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Hi guys,

I own a L series wagon with a carbed EA82 engine and i have recently installed a "new" catalytic converter. It's just a random small converter i got from the local wrecker to try and shut my car up (had the original bashed out...) and to stop it from backfiring. Now with the bashed out cat i figured it was backfiring due to the large hollow area that was now in the system, but it is still backfiring with the "new" one installed.
It only backfires when lifting off the throttle after high revs, and lifting off the throttle at speeds. What can be causing this, besides an exhaust leak?

Hey 92subbie
poor spark - it would be natural for an engine to not burn fuel on hi-rev deacceloration. The unburnt fuel passes through the engine cycle only to hit a hot exhaust and then combust, creating the popping sound you hear in the exhaust.

Check your timing, spark plug condition and spark plug lead condition. It could also be that your engine is running rich.

Cheers

Bennie

ok that makes sense. however i have replaced the spark plugs, leads, rotor button and dissy cap not long ago. The carby was professionally rebuilt around a year ago. I will check the timing again and leads etc, but how do i make it run leaner? The "idle mixture" screw was drilled out. (Standard Hitachi carb)

cheers

i'm in the same boat, how do i adjust (lean off) an ea81 carbie?

if the mixture screw has been drilled out and is no longer there then your only real option i think is to play with your timming to compensate.

by backfiring you mean popping through the exhaust? or do you mean backfiring through the carburettor? My L series pops through the exhaust something shocking on decelleration, no apparent leaks, I'm putting it down to poor mixture adjustment. I've finally found and gotten rid of all my vacuum leaks, and the dumb little valve that makes it hard to start and rev up really badly when taking your foot of the accellerator (its excuse for doing this was to let air in small amounts into the manifold when the throttle was closed thus allowing for more complete combustion less HC emissions etc). I'm not sure that you can do a lot for that other than putting an aftermarket carby on and tuning it properly.

If its backfiring through the carburettor, you have a very very lean mixture, or something horribly wrong with your valve or ignition timing.

air injection causes a terrific popping in the exhaust on decelleration. remove the air injection!! or replace the reed valves and adjust float levels/timing etc to minimise it.

Mine does the same. But i have a 2 1/2" straight thru muffler on mine so it sounds like a wrx anyways. I just pretend its antilag