for the past few months my 89 240sx will idle straight at 1000rpm then drop to 500rpm and then climb to 1000 then back again repeatedly. after awhile it will idle straight at 1000. i can't figure out what it is. anyone have an idea?

 

Mine does the same thing, I think it has something to do with the vacuum lines, but I'm too lazy to tear them all out and redo them.

 

could be a lot of things....some one correct me if im wrong
fuel filter, MAF, and vaccum lines. all possibilities of random idle.

 

yup all of them are suspect here... start there and see how things go from there...

 

Try your fuel filter. 10 bucks problem solved. At least for me.

 

no, we just replaced the fuel filter a couple of weeks ago. this started in january.

 

fuel regulator?

 

clean the maf with some brakecleaner. Mine was doing the same thing for a lil while. Now it does something else. STUPID MAFS

 

DO NOT CLEAN THE MAF WITH BRAKE CLEANER!!! It can ruin the sensor. To clean the MAFS, use carb cleaner. Much safer.

 

lol, I staight up used acetone *iotch

 

thanks revolutionz_s13 for setting me straight on that. I'll do that tonight then..