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DaGenesis 09-11-2002, 11:32 AM I have a jdm engine with cai, header, and jwt s4's and stock cat and stock exhaust. When I give it gas and let go it'll make a popping sound in the exhaust. So I'm guessing that I'm running rich and losing some power, and wasting gas. What can I do to fix this? would old o2 sensors cause this? thanks Loe Lyf 09-11-2002, 11:55 AM Running lean usually causes backfire in an exhaust. Running lean creates a lot of heat, so when you let off of the throttle, the exhaust fumes quickly ignite from the hot exhaust temperature causing backfire. 98sr20ve 09-11-2002, 12:29 PM Actually any car with the engine and exhaust heated will be able to ignite the un-burnt exhaust gasses by the heat stored in the exhaust and especially the catalytic converter. My car when running rich (dyno confirmed) did this, My car when running leaner (dyno confirmed) did this and it really did it bad when running rich and with no resonator. The engine has a small amount of fuel that is not burned completely when you close the throttle quickly. That and the combination of exhaust mods can make the small popping much more obvious. The evidence of that noise is not a good way to try and diagnose or tune your engine. DaGenesis 09-11-2002, 01:11 PM is there anything I can do?... or should I not worry about it? I have a greddy exhaust going in real soon... just waiting on a hi flow cat and gaskets 98sr20ve 09-11-2002, 01:18 PM Take it to the Dyno with a AFR gauge. It is the best way to know what your engine is doing. scmser 09-11-2002, 05:57 PM Did you check your PCV valve? A clogged PCV valve will cause backfire. Unscrew it, clean it with carb cleaner, shake it then reinstall it. After that doesn't work, retighten all your exhaust nuts and bolts. Exhaust leaks cause some backfires. My $.02. FastNX 09-11-2002, 06:07 PM High port cars are worse for the popping when you get off the gas. It is because the injector is so far from the intake port that a larger part of the intake runner and intake port get wetted with gasoline, and when you let go of the gas this gets sucked in and burned. I also have a GReddy exhaust and it is a bit more noticeable but i think it sounds kinda cool DaGenesis 09-11-2002, 07:45 PM ok, I'll tighten the exhaust and header bolts, and clean my pcv valve and report back | ||