BlueMonster94

I'm starting a new thread since my previous one about an idling problem when the engine reached 240 degrees seems to have died. After getting my car out of the shop still with the idling problem but no other issues, here's what has happened now.

I did a scan, I attempted to install a new TPS in case that might have been my idle problem. Upon installing it, the idle ran too high, around 1200 rpm or more. I put the old TPS back in and the idle decreased to about 1000 rpm. (That was Saturday. Today I reinstalled the new one and then the old one with the same results as below.) But now I have an SES light and Service ASR light with the old TPS installed. I assume that I buggered up the ASR's old readings when I put in the new TPS, since I didn't have the Tech 1 tool to teach the ASR the new "voltages".

Then I hooked up the scan tool. Here's a partial set of readings. If a parameter was at 0, I did not record it in most cases.

Codes were present during the Engine Off and Engine On scans. That code was 22, history and current. That code is TPS voltage too low.

Engine Off results:
IAC position: 101
Idle requested: 3188
Fuel Trim L/R: 128
Loop: Open
MAF (gr/s): 0
MAP (" HG) 29.65
IAT: 134
O2S left: 18
O2S right: 44
TPS (V): 0.04

Engine On results (at idle with AC off):
CYL ID: 47-87
IAC position: 54
Idle requested: 625
Knock sensor: 3
Loop: closed
MAF: 10
MAP: 9.16 to 9.49
O2S left: 71-852
O2S right: 71-844
Spark adv: 36
Throttle (%): 5
TPS (V): 0.0-0.02
Eng RPM: 1082-1100
TCC control: ON

Engine On (idle with AC on):
IAC position: 74
Idle requested: 675
ST Fuel trim L/R: approx 120-135
Knock Ret: 0 degrees
Knock sensor: 7
Loop: closed
MAF: 11-12
MAP: 9.81-11.01
IAT: 138 degrees
O2S left: 89-904
O2S right: 62-852
Spark adv: 37
TCC brake sw: on
TCC control: off
TCC solenoid: off
Throttle: 6%
TPS sensor (v): 0
Engine rpm: 1032-1112 at idle
TPS voltage remained at 0 with rpm increase

The old TPS was used in all of the above scans.

Before each scan run, I would erase all codes (22). As soon as I started the scan, the code returned. I ran NO scans BEFORE this TPS fisaco this morning.

Maybe this info will make sense to someone out there.

mseven

Can't tell you about ASR and MAF, I can tell you at idle in P,N, should show 0% throttle angle. No TPS reading or reference voltage might be found as a short at the weather pack connecter. That should be showing approx. .54 - .06 (@idle)I would start there by testing the wiring w/a vohm meter.

BlueMonster94

What is the weather pack connector? New one on me. Is that the connector for the TPS?

RRT vette

Looks as if you definately have a TPS problem. I'm not sure if a 94 has a nonadjustable TPS or not. As mseven stated you will need a voltmeter to see what voltage signal the TPS is sending the PCM. This could very well explain the surge in idle your experencing. TPS voltage should range from 0.54v closed throttle plates and >4.0v at WOT. You will need a 94 FSM (factory service manual) to correctly diagnose the problem by yourself. You could have a bad TPS, connection, or circuit (signal or ground).

mseven

Yes, the plug in part of the harness to the TPS. Perhaps pins/connecters are not making contact , dirty etc. It' s obviously not seeing the reference voltage.
The other thing that bothers me is that you are showing 6%throttle angle at idle. That may be attributted to the TPS. First get the TPS straightened out then see where the T.angle is, again I am not familiar w/ASR but I doubt it should show any angle at idle (0%).

BlueMonster94

I have the 94 shop manual. It'd help if I had a Tech-1 scan tool, but I'd need to win the lottery to afford one. I do have a multimeter though and can check for shorts.

But before I tried to install the new TPS, I didn't have the high idle nor had I scanned the engine before the new TPS install attempt. With either the old or new TPS I get the high idle; I surmize that I'd get the same scan readings.

The TPS for a 94 is not adjustable. Where I may have screwed up was not teaching the control module that works the ASR system the TPS voltages (which right now are 0.04 with key on, engine off and 0.00 with key on, engine on).

Corvette Kid

I've had issues like this before and it was nothing more than loose contacts in the TPS connector. They can be replaced if you have the release tool to get them out. If you have the matching small spade you can check them individually for 'feel' by how snugly they hold the spade. This particular type is a Metripak design and is very prone to cause contact problems when they get old and loosen up. I've dealt with them in many applications. NAPA should have the individual contacts to repair yours as well as a release tool and special crimpers, or can get them. Or if you can find an assembled TPS connector with leads, you can simply splice if in.

mseven

All you need is a lap top and a cable. Progrms are available from 30.-100. (tuner pro , datamaster) Also available as trial free for 30 days. Stand alone Auto x ray for around 300.
I believe all sensors/switch replacements are explained in the helms as removing the ground of batterey before installing, which does allow re-learning etc.
If your Helms is saying the control module needs to re learn, you should be following directions (removing batt. cable?) I still say connecter first.

BlueMonster94

I have a laptop, but no software or cable. I think the FAQ has info about software and cables. I will check the connector today. Right now I have other business to take care of.

PacWest

I've got the same problem on my '96 right now. I just replaced the TPS and experienced the same symptoms. The car idles too high (about 1,000 RPM) and turned on some lights...SES, ASR.

My shop manual says I need the Tech 1 tool to help the EBTCM relearn the idle voltage from the new TPS. If I put the old TPS back on the problems go away but the car does not run as well.

I'd like to find out how to setup the relearn procedure without a Tech 1. It sounds like this is possible with other scan software. Otherwise, I'll be going to the dealership later this week.

Corvette Kid

I'm not entirely sure but I think it will relearn in a period of time even if not reset. Mine's never been reset and I couldn't tell you how many different combinations of TBs and different TPS switches I've had on the car.

BlueMonster94

That is where I'm at. Same rpms and same lights. And the Chevy dealer here has a questionable reputation, I've been told. I guess I may end up finding out for myself if I don't find an electrical connection problem

For those of us who live in north Texas, it is raining in Greenville. I have no garage and my Vette is stranded in the rain. Latest report shows that it has not melted.

UPDATE 07/27/06: The car is back from the Chevy dealer and runs and idles normally. The problem was a TP sensor installed wrong causing no voltage to be sensed by the control modules. Once that was corrected, the GM tech relearned the EBTCM the new TPS voltage after clearing the offending code(s).
A side note, when I took the car into the Ford shop one of the problems I wanted fixed was a possible front end problem that I thought was there because of a metallic clunking noise. The Ford service advisor said that the front end tech looked at the suspension and found no problems. He was WRONG. After the vette was returned to me at the Chevy dealer, I took the car next door to get new BF Goodrich tires. After the tires were installed, the tech at Discount Wheel & Tire showed me how loose the right front wheel/tire was on the hub bearing. Yep, the bearing assembly was going bad. I ordered a new one from Autozone for $200 with tax. The tire store will install it for $65 this coming Monday. Sad to say (LOL) that I am disappointed with the Ford shop. Happy to say that I'm satisfied with the Chevy house and happier still with the tire store. Guess which outfit I won't take my business back to.....

BlueMonster94

Well, it quit raining long enough to check out the voltages and ohms, using a DVM, at the TPS connector.
Pin A is the 5 volt reference. Pin B is sensor ground. Pin C is TP sensor signal.
Across pins A and C = 0 ohms (short).
Acorss pins B (gnd) and A = infinity
Across pins B and C = infinity
Across pins A and C = 5.0 volts

With the TPS connected or disconnected, the rpms as shown by the dash tachometer did not change. That tells me that the connection is faulty. Someone tell me that I'm wrong, right or dumbfounded.

UPDATE for those are concerned....
I will take this car to the local Chevy service department so that the old EBTCM can relearn the new TPS voltages, per the TP Sensor Learn Procedure in 6E3-C1-14 5.7L (VIN P) DRIVEABILITY AND EMISSIONS section of Book 2 in the 1994 Corvette Service Manual. Failing that, I will let the GM techs solve my idling problem(s). I do NOT have the tools and other resources to chase down Corvette-related goblins.