Ive had the car for about 6 months now and in the last months ive been having problems while shutiing the engine off. Not all of the time, but maybe 1 out of ten of the times i turn the car off the engine stays on and starts to knock and sputter. I figured maybe its bad gas, so i went to a different station. Im running 89 octane on an LG4 with the quadra-jet carb. Should I try a higher octane?

Or is it possible that its something wrong with the carb? I didnt modify anything on the carb, im running an open element. Maybe it could be something on the carbs internal. I dont know alot about the actual carb so im not sure.

The car will usually sputter and then die after about 3 seconds of the knocking. However once it did it for about 45 seconds until i finally intentionaly flooded it. Any help would be greatly apreciated. Thanks in advanced!

 

check timing on the motor

 

What would eb the best way to check the timing? Timing light?

 

Yes

 

1. Ignition timing
2. Engine idle speed too high

 

Ok ill check that out then, thanks guys!

 

I kinda got the same problem (sorry for jacking the Thread) But my timing is at 2 deg of advance at idle. It loves to over run or backfire when I turn it off.

Could it also be because of richness?

 

What engine and what fuel are you using? Using a low octane fuel in something that requires more can cause that. Also, whats your idle speed? That being too high will also cause that.

 

Air_Adam is probably right. Usually caused by too high idle speed. If it's intermittent then the high idle or choke may be occasionally be sticking. This allows the carb to continue to let enough air/fuel into the engine to allow diesel combustion (ignite without spark). Lower octane fuel is more likely to diesel.

Note your idle speed (should be 500-700 in park) and does it ever stick higher? Is your choke functioning correctly? Could also be an intermittent vaccuum leak.

May want to clean the linkage with some carb cleaner on the choke side. I'd find and fix the problem rather than pay for higher grade fuel that simply masks it.