Further idle diagnosis....

[Roadster]

So what would be the overall consensus moving forward? Is it futile to try an adjustment? Or is it a better idea to send the unit out to be redone???
Guess I leaning towards a last ditch effort to see if any adjustment(s) will work or not, before sending the TB out!!!

Also another thought and question. When I first started the engine the other day, IAC counts appeared to be normal but then came down to "0" after a few stops. So that would indicate to me that the throttle was completely closed at first start up. And when doing hot restarts, although the idle would be what I consider "normal", the IAC still remained at "0". And since the "fog" tests points to the primary blade leaking, I imagine even with the idle normal, and the rpm's fluctuating somewhat, that would still indicate that the primary throttle is not completely closed, correct??? And that would also explain why the idle varies anywhere from 25-45, 50 rpm difference which I am considering to be in the "normal" range. And also why the IAC count is still "0" as opposed to the higher range as when the vehicle starts in motion, correct???
Just trying to get a better understanding of the operation of how and why!!!
Opinions, thoughts.....

[XfireZ51]

Originally Posted by Roadster

So what would be the overall consensus moving forward? Is it futile to try an adjustment? Or is it a better idea to send the unit out to be redone???
Guess I leaning towards a last ditch effort to see if any adjustment(s) will work or not, before sending the TB out!!!

Also another thought and question. When I first started the engine the other day, IAC counts appeared to be normal but then came down to "0" after a few stops. So that would indicate to me that the throttle was completely closed at first start up. And when doing hot restarts, although the idle would be what I consider "normal", the IAC still remained at "0". And since the "fog" tests points to the primary blade leaking, I imagine even with the idle normal, and the rpm's fluctuating somewhat, that would still indicate that the primary throttle is not completely closed, correct??? And that would also explain why the idle varies anywhere from 25-45, 50 rpm difference which I am considering to be in the "normal" range. And also why the IAC count is still "0" as opposed to the higher range as when the vehicle starts in motion, correct???
Just trying to get a better understanding of the operation of how and why!!!
Opinions, thoughts.....

There is a function named "Throttle Follower" where the IAC Opens and Closes in coordination w the throttle position. There are delays, and decay rates associated w that. So the variation in IAC opening is very normal. The IAC is usually the result of something not the cause. RPM variation can be due to a number of issues but that's another story.

[Paul Workman]

Originally Posted by Roadster

So what would be the overall consensus moving forward? Is it futile to try an adjustment? Or is it a better idea to send the unit out to be redone???
Guess I leaning towards a last ditch effort to see if any adjustment(s) will work or not, before sending the TB out!!!

Also another thought and question. When I first started the engine the other day, IAC counts appeared to be normal but then came down to "0" after a few stops. So that would indicate to me that the throttle was completely closed at first start up. And when doing hot restarts, although the idle would be what I consider "normal", the IAC still remained at "0". And since the "fog" tests points to the primary blade leaking, I imagine even with the idle normal, and the rpm's fluctuating somewhat, that would still indicate that the primary throttle is not completely closed, correct??? And that would also explain why the idle varies anywhere from 25-45, 50 rpm difference which I am considering to be in the "normal" range. And also why the IAC count is still "0" as opposed to the higher range as when the vehicle starts in motion, correct???
Just trying to get a better understanding of the operation of how and why!!!
Opinions, thoughts.....

Well, the "take-away" from this is/was intermittent idle rpm AND THE IAC COUNTS GOING TO ZERO.

The ECM uses the IAC to control the idle; when the primary plate is "closed" (except for a tiny amount afforded by the idle set screw) and at idle there are some nominal IAC counts e.g., 10+ (depending), but NEVER ZERO under normal (static) conditions...EVER.

And, the evidence is bolstered by the idle was observed wandering out of control; going to ZERO is a classic clue that air might be getting in somewhere else; idle set-screw miss-adjusted, or a LEAK elsewhere.

Occam's Razor: A philosophy that states (in effect): when there are two possible reasons for an event, the simplest is usually the answer.

LOGIC is an essential tool in troubleshooting. But, until proven out, a logical assumption is just a hypothesis until it has been VERIFIED BY TESTING. Just about everyone who ever tried to solve a puzzling situation has been guilty of "over-thinking" the situation and assuming "if this, then that, and then..." without VERIFYING the "if this..." - the first logical assumption in the first place is where trouble begins.

[Roadster]

Originally Posted by XfireZ51

There is a function named "Throttle Follower" where the IAC Opens and Closes in coordination w the throttle position. There are delays, and decay rates associated w that. So the variation in IAC opening is very normal. The IAC is usually the result of something not the cause. RPM variation can be due to a number of issues but that's another story.

I don't mind the variation in the idle, as long as its the "normal" idle.
Interesting info...thanks....

Originally Posted by Paul Workman

Well, the "take-away" from this is/was intermittent idle rpm AND THE IAC COUNTS GOING TO ZERO.

The ECM uses the IAC to control the idle; when the primary plate is "closed" (except for a tiny amount afforded by the idle set screw) and at idle there are some nominal IAC counts e.g., 10+ (depending), but NEVER ZERO under normal (static) conditions...EVER.

And, the evidence is bolstered by the idle was observed wandering out of control; going to ZERO is a classic clue that air might be getting in somewhere else; idle set-screw miss-adjusted, or a LEAK elsewhere.

Occam's Razor: A philosophy that states (in effect): when there are two possible reasons for an event, the simplest is usually the answer.

LOGIC is an essential tool in troubleshooting. But, until proven out, a logical assumption is just a hypothesis until it has been VERIFIED BY TESTING. Just about everyone who ever tried to solve a puzzling situation has been guilty of "over-thinking" the situation and assuming "if this, then that, and then..." without VERIFYING the "if this..." - the first logical assumption in the first place is where trouble begins.

Also logical thoughts......appreciated....

I am thinking that the logical thing to do is reset the idle adjustment screw in very small increments as needed to see if the primary blade will close completely. And in between those adjustments (have pizza & a beer)....
take a test ride and then use the fog machine to verify whether or not the adjustments are having an effect.

[Roadster]

Originally Posted by XfireZ51

Take a strip of paper and stick it between the primary throttle plate and bore. Pull it through. Is there any drag? Do it also after opening the throttle.

Also did this test with the idle stop screw against the stop and at first there is a drag and difficulty pulling the paper through. Worked the throttle a few times and now the result is less drag and no real difficulty pulling the paper through.
So I am assuming that an adjustment is needed. Just have to figure out what size nut that is, as I think I can loosen the nut with a long ratchet wrench. I have a 5/16' that fits, but not snug enough. Just need to find out the actual metric size it really is.

[XfireZ51]

U really need to replace the stock stud w a hex bolt. I think its a 7mm bolt head. The stud uses a very small allen wrench that's nearly impossible to reach because it was never meant to be adjusted. However, after 25 yrs everything wears. There is a procedure that I have documented on the registry for re-setting the throttle plates for Min Air.
You will want to use a scanner to set throttle plate opening based on amount of IAC steps desired at idle. I use somewhere between 8-15 steps and do this with coolant at operating temps w fans on for the extra load. Whenever you adjust the throttle stop, it then is necessary to check TPS v and possibly re-adjust to read >.53v and <.57v.

[Roadster]

Originally Posted by XfireZ51

U really need to replace the stock stud w a hex bolt. I think its a 7mm bolt head. The stud uses a very small allen wrench that's nearly impossible to reach because it was never meant to be adjusted. However, after 25 yrs everything wears. There is a procedure that I have documented on the registry for re-setting the throttle plates for Min Air.
You will want to use a scanner to set throttle plate opening based on amount of IAC steps desired at idle. I use somewhere between 8-15 steps and do this with coolant at operating temps w fans on for the extra load. Whenever you adjust the throttle stop, it then is necessary to check TPS v and possibly re-adjust to read >.53v and <.57v.

What section on the registry is the documentation? And is it possible to do with everything still connected? So I can use the Tech 1 and I assume as I close the primary blade then the IAC counts will increase, correct?

[XfireZ51]

You'll want to check the General and Technical sections. Part of the procedure is blocking of the IAC airway and disabling the IAC motor.

[Roadster]

Originally Posted by XfireZ51

You'll want to check the General and Technical sections. Part of the procedure is blocking of the IAC airway and disabling the IAC motor.

For further info on Dominic's procedure for Minimum Air Idle Adjustment Thread
here is the link...

http://www.zr1.net/forum/showthread.php?t=27764

Thanks again for posting.....

[Dynomite]

Originally Posted by Roadster

Just got back from a short ride, on start-up engine idle was normal, and even my first two stops at low speed. Once I reach a higher speed, and then stop, it is with the high idle. It has never been at high idle 900-1000+ during any cold, or hot restart. The high idle only happens when driving the vehicle.

When you completely stop the vehicle, how long will the high idle 900-1000 stay? Forever? a few minutes? a few seconds?