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you like copy and paste huh? And I said it seems like its fouling out and then running rich. I also noted that blocking off the air pump fixed it right up. Something about air pump without cats I figure.
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THink here for a second.
Back fire is unburnt fuel. Unburnt fuel needs air to burn. The prupose of a air pump is to help completly burn the 'NORMAL" amount of unburnt fuel that will be expelled.
a good rebuilt engine that is not burning oil and has proper compression and a reasonable cam is going to run right. When you screw upo the fuel mixture is when your going to have problems.
A auto manufacture is not going to pu anything on a vehicle that is not absolutly needed. Even if it's only .05 cents when you build a million of them that's a lot of cash.
You have three posts. One from two days ago saying you modified the choke and messed with the blend doors on the secondaires including removing the vac operated door lock out that shuts down the secondaries on deceleration.
http://coloradok5.com/forums/showflat.php?Cat=&Board=garage&Number=739179&page=3&view=expanded&sb=5&o=&fpart=
You have a post about how you just failed emmisions today and this post. It's all related.
You need to put that carb back to stock or your not going to pass emmissions. You have to have the air pump to pass visual an if it's backfiring they are going to know something aint right and look for problems.
If it's running right it will pass even with gutted cats. I know because I have done it twice and I didn't have gutted cats I had straight pipe and the dork didn't look for the cat the first time. The dork looked the second time after he already ran the sniffer and had it logged in the computer and no easy way to back it out. I did it on r92 octane pump gas with no additives.
What did I do....I tuned the engine for optimum performance. The truck barked second gear under full throttle. My wife had a habbit of running hondas off the road with it when they tried to jump traffic on her. 10 degrees of timing and set the carb up properly so I was geting the proper stoic mix. I didn't just mak the grade I showed lower emmisions then my other car that was a 4cyl with fuel injection. Cats are a patch for a mildly out of tune engine from owners that don't take care of their junk. It was pushed by big buisness to shift the blame for smog namely the local power companies.
Hit the parts store and pick up a book called Rochester tuning and perfomance. It will have the information you need to fix your carb. If it's trully screwed up then get a rebuilt carb.
