ericdwong

...I have a problem with high idle. The car idles at 1,000 RPM instead of 600 or so. I theorize this is because I redid the throttle body coolant bypass.

Anyway, I cleaned out the TB, by removing it from the car. Wow that thing was dirty alright. Using a toothbrush I made sure I cleaned it completely off. I will probably undo the redo of the throttle body coolant bypass to see if this improves the situation any.

Sonic

Did you move the idle control screw at all?

Sonic

Did you move the idle control screw at all?

ericdwong

I redid the throttle cooling (or in this case... heating) system, and immediately my idle went down to normal. Because there are no solenoids visible I think something in the TPS senses the temperature and when it senses it is cold, it "idles up" the engine in order to try to warm it up.

I was not aware there is an adjusting screw on it, so no I did not tinker with that. Medsonic, did you ever find out what was wrong with your car?

MardiGrasMax

iTrader: (14)

The TB coolant bypass has no electrical parts involved. The solinoid is pushed forward when the cooling system heats up and pressureizes the coolant system. When the cooling system is cold and not pressurized the throttle body valve is slightly openend by the cam wheel allowing more air to pass and rasing the idle speed slightly. When the cooling system is hot and pressurized the solinoid pushes the cam wheel so that the throttlr body is in a normal operating closed position, this allows the idle air control valve to more precisley do its job. When I did my TB coolant bypass I adjusted the cam wheel back screw adjustment so that it allows the TB valve to be in the closed position as if the coolant was hot.

Daniel B. Martin

Which solenoid is pushed forward?

MardiGrasMax

iTrader: (14)

The one behind the fast idle cam. It pushes forward as the cooling system pressurizes. 99' FSM Page EC-39, diagram SEF069V "Thermo-element".

Daniel B. Martin

Thank you for the specific page reference. I studied that page and cannot find the word solenoid anywhere, nor do I see anything that looks like a solenoid.

A solenoid is a device which has two components: an electromagnet and a plunger which moves when the electromagnet is energized. I don't see any kind of solenoid on the Throttle Body.

ericdwong

What screw is this that you describe to adjust the idle down? I looked for it and cannot find it.

Another word of advice to all other DIYs, ALWAYS replace all clamps... I did not replace the clamps at first just for the sake of testing my "idle down" theory and the thing spewed and leaked coolant like crazy. btw... I HATE those damn clamps that you gotta squeeze with robo-cop hands and are impossible to manipulate! I'm replacing the feasible ones with your normal screw type clamps...

Daniel B. Martin

Go to Steve Cutchen's excellent MaxFAQ page:
http://web2.airmail.net/scutchen/max_faq/
Click on SUBTOPICS below Maintenance.
Click on Adjusting 4th Gen idle speed
Scroll down to Diagram H.

MardiGrasMax

iTrader: (14)

Oh ok, thanks for clearing that up. So would you just call that a "Thermo-element"?

ericdwong

Alright I redid the TB coolant bypass (and tightened all the clamps down well), and I tinkered with the adjustment screw. I turned it all the way clockwise as far as it would go (about 2.5 revolutions) and it seemed to have taken care of my problem of high idle. My car seems alot more powerful now... more on this in another thread...

Daniel B. Martin

That's what Nissan calls it, so that's what I'll call it.

As I recall there is a wax pellet inside that Thermo-element which expands as its temperature increases. I think this is the same kind of material as used in the cooling system thermostat.