Stumped...
Thread Starter
Racer
Joined: Jul 2013
Posts: 275
Likes: 1
From: Colorado Springs
Stumped...
1988 L98 4+3 Trans
Issue: When I depress the clutch or in N, my RPM's clime to 13-14 but one you release the clutch they return to normal.
If you have the clutch depressed, say at a stop sign the car will idle at 13 to 14. If you hit the gas real quick, the RPM's will return to normal every single time.
I have checked and adjusted the TPS and IAC on the throttle body as described in this forum using my voltage tester ect. The idle seemed better for a day or so. My TPS was reading .59 prior to me adjusting it back to .54 but I am still having the same issue.
I have also replaced the plugs, wires, cap, rotor - checked for vacuum leaks on the intake, plenum, throttle body and all the lines in the engine bay.
I am starting to wonder if the stock throttle body is sticking on me, has anyone else had this issue before?
I have no engine codes either.
Issue: When I depress the clutch or in N, my RPM's clime to 13-14 but one you release the clutch they return to normal.
If you have the clutch depressed, say at a stop sign the car will idle at 13 to 14. If you hit the gas real quick, the RPM's will return to normal every single time.
I have checked and adjusted the TPS and IAC on the throttle body as described in this forum using my voltage tester ect. The idle seemed better for a day or so. My TPS was reading .59 prior to me adjusting it back to .54 but I am still having the same issue.
I have also replaced the plugs, wires, cap, rotor - checked for vacuum leaks on the intake, plenum, throttle body and all the lines in the engine bay.
I am starting to wonder if the stock throttle body is sticking on me, has anyone else had this issue before?
I have no engine codes either.
Drifting
Joined: Feb 2006
Posts: 1,423
Likes: 96
From: Magnolia Tx
Sticking throttle body is very common. The throttle shaft wears and binds in high
vacuum condition, but feels normal with the engine off when you are working on it.
I think the stick cars are more prone to it but the autos do it too. I adapted a '94 LT1
throttle body to mine, but looking back, an aftermarket model would likely be as cheap
and a lot less work. I've had 3 TPI cars and an LT1 car with this issue.
vacuum condition, but feels normal with the engine off when you are working on it.
I think the stick cars are more prone to it but the autos do it too. I adapted a '94 LT1
throttle body to mine, but looking back, an aftermarket model would likely be as cheap
and a lot less work. I've had 3 TPI cars and an LT1 car with this issue.
Race Director
Joined: Apr 2003
Posts: 17,700
Likes: 1,667
From: moraga ca
Most likely the throttle shaft is worn causing the throttle blades to hang up slighly open. Try cleaning the blades (inside and out) and the throttle body area with throttle body cleaner. Sometimes that will clean out the gunk that is holding the throttle body open.
Thread Starter
Racer
Joined: Jul 2013
Posts: 275
Likes: 1
From: Colorado Springs
I think I will take the TB off and clean it up. I am juggling a LS swap or a Stroker after tax season - So I want to wait to purchase a new TB till I know what I am building. If I do a 383, I will prob use the TPIS Intake setup and replace the TPI.
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
Yeah my car needs a new throttle body too. I was looking around and they don't seem to have a stock one online that I can find. I'm looking to spend like $150, if I have to pay $300 I'll just go with a 52 or 58mm.
Safety Car
Joined: Jan 2004
Posts: 3,556
Likes: 13
http://www.ebay.com/itm/TPI-52mm-bored-port-throttle-body-85-92-Z28-TA-Corvette-/230426189214?pt=Motors_Car_Truck_Parts_Accessories&hash=item35a6789d9e&vxp=mtr
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Safety Car
Joined: Nov 2008
Posts: 4,328
Likes: 15
From: Jacksonville FL
My car does about the same thing. Next time you drive and are experiencing the high idle, check and see without blipping the throttle if it settles back to normal. Watch the speedo next time and see if it does settle after about 2-3 seconds at a stop. If the idle drop corresponds with the speedo zeroing out I think the IAC is reacting to the info the ECM is receiving and I am not sure what can be done to stop it.
I cleaned my old TB in the hopes it would clear the high idle. I also bought one of the remanned TBs in the link above and the car still has the slow to return idle. I still think it has to do with the IAC or the input to it.
I will be watching this thread for a solution and if I find one I will post it up.
Good luck!
I cleaned my old TB in the hopes it would clear the high idle. I also bought one of the remanned TBs in the link above and the car still has the slow to return idle. I still think it has to do with the IAC or the input to it.
I will be watching this thread for a solution and if I find one I will post it up.
Good luck!
