thanks for all the help guys. great to see a helpful forum for a change. when i get home tonight i'm going to put it on jack stands and take a peek at the underside, and possibly at the clutch. who knows i might have it half torn apart by tomorrow morning. I will clean the maf and see if that makes a difference. I might do this on my envoy as well. It isn't throwing any codes, but it does get poor gas milage, as well as poor power.

I didn't have the clutch replaced, the guy i bought it from did, and im assuming that's why it shakes so much. I'm going to replace the u-joints while im down there. Thanks again guys. I'll let you know tomorrow how it went.

 

where any of the gages showing out of the ordinary readings. you may have a temp sensor giving false info to your computer. you can test temp sensors with ohm meter. #18 here http://shbox.com/1/how_tos.html

 

No the gauges were fine temp at 210 fuel at half a tank oil at 50ish close to 60 etc I tried cleaning the maf but once I removed it, it looked brand new. I had a chevy tech come ver and have a few beers, he's pretty sure it's a bearing on one of the pistons or the crankshaft is out of balance( I didnt know this could happen) I guess I'm just going to run it til it gives way then swap it. Maybe I'll throw a ls1 in it.

 

well that stinks, if that's it... how are the coil packs and plug wires? If they're not 100% they could give you codes too...

It's cheaper and easier to just sell the v6 and buy a v8 car... I steered away from the v8 swap option for that reason.

 

double, triple check to make sure you plug wires are in the right places. you may very well have a couple crossed.

 

Possible, not real likely. Not unless someone was in the bottom end for some reason.

This is more likely. If someone took apart the clutch, and didn't reinstall it correctly, then I can see how something may not be lined up correctly. Another possibility would be if the harmonic balancer was removed and not reinstalled in the proper orientation.

It can be done, but it is not nearly as easy as most think.

An unbalanced rotating assembly can cause vibrations at low rpms and when under load. The vibrations can seem to lessen when cruising at a constant speed, but become more noticeable when accelerating.

 

I'm not quite sure where to go from here. I don't think it would be be harmonic balancer, more likely the clutch assembly? I've only replaced one clutch in my life and that was on an 87 BMW 325is. That was ten+ years ago. I used a clutch alignment tool and it went together pretty smooth. Drove great afterwards. What is it exactly that can go out of balance back there? Main bearings?

 

if a bearing were going to the point of vibrating you should see fluctuations in your oil pressure. are you sure your not missing a cylinder. try unpluggin a spark plug at a time while its running to see if they all make a difference in how its running. also could check the plugs to see if one or two are fouling.

 

I'll try unplugging one wire at a time tonight to see if there's a difference. I have only put 300 miles on Ngk iridums and I checked the gap of every single one before installing. It felt the same after I changed the plugs. I did unplug the wires from the coils one at a time and plug it back in to ensure good connection. I also checked on the forum for the proper order if I'm right it should be

6 5
4 3
2 1
And the coil packs are
1,4
5,2
3,6

Is it possible to have something going on in the lower end of the motor like a rod bearing, or timing issue?

 

Run a good high quality fuel system cleaner through the engine and see if that helps. I recomend Lucal Fuel system cleaner and get the 32 oz bottle. Use about 6 oz each tank till the bottle is gone and see if that helps. Even if you have already used something like STP or what have you for a fuel system cleaner still go and get the lucas stuff it is just that much better.

If the flywheel is not balanced properly or not installed properly then that could give you the vibrations you speek of. Bearings going out or what have you that your GM buddy was talking about is new engine territory, trust me here I already went through that with my Sarah. You will know if it is the case by extremely high or low oil pressure. You should be running right about the middle of the gauge which is 60lbs.

If you have not ever replaced the O2 sensors then you may be needing to do that. Bosch are OK ones but not the best you could buy, alot of guys here like the Delphi sensors and they seem to have a faster switching rate then the bosch ones do. Also if the heater circuit is not working properly then that will also keep the sensors from functioning normal since they will not get hot enough internally to measure the exhaust properly.

Make sure your MAF has it's screen and that the screen is clean. DO NOT REMOVE the MAF screen that will throw readings all to hell and you will never get your engine to run right.



Massey