Carbon in Plenum
Thread Starter
Intermediate
Joined: Sep 2005
Posts: 26
Likes: 0
From: Perth Western Australia
Carbon in Plenum
Have an 85 runnung rough on idle and also when running. Going through the usual list checking everything, now down to the EGR valve. Just took my Plenum off and found alot of carbon deposit inside. Is this normal?
Tried getting the valve off but have given up too hard to get to the bolts off. I was going to check if there is any depsit in the valve.
Andy help would be apprceiated.
Thanks
Andy
Perth WA
Tried getting the valve off but have given up too hard to get to the bolts off. I was going to check if there is any depsit in the valve.
Andy help would be apprceiated.
Thanks
Andy
Perth WA
Race Director
Joined: Nov 2003
Posts: 12,221
Likes: 446
From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019
I third the confirmation of carbon being normal for the plenum/runners. It is that EGR that controls exhaust being recirculated back thru your intake.
Have you checked your injectors?
Have you checked your injectors?
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Melting Slicks
Joined: Feb 2006
Posts: 2,753
Likes: 15
From: backwoods upstate ny
most have a coating of carbon caused by normal 'reversion', aggravated by 'retarded' cam timing to meet emissions mandates...excessive carbon build-up may be due to camshaft lobe/tappet wear, that wear will also produce rough idle and driveability probs...to check cam/lifters pull rocker covers and check lift at every rocker arm (one worn lobe will mess all)
Last edited by redrose; Jul 13, 2009 at 11:53 AM.
Safety Car
Joined: Jan 2004
Posts: 3,759
Likes: 8
most have a coating of carbon caused by normal 'reversion', aggravated by 'retarded' cam timing to meet emissions mandates...excessive carbon build-up may be due to camshaft lobe/tappet wear, that wear will also produce rough idle and driveability probs...to check cam/lifters pull rocker covers and check lift at every rocker arm (one worn lobe will mess all)