So I'm driving into work today and all of a sudden I hear this clacking noise coming from the engine compartment. It's intermittent at speed, but at idle it follows the speed of the engine. I turn around and start to come back home and about half way there, the noise goes away, but the engine is now idling extremely rough with a notible misfire, as well as choppy acceleration and a intake backfire or two.

I get home, pull the spark plugs out and discover that the #5, #7, and #8 are completley black. It looks like black soot- all over the center ceramic and electrode. The #6 plug has an oily residue on it, but it's not black like the others. I can still see the tan color underneath. #1, 3, 2, and 4 are just fine.

I tightened all of the exhaust bolts thinking maybe it was an exhaust leak or something causing the noise. Indeed, the rearmost header tubes were a little loose. Loose enough for the noise? I'm not so sure.

As far as the fouled plugs, about a week and half ago changed to a different PCV valve. Since then I've put on about 100 miles. I put the old valve back in, but no change. Are those plugs shot now? Do I have to buy new ones?

What gives? http://www.nastyz28.com/ubb/frown.gif

------------------
Pro-Touring 71

1996 LT4 Corvette Wheels are 17x8.5 front, 17x9.5 rear
Wheel adapters are 2.0" front, 2.5" rear
Baer Brakes four wheel discs
Fuel Injected ZZ4, custom burned EPROM, AFR heads, TPIS Mini-Ram intake,
Comp Camshaft, TH700R4 Transmission.
God Bless the USA
Project Photos on ULTM8Z project photo album (http://photos.yahoo.com/ultm8z)
See me in Chevy High Performance (http://chevyhiperformance.com/featuredvehicles/86018/)
ULTM8Z Website (http://www.ultm8z.com)

[This message has been edited by ULTM8Z (edited January 21, 2005).]

[This message has been edited by ULTM8Z (edited January 21, 2005).]

WHAT THE....????

I just pulled the passenger side rocker cover off and the #6 intake pushrod is GONE!!! How the hell could that happen? I'm assuming somehow it got bent and slipped out from under the rocker arm.

Some questions though:

1.) How does this explain the fouled plugs on #5, 7, and 8. BTW, I checked the plugs last week for a different reason and they were all perfect. This is the first time I've driven the car since then.

2.) Could there be any collateral damage to the cam or cylinder heads. Man I hope there isn't. I seriously don't have time for that right now!

------------------
Pro-Touring 71

1996 LT4 Corvette Wheels are 17x8.5 front, 17x9.5 rear
Wheel adapters are 2.0" front, 2.5" rear
Baer Brakes four wheel discs
Fuel Injected ZZ4, custom burned EPROM, AFR heads, TPIS Mini-Ram intake,
Comp Camshaft, TH700R4 Transmission.
God Bless the USA
Project Photos on ULTM8Z project photo album (http://photos.yahoo.com/ultm8z)
See me in Chevy High Performance (http://chevyhiperformance.com/featuredvehicles/86018/)
ULTM8Z Website (http://www.ultm8z.com)

how did you lose a push rod???? that isn't good !!!!is it still on the top end????good luck!!

Just a guess but your push rod most likely broke/bent in the middle jumped out of the lifter and is in the lifter valley for now. You can try and fish it out through the head or the dist hole with a magnet. If it is on your ZZ4 your cam should be ok because of the lifter retainers on a stock hyd cam. The head should be OK to. I would try to get the pushrod out of the engine before it gets hung up somewhere down below. I am not sure about the plugs unless the back firing caused some problem with your map sensor or something wanting to richen the system (could see a loss in Vac or a back fire pressure as the engine under load). Have you been buzzing your engine and had a valve float?

I lost two before at the track! stuck new ones in and kept running!

Well if you lose a cylinder and it doesn't fire the O2 will see the excess air and richen the mixture. Why it would affect only one bank I'm not sure though.

If you lost a lifter and it pounded I would expect the cam to be scuffed. Usually the cams can be resurfaced/buffed, tweaked and polished as Dema at Elgin calls it, back to new condition.

You have a complete teardown in your near term future I think. When I have had this happen I never had an issue with the heads being damaged.

Was the rocker arm nut threaded as far as the other ones? If not it could have come loose and thats why your pushrod fell down into the intake valley.

Is your efi batch fired? If so the extra fuel floating around (esp with a missfire the ecm will comand full rich do to the excessive O2) it could have made the rear cyls even more rich. #6 intake valve not opening causes fuel to puddle in the runner, as you drive and turn corners the fuel puddle spills back into the rear most cylinders, #8 being the one that would get the most fuel do to it being so close to the bad hole. That my theory.

I would say pull the intake and see what, if any, carnage there is and go from there. I would replace the plugs also, baldly fouled plugs never seem to fully recover.

[This message has been edited by Joekool (edited January 21, 2005).]

<font face="Arial,Verdana" size="2">Originally posted by Rick WI:
Well if you lose a cylinder and it doesn't fire the O2 will see the excess air and richen the mixture. Why it would affect only one bank I'm not sure though.

</font>


That's what I was thinking....batchfire. I've lost a couple pushrods that way. It's weird that a pushrod would all of a sudden decide to let go, but they do!

I just read on your site that you are using the GM electronics. They used batchfire back then.

<font face="Arial,Verdana" size="2">Originally posted by Joekool:
Was the rocker arm nut threaded as far as the other ones? If not it could have come loose and thats why your pushrod fell down into the intake valley.

</font>

That's probably what happened. I managed to fish the pushrod out with a magnet (PHEW!). It isn't bent or damaged, but the nut on the rocker stud felt very loose. It probably backed off and let the pushrod slip out. I'll just get another nut and stick it on.




------------------
Pro-Touring 71

1996 LT4 Corvette Wheels are 17x8.5 front, 17x9.5 rear
Wheel adapters are 2.0" front, 2.5" rear
Baer Brakes four wheel discs
Fuel Injected ZZ4, custom burned EPROM, AFR heads, TPIS Mini-Ram intake,
Comp Camshaft, TH700R4 Transmission.
God Bless the USA
Project Photos on ULTM8Z project photo album (http://photos.yahoo.com/ultm8z)
See me in Chevy High Performance (http://chevyhiperformance.com/featuredvehicles/86018/)
ULTM8Z Website (http://www.ultm8z.com)

I only had this happen once and it ended up wiping out the lobe. I pulled the head and lifter to check everything and it all looked good. However, after a half dozen passes the lope was gone. Just my .02.

It's a billet steel roller cam.

Anyway, I put everything back together and it runs like it did before...thank goodness!

Geez, it scared the crap out of me. All I could think of was- spun rod bearing, or someother catastrophic multi-thousand dollar failure! http://www.nastyz28.com/ubb/eek.gif I definitley cannot afford another ZZ4 right now!

And not that this helped... http://www.nastyz28.com/ubb/wink.gif

<font face="Arial,Verdana" size="2">Originally posted by Rick WI:
You have a complete teardown in your near term future I think. When I have had this happen I never had an issue with the heads being damaged. </font>

Thanks alot Rick! http://www.nastyz28.com/ubb/wink.gif

------------------
Pro-Touring 71

1996 LT4 Corvette Wheels are 17x8.5 front, 17x9.5 rear
Wheel adapters are 2.0" front, 2.5" rear
Baer Brakes four wheel discs
Fuel Injected ZZ4, custom burned EPROM, AFR heads, TPIS Mini-Ram intake,
Comp Camshaft, TH700R4 Transmission.
God Bless the USA
Project Photos on ULTM8Z project photo album (http://photos.yahoo.com/ultm8z)
See me in Chevy High Performance (http://chevyhiperformance.com/featuredvehicles/86018/)
ULTM8Z Website (http://www.ultm8z.com)

[This message has been edited by ULTM8Z (edited January 24, 2005).]