idle problem
idle problem
HI, I'm experiencing a severe idle problem with a 91 240sx. Here is a brief history: Rebuilt the engine at 165k, used 89 pistons for higher compression, removed a bunch of emissions stuff, including the box on the drivers side, the butterflies in the manifold and their vacuum hoses and appurtenances.removed the clutch fan, ported and polised the heads and matched the intake manifold. installed hotshot headers, apex n-1 exhaust, hi flow cat, injen intake. Lastly, i installed a zex NOS kit, but never had a chance to try it. While i was still breaking in the motor,(<2K) the radiator cracked, the car overheated and i have been having the idle problem since that time. it ran like a bat out of hell before this. I did a compression check and found almost no pressure on the #4(60psi). the rest were at 180. i thought that this was the problem. We pulled the engine and removed the pistons. #2 & #3 had broken middle ring landings and the #4 had first and second landings broken. No explanation for this.(Possible detonation) put engine back together with 91 pistons this time but it still would not idle. checked all remaining vacuum lines, replaced temp sensor, iaa, pressure regulator, spark plugs, cleaned egr, checked injectors. still not idling. last thing is the MAS, but at $400 i want to be sure. Any suggestions? Help, PLEASE!!
Thanks for the reply. Yes I did check for vacuum leaks at the intake, the compression is back up in all 4 cyls. did not check the voltage at the flow meter. I did disconnect it and the engine does idle well, even though a bit high, but it will not rev past 2500 rpms. what does that mean, that the flow meter is good or bad? another thing i noticed when checking for vacuum was that when i checked before the B.P.T.(?) valve, I had good vacuum, but when i checked after it the idle fluctuated wildly from zero to 10. I bypassed the valve and sent the vacuum straight to the EGR valve, but it made no difference. how do i check the voltage on the flow meter? Thanks!
sounds like you might have a bad flow meter. but to check it one wire will be 12v another will be ground and the other is your signal wire. this wire is the one you wanna check. you'll need a volt meter to do it but once you have it check your voltage on that wire should be somewhere in the neighborhood of 1.3 to 1.4 volts
I got a junk yard flow meter but it didn't fix the problem. i checked both meters and they had the exact same readings, 1.5 volts. they also both checked out the same for resistance from post set to post set. either they are both no good or both good. I still am leaning towards a vacuum problem. does anyone have a vacuum diagram for the de engine. the stupid chiltons has every engine vaccum diagram including the ka24e but not the de. please help!