My van has a significant vibration when idling in drive or reverse. There's a little while idling in park or in neutral, but much worse when in gear. And only when idling - give her some gas and it smooths out.
Just spent the weekend replacing both motor mounts and the transmission mount (all aftermarket) but unfortunately the vibration is still there...
Any thoughts on what I should try next? Or just accept that I'm getting a free chair massage at red lights?...
I should also say that the vibration itself is very consistent. Not bouncing around like I would assume a rough idle would.
There are three versions of the 4.3, the later had the balance shaft. If you have plastic valve covers there is a good chance you have the stronger odd fire engine. Look up what you have. Check your balancer like frscke1 said, remember if the balancer is external balance the outer ring can slip and be out of place and be out of balance. If you have the balance shaft engine, the shaft may have jumped a tooth. GM used nylon gears back then for noise reduction. Back in the 80's many cars went to the boneyard for broken gears at 75k on the clock. The other thing to look for is the balance weight on the flexplate, it is spot welded and can break off. If you have the odd fire engine you may need a timing chain set. Of all the stupid things make sure you're running on all cylinders. Plugs, wires, cap, does 93 have the fuel injector spider? Are you getting fuel to every cylinder?
Check the PCV valve and tubing for clogging, leaks or poor operation.
Check the throttle linkage for smooth operation and closure without binding. Also you'll need to check that the throttle and TPS are adjusted properly. The TPS should read less than 1.25 volts with the throttle closed. If the throttle stop has been messed with in the past it could be off.
A quick check for any small vacuum leaks using some starting fluid would be easy and cheap.
Other thoughts: Does the engine idle change or smooth out with the AC turned on? The module should raise the idle slightly when the compressor is engaged. If not then you may have a communication problem with the AC control and the module.
You might want to remove the IAC and check it for proper operation and cleanliness. (The internet can tell you how to properly set it for a reinstall).
A leaking injector can cause a rich idle and can be hard to spot if it's only a slight leak.
Also know that the 4.3 V6 engine is not a smooth idling engine anyway. An internet search will show you quite a bit of info and a search of some of the S10 forums will reveal many threads on the subject.
Thanks jcd74!!! The Haynes manual implies that only the 1995 4.3 V6 has the balance shaft - is this the one with the odd fire? I assume mine isn't this version since it is a 1993. Still worth it to check the flexplate I guess, and thanks for the advice.
Great thoughts CatFish - thank you. I just replaced the PCV but didn't check the hose, and I'll certainly look into the other things you mentioned. I just tried to see of anything is different with or without the AC on, and I'd say that it doesn't really change anything regarding vibration. I can feel the compressor kick on, but I guess the extra RPMs aren't enough to get it out of the "vibration zone".
So I captured a video of the harmonic balancer while idling in park (doesn't vibrate as bad as when in drive, but some still there). Is this level of wobbling concerning? Can really see it in the shadow cast by the balancer.
Good to know - I was thinking it was a lot, and I'm scared to look when it is in gear and the vibration gets much worse... I did just change the water pump, belt, fan clutch (and other cooling system components) a few weeks ago, so I hope it isn't the water pump bearing? AND, the van was having the vibrating issue before then, so fingers crossed it is something I haven't addressed yet, like the balancer.
Thanks frscke1. My fan appears to be the right one, but definitely wonky - the blades aren't spaced apart evenly. Almost have the new balancer on and going to see if the vibration is better before putting the belt back on for a before and after test.
The old balancer doesn't look too bad, but the rubber is showing some cracking. It also has a stud in one of the outer holes, which the new one does not.
Installed the new harmonic balancer and cranked her up with the belt off - still vibrating like crazy at idle when I take it out of park... I bought the FSM and it has a great section on diagnosing vibration, but being a novice mechanic, a lot is over my head. Next steps will be to doublecheck the advice you guys have given me here - misfire, flexplate, etc.
For "engine speed sensitive" vibration - which I believe this to be since it is happening only at low RPMs - after checking for misfire, the FSM says to "check transmission converter and correct if necessary". There is a "Flexplate / Torque Converter Vibration Test Procedure" which I assume this is referring to? Seems like it is a process of removing the flexplate and rotating the torque converter 120 degrees, then reattaching the flexplate to see if this gives better balance. Sound simple enough, but am I overlooking something that makes this a royal pain?
Id Mark the drive shaft before removing ... what you say sounds simple . drop the drive shaft .. put the tranny on a rolling lift .. but as you say there's always somthin ...
good luck on your endever ... do it right or do it twice .. I live by that.
Removing the dust cover, removing the converter bolts and relocating the converter to flexplate is a simple enough job. Be careful not to push the converter back into the trans as you might disturb the front pump seal. Mark them first in case you need to return them back like they were.
Wanted to close the loop on this issue with some good news, in case it could help someone in the future. I abandoned the idea of rotating the flexplate position on the torque converter because despite much effort, I couldn't remove an exhaust pipe that was preventing removal of the inspection plate. So I focused back on ignition. The previous owner had just replaced the spark plugs, wires, distributor cap & rotor, but not the ignition coil - which was the original with 30 years and 107k miles on it. I could see/hear/fell the engine was pulsing 2 to 3 times per second or so when idling in gear, which seemed odd, and it was also struggling to start after frequently starting and stopping when troubleshooting. So I replaced the coil and I'm very happy to report it is running much smoother now! (In fairness, I also replaced the cheap cap and rotor with ACDelco's versions). The vibration is considerably better - not gone completely, but better for sure. And in the process of getting advice and opinions (thank you very much!) and having never owned a 30 year old van, a vehicle with the 4.3L V6, let alone a Chevy before, I've lowered my expectations as to what "normal" vibration would be. Id have to say I'm quite happy at the moment. Thanks again for all the input.