Setting timing and engine vibrations

[Blake]

While trying to set my timing, I had trouble getting the timing to stay steady, with tan wire disconnected, timing and rpm would flare up and down. When going down, the engine would almost die and then flare up again.
In the meantime I noticed that when in park or neutral, if I rev the engine, the truck will shake as rpms go up(compression check was fine).
Are these related? Any ideas?
I found this while looking for ideas:

The Shakedown on Vibration Issues, Underhood Service, May 2001

Motor Mounts
Often-overlooked engine components that may need to be replaced to eliminate vibration are motor mounts. These rubber mounts can deteriorate, collapse and/or separate with age. Fluid-filled "hydraulic" type mounts can often leak, allowing annoying engine vibrations to be transmitted to the chassis.

Most mounts are designed so that separation won’t allow the engine to fall out onto the roadway. But a bad mount may cause a myriad of problems - many easily misdiagnosed.

Often, bad motor mounts allow the engine to rock and move around, causing noise and interference problems with the throttle, transmission and clutch linkages. For example, a thumping noise when the transmission is put into gear or when the vehicle is accelerating is a classic symptom of a bad mount.

Some Warning Signs of Harmonic Balancer Failure in a Vehicle Are:

• A leaking front main seal;

• Visible deterioration of the rubber between the balancer hub and outer ring;

• Visible cracking or warping of the balancer hub or outer ring;

• Excessive engine vibration;

• Slipping, squealing drive belts, belt damage, accelerated belt wear or frequent belt replacement;

• A highly polished spot on pulley grooves (warped balancer);

• Elongation of the balancer keyway or wear on the balancer hub/crankshaft;

• Alternator, power steering pump, air conditioner or water pump failure;

• Engines that do not run properly when adjusting the timing, or poor performance and irregular idle.

Courtesy of Pioneer, Inc.

 

[Daron]

When I put my timing gun on my truck, the mark stays solid, doesnt jump around. I can rev it up a bit and it still hangs in there. The Harmonic balancer flopping around could theoretically cause your problems? I wonder how to check....

 

[Guest]

you can use a piston stop and see if the timing marks are off. maby the chain is bad. maby it needs a major tune up.

 

[ronniejoe80]

Take the dist cap off and try to move the rotor back and forth. I had to replace the dist drive gear on mine. Also, with the cap off and plugs out rotate the engine slowly until the rotor starts to move and the turn it the oposite direction to see how much play is in the timing chain.

 

[JoeLutz]

Could be a problem in the distributor like a loose pickup coil or something. Are your cap and rotor good, tight, loose? See if you can twist the rotor on the shaft. Like Daron said, my timing is rock solid with the wire unpluged at any rpm. The off idle vibration is normal, because our engines don't have balance shafts.

 

[just a 6]

I assume you are talking about the tan wire under dash? Did you unplug it while the engine was running or turned off? Have you checked the spark plug wires so none is loose, it sound like your engine is missing one cylinder or more. Was the truck running like this before you tried to adjust the timing?

On 2002-01-17 22:27, Blake wrote:
with tan wire disconnected, timing and rpm would flare up and down.
In the meantime I noticed that when in park or neutral, if I rev the engine, the truck will shake as rpms go up

 

[Blake]

Yeah, the truck runs "perfect" so to speak when the wire is connected(when I set timing I disconect it while the truck is off,turn truck on,set timing, turn the truck off, then reconnect it, then clear the trouble codes). It did a tuneup when I did the compression test.
It'll run the full stock 13.8pounds of boost(I checked the bin for correct desired boost with Promgrammer2001) with zero knock and o2 millivolts are in the 930 to 940 range. TPS is new. It exhibits none of the common signs of bad ignition. The engine just vibrates when you sit at idle and rev it up. It doesn't vibrate with your foot off the throttle. It will vibrate after you start reving it up slightly. I wanted to do an injector balance test but can't get the tool. I checked the rotor button yesterday and it does not move at all. Yeah the truck ran like this before I adjusted the timing. That was why I did the compression check.
Something else that I noticed after setting timing "close" to zero was that the truck idles lower(rpms are ok)it is just lower than it was before, but, when I turn the A/C on the compressor engages and then immediately kicks off because the rpms drop too low. As soon as the rpms come back up, the compressor reengages. This may be due to a crudded IAC. I have a new one. Waiting on the mini van purchase so I can get the time to rip the throttle body off, clean it, and put the new IAC valve in. Don't know if it will help with that problem or not though. Of course that probably has nothing to do with the vibration.
Thanks for any ideas you have. I still have yet to pull the plugs and turn the alternator pully back and forth while looking at the rotor to check for slop in the timing chain.

 

[Blake]

I took the truck out to get groceries today so I could get warmed up. The engine does not vibrate when reved up in "P" or "N" after it has been driven for a while.

Does our engines use a "cam button" or something like it? I found several sources that said this could happen if the cam walks back and forth.
Thanks

 

[just a 6]

No cam buttons.

On 2002-01-20 18:11, Blake wrote:
I took the truck out to get groceries today so I could get warmed up. The engine does not vibrate when reved up in "P" or "N" after it has been driven for a while.

Does our engines use a "cam button" or something like it? I found several sources that said this could happen if the cam walks back and forth.
Thanks