hunting idle when cold - Page 9

Gouldy · 27-02-11, 11:05 AM

i know the switch clicks when the throttle is moved, however havent had a look at the readings,

Phil Payne · 27-02-11, 11:13 AM

Quote:

Originally Posted by fj1200

Forgot to mention, make sure the micro switch on the throttle valve is working properly. Unplug the connector, usually 3 pins and jumper the obvious pins leading to the idle switch, see if the idle simmers down.

Stone me! A newbie talking perfect sense!

Yes, you're right. We don't set by duty cycle this side of the pond because Audi (in their infinite wisdom - let them be praised) deleted the test connector from the engine bay.

Substituting for the gas analyser, we often use the Colortune. It's a spark plug replacement with a quartz window that lets you observe combustion. Roughly speaking, four 'blue' flashes to one 'yellow' equals about 1.25%. Our MoT limit on older cars is 3.5% - so it's pretty easy to set up a pass level.

BIGGYIN · 27-02-11, 11:19 AM

Takes a bit of pressure off you,to come up with the answers all the time.

More brains,for everyone else to pick.

fj1200 · 27-02-11, 01:23 PM

Setting for a pass level is one thing, setting CO so the car runs properly is another. At 3.5% the car will run pig rich and probably load the plugs at an idle. Does this car have an O2 sensor? Phil mentioned the test connector was deleted, if there is in fact an O2 sensor and frequency valve then no test connector is needed. Simply backpin at the frequency valve and read the duty cycle directly. Make sure to do this with the exhaust good and hot after a drive to make sure the O2 sensor is up to temp and swinging properly. Aldo if there is O2 control there should be a white 2 pin temp sensor on the bottom of the upper coolant neck. This will report to the jetronic control unit when to allow O2 control. Make sure this sensor is working properly. I can dig out the book of Bentley later this afternoon and verify pinout and functionality. I need to get the house picked up and go to our annual free whisky tasting

Cheers

Dan

Gouldy · 27-02-11, 02:07 PM

i am sure its the sensor on the bottom of the stat housing after testing the resistance

BIGGYIN · 27-02-11, 02:33 PM

I had a similar problem and I renewed the sensor.
Main problem gone,but I now have a bumpy idle.Think the engine must have been set up,with dud sensor??Checks,to be done.
http://www.classic-audi.co.uk/forum/...ad.php?t=16214

Phil Payne · 27-02-11, 07:16 PM

Quote:

Originally Posted by fj1200

Phil mentioned the test connector was deleted, if there is in fact an O2 sensor and frequency valve then no test connector is needed.

It depends exactly what you use to measure - the line from the ECU is resistive and documented at 10 Ohms, so it distorts the waveform. You have to go to the ECU (pin 8 on most implementations) which is what the test connector actually does for you.

Orin Eman (on the original US-based quattro list) developed a little PCB that showed the duty cycle digitally - I have one of his PCBs on my MAC12 breakout box.

fj1200 · 03-03-11, 11:41 PM

Hey man,

How we making out here, did you get a new sensor? Is it time drink beer and put our feet up yet?

Cheers,

Dan

Gouldy · 04-03-11, 01:47 PM

been too busy this week sadly, and i havent been with the car due to working away, will be ordering one up this week with any luck

27-02-11, 11:19 AM	#83
BIGGYIN 4 ring whore! Classic Audi Club Member Join Date: Mar 2009 Location: Merseyside Posts: 7,976	Takes a bit of pressure off you,to come up with the answers all the time. More brains,for everyone else to pick. __________________ q90 B2 Type 85 - q90 B2 Type 85-PROJECT-ABY 20vt KARL. Injection is nice but I'd rather be blown

27-02-11, 02:33 PM	#86
BIGGYIN 4 ring whore! Classic Audi Club Member Join Date: Mar 2009 Location: Merseyside Posts: 7,976	This,may help? I had a similar problem and I renewed the sensor. Main problem gone,but I now have a bumpy idle.Think the engine must have been set up,with dud sensor??Checks,to be done. http://www.classic-audi.co.uk/forum/...ad.php?t=16214 __________________ q90 B2 Type 85 - q90 B2 Type 85-PROJECT-ABY 20vt KARL. Injection is nice but I'd rather be blown

27-02-11, 11:05 AM	#81
Gouldy Senior Member Join Date: Feb 2010 Location: W.Somerset Posts: 1,083	i know the switch clicks when the throttle is moved, however havent had a look at the readings,

27-02-11, 01:23 PM	#84
fj1200 Grown up member Join Date: Feb 2011 Location: Shrewsbury, MA U.S.A Posts: 21	Setting for a pass level is one thing, setting CO so the car runs properly is another. At 3.5% the car will run pig rich and probably load the plugs at an idle. Does this car have an O2 sensor? Phil mentioned the test connector was deleted, if there is in fact an O2 sensor and frequency valve then no test connector is needed. Simply backpin at the frequency valve and read the duty cycle directly. Make sure to do this with the exhaust good and hot after a drive to make sure the O2 sensor is up to temp and swinging properly. Aldo if there is O2 control there should be a white 2 pin temp sensor on the bottom of the upper coolant neck. This will report to the jetronic control unit when to allow O2 control. Make sure this sensor is working properly. I can dig out the book of Bentley later this afternoon and verify pinout and functionality. I need to get the house picked up and go to our annual free whisky tasting Cheers Dan

27-02-11, 02:07 PM	#85
Gouldy Senior Member Join Date: Feb 2010 Location: W.Somerset Posts: 1,083	i am sure its the sensor on the bottom of the stat housing after testing the resistance

03-03-11, 11:41 PM	#88
fj1200 Grown up member Join Date: Feb 2011 Location: Shrewsbury, MA U.S.A Posts: 21	Hey man, How we making out here, did you get a new sensor? Is it time drink beer and put our feet up yet? Cheers, Dan

04-03-11, 01:47 PM	#89
Gouldy Senior Member Join Date: Feb 2010 Location: W.Somerset Posts: 1,083	been too busy this week sadly, and i havent been with the car due to working away, will be ordering one up this week with any luck