Rob Edwards

Well, I did an intake R&R about 2 months ago, and when I got it all finished, I had a bad surging-then-dropping-to-400-rpm-idle for the first minute when the car was cold. I knew that I didn't index the TPS on the throttle shaft, and yesterday I verified this by testing for continuity at pins 2 and 17 on the LH connection, and 8 and 18 on the EZK connector - I got infinite resistance for all pin combos.

Well, tonight I pulled the intake (Note- once you've done it, and everything is clean and been apart recently, it comes out fast- I got the whole intake off in 2 hours.) Lo and behold, I had forgotten to connect the $*%($&ing 3- pin connector to the TPS. No wonder there was no continuity...... So that was problem #1.

Now, I moved the throttle off of idle and didn't hear a click, so I re-indexed it until I got the click. Had to have the unit fully clockwise as possible:


Just to test things directly at the TPS pins, before reassembly, I pulled out the LH and EZK troubleshooting guide, and turn to page 24-12. Maybe it's 'cause it's 1AM and I'm tired, or things are lost in translation, but the way it reads, one is supposed to put test leads across pins 1 and 2 (the lower 2 pins when the TPS is mounted on the intake):




You're supposed to get <10 ohms when the throttle valve is closed, and infinite when the throttle valve opening angle is > 1 degree.

Well, when the throttle is closed AND just after the click (just off-idle), I get an infinite reading (multimeter display says "1":



And I don't get less than 10 ohms until I'm at the 2/3 open throttle position:



What am I misinterpreting here? I'd hate to get this back together and have the same idle issues. Thoughts?

WICruiser

Is the click you are hearing the idle switch or the WOT switch?

I don't have the manual out but it sounds like you are actually measing the WOT switch because that is suppose to happen at about 2/3 open.

worf928

Re-review the troubleshooting guide.

The sender has two switches - one for idle and one for WOT. Test both functions at the sender and at the LH and EZK plugs.

borland

I've addressed the adjustment of this component in my posts on the GTS Dynamic Kickdown mod thread.

Rob Edwards

Thanks for the suggestions- Borland, I'll go review your posts. I think that I have the switch indexed properly, as I get the click just off idle, and I get a switch in resistance at 2/3 throttle, it's just that the pinouts in the manual don't jibe with what I'm seeing on the parts in front of me. I have re-reviewed the LH/EZK diagnosis guide, and this still doesn't make sense.

If you're connecting directly to the TPS pins, for the idle test you connect to pins 1 and 2, which are the middle and bottom pins when the TPS is mounted on the intake. I get the exact opposite of what the troubleshooting guide says



For testing the WOT part, you connect to pins 2 and 3, which are the top and bottom pins. I get infinite resistance regardless of throttle position.

I wonder if I've got a bad switch, right out of the box.....

Sorry to be retarded about this, and thanks for everyone's patience. I just don't want to put this back togehter until I'm sure it's right.


Here are the two tests to be done directly on the TPS switch itself, as written. Who the hell labels 3 pins 3 - 1 - 2?

worf928

Try this.... The middle pin on the sender is ground. One outer pin is WOT. The other outer pin is Idle. Figure out which outer pin is idle by using your MM and listening for the 'click." With the sender rotated all the way to the idle stop, one pin will give you continuity with ground (middle pin) and one outer pin will not. When you rotate the input and hear the click, the pin that had continuity with ground should go infinite. That's the idle pin. The other outer is WOT.

worf928

Rob, I think the TEXT of the troubleshooting guide is wrong. Take a look at your wiring diagrams - they show that the middle pin "1" is ground (like I write above.)

Bill Ball

Or the pin numbering is wrong: 1,2,3 would work.

Here is the guide for 84-6 which is the same except the switch is mounted backwards relative to 87+, but the function is the same.

Rob Edwards

Dave-

You're absolutely right. The pins are labeled (top to bottom) as 2, then 18(ground), then 3. So when I test across 2 and 18 for idle, I get <1 ohm at idle, then infinite as soon as I open the throttle. Testing across pins 3 and 18 for WOT, I get infinite ohms at idle, and <1 ohm at 80% throttle opening.

So it works exactly as indicated, they just got the text wrong.

Will report back and add some pics once I'm up and running.

JP Rodkey

Oh yeah! I found out the manual was wrong when I did what you're doing last month. The WSM does not agree with the markings on the TPS and the wiring diagram does not agree with the section in the manual, either. I thought about doing a writeup, but since so many people had already gone through TPS disco, I figured it must not be the problem I thought it was. In the end, the switch needs to show one circuit closed in it's normal (no rotation of it's shaft) and the other circuit closed when at WOT. So long as that's the case, it is highly likely the TPS is functioning properly and you can proceed with installation and adjustment.

worf928

... and that data is in agreement with what I've seen: that the WOT triggers at ~80%+ on a lot of new switches (all that I've tested) rather than 2/3s as described. In my experience this translates to the last 1/4" to 1/2" of go-pedal movement. Test for yourself from the ECU connectors once you have everything back together.

Rob Edwards

I'm officially a member of the rock-steady idle club! Put everything back together, bridged the FP relay to check for leaks, fired it up, and she idles right at an indicated 800 rpm cold. When cruising along, if I let off, the indicated mpg drops to 90 mpg. In fact, the rev drop off-throttle is a good bit faster than it used to be- I will have to adjust my clutch use. And while I'm sure it's psychological, this car has never felt stronger. Life is good!!

Just for posterity, here's the idiot's (me) visual guide to TPS testing:

Pins for testing idle:


Low ohms at idle:



High ohms just off idle:



Pins for testing WOT:



high ohms at idle:



and low ohms at 80% throttle opening: