THIS SEEMS TO BE GOING AROUND!

[oricale]

Hello all!..as you know I have been rebuilding my Z, and with much help from the site and WAZOO, It is running and looking better every moment,...BUT

As with some of my brethren here I have a IDLE ISSUE AS WELL!

here is where I am...

*upon start up idles at 1000 to 1200 RPM, NO fluctuation
*after warm up it starts to fluctuat from 700-1200 over and over and over...
*on the road throttle wants to stick on slow-down at around 2000 and i have to tap the gas to get it down,...NOW..coasting at 10-15 MPH will not allow it to drop...you can tap on it and stays as about 1400....difference?...when at stop it WILL go to 700 RPM,..

what have I done?

*replaced the vacuum tube to the LIMITED things I have due to eliminating the scondaries....
*replaced the IAC valve
*cleaned the PCV valves so they have that "sound"
* plugged up the PCV line to the plenum as well as the booster line (to eliminate the booster and pcv lines)>>>>>>>>>>>the idle drops down but still cycles at that lower rpm
* made sure the throttle body was tight.

But!!!!!!the throttle seem to need forceto open up the larger plates when driving....(sort of like needing to push th peddle over a slight "cleft" to make the mopen...IS THAT NORMAL?....IT SHOULD BE A SMOOTH TRANSITION RIGHT?



OK, I will be uploading everything since the timing and installation,....there are a few other small issues but I am doing everything I can to make it ready for BG.

question: could a small hole in the cruise control bellows cause this???



Could you use your help, ideas please!!!:cheers:

[GOLDCYLON]

Hello all!..as you know I have been rebuilding my Z, and with much help from the site and WAZOO, It is running and looking better every moment,...BUT

As with some of my brethren here I have a IDLE ISSUE AS WELL!

here is where I am...

*upon start up idles at 1000 to 1200 RPM, NO fluctuation
*after warm up it starts to fluctuat from 700-1200 over and over and over...
*on the road throttle wants to stick on slow-down at around 2000 and i have to tap the gas to get it down,...NOW..coasting at 10-15 MPH will not allow it to drop...you can tap on it and stays as about 1400....difference?...when at stop it WILL go to 700 RPM,..

what have I done?

*replaced the vacuum tube to the LIMITED things I have due to eliminating the scondaries....
*replaced the IAC valve
*cleaned the PCV valves so they have that "sound"
* plugged up the PCV line to the plenum as well as the booster line (to eliminate the booster and pcv lines)>>>>>>>>>>>the idle drops down but still cycles at that lower rpm
* made sure the throttle body was tight.

But!!!!!!the throttle seem to need forceto open up the larger plates when driving....(sort of like needing to push th peddle over a slight "cleft" to make the mopen...IS THAT NORMAL?....IT SHOULD BE A SMOOTH TRANSITION RIGHT?



OK, I will be uploading everything since the timing and installation,....there are a few other small issues but I am doing everything I can to make it ready for BG.

question: could a small hole in the cruise control bellows cause this???



Could you use your help, ideas please!!!:cheers:

Did you look at ripsters recently uploaded video on the sticking below the TB. As to the small hole in the bellows anything is possible but I doubt this is your issue. GC

http://static.photobucket.com/player...-04-26_724.mp4

[scottfab]

I agree it's not the bellow leak. That is up stream.

The fact that it comes down to 700 rpm or so at a stop is encouraging.
Do you have way of measuring what the IAC is being told to do?
Can you take the bellow off and then wait for it to start cycling and look in at the plates for movement?
Could there be oil in the MAP sensor line?

[oricale]

By the way I also have a code 42

[USAFPILOT]

When my car is warm the idle at a stop is much lower than when it first cranks up. That is for sure, and when the car is still moving I don't think it drops all the way down to that low idle. I notice it more since I have installed the headers and B&B. When it drops to the 700, (my car might be 600, barely off the 500 mark) the car sounds pretty sweet inside. I never thought i could have a problem, unless y'all say this isn't normal. Other than the 2 different idle speeds it runs perfect. Although I have a plug wire that keeps backing off the plug causing a miss every now and then.

[MikeGolf]

Mine is also starting to have those troubles. But my cruise will not hold the speed going up a hill. Do you have a problem with your cruise. Just wondering. I have done nothing to mine yet because it is running well and can get me to BG and back.

[scottfab]

When my car is warm the idle at a stop is much lower than when it first cranks up. That is for sure, and when the car is still moving I don't think it drops all the way down to that low idle. I notice it more since I have installed the headers and B&B. When it drops to the 700, (my car might be 600, barely off the 500 mark) the car sounds pretty sweet inside. I never thought i could have a problem, unless y'all say this isn't normal. Other than the 2 different idle speeds it runs perfect. Although I have a plug wire that keeps backing off the plug causing a miss every now and then.

Does it vary rpm if AC is off? Sounds normal to me.
My #3 plug wire backs off at times. I think the seal between the cover and head is leaky.

[Pete]

On the 42.

Did you recently change Knock sensor or take it off to fix your motor.

If you have access to a scanner check for knock retard.

Check the knock sensor wiring/plug or it's not melted on the header/exhaust.

Pete

[mike100]

The LT5 does have an 'idle hang' programmed into it. It will not drop to true idle until you get below 4 mph or so.

Theories abound, like emissions reasons and smoothness of idle control, but my personal observation on some experimentation with restricted PCV flow back to the TB and low idle targets programmed in-- is that they did it to help keep power steering pressure high enough to run 275's with the big heavy LT5 over them at low speeds.

It seems a fair number of these cars have a little TB bypass leakage along with the usual PCV leaks. The idle hang strategy will make the car hard to drive if you have a high idle, but if everything is ok, it will be much better.

One thing to try is to restrict the PCV hose back to the plenum and tee it off to the atmosphere. you still get PCV ventilation, but much less excess to the plenum. This will compensate for other leakages and get your IAC counts off of zero.

[oricale]

Allright...shouldnt the IAC disconnected make the engine react???...when I unplug mine, nothing changes....(and its new)

[mike100]

Allright...shouldnt the IAC disconnected make the engine react???...when I unplug mine, nothing changes....(and its new)

if you unplug it while it is 100% closed- it will just stay closed, won't it?

a scan tool will tell you its position with iac count values. zero is maxxed out- blocking the port completely.

[oricale]

Allright so I checked the cruise...no change

I plugged the airhorn and the engine stalled so I dont think I have a vacuum leak.

still surging!

[phrogs]

I have that same pedal feel in my car at times usually low mph and just trying to push a little more and it feels like its stuck and then bam your hitting the gas hard. I have a ported throttle body as well.

[secondchance]

I have a plug wire that keeps backing off the plug causing a miss every now and then.

Just in case, check and make sure the spark plug is still torqued correct. I had a pulg boot that kept popping off and turned out to be a cylinder leak caused by a loose plug.

[oricale]

ALTHOUGH !! I did get a 22 code this time..its the TPS sensor voltage under .24 volts at one point BUT....I have checked it and it is at .55!

[mike100]

ALTHOUGH !! I did get a 22 code this time..its the TPS sensor voltage under .24 volts at one point BUT....I have checked it and it is at .55!

if you have a bad tps pot or a loose connection, I'm sure that is playing havoc with the control loop in the ECM idle strategy.

[XfireZ51]

Allright...shouldnt the IAC disconnected make the engine react???...when I unplug mine, nothing changes....(and its new)

If you unplugged the IAC and it was already at 0 steps, it won't make any difference. So the IAC is not controlling idle suggesting that there is enough air(too much actually) coming through the TB. If you don't have a leak, could be the Min Air or the throttle blades.
BTW, unplugging the IAC will require you to do the IAC reset procedure.

[oricale]

How does one do that?