Hi Co Emmisions
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Senior User
Joined: Sep 2000
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Hi Co Emmisions
Hi all, just came back from state emmisions. My 84 in-line six had high CO levels at idle & 2500 rpm (9% at idle, 3 allowed, 3% at 2500, 2 allowed). Any help getting it down? I'm running timing at 8 btdc (not the 10 recommended). Someone told me to change oil. Also, the pre-cat that connects to the air pump is disconnected from the air pump. What does this do?
Thanks in advance
Walter
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Joined: Sep 2000
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Hi Co Emmisions
Hello. High CO levels usually indicate air restriction into the engine. Try a new air filter or leave the cover off the air cleaner when you go through an inspection. Also try adjusting the lean/rich mixture on the carb. An oil change could help a little also. If all fails one problem could be the catalytic converters. Mine on my truck are causing me to get a big 10 mpg. Can't wait to get a new exhaust system! Greg.
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Senior User
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Hi Co Emmisions
I do have a O2 sensor on the exhaust manifold. Had to change intake & exhaust manifolds recently (exhaust was warped) & got them at the junk yard. It looked good when I put it in, but I guess looks CAN be deceiving.
Any idea about the pre-cat thing that is supposed to be connected to my air pump? It is not connected at the moment, & the pre-cat thing is welded shut.
Thanks
Walter
Any idea about the pre-cat thing that is supposed to be connected to my air pump? It is not connected at the moment, & the pre-cat thing is welded shut.
Thanks
Walter
Fleet Mechanic
Joined: Aug 2000
Posts: 1,504
Likes: 1
From: Texas
Hi Co Emmisions
The tube connecting the pre-cat to your A.I.R. pump, should be connected. The pump injects air into the catalytic convertors to help burn off the pollutants that were not comlpletely burned during the combustion process. This could be part of your problem.
Just my opinion though.....
1988 F-150 Custom to XLT Lariat conversion, 5.0 EFI (formerly 300 I6), 5-speed M5OD, 3.08 rear gears (will be upgraded to 3.55's), Summit headers, Flowmaster muffler W/ dual 3.5" tips 24" long.
Pioneer CD, AC, Tilt, Cruise, Mobile Radio, Lightbar (Force 4 LP6000), Federal Signal PA300 Siren W/100W Siren Speaker. Caution Customizing in progress, Watch for flying tools & Parts!
Just my opinion though.....
1988 F-150 Custom to XLT Lariat conversion, 5.0 EFI (formerly 300 I6), 5-speed M5OD, 3.08 rear gears (will be upgraded to 3.55's), Summit headers, Flowmaster muffler W/ dual 3.5" tips 24" long.
Pioneer CD, AC, Tilt, Cruise, Mobile Radio, Lightbar (Force 4 LP6000), Federal Signal PA300 Siren W/100W Siren Speaker. Caution Customizing in progress, Watch for flying tools & Parts!
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Senior User
Joined: Sep 2000
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Hi Co Emmisions
Well, went & bought a new oxygen sensor friday ($31.00). Best money I spent. Now I can pass a gas station without pulling in. Thanks for all the help. I will be connecting that pre-air thing, & will let you all know if I get my sticker
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Posting Guru
Joined: Jan 2000
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From: Cullman Alabama
Hi Co Emmisions
Get some good gas. Buy it from a station that sells a lot of gas. Put the High octane in it, and when you take it back it's likely to pass.
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Hi Co Emmisions
I was wondering about the octane thing. When I originally went, I put a tank of 93 in (normally get 87). Then ran around the highway a bit. I failed CO, & someone said that the high octane might have caused it to peg the meter. Any thoughts on this?
Posting Guru
Joined: Dec 1999
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From: Copley, OH
Hi Co Emmisions
High octane fuel actually burns slower than low octane. Running higher octane fuel than the engine is designed for is going to cause some portion of the fuel to be burned inefficiently in the exhaust system. This in itself would not raise the CO levels much, if at all.
But your engine had/has several other problems. The defective O2 sensor would cause the engine to go into safe mode which is very, very rich as evidenced by the poor fuel economy. On top of that the air pump was disconnected from the cats. That tube supplies the additional air required to burn excess fuel efficiently.
CO is formed when the combustion is incomplete or inefficient. If the engine is working perfectly, which it never does, it all comes out as CO2. Virtually everything that was wrong with your engine generated excess CO. Once you get it all fixed, the type of gas you use will be largely irrelevant, but high octane gains you nothing.
But your engine had/has several other problems. The defective O2 sensor would cause the engine to go into safe mode which is very, very rich as evidenced by the poor fuel economy. On top of that the air pump was disconnected from the cats. That tube supplies the additional air required to burn excess fuel efficiently.
CO is formed when the combustion is incomplete or inefficient. If the engine is working perfectly, which it never does, it all comes out as CO2. Virtually everything that was wrong with your engine generated excess CO. Once you get it all fixed, the type of gas you use will be largely irrelevant, but high octane gains you nothing.
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Hi Co Emmisions
Just thought I would let you all know that I failed again. I had the new O2 sensor in, but still had high CO. Well I snooped around for awhile & learned that you must disconnect the battery before changing ANY electric part. This will allow the computer to reset itself. A quick call to the local dealer confirmed this. He said that is the 1st step on any electric part change. Suggested to wait 10-20 minutes before connecting it again. So I learned something new, just wanted to pass it along.
Walter
Walter
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