Car backfires when shifting.

[95Vert]

JT, aftermarket mid-pipes without cats, still have a hookup for the smog tube. I actually hooked my smog tube up to the h-pipe, although it just blew air through. Now since I don't have smog, I capped off the pipe on the h-pipe.

 

[xr8d302]

I had the same problem, though mainly it happened when i was coming down from high revs.

If you're still running a smog pump with an O/R h-pipe, a quick fix is just to look inside your engine bay, down by the passenger side headers, you'll see a little canister hanging there, with a big black tube running into both sides....yank off one of those, it'll stay in place, but it won't be hooked up...backfires gone

quick fix if it annoys you

 

[Starman]

Wow, I learn something every day. I would have never guessed that a non-catted pipe would have a hook up for the smog heffer. That is kind of like tits on a bull.

Thanks Chris - now this all makes more sense.

True, but many people don't remove the smog pump and all the tubing/diverter valves when they run a non-catted pipe. So most have the provision to accomodate it.

 

[OrangeMustangGt]

a car has less vaccume at high rpms

What it is, most likely is a rich condition. That will cause a backfire, you most likely just have your FP set too high. get it on a wideband and get it right!

 

[94-302-vert]

My car also has the O/R pipe and my air pump still on. I had heard about the air pump causing backfires by fueling the unburt fuel under decelaration. I actually want to crimp my pipe down to limit flow on my O/R pipe (the air injection pipe). Will this hurt my air pump at all? I ask because I live in CT so I still need everythng in place and working to pass emissions.

Thanks!

 

[OrangeMustangGt]

if you think its the smog, do what i did, get a short belt so it eliminates the smog pump, and cap off the bung on the off road h...it does nothing anyway.

 

[94-302-vert]

What belt lenght will bypass the smog?

 

[gt-351]

Dyno (wide band) looks good,13.2 . I have no smog pump. I got the backfire while I was on the dyno a few times but not as loud. The guys that burnt my chip did not turn off my egr. Will this have anything to do with it?
I moved the timing and f/p all over. I found 10 more hp over the last dyno but my backfire is still there.
I have all msd inj and coil too.

 

[HISSIN50]

Edit: schematic did more than desired. Need a different one.