High Idle

[CJ_ZR1]

Need some help guys...

Finally got my car back together after refinishing the engine and doing a couple other things. First start up: starts up great but idling at 2100 rpm, take my foot off clutch and it climbs to 2500 rpm then after about 4 secs climbs up to 2800ish. I shut off car at that point, engine ran for no more than 30 secs.

We check throttle cables, they seem to be fine. Belt had slipped off so re-positioned it and started engine a 2nd time. Same exact symptoms, starts at around 2100 rpm then climbs up to right under 3000 rpm, I shut engine off again at that point.

List of everything we did to car while apart:
Secondary system removed
Charcoal system removed
New FIC SS injectors
Chip tone (Pete)

Any suggestions would be greatly appreciated

[Pete]

Sounds like you have a big vacuum leak.

By the way how did you plug the holes when you took off the secondaries.

I had a freeze plug fell off on one of the secondary holes.

Did you plug the vacuum port under the plenum that went to the EVAP solonoid?

When you ported the TB are the throttle blades closed?
Just in case i doubt it but try stock chip.
Pete

[scottfab]

It maybe tiime for a data logger. Need to find out if it's getting
into closed loop. The fact that it's going backward over
time is curious. (going higher rather than lower)
See what happens when you unplug the IAC.
Also pull the bellows and watch all three plates
for movement as the idle increases.
Getting any codes set?

[QB93Z]

I agree with Pete. The symptoms you describe sound like a vacuum leak. I have had it happen to me. Did you put o-rings on all 16 injectors at the injector housing. Some year LT5's require an oring that is in the housing.

Try removing the bellows at the throttle body air horn and block the air flow to the throttle with a STIFF board, a binder cover works well. With the air horn blocked, the engine should stall. If the engine doesn't stall, you have a vacuum leak.

Good luck

Jim

[XfireZ51]

Since you ported TB, have you done the Min Air adjustment?

[Daniel_Mc]

Originally Posted by Pete

Sounds like you have a big vacuum leak.

Originally Posted by Pete

By the way how did you plug the holes when you took off the secondaries.

I had a freeze plug fell off on one of the secondary holes.

Did you plug the vacuum port under the plenum that went to the EVAP solonoid?

When you ported the TB are the throttle blades closed?
Just in case i doubt it but try stock chip.
Pete

Pete,
I couldn't find a vacuum leak this was my first thought I will pull the plenum and check. The Dorman plugs were used to cap the secondaries and I don't see them coming out but will also look at that. The port under has been capped. The TB was done by the PO all I did was refinish it and reinstall. Everything operates smoothly without any binding. I don't have a stock chip but I will pull the one off of my Z and see how that works or if it changes anything.

It maybe tiime for a data logger. Need to find out if it's getting
into closed loop. The fact that it's going backward over
time is curious. (going higher rather than lower)
See what happens when you unplug the IAC.
Also pull the bellows and watch all three plates
for movement as the idle increases.
Getting any codes set?

Scott,
No codes are being thrown. I will try the IAC tonight and see what that gets me.

I agree with Pete. The symptoms you describe sound like a vacuum leak. I have had it happen to me. Did you put o-rings on all 16 injectors at the injector housing. Some year LT5's require an oring that is in the housing.

Try removing the bellows at the throttle body air horn and block the air flow to the throttle with a STIFF board, a binder cover works well. With the air horn blocked, the engine should stall. If the engine doesn't stall, you have a vacuum leak.

Good luck

Jim

Yes, new O rings in the IH's (where needed) and on the injectors form FIC (where needed) had the O rings already installed so it is all new. Thank you for the tip I will give it a shot.

Since you ported TB, have you done the Min Air adjustment?

We did not port the TB just refinished it when Tommy Morrison had the car the TB was done this was in the late 90's.

Thanks for all the advice guys we will see where this takes us.

Daniel

[CJ_ZR1]

Originally Posted by Pete

Sounds like you have a big vacuum leak.

By the way how did you plug the holes when you took off the secondaries.

I had a freeze plug fell off on one of the secondary holes.

Did you plug the vacuum port under the plenum that went to the EVAP
Pete

Pulled plenum, freeze plugs look good and everything seems to be connected or capped off from secondary system...

[scottfab]

Originally Posted by Daniel_Mc

.. snip..
Thanks for all the advice guys we will see where this takes us.

Daniel

Your pain is our pain.
Another ZR-1 on the road is the goal.

[A1990]

I don't know if it is the same problem as what I had, but I had my throttle body enlarged to 63mm and I assume new throttle blades were installed to fit the new sized bores.

Then later I had the throttle body powdercoated.

Afterwards I experienced high idle. Mine would start off with normal idle until I drove it, but then after driving it would always idle high until I shut it off and restarted it.

I was told that the baking of the throttle body in the powdercoating process that the bores might be now odd shaped from the blades. Made sense to me that heating of aluminum could make these openings change shape.

I sent my throttle body to Marc Haibeck for rebuild and all is good now.

Did you do the test Jim mentioned or the adjustment XfireZ51 suggested. If you don't have a vacuum leak, you might be experiencing what I did.

[Daniel_Mc]

Originally Posted by A1990

I don't know if it is the same problem as what I had, but I had my throttle body enlarged to 63mm and I assume new throttle blades were installed to fit the new sized bores.

Then later I had the throttle body powdercoated.

Afterwards I experienced high idle. Mine would start off with normal idle until I drove it, but then after driving it would always idle high until I shut it off and restarted it.

I was told that the baking of the throttle body in the powdercoating process that the bores might be now odd shaped from the blades. Made sense to me that heating of aluminum could make these openings change shape.

I sent my throttle body to Marc Haibeck for rebuild and all is good now.

Did you do the test Jim mentioned or the adjustment XfireZ51 suggested. If you don't have a vacuum leak, you might be experiencing what I did.

That makes sense but it seems to work just fine. The Z hasn't run long enough to heat up yet. I have not had a chance to try any of the tests I am still at work for a few more hours at the moment But come Monday I'm heading my butt to Vegas for SEMA

Daniel