I have a 95 civic with ls/vtec swap. The idle has been loping and i cant seem to fix it no matter what i do. I was wondering if a bad fuel fliter could cause my loping idle. The fuel filter has been in the car for longer that i have had the car which is 5 years and the car was sitting for a long time while i did the engine swap. Is it possible that my fuel filter is not allowing enough fuel into the engine which is causing the idle to lope?

 

probably not, it would just die or run real shitty. They're cheap though, you should replace it anyways if it's been that long.

 

If it was the fuel filter leaning out the fuel mixture at idle then the engine would not run at all off idle (higher than idle). So you would not even be able to drive the car. Then you question would be, Would a bad fuel filter cause my car to die off idle . . .

The engine demands the least amount of fuel at idle and therefore the filter willl need to flow the least at idle.