failed calif. smog test
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New User
Joined: Aug 2003
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From: north of sacramento,calif.
failed calif. smog test
This is my first entry on this site. Please be patient. I have a question regarding a failed smog test. I have an 86 F150, with the 300 ci. engine, manual trans, and single barrel carb. The test failed on the low speed run and had a high NO (ppm) reading. I had a single catalitic converter replaced 2 years ago, and the carb. was also rebuilt. I passed the smog test 2 years ago.
I am now asking if anyone has a clue as to why I failed this time.
I would appreciate any help Thanks, allen
I am now asking if anyone has a clue as to why I failed this time.
I would appreciate any help Thanks, allen
Logistics Pro
Joined: Jan 2002
Posts: 3,739
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From: GANS
failed calif. smog test
well, first thing everyone says to do is: change oil before you do the emissions, and have the truck 100% warmed up before you take the test. on the single barrel carb, you need to make sure the choke is opening 100%. those are a couple things to check up on, also change your plugs, wires, pvc, and air cleaner..
Post Fiend
Joined: Mar 2002
Posts: 19,402
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From: Bonita Springs FL
failed calif. smog test
NO is produced by high combustion chamber temperatures. The EGR system is designed to reduce combustion chamber temps, so I'd start with checking the EGR valve. Then maybe give the cooling system a flush.
Also, I just had my '86 Bronco smogged. The shop did the diagnosis, yours should do the same. It will cost you, of course, but at least you'll find the problem a lot quicker.
Also, I just had my '86 Bronco smogged. The shop did the diagnosis, yours should do the same. It will cost you, of course, but at least you'll find the problem a lot quicker.
Thread Starter
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New User
Joined: Aug 2003
Posts: 2
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From: north of sacramento,calif.
failed calif. smog test
To all that answered my failed smog test on my 86 f150. thanks for the ideas. I had already changed my oil and air filters. I also changed the oil and the engine was driven for 40 minutes to get it warm enough. My egr valve should be o.k. because I bought it new 2 yrs ago from the ford dealer. -- I guess I should still check it because you can get a bad one right out of the factory. Before I changed the egr valve,I was having rough engine conditions -- then everything got very smooth after I installed it. I sure hate to take this truck to a garage -- I have always prided myself in fixing things myself. I guess I'll have to swallow my pride and break out the old bank roll. Thanks for your help Allen
Posting Guru
Joined: May 2003
Posts: 1,242
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From: Joliet, Illinois
failed calif. smog test
I had an engine that had tested as a bad EGR that turned out to be the EGR passages that had closed up with carbon deposites over the 250,000+ miles I had driven in it so far.
I had to disassemble the 2 piece manafold and remove all the small core plugs to clean it all out.
I threaded the holes and replaced them with pipe plugs.
I had to disassemble the 2 piece manafold and remove all the small core plugs to clean it all out.
I threaded the holes and replaced them with pipe plugs.
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Joined: Dec 2002
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From: peoria, az
failed calif. smog test
this is going in the right direction,these readings are a result of high combustion temp's. The egr is used to control this but, not at idle.If your problem is just "off idle" it may be a bad valve. I have seen them idle smooth but start to get kind of rough just as you give it some gas.You may want to look for something that is raising your idle temp's such as too lean a mixture, (that could be either a carb adj. or maybe a vacuum leak). You don't say if you checked your timing. Some vehicles are sensitive to this and I've found that most have to be right on or even on the retarded side by 2 degrees (from specs).Then sometimes you just have to break down and take it where they have a machine so that they can watch the results as they make adjustments.
