Mike B

This car definitely tests my patience and diagnostic skills...which are limited at best.

Last weekend I went through the vacuum lines and located an uncapped port and a damaged rubber elbow. Fixed those and it ran like a top...satisfaction at last!

Sunday I button everything up in the engine bay (filter housing, air tubes) and go to start it. The demon returned! It idles fine for 20 secs and then up to 1K then almost stalls then back to 1K....after several minutes of this she stalls.

WTF!!!

Today I attack the problem again. I;m trying to look under the intake to make sure everything is plugged in...I can't see the ISV plug so I remove the Temp II connector so I can under the intake. Can't see squat!

I forgot to connect the Temp II sensor back and started the car. It idles perfectly for 5 mins until I see the Temp II connector not connected. I attach it and don't even get it seated when the surging starts again.

I remove the Temp sensor and put it in a glass of cold water...Ohm meter registers infinity...nothing! When it warms up to room temperature, still not in the block, it registers 1.9K ohms.

Would a new Temp II sensor fix this issue? Thanks for reading!

michaelathome

My problem is my throttle positioning switch (tested today at Frenzy 12 using the diag tool found here http://928-ecu-repair.com), when at idle the switch should trigger the ICSV to manage engine idle. The switch is the black square like box on the bottom of the plenum/intake. It has a small amount of rotation available when mounting and if not adjusted properly it will not trigger correctly and your car wont idle but just hunt randomly between 300rpm-1000rpm and stall. I need to get back in there, just finished an intake refresh, and didn't get mine adjusted correctly.

Michael

aggravation

Are you testing the Temp II sensor by reading each of the two terminals to ground and not between each terminal? That is the way it needs to be checked. When it's not in the engine I'm guessing your reading each terminal to the threads of the sensor. I think cold it should be 2k ohms and when warm, as in warm enough for the cooling fans to come on, it would be 200 - 300 ohms.
And just to be sure, infinity means no continuity not zero ohms.

Sorry if these are stupid questions to you but lots of people, when trying to measure resistance, get these things confused because so many instructions out there are unclear since the author assumes the reader knows the fundamentals of multi meter use.

Mike B

Thanks Mike and Craig.

Craig, not stupid at all. I tested the resistance from terminal 2 on the sensor to it's base with the sensor in my hand. That's where I recorded 1.9K ohms. I'm guessing the sensor, which looks new, is OK.

Perhaps the wiring to the sensor is the problem? The TPS clicks when I advance the throttle and then clicks again when I release.

soupcan

Temp II testing

http://www.electronikrepair.com/page9.html

Mike B

Thanks Brian...I did try that.

I apologize for bumping this up. I know some threads aren't the most fun to read. Short of a 928 BBQ I'm lost. My next plan is to replace the O2 sensor, possibly the TPS (although it "clicks" fine) and send both ECU's for a look.

I've read about everything posted...and I mean everything! If I've missed anything I would appreciate your input. Thanks !

soupcan

Is it repeatable with the Temp II sensor? Meaning every time you remove the connector runs good, reattach and then bad.

soupcan

Throttle Switch Check

Idle Switch Contact
With ignition Off, disconnect multiple pin plug from ECU.
Connect suitable ohmmeter across ECU connector terminals 3 and 5.
With throttle closed, resistance value should be 0 ohms.
With throttle opened, resistance value should be infinite. Switch over from throttle closed to throttle open should take place with a throttle gap of approximately 1°.

Full Load Contact
Connect ohmmeter across ECU connector terminals 5 and 12.
With throttle closed, resistance value should be infinite.
With throttle in full load position, resistance value should be 0 ohms. Switch over from throttle closed to full load position, should take place at approximately 3/4 total throttle travel.
If test results are not as specified, check resistance values directly at switch.

soupcan

Temperature Sensor Check

There are two temperature sensors which work independently of one another in the temperature
sensor housing.

With ignition Off, disconnect multiple pin plug from ECU.
With temperature sensor wire connector attached, connect suitable ohmmeter test leads across ECU connector terminals 2 and 5. Resistance should be as follows:
With engine temperature at 32°F, resistance should be 4400 - 6800 ohms.
With engine temperature at 75°F, resistance should be 1400 - 3600 ohms.
With engine temperature at 104°F, resistance should be 900 - 1300 ohms.
With engine temperature at 140°F, resistance should be 480 - 720 ohms.
With engine temperature at 176°F, resistance should be 250 - 390 ohms.

Shark_gts

The o2 sensor causes idle issues, surging, stalling etc. Almost mimics a MAF or Temp sensor because it switches to o2 control after about 5 minutes of warm-up from cold. I would check that wiring/ sensor first.

Mike B

Appreciate the feedback...Thanks for those directions Brian...I'll try them all.

Mike B

I think I figured it out...at least she is idling fine for today.

I started unplugging things one at a time. The temp II sensor threw me off as it sorta idled fine when I unplugged it but then would start the surging when I reconnected it. Plugged that back in and then tried the O2 sensor. That had no effect so I went to the MAF plug. I thought perhaps the wires wre shorting out. I unplugged that and the idle stabilized. Connected it up and it immediately started surging...bingo!

Replaced it with the MAF that came with the replacement engine and she idles perfect! Why didn't I check it earlier you ask. It was a rebuilt MAF that was on the car for about a year. I have the receipt dated April of 2006 and the car has hasn't really moved since April of 2007. It still looked like new.

Bottom line...just 'cause a part is new or rebuilt doesn't mean its good. What a relief...beer time