Corvette_Brett

I posted this in general to start with but I was told here would be a better place.

Car is a 2000 Z51 coupe.
Mods are : small cam 226/236 lsa110, long tubes, no cats x pipe and a dyno tune. And now a Ls6 intake.

Problem: high idle (1300-1500) when moving with clutch in.
This started when ls6 intake was installed.

More Info:
If the car is started, idle is normal.. a little high for a min then drops down to 850(tuned idle). If you rev the motor the rpms drop back to 850 as they should. But if you put the car in gear and take off driving for a few min and the car goes into open loop when you press in the clutch the idle stays up at 1300-1500 rpms until you come to a complete stop. Then the car returns to the 850rpms. I did noticed if I went into a store and let it set for 10 min and come back out the car some times doesn't do the idle up thing for some reason.

I've been all over the intake, tb, air bridge, and pcv system with a can of carb cleaner and a propane tank with a hose attached on 3 different occasions. I have also loosened and reseated the intake then re-torqued in the proper sequence. I've also done the idle relearn thing. Nothing has help.

Is the ls6 intake just flowing so much extra air at idle and just needs to be tuned or is this a vacuum leak I just can't find..

Any help would be greatly appreciated

adi4

baxsom

Vacuum leak somewhere. At idle there is not enough of an airflow difference to make that much of an idle change with the LS6 intake. I had the same thing happen and turned out the hard plastic line that goes to the back of the intake got cracked during install and I had to do it all over again.

Corvette_Brett

Well I've got access to a scan tool so I was watching the throttle blade angle. It has a desired and actual. My thinking was if the throttle blade was in its normal position and the idle comes up I've of a vacuum leak.

So after playing with it for 10 moles or so with intermittently doing the idle up crap. I saw that every time it idled up the computer was telling the throttle blade to stay at 9* when normal idle is around 5* ..

So I'm thinking the flow of that intake at idle is more or less and the computer can't fully adjust it out with in the parameters of the tune.

I'm 99% sure there in no leak at this point. I've soaked this thing in brake cleaner on 3 different occasions and hooked a hose to a propane tank and followed every single vacuum line, tube, fitting, and coupler with no change in idle.

lionelhutz

Sounds like the throttle cracker.

Corvette_Brett

That's what the tuner thinks also and asked me to bring it back.

The blade would not be opening at the high idle times if it was a vacuum leak correct.

I would think if anything the computer would be trying to reduce the TB angle as air got in from somewhere else to maintain its programmed idle. If there were a vacuum leak. But instead the computer is telling it to maintain a airflow that is higher than what is needed to achieve 850rpms. And that's why its hanging.

Please someone correct me if my way of thinking is incorrect.

Corvette_Brett

Just to finish this out for people who may have the same problem down the road..

It was the the idle airflow tables. The tuner said he had to remove quite a bit.
More than he would have ever thought it would have needed.

I smoked the intake with no leaks. Before it went to him. So evidently the ls6 intake flows a little better than I thought it could, over the ls1 when a cam is added

Bill McCassey

Glad to hear you have it worked out Brett.

Corvette_Brett

I truly appreciate all the help from you and others who have replied

baxsom

was there any other tuning that had been done to it previously because if the stock tune was doing it you have the honor of it being the first time happening with this swap.

Corvette_Brett

No this car had been tuned after the cam swap. The intake went on a week or so later..