Christi@n

I'm close to properly tune my lt1 1995 idle.

At this moment idle at 900 rmp, if car is stopped in neutral (man trans),
Obtained by idle regulation screw on TB

The Only one issue remain is on running

As instance: go 3rd engine 900 rpm, step on clutch and go neutral for a while idle doesn't come back to 900 rpm, but stay up, about 1100-1200 rpm,
Until car is stopped Again, then slowly come back to 900 rpm


Any idea? Seems like to be something related to the speed.

ASR cable, speed sensor on transmission?
Already check for vacuum leaks seems not to be, even since that if idle works properly with car stopped should works properly on run too.

DanielRicany

That's not the proper way to adjust the idle. You need to do an idle reset procedure. The ECM controls the idle not you at the throttle body. You're forcing a higher idle than what it should be.

Christi@n

Could you explain me the proper idle reset procedure for 1995 lt1 corvette

bjankuski

Go to the scalers and look for an IAC adder that is based on mph typically there will be an adder that raises the iac count the faster you go, when you stop the iac adder will decay away. Use a scanner to set your base idle speed if you want a 900 RPM idle warm you would like to see a iac count of 10 to 20 when the car is warm and stopped. (Adjust the idle screw to achieve this result)

Christi@n

Got it, just what's scalers?

aDigitalPhantom

What speed are you driving at in 3rd? If I read your post correctly you have manual not an automatic? If yes then maybe you should be in 2nd.

Christi@n

Don't know exactly At this moment i've need to check it, anyway could be 20-25 mph, but the problem is always the same for any gear ratio

Go 1st 2nd 6th any speed you want, then engage neutral, don't allow to the car to stop it and idle stay high 1200 rpm, when I stop car idle slowly come back to 900 rpm

Yes i've manual trans

armysnipe

I've had a failure with my TPS and it caused a high idle condition. Luckily, I had an old throttle body with an old TPS and was able to compare the two. Something you may want to consider.

Christi@n

Thanks, I will check it with multimeter, should it works to discover any malfunctions?

bjankuski

What program for tuning are you using? Typically you have flags (On/off changes), then you have (Scalers or constants which are 2d tables or changes) and then you have tables which are 3d tables. The IAC offset per speed of car is usually under scalers.

bjankuski

I found the IAC adder in Tunercat, it should be similar in other programs. It was under tables for the 1995 vette.

Christi@n

At the moment Any program any scanner, I'm without these tools, just readed codes with paper clip...

I will purchase them as soon as possible

Christi@n

Two links welll explained on how to check tps, i've found out...



http://www.enduringautomotive.com/tps/

http://www.enduringautomotive.com/ho...robe-a-sensor/

Christi@n

possibily i've find out the reason of rough idle.

I've tested with multimeter TPS both wiring and TPS sensor

Well First wiring its ok

Ground Black Wire 11.58V
Blu Wire 0.5V
Grey Wire 5V

Then with multimeter set on ohm scale

With TPS to 0 read was 6.60 K ohm, rotating TB shaft any difference appear in dispay, so any change in TPS resistance, I would assume that this is a BAD TPS sympthom

aDigitalPhantom

What wires are you using for your ohm test?

PS
Also you need the connector unplugged to correctly ohm the TPS.

Christi@n

I've connected the negative multimeter wire to the TPS plug where black ground connector wire is,

positive multimeter wire to the TPS plug where grey wire is,

during test TPS wasn't connect as above mentioned, just connect with TB shaft

aDigitalPhantom

There is your problem. Black is ground, grey is 5V+, and blue is the signal to the computer. Reading the ohms from black to grey will not vary with the change in throttle position.

Christi@n

Is The right couple blue and black? I don't rember if i'v already done this test too, seems yes, and if I remeber correctly, even blue black show any change in resistance.

I will re check tomorrow...

aDigitalPhantom

Not entirely sure. It will be blue and black, or blue and grey. They will just change resistance in different directions.

Christi@n

Will re check tomorrow