I've been having some idle quality problems. The car idles smooth, but there is a resonance in the car.. Its like a bass drum, and it drives me nuts. I think its because the engine is not running as smooth as it could at idle. I had this problem last year, but it went away when i switched to an auto trans. At the same time, had the distributor curved, so i figured that had smoothed it out so the bass effect went away. So now I have a tremec 5 speed in the car and my bass drum effect is back. if I crank up the idle to close to 1000rpm, it somewhat goes away. thats way too high an idle though. I'm running an edelbrock performer AFB, which seems to be adjusted correctly.. I had it dynoed last November and the fuel was right where it should be. The car smells very rich and my eyes burn after driving it because it stinks. There is no black smoke coming out the exhaust and all the plugs are perfect with just a light hint of brown on them. I'm running an MSD 6AL with a pertronix ignition and I had the plug gap at .055. I changed it to .45 to see what would happen. It didn't change much, but MSD says to open up the plug gap to between .050 and .065.. I'm using flowmaster stainless mufflers and an X pipe for exhaust, but I've used other mufflers and I still get the bass effect. Any ideas on what is causing this bass drum effect at idle and whats a proper gap to run on my car? Thanks Bob
I would close up that gap to .035, It will idle smoother and have better response down low. I like autolight #25's.....
I bet the problem is still in your exhaust system. The X pipe often takes this out or minimizes it but does not always eliminate it. Usually they resonate the most at a low rpm cruise like around 2200 rpms. Ford used to stagger mufflers in addition to the H to eliminate this. Also as you know the Flowmasters are notorious for this. Some times people have ill set up hangers etc that cause pipes or muffs to rub the body when the car is moving. Some rubber in-between the hanger and the body might help also.
