Cascade Crew

83Z28BlackBetty · Posted: Thu Nov 19, 2009 9:37 pm Post subject: engine shudder/vibration

Hey all, My car has been acting up on me lately and i'm almost at a loss.

At first it was a pulsing vibration feeling i would feel under load. It would pulse at about one beat per sec. da da da DA DA DA da da da DA DA DA
It seems worse when in 3rd and 4th gear getting onto the highway or going up a hill. but it is faint and noticeable when in park as well. Seems it is worse at around 2K.

I replaced the Cap and Rotor last week because they needed it anyway and it was a cheap guess. nata... I was sure it was an electrical issue at first but the last 2 days my carb seams to be hesitating slightly, stalling out at a stop, and smelling rich.

i was thinking about tearing the carb down and cleaning everything out tomorrow but if you all have any advice i'd greatly appreciate it.

(I have a Holley 600cfm 4160 vacuum secondary)

Thanks
~JAKE

Twilightoptics · Posted: Thu Nov 19, 2009 9:47 pm Post subject:

I see in your other post you've got bad plug wires. Replace those.

aaron_sK · Posted: Thu Nov 19, 2009 9:58 pm Post subject: Re: engine shudder/vibration

83Z28BlackBetty · Posted: Thu Nov 19, 2009 10:04 pm Post subject:

any reason this would just go bad instantly? If i remember correctly, it all started on a drive back from San Antonio.

Good advice paul, Maybe i'll pick up a set of cheap wires from work to see if this solves anything. I may also pull a few plugs tomorrow and see if any are fouled up.

townaj · Posted: Sat Nov 21, 2009 7:41 pm Post subject:

When were you in SA?!?! You should of told me - i live about 20 miles southeast of it. Let me know when you'll be around and if you have some spare time. I could use some extra hands with my car...

Anywho, my car would do the same thing. It was running too lean, but it wouldn't do it in park, like yours is. Mine only was bad cruising or under a load (like going up a hill) I also have a Holley with vac secondaries. But once i started putting premium in the pulsing stopped. So maybe this will work for you?

83Z28BlackBetty · Posted: Mon Nov 23, 2009 2:36 pm Post subject:

So i put new plug wires on and the problem persists.

I've noticed that i can almost hear an audible vibration sound coming from the back of the engine bay while sitting in park.

Does this sound like it could be coming from the flexplate? I may climb under there and check those bolts. or maybe something under the valve covers?

~JAKE

aaron_sK · Posted: Mon Nov 23, 2009 3:03 pm Post subject:

You just replaced the 700R4, so the converter bolts might have backed out.

83Z28BlackBetty · Posted: Fri Dec 04, 2009 8:05 am Post subject:

Update:

I've replaced the plug wires, plugs, and rebuilt my carb in the last 2 weeks and my problem is still there. I checked my torque converter bolts and none seemed loose, but i may try and remove all the bolts to disengage it and see if the engine still does it.

However the engine now makes an audible knocking sound that can be heard coming from towards the back of the engine and also under the car. I borrowed a stethascope from a friend at work and am going to listen to it today. not sure what else to do at this point. the car does have 194,000 miles on it.

~JAKE

flea · Posted: Fri Dec 04, 2009 12:49 pm Post subject:

its homesick, send it back up here.

83Z28BlackBetty · Posted: Fri Dec 04, 2009 4:17 pm Post subject:

So today i unbolted the torque converter and sure enough... sound and vibration ceased. Bolted it back up and its back.

Started probing around with a stethascope trying to locate the source and found it was loudest on and around the bell housing. So i'm thinking that the "remanufactured" TC i got could have taken a crap on me.

is there anything inside the Trans that while sitting in park could be making a steady knocking sound?

Also, just for kicks i did a compression test and all cylinders had 145 to 155 PSI of compression. so maybe this motor was rebuild after all.

~JAKE

chevymad · Posted: Fri Dec 04, 2009 5:37 pm Post subject:

Probably a cracked flexplate. That will make a knocking noise that sometimes goes away under certain loading conditions.

305 302eater · Posted: Sat Dec 05, 2009 2:53 pm Post subject:

I was just going to mention the flex plate idea. That happened to me in my rs when it had a 700r4. The flexplate ended up sheering completely at the crank. It was making a knocking noise that I thought for the longest time was rod knock.

Schultzy89GTA · Posted: Sat Dec 05, 2009 3:20 pm Post subject:

Seems like we have seen a pretty good number of cracked flexplates here over the years. Definitely something to check.

-Schultzy

fiveoformula · Posted: Sun Dec 06, 2009 5:30 pm Post subject:

I thought for sure I had a cracked flex plate when I had the 700 in, when I swapped it out for the T5, there were no cracks that I could see... But I haven't heard the sound since I've had the 5 speed in.

83Z28BlackBetty · Posted: Sun Dec 06, 2009 8:18 pm Post subject:

I checked the flex plate when i pulled the torque converter loose and it looked fine to me. But that doesn't mean it doesn't have a hairline crack somewhere. Is there any way to tell? I don't want to pull the tranny out to replace the flex plate only to find out it is in-fact my TC.

So here's something even more strange... the knocking sound is sometimes still present, but the bad vibration/shuddering feeling is just about gone. The TC bolts weren't "loose" but they weren't tight and pretty easy to take off. I tightened them down with some thread locker this time and like i said, the vibration has dramatically decreased.

~JAKE

chevymad · Posted: Sun Dec 06, 2009 8:24 pm Post subject:

I still say flexplate. You'll need to pull the tranny for either. You cant see where the plate cracks without pulling hte trans. Generally a knocking noise like that will change with different load if its the plate. Like maybe go away in gear.. not much other way to test.

83Z28BlackBetty · Posted: Sun Dec 06, 2009 9:36 pm Post subject:

well considering i can get a flexplate for about $20 vs the $250 for a new TC i may start there.

Now i'm just kicking myself for not replacing that while i had the whole mess apart 3 months ago... does the whole tranny need to come out to do this, or can i just disconnect the crossmember, bellhousing, and TC and move it back to get access to the Flexplate bolts?

~JAKE

fiveoformula · Posted: Sun Dec 06, 2009 9:40 pm Post subject:

Im sure you just need enough room to get torque wrench in there.

aaron_sK · Posted: Sun Dec 06, 2009 9:49 pm Post subject:

Depends on how much faith you have in your air ratchet, or breaker bar and brace.

Don't use a torque wrench to remove bolts. Breaker bars for that. Smile

*Edit: For the record, I've had most come out nice and easy with the ol' flathead jammed in the teeth, but a few tough ones, and one in particular (60* Chebbie) that needed a full-power 1/2" air wrench to get off.

Twilightoptics · Posted: Mon Dec 07, 2009 7:43 am Post subject:

Philips screw driver through a hole mated against the bottom of the block keeps everything in place if you don't have the right tool.

Yess you can slide the trans back. Usually you can leave the cooler lines on too.

This is usually what happens: