there does not seem to be a lot of play but I am still not sure if that means they are still half decent or not???? I just hate the prospect of getting into the K member to get those bolts! DO you really think they could be a problem given this info??? What about the shifter (T5)....should it move a lot to the side if the mounts are going??? What is the best way to accurately test the mounts?

V6sucker

really the only way to test the motor mounts is to use an engine lift and take some of the weight off and try to move the engine around. If the engine can move, you got bad mounts. People have also used a jack and wood to lift the engine just enough to get the weight off the mounts.
Just grab the intake and try to move it around. It should not move much at all.
Rememebr though, you just BARELY want to lift the engine.

TomP

#1 can be anywhere on the distributor cap- you shouldn't base it off of "it's on the passenger side front of cap". Even if 90% of people put it there, you still can't go by it. Bring #1 up to TDC compression, remove the cap, and make sure the rotor is pointing towards that cap terminal. And technically if your motor is exactly at 0 degrees TDC #1, your rotor should be between the #1 and #2 cap terminal.

(If the motor was at 0 degrees TDC #1 and the rotor was pointing exactly at the #1 cap terminal, then that's 0 degrees advanced, and the motor might not run.)

eddie jr

Thanks for the tip. Wires are definitely on right. Checked a few times and the timing mark is also perfectly steady now. If the wires were wrong the engine run really bad, even if only one was wrong (at least it did when I was pulling them when testing )

Going to have to try a pry bar on the mounts maybe tonight or tomorrow (although all indications so far is that there isn't much play.....but we'll see) but other than that still have no clue what it could be

camaro_junkie

A vibration is hard to diagnose unless you are actually with the car. So everyone can only give suggestions based on your descriptions. It's pretty hard. Drive it out to Vancouver and I'll lend a hand.

eddie jr

I agree, vibrations are the pits to figure out I even had an actual mechanic come out last week to see it and test drive and even he was stumped I really appreciate all the suggestions so far though. The best thing to do I guess is to try to eliminate things one by one.

One positive thing though is that the timing chain (which some of you guys helped me through...thanks ) has made a noticeable difference The driveline seems tighter (manual) and the engine runs better all round.

Hey, a cruise out to Vancouver would be cool! Still haven't made it out west yet....hopefully soon. Especially Whistler