Ok, I had this problem last year as well before the motor broke.

Low RPMs, when you shift its fine, the throttle drops and everything works fine. When you get up to around 4k or so you push in the clutch pedal and the rpms just do not drop. I don't understand it at all.

The car is a blow thru design (LT1 car), with at D1SC blower, twin intercoolers and the by-pass valve is open to atmosphere and it is open under vac. I'm still breaking the motor in so I haven't gotten under boost yet but last year it didn't matter. I did put one more turn on the return spring to give it a little more force. Still nothing.

Ideas?

The only way I can get it to not do it is by giving it some pedal then snapping it shut when I shift and then it will drop.

Things changed since last year that might affect it:
Solid roller and shaft mounts
SD Concepts belt system
Open by-pass valve

This is really bothering me and no one and I mean no one can figure this out. If you want to see my program for the PCM, email me and I can send it if you think its in there....mind you this is a baseline from last year, gotta get it broken in first before I get it on the dyno.

HELP

 

Check the spring on the throttle body. Check egr operation, I would personally get rid of it, if you have not already. Last is your iac is going out or sticking. Nothing else would allow more air in the motor, one of these

 

Brand new Arizona Speed and Marine TB, complete with new IAC and TPS. No leaks as I can find intake system.

I did put one more turn on the return spring to give it some more pressure.

No EGR...hell no emissions period.

Last time I got it to do it in the garage...the TB just isn't closing, I don't know if that is still the case or not..but even a HUGE return spring didn't solve it...just make it really hard to push on the pedal

 

Well I know you have a new AS&M but I have an OLD AS&M. - about 7 years old.

I get the same thing and it is because the throttle blade shaft has in some way worn the bushings and sometimes the blades do not close properly. In fact, if I hold the throttle blades, I can wiggle and feel a very small movement. Actually, this problem started AFTER I had a problem with my surge valve. Basically it was not working and I had a number of times where I got into boost and the surge backed up through the blower. I think that the pressure also damaged the bushing for the TB

AS&N said that no longer repaired these TB's and offerred $50 toward a new one. (thanks a bunch)

My sympton tends to be under cruise, that when I lift, sometimes the the rpms do not come down and for the moment I just give the throttle a pop and it is fine. I have not had the problem at 4000 rpm because usually that only occurs after a heavy excel followed by a decell and the shaft does not stick under those conditions.

So I would take off the TB, hold the body and see if there is any play in the blade shaft.

 

no offense but stop trying to nick pick at your problem.....

replace your ENTIRE tb with a completely different one and then see if it still occurs

 

Well you see after I spent the $500 or what ever it was on the AS&M piece...one would think that wouldn't be the problem. I would have swapped it out long ago but everyone around here is selling there Z's and getting C5s so not really a way to do it cheaply.

I think I might just order a BBK one or something. I'm really going to be dissapointed if a freakin $500 TB is the problem.

 

Just put your stock one on for a test. If the AS&M one is a problem, they should repair it.

 

that is what i meant

 

If I still had it, I would.

I have a friend with a Grand Sport, hopefully he'll let me borrow it for a couple days and see what it does.

 

now that I think about it I had a similar problem before. The screw holding the TB blade spring tight would loosen causing my idle to rise and the rpm would fall very slow after reving. I put some loc tite on it and never had the problem again.

 

I'm going down to campus probably thursday... I've got my stock one in my closet so if ya want to give it a try I can bring it down