Chuck Haynes

My car idles at like 1250 RPMs in Park/Neutral and like 1100 RPMs in Drive?!?! I have cleaned the Throttle Body and IAC passages, removed and cleaned the IAC, tested the TPS (with a machine at AutoZone). I have tried to set the minimum air like the tech article says. I put a jumper into the A and B terminals. Turn the key on and wait like 2 minutes. Then unplug the IAC. Then turn the car off. Unplug the A and B terminal jumper. Start the car up. It idles at 1250 RPMs even with the mimimum air screw backed all the way out and the IAC unhooked?!?! Does anyone have any ideas?!?! I have also replaced the Oxygen Sensor.

-Thanks

94-6spd

Have you checked for vacuum leaks?

Chuck Haynes

I have checked... I have even replaced all the larger softer lines. I didn't replace the small hard plastic ones though... perhaps, I should re-check everything again.

Vader

I'm thinking that 6-Sp is all over this one. You've got a wicked vacuum leak somewhere.

Connect a vacuum gauge at the port that connects to the fuel pressure regulator, start the engine, and read manifold vacuum directly in inches of mercury ("Hg).

It sounds like you disabled the IAC correctly.

Chuck Haynes

OK, Vader... I will try that.

Thanks

Vader

Sources of some vacuum leaks that can affect RPM that much are:

• Gasket leaks;
• Vacuum hose leaks;
• Injector lower 'O' ring leaks;
• An incorrect or stuck PCV valve;
• A stuck EGR valve or internally leaking EGR vacuum control solenoid;
• An internal leak in the power brake booster;
• Severely worn / sticking throttle body;
• Throttle plate misalignment;
• Damaged / binding accelerator cable or cruise control cable;
• Debris in the IAC valve or air passages;
• Cracked casting, like the intake, plenum, or throttle body.

The major suspects can be eliminated easily. Unplug the PCV and cap the fitting. Unplug the power brake booster vacuum line and cap that fitting. Remove the throttle cable, cruise control cable, and transmission TV cable. Just unhook them from the belcrank on the throttle shaft. Remove the intake bellows and inspect the throttle plates closely to make sure they are fully closed.

aussierob

Does it idle high when cold and when hot???
Check your thermostat or temp sensor. maybe computer thinks car is cold and runs on fast idle continuosly.

Denis.V

Discard probable "Battery mode": When the bat is bad, ECM put the idle at high RPMs for voltage compensation. It's a comment in Chilton's manual (I can see that you are "Haynes" but check "Chiltons" too).

For fix it clean/check battery terminals and compare RPMs now.


Regards.

8Mike9

1250rpms is kind of a coincendence <sp> for cold start idle. Seems to me the IAC isn't extending.

Next time you "reset" the IAC, have someone else do the jumper thing, while you're under the hood with your hand on the IAC motor, you should feel it's movement and the pintle is extending (closing the passage and lowering the idle speed).

If you have a scan tool, you could monitor IAC counts as you rev/decel the engine just to make sure it's functioning/changing.

If in fact you have a vacuum leak, the IAC count should be close, if not, zero as it tries to compensate for the high idle.

Chuck Haynes

Update
----------

Vader, ok... I tried everything that you listed, but the problem still remained. Out of a desperation move, I removed the IAC again. Last time it was VERY dirty (like it had never been cleaned), so I cleaned it with water and liquid dish soap. Then I scraped it clean with a screwdriver wrapped it a cloth (so it wouldn't damage the surface). I also used Intake Cleaner on the IAC passages. Well, this time it was VERY clean (almost perfect). However, I went ahead and cleaned it with water and liquid dish soap again (I let it soak for an hour). Then I took a toothbrush and a scrub brush to it. Finally, I soaked it in Intake Cleaner. I once again sprayed out the IAC passages, however this time... I took the toothbrush to the inside of the passage way. I hooked it back up and set minimum idle... NOW IT IDLES CORRECTLY!!! Perhaps the toothbrush to the passage did the trick. It idles at 600 RPM in Drive and 750 RPM in Park/Neutral. When the A/C is on it goes up like 100-150 RPM. Everything seems fine, however... sometimes when I start it, it will idle at 1000 RPM then I rev it up... after it comes back down it goes to normal idle (750). Sometime the Drive idle varies between 600-750 and the Park/Neutral idle varies from 750-900?! It just has a mind of it's own and idles anywhere in that range that it wants to. One stoplight it may be 600, the next 750?!?! Does this make sense? Does the IAC need YET more cleaning? Replaced?

-Thanks

Red Devil

Do I read this to mean you soaked the entire IAC in water for an hour?

Chuck Haynes

Haha... no, I just put the spring and the pindle in. I did NOT put the motor in. I took a cloth covered screwdriver and cleaned the top of the motor (where the circle with that little indention is). The O-ring was not ripped and didn't have any cuts in it... so I ran a little water over it, and gently wiped away some 'debris'. Then I let it dry a bit. I took a knife and tried to clean the inside of the motor (where the contacts are). I also cleaned the electrical connector (on the car) that plugs into the motor.

WAIT a second... I just remembered something. This time when I went to unplug the IAC (for minimum air setting), I felt it 'vibrating' like it was opening the pindle. I didn't feel that before... maybe when I cleaned it the first time, somehow the spring got wedged and would not open/close?!