What could this studdering be?

**mnm99** · 03-27-2003, 06:56 PM

Here are some things I wrote on other boards, so bare with me.

At idle it sounds ok, when you rev it a little I have a slight vibration. When it's reved hard the vibration is pretty bad when it's comming down from idle. I changed the plugs ( they all looked good )and cleaned the IAC and no change. I also adjusted the bypass valve no change.

Could I have bent a rod or something? Please help....

Would a compression test tell if it's a bent rod or something?

All the plugs looked the same , a light whitish/gray color.

The only thing I could think of is , a couple of days ago I spun 1st gear and when 2nd hit it pulled real hard with no spin. The car sounded like it bogged a little

Update..
I just did a compression check. I have 150 -155 on all cylinders. I guess thats ok. I also cleaned the MAF , nothing changed. I did notice when I take the vacume hose off the bypass valve I have the same shaking , but much worse. I know that would cause something like that, But my piont is it's the same shaking but worse :? It idles OK. I may go back to the NGK TR6 though. I tried the Motorsport 12C's and it seems a little rougher.

Any other ideas?

Thanks...

**WA2FAST** · 03-28-2003, 07:31 AM

Does it feel like an inballance in your motor or does it feel more like it's missing? I am trying to figure out what you mean. When you pull the vacume line off of the bypass valve, is it idling different or does it want to stall? It sounds like you may have some sort of vacume leak then if you are saying that when you pull a vacume line off, it is acting the same way... leads me to beleive that you have a small vacume leak, but it would most be affected at idle, not as you are explaining.

**paluka21** · 03-28-2003, 08:43 AM

So its rpm based?
You said that the car hooked real hard in 2nd when you mashed it?
Have you checked your stock balancer?
May also want to look at your driveshaft to see if you have a bad U-joint. I had a badn U-joint on my driveshaft and it would vibrate badly according to rpm.

You can jack the rear of the car up, start it, and have someone go through the gears, and watch the driveshaft to see if its wobbling.

good luck

Dan

**WA2FAST** · 03-28-2003, 09:04 AM

That's what I was getting at as well... if it's speed related, I would think driveshaft/U-joints. RPM related, harmonic ballancer. If you pull your vacume line off and it acts similar, I would tend to lean towards a vacume leak. If it is missing under load, I would think plugs or something along the lines of fuel system or ignition (including plug gap).

Let us know some more information and/or troubleshoot a bit more and report back.

**mnm99** · 03-28-2003, 12:12 PM

OK I'll try to explain better. It happens in park so it has nothing to do with the drive train. It idles fine and revs fine. If I rev it slow and bring it down slow it's fine. If I rev it hard and let go When the idle is coming down it sounds like ba ba ba ba . Not really a miss ,but kinda off balance. The harmonic balancer is straight and the rubber looks good. I put a screw driver steady next to it when it was running and it looks straight.

As for the bypass, if I adjust the screw on it the problem gets worse

When I get home I'm going to remove the belt and run it with nothing for a sec and see if it's still there. I was told maybe it's a pulley or a tentioner when it's on deceleration. If it goes away It will have to be something that the belt is connected to?????

**WA2FAST** · 03-28-2003, 02:09 PM

Still hard to follow... it just sounds like your computer needs to learn... that's all. My buddies 96' w/P1SC freaks out when you rev it hard... when it comes back down, it pops over and over and over again... almost like backfiring over and over again... just running pig rich... then once at idle, it is a little low for a few seconds. Also, if you get on it (making boost) and jump off of it all of a sudden... the car surges like crazy... up and down and up and down with the RPM's for a few till it calms down.

Same thing?