throttle position sensor..etc...

[TedC]

Yes, it is one in the same. It is not for setting minimal idle speed!!! The ECM controls idle speed. This is the minimal air flow setting that produces around 450 rpm. Some with higher lift after market cams need to set it higher, but don't do that with a stock cam. The ECM adds additional air via the IAC valve. I've watched with a scanner and it does a pretty decent job considering the vintage of the L98 ECM. You can turn that screw in and out and the ECM will hold the idle speed steady. However, you messed up the calibration between the IAC and the ECM. I wire brushed my throttle body. My car is not for show, so I'm sure I could spend hours detailing it. I see you found my old post. A scanner can also be used instead of the tach. I've found that a clean and properly adjusted minimal air and TPS can significantly improve how well the L98 runs.

 

[joshwilson3]

Yes, it is one in the same. It is not for setting minimal idle speed!!! The ECM controls idle speed. This is the minimal air flow setting that produces around 450 rpm. Some with higher lift after market cams need to set it higher, but don't do that with a stock cam. The ECM adds additional air via the IAC valve. I've watched with a scanner and it does a pretty decent job considering the vintage of the L98 ECM. You can turn that screw in and out and the ECM will hold the idle speed steady. However, you messed up the calibration between the IAC and the ECM. I wire brushed my throttle body. My car is not for show, so I'm sure I could spend hours detailing it. I see you found my old post. A scanner can also be used instead of the tach. I've found that a clean and properly adjusted minimal air and TPS can significantly improve how well the L98 runs.

Thanks, yeah I don't have a scanner, and I think those are expensive. I'm mainly wanting to get it to spec as best as I can with a volt meter. As when I pulled it to clean the throttle body, I didn't pay attention to where it was at. But then again, the PO could have messed with it and it was off anyways.

I just found out my smog pump is seized. I sprayed water all over the engine cleaning all the grime. I pulled the alternator, battery, cap, and rotor. And I seran wraped and tin foiled the distributor top. Tin foiled the spark plugs on top and all open electrical connections.

I've never read anywhere the need to pull the smog pump when power washing the engine, but I guess I should have. I noticed either later in the day or the next day I did it, the smog pump was stuck a little when I turned it, but then turned freely. A few days later, which is today, the pulley doesn't even turn. Got any idea if the smog pump from autozone would be decent? I guess I could get one from a parts car, but then again, it would be 20 years old and I figured a remanu one from autozone for $50 might be a little better. I might get it priced at Napa. Though in the past, I've had to replace Napa parts 2-3 times over, but have had good luck with Autozone for some reason.

 

[TedC]

Never had to replace one. Eckler's shows one in their catalog for $90 (remanufactured with new bearings and filters). Corvette A.I.R. Pump, Rebuilt, 1986-1991

 

[John Robinson]

Hope this sheds some light on the tps for you

Broken Record
I know that some of you may be getting tired of my posting this information on the TPS but after buying a new ECM only to find out how the TPS works and it was why my car would not start. I offer this in the hopes someone will be able to fix their car by looking at something most people do not understand what it's function is.

Throttle Position Sensor (TPS)
Copied from 1993 Service Manual​

The Throttle Position sensor (TPS) is a potentiometer connected to the throttle shaft on the throttle body. It is a potentiometer with one end connected to 5 volts
from the ECM and the other to ECM ground. A third wire is connected to the ECM to measure the voltage from the TP sensor. As the throttle valve angle is changed (accelerator pedal moved), the voltage output of the TP sensor also changes. At a closed throttle position, the voltage output of the TP sensor is low (approximately .5 volt). As the throttle valve opens, the output voltage should be approximately 5 volts.

By monitoring the output voltage from the TP sensor, the ECM can determine fuel delivery based on throttle valve angle (driver demand). A broken or loose TP sensor can cause intermittent burst of fuel from the injectors and cause an unstable idle, because the ECM detects the throttle is moving.

If the TP sensor circuit is open, the ECM will set a DTC 22. If the TP sensor circuit is shorted a DTC 21 will be set. A problem in any of the TP sensor circuits will set either a DTC 21 or 22. Once a DTC is set, the ECM will use a default value for TP sensor, and some vehicle performance will return.

A personal note, when my TPS failed it DID NOT set a code other than to tell me the ECM was bad.

I used a couple of straight pins through the wires to hook the meter on

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[joshwilson3]

Never had to replace one. Eckler's shows one in their catalog for $90 (remanufactured with new bearings and filters). Corvette A.I.R. Pump, Rebuilt, 1986-1991

Thanks. That is cheaper than Corvette Central of $150 for some reason. I think I'll get the Autozone one. It is $50 and has a 1 year warranty. It is probably the same thing anyways as I'm sure there probably isn't alot of companies making remanu smog pumps compared to alternators or other items.