Backfireing question
 

Hey guys, I have a euro 1980 sc. Recently the car has been running rough. I was getting a lot of backfireing through both the exhaust and the pop valve in the air box. I advanced the timing and the car is no longer backfireing through the airbox and it has steady acceleration but if i take the car up to 6000 rpm, it lets out an extremely loud backfire during shifting. The car runs smooth but the backfiring doesnt seem normal :) any suggestions?

Sounds like it is running a little rich. Have you had the mixture checked?

The CIS is continuous injection system, so it is always injecting fuel. If the throttle closes while shifting, fuel can build up and then combust improperly when the throttle is opened again.

Is the car backfiring through the exhaust or intake? If exhaust, check for lean running (vacuum leaks)

Yeah it is coming from the exhaust. If a pop the throttle while shifting then it doesnt do it.

I would guess fuel is pooling when the throttle is closed and then gets dumped into the engine when you get back on it. That causes a rich mixture that burns as it comes out of the cylinder.

Well it backfires as soon as i get off the throttle while the clutch is in. And any solution you suggest?

Don't come completely off the throttle, just ease up to 2000 rpm, say?;)

From what I have heard, the backfiring is a problem inherent to this system

Sorry I cant be of more help:(