What's this do?
01-20-2005, 05:09 PM
#4
Advanced
Thread Starter
Join Date: Oct 2002
Location: Gibson City, Il
Posts: 92
Likes: 0
Received 0 Likes
on
0 Posts
Damn, now that it idles at less than 2000 rpm I need motor mounts. Kinda suspected that. My dream is to one day own an expensive Porsche that requires cheap maintenance rather than a cheap Porsche that requires thousands of dollars of maintenance. Live Devildog's dream.
01-20-2005, 06:14 PM
#5
Three Wheelin'
Originally Posted by hosrom_951
Just don't mess with it unless you bypass the idle actuator
As far as repairs go, the initial expense may be on the high side, but once you have the car sorted out and do normal maintainence, it will be darned near bullet-proof.
01-20-2005, 06:24 PM
#6
Banned
Join Date: Feb 2004
Location: In self-imposed exile.
Posts: 14,072
Likes: 0
Received 8 Likes
on
7 Posts
Early cars most certainly do have idle stabilizers. There's a fairly thick hose (maybe 3/4" in diameter) that runs left-right just aft of the air box. Where it goes into a little device with two 10mm bolts affixing it to the air box bracket - that's the idle stabilizer.
01-20-2005, 07:10 PM
#7
Three Wheelin'
Originally Posted by Porsche-O-Phile
Early cars most certainly do have idle stabilizers. There's a fairly thick hose (maybe 3/4" in diameter) that runs left-right just aft of the air box. Where it goes into a little device with two 10mm bolts affixing it to the air box bracket - that's the idle stabilizer.
Nope.
That device is an Auxiliary Air Valve, whose main fucntion is to supply the engine with additional air flow during cold starts. The device has an electrically heated bi-metallic strip that controls a rotary valve with a variable slot.
When the engine is cold this valve is open, and is closed when the bi-metallic strip reaches a set temperature.
The only other idle compensation on the early cars is a solenoid operated valve that supplies additional air flow when the A/C is running. This valve is mounted at the rear of the air box.
Later cars do have an idle stabilizer which opens and closes to maintain engine idle. Later cars do not have the solenoid valve for the A/C.
If you look at the electrical connectors for an ISV and an AAV you will see the ISV has three connections, while the AAV only has two. The ISV has an "open" lead, a "close" lead and a common or ground. The position of the valve, and therefore engine idle RPM is controlled by the DME.
The AAV gets +12 volts and ground and is not controlled by the DME.
Trending Topics
01-20-2005, 07:12 PM
#8
Three Wheelin'
Correcion: The valve on the air box is used to compensate for the additional mechanical load of the A/C system. The AAV is mounted under the intake, just like the ISV is on later cars.
01-20-2005, 10:23 PM
#11
Three Wheelin'
In that case, special tool and hosrom_951 are correct.
However, since your engine was obviously "over idled," I'd recommend verifying that the throttle body is set up properly. I've seen more than one TB that a "mechanic" had tweaked because he couldn't get the engine to idle properly otherwise.
To check the TB set up you need to remove the TB.
After you have the TB out, loosen the Throttle Position Switch hold down screws, loosen the lock nut on the mechanical stop screw, and then back the mechanical stop screw out until it does not touch the throttle plate arm.
Verify that the throttle plate closes fully (there will be a very small gap between the throttle plate and the seat) and does not bind. If the seat and/or throttle plate have a lot of oily crud built up, use some spray carb cleaner to remove the crud.
Once you have verified that the throtte plate can close fully, turn the mechanical stop IN until it just touches the mechanical stop arm.
Next, turn the mechanical stop screw IN 1/2 turn and tighten the lock nut. The throttle plate mechanical stop is now set.
Next, hold the throttle plate closed, and adjust the TPS so that it the internal micro switch makes an audible 'click' just as the throttle plate starts to open.
Once you have the TPS set properly, install the throttle body, disable the Idle Control Valve, start the engine, and use the Throttle Body Idle By-Pass Screw to set the idle to 840 +- 50 RPM. NOTE: If the TB has been "over tweaked" you may have to open the Idle By-Pass a turn or two to get the engine to run with the ISV disabled. BTDT too.
Once the idle is set, enable the Idle Control Valve and you're done. Don't be suprised if the engine RPM goes up a tad when you enable the ISV. As long as the idle stays within specs you're OK.
Turn on the headlights, fog lights and A/C (fan set to '4') to load the engine. If the ISV is working the engine RPM should not change.
However, since your engine was obviously "over idled," I'd recommend verifying that the throttle body is set up properly. I've seen more than one TB that a "mechanic" had tweaked because he couldn't get the engine to idle properly otherwise.
To check the TB set up you need to remove the TB.
After you have the TB out, loosen the Throttle Position Switch hold down screws, loosen the lock nut on the mechanical stop screw, and then back the mechanical stop screw out until it does not touch the throttle plate arm.
Verify that the throttle plate closes fully (there will be a very small gap between the throttle plate and the seat) and does not bind. If the seat and/or throttle plate have a lot of oily crud built up, use some spray carb cleaner to remove the crud.
Once you have verified that the throtte plate can close fully, turn the mechanical stop IN until it just touches the mechanical stop arm.
Next, turn the mechanical stop screw IN 1/2 turn and tighten the lock nut. The throttle plate mechanical stop is now set.
Next, hold the throttle plate closed, and adjust the TPS so that it the internal micro switch makes an audible 'click' just as the throttle plate starts to open.
Once you have the TPS set properly, install the throttle body, disable the Idle Control Valve, start the engine, and use the Throttle Body Idle By-Pass Screw to set the idle to 840 +- 50 RPM. NOTE: If the TB has been "over tweaked" you may have to open the Idle By-Pass a turn or two to get the engine to run with the ISV disabled. BTDT too.
Once the idle is set, enable the Idle Control Valve and you're done. Don't be suprised if the engine RPM goes up a tad when you enable the ISV. As long as the idle stays within specs you're OK.
Turn on the headlights, fog lights and A/C (fan set to '4') to load the engine. If the ISV is working the engine RPM should not change.