Idle Problem

[jspecnitemare]

Hey everyone... Iv'e searched and searched...and I can't fix my problem so here goes:

I have a 89 (KA24E) with severe idle problems. When I start it up, the idle goes to about 1500, then after about 30 seconds it stalls out. It is drivable, although very difficult because I cannot rev past about 3000 rpm or it becomes a mechanical bull. Also, if I let off the gas, it will die. I serviced the AAV valve, located behind the intake manifold and I have also cleaned MAF using a q-tip and rubbing alcohol. After cleaning it, it lasted a little bit longer but eventually gave out. The fuel filter has recently been replaced with a 300zxTT one, so I don't think it's that. Any answers would be awesome, thanks.

[gyfer]

FSM , page EF & EC -59 : Engine stall, while decelerating/just after stopping

possible causes:1. Mixture ratio : i. run self-dianosis mode 2 check mixture ratio by flashes of inspection lamps ii. Dsconnect exhaust gas sensor (O2 sensor) improved - replace sensor no change - check mixture ratio feedback system pg. 26

2. Ignition sparks timmming (missing) i. check timing. check flashes of timing while decreasing engine speed

3. ignition system: i. option 2 (above) ii. perform self-diagnosis mode v, and crank angle sensor.

4. Intake System. i. adjsut idle speed ii. Check terminal voltage of A.A.C valve

5. Exhaust gas sensor i. follow option 1 (above) ii. Crank angle sensor iii. Idle switch ( follow option 4 i ) iv. Load switch. ( follow option 4 i, 4 ii )

any engine error code ?

[jspecnitemare]

I got it checked out and my mechanic (my friend as well) said the MAFS voltage is off. He also said that if the MAF is faulty, the ECU will go into a safe mode and not let it rev past like 2500, which would explain the bucking on acceleration.

I took the MAF apart and cleaned it again...I can see nothing wrong with any part of it...but I have no idea if they change when they go bad.

[powerband]

I just went through a painful ($) learning experience with exactly the symptoms you describe. The final result was that the MAF was indeed bad. The ECU would not indicate bad MAF code, but after running the engine with problems as you describe would indicate bad knock sensor, bad speed sensor, O2 sensor, or other seemingly related problems. Not wanting to just throw parts in it I checked every sensor according to FSM and found no problems. Finally I got a MAF on E-Bay and it fixed problem and no more error codes appear.

PS - Searching this forum I found many MAF problems and resulting engine drivability problems appear related to after market intake equipment. I don't mean installation related problems but MAF degradation or failure due to other unknown factors. Since MAF problems in genereal are rare, this link can't be disregarded.Also, the first recycled MAF I bought was a slightly different model(40FOO) and although the car ran great, it would hunt and stall at idle. The correct MAF for the KA24DE was the 53FOO version I purchased on E_BAy second and that was the final fix.

[jspecnitemare]

I unhooked a vaccum line from the intake that leads to some valve or sensor under the throttle body. This fixed the idle problem, but it still won't rev past 2400 rpm....MAF? By the way, when I disconnect the MAF, it makes no difference...it still won't rev. Does that mean my ECU is fried? Iv'e cleaned my coolant temp sensor and my 02 sensor is relativley new... Does anyone know if it's the MAF or not? How can I test to see if the MAF is working right, I have a multimeter...

[nissandrift]

I had the same prob. on my KA24de, I bought 2 MAFS and it didnt do anything. My ECU kept trowing a code 12, but it turned out my ECU was bad. Try and find someone with a running car then switch MAFS, and check. If thats not it I reccomend an ECU.