Shaky Idle?!

[Ignoble]

My dad's Automatic 1990 240sx has really shaky idle. When I press on the gas it's fine tho only when its idling it shakes the whole car. I don't feel a loss in power or anything. It idles steady around 800-850 rpms when in park, in drive with my foot on the brake it drops down to like 550-600 rpms steady. But always when it idle's its super shaky. I checked the plugs and wires. Put in a new fuel filter. I checked the MAF, cleaned out the throttle body and iacv. Im guessing it might be the mounts but I'm not sure whats a clear way to check if its good or bad? Anyone have any inputs and can help a noobie out?

[SCANDALEX]

check ur injectors maybe one is clogged or just stuck open

[DJ_Sunrise]

Put your hands on the motor after it has cooled down and try to move the motor side to side. Either way.. if the mounts are bad, it isn't hard to figure out.. the engine flops around. Shouldn't affect the idle though.. Something is wrong with the vacuum in the car. When you press on the brakes, RPMs should dip.. but not that much. The brake booster has a valve.. but I've never heard of it going bad. Check the FSM for specifics on the idle.

-Bart

[maximaRIP]

Check your dis cap and rotor and change your coolant temp I did to my and the car idle like a baby...and that with semi soild motor mounts....

[swartztech]

does it shift pretty hard? or does it shift nice and easy? if its a hard shift then you need a transmission flush, if it shifts easy than it could be your torque converter that is making it rough idle...ive fixed many rough idles this way

[Azrial]

I would try running some injector cleaner. How long has it been doing this if it was just since the last time you filled up with gas it could just be bad gas. I'm unsure where you buy gas at. But I had this same problem when I filled up at United Dairy Farmers. So I ran the gas out and went to speedway to fill up the next time and it ran great. I would try the simple things before going all out and thinking it's a transmission problem just makes more sense IMO to start small and work your way to big. Maybe a bad sensor or something as well. Could be water in the gas. 240's always run real funny unless you put premium gas in them like they recommend. Can't say 100% what your problem is but hope I could lend some inexpensive ideas for you to try.