black buildup in the plenum
Thread Starter
Pro
Joined: Feb 2003
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From: Flower Mound TX
black buildup in the plenum
My car has not been "running like it should" lately, so I decided to have a look. When I took the plenum apart I found it coated with a wet black goo that smelled of gas. Any ideas what the cause (causes) could be? Thanks all :confused: I have replaced the plug wires and fuel filter recently and the plugs look good???
Melting Slicks
Joined: May 1999
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From: Sarasota FL
Re: black buildup in the plenum (ckgunn)
How many miles? Some carbon is normal, especially on a car that old. If it's wet, my guess is the evap system is letting fuel into the TB, or your car is burning oil and coming in through the EGR holes, or the PCV is letting oil in. What are the "not running like it should" symtoms?
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Pro
Joined: Feb 2003
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From: Flower Mound TX
Re: black buildup in the plenum (ckgunn)
sometimes it idles low, like it wants to die. It dosent have the power like it should. When i drive at low rpm it shakes. Are there any adjustments to the evap sys? My car has 87xxx
[Modified by ckgunn, 6:14 PM 3/8/2003]
[Modified by ckgunn, 6:14 PM 3/8/2003]
Melting Slicks
Joined: May 1999
Posts: 2,037
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From: Sarasota FL
Re: black buildup in the plenum (ckgunn)
Those symptoms could be due to any # of problems. To get it running right, you'll have to go through it with a fine tooth comb. Do a compression and/or leakdown test, check fuel pressure and injectors, change fuel filter, change air filter, change PCV, check for vacuum leaks, change plugs, wires, cap, and rotor, clean out the throttle body, lots of other things. The evap system has a couple of key parts that need to be checked. The best thing to do is get a real service manual and follow the troubleshooting trees.
Or, run a can of GM top engine cleaner through it and hope it clears up.
Or, run a can of GM top engine cleaner through it and hope it clears up.
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Re: black buildup in the plenum (Aaron's 87)
:iagree:
All that should be done to insure top performance and perhaps solve your problem.
You may want to Start with the Idle Air Control Valve. Carbon and just plane dirt ver the years can clog this valve and cause some of your symptoms.
The IAC is in the base of the TBI.
Do a search on the FORUM for IAC and you should come up with everything you everwanted to know
:steering: [ I love that Lil Guy! ]
All that should be done to insure top performance and perhaps solve your problem.
You may want to Start with the Idle Air Control Valve. Carbon and just plane dirt ver the years can clog this valve and cause some of your symptoms.
The IAC is in the base of the TBI.
Do a search on the FORUM for IAC and you should come up with everything you everwanted to know
:steering: [ I love that Lil Guy! ]
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Joined: Dec 2000
Posts: 90,675
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From: SE NY
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Re: black buildup in the plenum (ckgunn)
You may indeed have multiple problems.
After you button it up, disconnect and plug the evap line to see if that clears up any problems. Indeed gasoline in the plenum would be from the evap system. That could effect idle and power, so correct the problem(s) in that system first.
After you button it up, disconnect and plug the evap line to see if that clears up any problems. Indeed gasoline in the plenum would be from the evap system. That could effect idle and power, so correct the problem(s) in that system first.
Pro
Joined: Oct 2001
Posts: 554
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From: CA
Re: black buildup in the plenum (ckgunn)
Do you smell recent gas in the plenum or just the black goo smells like gas? I had a strong gas odor in the plenum and it turned out the I needed to have the fuel pressure regulator bladder replaced. Didn't affect performance before I fixed it....it was just a little hard to start sometimes. I recently did the TB cleaning and cleaned the IAC valve too. It reallly helped my idle surging/rough idle problem. Give it a try..it's a quick $7 project (gaskets and throttle body cleaner)
Thread Starter
Pro
Joined: Feb 2003
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From: Flower Mound TX
Re: black buildup in the plenum (ckgunn)
Sounds like a plan, i'll start with the evap sys. :smash: Oh, by the way, where's my evap sys? :confused: I appologize for the ignorance but I have never delt with the evap sys before. I'll do a search, but any info is welcomed :flag
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Melting Slicks
Joined: May 1999
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From: Sarasota FL
Re: black buildup in the plenum (ckgunn)
The EVAP system tries to reduce emissions by burning the extra gas fumes instead of dumping them into the air. The reason I suggested it as a place to look is because you said the plenum was wet and smelled like gas. To see if you're getting too much gas into the TB, unplug the EVAP line going into the TB. I don't remember which one it is from memory. There are three lines on the passenger side of the TB. I think it's the one in the middle. It comes from the charcoal canister behind the driver's side fog light. But, I think it could be any number of other problems too.