Air-Adam

Hey guys... new member, but I've been a lurker for quite a while.

Anyway.. I have a 6-spd '97 Z28, all stock, but over the last year or so its developed an intermittent sticky throttle problem. Doesn't happen all the time, but often enough to bother me. Driving at a constant speed, I can let off the throttle, and the rpm will not drop - acts almost like the cruise is on. If I quickly stab the throttle, then it will drop down to normal (this is why I think its a mechanical issue).

It started to happen a little bit in the summer. I cleaned the throttle body and it didn't really help anything - though it wasn't really dirty in the first place. I've checked the throttle cable and it doesn't feel like its binding up (unhooked from the TB unit) and it doesn't look like its routed in a way that might make it stick.

Has anyone here dealt with this before? Suggestions?

Maverick_997

Welcome
when i bought my car it was sitting for 3 years and when i replaced the head gasket i took it out and brought it to WOT and it got stuck so i had to turn it off and bring the plate closed from under the hood.. anyways i sprayed it with pb blaster a few times prety much everywhere on the tb that moved and it hasnt happened since.

Jeremy

Air-Adam

I did spray the throttle shaft with some oil a few weeks ago (at least, what can be reached without taking the intake duct off, its too cold here now to be moving around rubber parts lol) and it did seem to get a little bit better for awhile, but it still does it...

NJ-LE

Air-Adam:
The LT1 ECUs are programmed to hold a high idle when the car is moving, even if your foot is completely off the gas. Interstate M6 (3.42 rear) highway rpms are ~1500 and I found the IAC would try to keep them 1200-1300 when off the gas. Not much engine braking effect. Also, the IAC valve under the throttle body, is prone to sometimes sticking. when you do stop the idle may still stay above 1000 until you "exercise" the gas pedal and the IAC will try to respond and usually will free itself. After the hassle of cleaning the valve a number of times only to have it happen again after a month or two, I finally plugged the throttle body airhole passage to the IAC. Now, the IAC can do whatever it wants to but has no effect. Winter cold start is ~550 rpm and within a few minutes of warming up is at a steady 800 rpm. This didn't seem to affect the emission numbers at all. They are still very low.

Air-Adam

Oh ya, I realise they have the fast idle programmed in for use whe the car is moving, mine does that too (around 1200rpm) when I don`t have the sticky throttle problem. But I know something isn`t right, because if I`m spinning 2000 in 5th for example, if I push the clutch to take the load off, it will jump to maybe 2200 or 2500 and stay there. If I quickly stab the throttle, then it will drop down to idle speed (1100-1200 if moving).

NJ-LE

Air-Adam:
I never saw the rpms get that high with the pedal up so maybe something is binding but if the IAC can control at 1200-1300 rpm I suspect it can allow enough air for more than that. I don't know just how much max IAC air flow is. I also tried squirting some spray carb/fuel injection cleaner into the IAC air hole. It would help but only for a few days to a week. I assume if you have cruise control (I don't) you've tried disconnecting it's connections to the throttle body linkage.

NJ-LE

Air-Adam:
I just remembered that when I installed my 52mm TB, I initially had a 2000 rpm idle until I elongated the screw holes on the TPS and adjusted it to have ~.5 volt signal back to the ECU ... I never had to touch the TB adjustment. Check if your TPS mounting screws have loosened up. Just a thought.

Air-Adam

Not a bad idea... I'll have to check that out. I kinda doubt its a computer related issue though, I'm almost certain its a mechanical issue.

Are there rebuild kits available for a TB? I know with carbs, which I do have more experience with, one can repair a worn throttle shaft hole by boring it out a little and installing a small brass bushing. Can this be done with an LT1 TB? I'm kinda thinking my TB might just be worn out, and the shaft binding up in the worn out hole? Does this happen with throttle bodies like it does with carbs?

95TA04GOAT

I don't know of any rebuild kits but you can probably find a used (hopefully less then yours) stock TB for the price of what you might expect to pay for a rebuild kit.

canuck94z28

Have you ever sprayed some wd40 on the throttle linkage?I do this 2 times a yr or when the gas pedal feels tight.Btw i had a BBK 52 t.b at one time and the spring was slightly heavier than the stk 48 t.b one.Hope this helps.

Air-Adam

I sprayed it about 2 or 3 weeks ago, and it helped a little bit, but its still got the problem. This is why I'm leaning towards it just being worn out. I know with a few Holley carbs, what I've done with worn throttle linkage is to take the butterflies off and pull the shafts out, drill the holes out of the base a little, and knock in a brass bushing - worked like new after that. I was hoping there might be something similar for a TB unit?

I am in the midst of buying a used stock TB with half the mileage (on the motor) of mine, so hopefully if I can't fix it by the time it gets here, that one will work and the problem will be behind me.