Paul Riccioli Jr

iTrader: (1)

I know there is another post about idle problems, but mine seems slightly different.
I was having a problem with my car losing power between 1500-2000 RPM's and idling too low at a stop in Drive.
I turned the idle and TPS voltages up. It now idles at 1200 in Park and about 900 in Drive. The TPS is around .68 as suggested by my chip burner.
These are the problems I'm still having: After the car has been driven a few miles the idles hunts around when I'm at a stop in Drive. It will fluctuate in about a 500-600 RPM range.
Also when I put the car back into Park after driving it will idle at like 2000 RPM's and only come down when I shut the car off and restart it. The IAC is new, but maybe it's defective?? With WinALDL hooked up, what kind of IAC numbers should I look for?? Mine increased from like 50 - 160 as my RPM's went up. I thought they would go down as RPM increases?? Should I try cleaning and reinstalling my old IAC motor in place of the new one??

88IROC-LT1

Did you measure that IAC valve and pintle before you put it in? If not that could be the problem, it has to be a specific length before replacing it. It also sounds like you are have vacuum issues. Get a vacuum tester and try it out to see what is going on.

Paul Riccioli Jr

iTrader: (1)

Holy Hell....I definately did not measure it!! I have my old one though so I can still measure it. Does it matter that the old one was in a 305 and I now have a 383?? Also how do I adjust the length??

88IROC-LT1

With the IAC in hand, measure from the gasket mating surface of the housing (without the gasket on). The length should be 1 1/8 of an inch. Slowly pull it out if need, or if it needs to go in, pull the spring towards the housing and twist the pintle inwards in a clockwise motion. The is a worm gear inside, so be easy when moving it.

Let me know.

Morley

The IAC does not need to be a "specific" length to install it. What you do need to do is collapse or retract it all the way before you install it to prevent the pintle from binding in the bore.
Just put it in your hand and put your thumb on the pintle and push on it while wiggling it back and forth, it will make a sound like threads stripping as it retracts into the housing (this is normal). Now, install it into the housing and torque it to spec (with gasket in place). Next, with the IAC connected jump pins A&B of the ALDL and turn the key on but leave the engine off, let it sit for 30 seconds then remove the connector from the IAC. Remove the jumper from the ALDL and start the car (key should be left in the ON position while disconnecting the IAC). Check that your minimum air RPM is correct with engine running, if it isn't, adjust to proper RPM. Shut down the car and reconnect the IAC. The idle should be normal now.

Paul Riccioli Jr

iTrader: (1)

Ahhhh...very interesting. The tech article on the side neglects to tell you to remove the jumper from the ALDL when you start the car and set the minimum air. I would assume this is why I've been having so many problems?? I will try this tomorrow.

Thanks.

Morley

I doubt it would cause idle problems but could potentially damage the ECM (or so they say).

With Winaldl running and the 10k ohm resistor across pins A&B what is your idle? It "should" lock the idle at 1k RPM or there abouts.

have you checked the induction system for air leaks? Check everywhere on the throttle body, rods, IAC housing, top plate, TB to plenum. Check all runners, vacuum hoses and the intake base for leaks as well. Also check for ANY binding in the throttle cable/pedal.

Paul Riccioli Jr

iTrader: (1)

I am going to readjust my IAC tonight without the ALDL jumped and then set my TPS with the laptop connected. We'll see how it turns out. Also this weekend I'm going to hunt for vac leaks again and see what comes of that.

Paul Riccioli Jr

iTrader: (1)

!@!&!%@&^%!@&^!!!
I tried readjusting the IAC tonight after removing it and pushing the pintle in and without having the ALDL jumped while adjusting. There was no improvement. After I adjust the idle to where I want it and then put the car in drive it will idle in Drive where I want it, but then when I put it back into Park the RPM's shoot up to like 2000!!! What's the deal with this??
Also if I don't get the TPS adjusted exactly right again after adjusting the IAC my studder between 1500 and 2000 comes back!!

I'm really getting frustrated with this problem now!! Any other suggestions are welcome.

Vader

Wow. I've seen a lot of IACs, but never an "adjustable" one. Usually, the ECM takes care of that.

Follow the procedure for adjusting the minimum air position of the throttle plates (idle stop screw) and that's all you can do. If the idle is correct in DRIVE, there may be a vacuum leak, dirty/sticky IAC, or worn throttle body. Got any vacuum readings at idle?

88IROC-LT1

2k rpms is normal!!! You need to drive the car around 40mph at running temp, this will let the computer move the pintle in and out and adjust it for you. Just drive it around until it settles down.


Morley <-- Also it DOES have to be a certain length, they give the measurement in ALL of the books and at the dealership!!! This is so the pintle does not get damaged, if you think I am wrong go read some more before giving advice!!

Vader

If you read Morley's post carefully, it contained the passage

"The IAC does not need to be a "specific" length to install it. What you do need to do is collapse or retract it all the way before you install it to prevent the pintle from binding in the bore. "

That specified length in the manuals is the safe length required to install the stepper motor. As long as it is retracted fully, it is at or below the specified length.

Those same factory manuals indicate that the rocker arm lash should be preloaded at 3/4-1 turn after zero lash, but who among us runs them that tight?

Those same manuals indicate that 5W-30 mineral oil is satisfactory for all season operation, but who believes that?

Those same manuals indicate that the lower ball joint cannot be replaced, and instead the entire lower control arm must be replaced as an assembly, but how many ball joints have you installed?

The manuals aren't always right, just usually.

It's not that Morley needs and defense from anyone else, but I agree that retracting it fully is the accepted method, and to not get hung up on a specific length. As long as the pintle position is less than the specified measurement, the IAC motor can be safely installed in the throttle body. If the pintle is fully retracted, it should be well short of the specified length. The ECM will learn the IAC position within about 15 seconds of the first start.

Morley

You should really read my entire post for the proceedure, not just the first few words.

88IROC-LT1

If someone has never put one in before, that is no the person to learn trial and error. Plus you said that it doesn't have a specific length before installing a new one, or old one. There is a TOO LONG and a TOO SHORT. For what he might have read, could cause more damage, and money.

That's cool, I have had some people tell me different things. Trial and error for something shouldn't be learned on these cars. The old computer, the way that it is connected to the harness, is not safe to say "it shouldn't hurt it". This is supposed to be a tech board, tell people what not to do if you tell them to try something.

Paul Riccioli Jr

iTrader: (1)

Ok gentlemen let's focus on the problem at hand here.

Vader when I said I adjusted the IAC I meant the minimum air setting.

I'm going to give it another shot tonight and this weekend check for a vac leak while the engine is warm because my idle is fine when I first start out, but after about a half hour drive it will fluctuate in about a 200-300 RPM range at a stop in Drive.

Also my hesitation/dead spot seems to come and go as I continually adjust the min air and TPS settings.....any ideas why??

Morley

No such thing as the IAC being "too short" unless you collapse it with a vice or something. The method I described for setting the IAC is the one provided by Borg Warner and a few others when you buy an aftermarket IAC. As long as you collapse it down below the GM recommended lenght it should be safe...but if you collapse it all the way you'll be sure it won't bottom out in the pintle bore when you put it in.
The proceedures I use when working on my car work, I have 17 years of proof that they work, and I wouldn't trust a GM tech or tech writer to change the padals on my 2 year old's tricycle. They have proven themselves to me to be unreliable and ignorant of the products they "service". My IROC hasn't seen the inside of a GM service center since 1987 when they replaced the differential, and it never will.