350 HRSS

Alright, I hope someone can help us out here

We had to fix the infamous oil leak on a 94Z. We took the intake off, put it back on, and bolted everything back up. The only change we made was putting a 52mm TB on. I played w/ the throttle screw, no changes. I even backed it all the way off, the idle didn't get any better. Then, I tried the TPS. I slotted it out, and played w/ it a couple if times, different positions. It seemed to help a little, but not near enough.

The car idles at 1400-1500 in Park. When we put it in any gear, it drops down to where it needs to be. In the 900-1000 range. It sounds a LOT better anyway. We checked for vacuum leaks, since that is what normally causes erratic idle. But we couldn't find any

Should we just put the 48mm back on, and try that??? I had this 52mm on my 95Z and had no issues like this. I don't have a scanner to check the IAC or TPS position/volts. I am not sure what is causing this, and if there is a leak somewhere it beats me.

Can anyone give us some hints on this? Or should we just try removing the 52mm TB and put the stock 48mm back on?

This is really frustrating. BTW, there are no codes. Just a high idle in PARK at 1400-1500.

I hope some of you out there can help us out. His car has no mods except a K&N FIPK, and Optima battery. This should be really simple. I only have LT1 Edit, Scanmaster, etc. for my 95Z.

Hope to get some ideas.

NtenseZ28

What is ur TPS Voltage at idle? Is the IAC motor functioning properly? What brand TB is it? You shouldn't have to touch the idle screw...that is why there is a solenoid under the TB, it takes care of that for you. Spray around the sealing surfaces of the intake with something like carb cleaner...anything that'll make ur motor begin to idle up or gag out when the motor sucks it in...sure way of telling if you have a leak.

If you don't have a scan tool, you can back probe the TPS connector, the return wire and ground. The TPS is a potentiometer, the computer supplies 5V, then as the position changes the resistance varies, delivering more or less voltage back to the computer. 0 (or real close to it) is idle, 5 is WOT.

If you take the IAC motor out, and plug it in to the harness (while it is out of the TB) and turn the key on...it should retract all the way (the default position). If it's idling high cuz of a air leak...then it will still be sticking out most of the way because the last time the car was idling, it was trying to close off the Idle Air passage.

Start there, if it's easier for you, put the 48mm back on, but since you slotted ur TPS sensor, you're going to have to check ur return voltage anyway. Make sure the reference voltage is somewhere around 5 too!

HardcoreRM125

Since the other stuff has been discussed ... Heres a possibility ... Try Disconnecting and reconnecting the battery. Maybe the computers BLM's are off from it running bad all that time and it hasnt relearned yet so its running rich now, causing it to idle high in park/nuetral, but once its in drive ( And under the load of spinning the stuff in the tranny, it bogs it back down to where it should be. My dad's old truck did that once from running slightly rich. Idled high, but then as soon as he put it into drive it was ok. He leaned out the carb a hair, and it was perfect after that. Althoguht it only idled about 200 RPM high.

350 HRSS

That is what I was saying, I don't have a scanner for this car, so I am not sure about the TPS voltage. It is a ASM 52mm TB. I put the idle screw back to where it was. We were going to take a cigarette and go around the intake
to try to find the vacuum leak.


I know the volts should be 5 max. And I know the ideal voltage at closed throttle should be between .60-.67 or so.


Well, we would like to see if putting the 48mm back on totally fixes the problem or not. If it does, we will know it is totally throttle body related. If it doesn't fix the idle issue, we know it probably isn't the 52mm TB causing it.
And still a vacuum leak.

Slotting the TPS makes it a lot easier to work with. I had to do it w/ my BBK
to get it to the proper voltage at closed throttle.

Thanks for your help

350 HRSS

We did try that actually. We disconnected it a couple of times, and let it set.
When he drives it, it seems to be fine, it is just that high idle in PARK.

We had it disconnected 3-4 times, and drove it around 3 times to let it relearn a bit. I can tell it is *trying* to come down to the right idle. If you give it a little gas while sitting there, it goes up to about 2k RPM slow....and then sits there at 2k, and barely drops down....

rskrause

"Dollars to doughnuts" it's a vacuum leak.

Rich

350 HRSS

That is what I am thinking. I never had this problem w/ a TB before.

WS Sick

Definately double check for vacuume leaks, then set get a scanner on it and set the TPS to proper voltage. I would then reset the IAC just to be safe and set minumum air.

wwarnke

you can check your TPS voltage with a VOM (volt ohm meter)

I am not sure of the wire colors, so just test around.

You should get +5v when reading across two of the lead wires, then move the positive to the third wire, and now you should be reading your TPS voltage.

Good luck

StickMaster

You didnt mess w/ the throttle cables at all did you? maybe they are binding a bit?