Its a 99, v8 318, s pd standard.

While im at a stop it idles perfect at 600.

When im slowing down I usually slow myself down through the gears instead of just pushing the clutch in and brakes. But when I do, moving but slowing down with clutch in the idle should drop to 600, but its super wavey, from 4-800.

I replaced TPS, Have run all kinds of fuel addictives and cleaners through it, high octane fuel. I pulled a code , P0420, Saying my cat is shot, But I have an exhaust leak, So thats what ill get fixed first. If its still there ill replace 02 sensor, Then if it still is ill replace cat. Now that I think of it could exhaust leak cause rough idle while moving because funny amounts of emissions on 02 sensors because its leaking.. hmmmmm things it could be..

 

Im pretty sure its supposed to idle at 750 RPM. Have you replaced the IAC or MAP sensor? And just FYI using your gears to slow you down can increase wear on your clutch and throw out bearing.

 

well its about 6-650. Stays solid when im stopped. If im moving in bounces up and down, No I have not changed IAC or MAP sensors, I figuerd i'd pull a code for them if that was the issue, Thats ok if I burn out my clutch then goes in a centerforce stage 3

 

I would say its probably the IAC.You can try cleaning it first and see if that helps.

 

how do you clean the iac? i've been told there's certain types of cleaners that you shouldn't use. my 03 randomly has a bouncy idle and has stalled twice. i'd like to try cleaning the iac before replacing it.

my 4.7 normally idles around 700 or so but will randomly bounce between 500-1100 at times.