RetiredSFC 97

I may have figured out my no idle issue. I took the IAC off and turned the key on and the IAC just stood there looking at me like I was stupid.

Aren't these things supposed to move some when they get power, or was the IAC correct, I am stupid?

ch@0s

http://www.thirdgen.org/techboard/te...t-working.html

Al Borman

with just the ignition on, the IAC won't budge since the PCM has not yet determined the RPM. The IAC is a stepper motor and will "extend" into the TB to reduce idle, or "retract" to increase idle.....all of which is controlled by signal voltages from the PCM.....

RetiredSFC 97

This is the information I have researched. Is it wrong?

An IAC (idle air control) motor is designed to adjust the engine idle RPM speed by opening and closing an air bypass passage inside the throttle body. The cars computer or ECM (electronic control module) receives information from various sensors and will output signals to adjust the IAC motor in or out to adjust engine idle speed by controlling engine idle air. An IAC motor can fail one of two ways, either the motor short circuits and stops working or the motor will develop high resistance and cause the IAC control motor to react slowly, either failure can cause the engine to stall at idle. When a trouble code scan is performed it sometimes won't always detect a failed or weak IAC motor. To check the IAC motor remove the unit, with the wires connected turn the key to the "on" position without starting the engine, the IAC should move in or out. If the IAC motor does nothing it has probably failed, replace it with a new unit and recheck system. Note: while the IAC motor is removed clean (use aerosol carburetor cleaner) the passages the IAC uses to control idle air speed, also inspect the IAC for a build-up on the seating (pointed) end and clean as necessary.

SunCr

Key on, unless the Diagnostic Link is grounded, shouldn't do anything. When you turn it off, the Pintle is retracted to allow in more air for a quick restart. It isn't going to move again until it's started. The IAC test is to warm it up; note idle speed and then turn it off. When you restart - because the Pintle was retracted - it should have an idle that was higher than what you noted, but return to that noted speed within a couple of seconds. If so, the circuit and IAC is working as designed.

If you've been monkeying around with things - particularly since you've removed it; you should reset it: Depress the accelerator slightly and start it; let it run for 10 seconds, and then off for 5 seconds. Restart and it should Idle at +/- 100 rpms from Targeted in Park/Neutral. 50 +/- rpms from Targeted in Drive. Monitor Targeted, Actual, TPS, and CTS with your Scanner.

RetiredSFC 97

that's the thing, the spindle appears to fully open no matter what I do. If I am understanding you correctly.

When I took it out it appeared to be fully extended, so no air is getting in at all.

SunCr

You could reinstall and use the method I outlined to reset it OR carefully retract the Pintle with finger pressure; then reinstall and use the reset procedure. You can also check the coils with your DVM - should be more than 20 ohms across A & B; C & D. Check the ECM circuit with a test light from each harness terminal to ground with the Diagnostic Link grounded, key on, harness disconnected. The light should flash or be steady at each terminal.

RetiredSFC 97

I think I may clean it up and give it a try just for practice and giggles. I did order a new one today because even if this isn't the issue, from the looks of this thing it will be sooner than later. It's all gummed up with carbon and nasty looking.

I still have a fuel pressure drop off problem to contend with but I believe the the no idle and fuel drop off are unrelated. I thought they were related but the more I fiddle with this thing the less I'm inclined to think they are one in the same. reason is, I had the intermittant hard start way before this idle thing reared it's ugly head. The idle thing just makes completing the diagnosis of the pressure thing much more complex because I can't get the thing to idle.

It did try the other day but it was starving for something and it has to be air. Or at least that's the direction I am heading. If you give it just the slightest pedal it runs like a champ. We'll see.

Thanks!! When I do get this resolved I will let everyone know what the issues were and what resolved it.

Oh did I mention I dropped my 10mm socket and extention down in the bay somewhere, probably never to seen again. At least I can't find it.

Oh and as a side note. I did try to reset the thing and that didn't work.

AGENT 86

Since you have a new one coming, pull the IAC out, jump "A" and "B" on the ALDL connector, turn on ignition, and see if the pintle shoots across the garage.

RetiredSFC 97

thought I might do that tonight Started to throw it across the garage last night.

Wanta hear something odd and funny? Obviously I'm not a mechanic, that is for certain. Mechanical but not a mechanic.

I was going through my FSM last night going step by step what the manual told me to do. Couldn't do it, so I said the heck with it and took the whole throttle body off. Still couldn't see what the stupid manual was telling me. So I go get my Chilton manual and it tells me there are two types of these things. One that bolts in and one that screws in. (not to mention the thing wasn't where the FSM told me it was)

The whole time I'm trying to take this thing out I'm scratching my head saying, that sure looks like a screw in to me.

So after all this and breaking two light bulbs in my shop light and losing my 10mm to engine bay heaven, I about threw the thing across the room. Had a beer instead!!!


Update: I don't mind poking fun at myself for doing something stupid so I will. I got home today and looked at my FSM again. Last night in my flustered state I was looking at the J (LT5) instructions and not the L98. So there you go.

Midnight 85

Sounds like an average day in my garage. Agent 86 is right, if you jump the A-B terminals on the diagnostic plug and turn the key on the pintle will go airborn, sometimes never to be seen again. This, of course is only if it is working correctly

Al Borman

I feel your pain. Loosing a 10mm socket is not a good thing. Sometimes I spend hours looking for lost tools in my engine bay !!!!!

Find that socket man !!! If you don't, it will bother you forever !!!

(-;

M.J.L.

M.J.L.

I loose tools all the time working on the C4...

M.J.L.

RetiredSFC 97

I did finally get it fished out with my magnet thingy


I didn't try to shoot it across the garage, this time

http://forums.corvetteforum.com/c4-t...ue-solved.html