running rich at cold idle - 86 951
04-03-2007, 12:28 AM
#16
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It did run rich at startup, only because it wasn't getting enough air. I didn't even look at my AFR as the car started immediately after I'd replaced my valve.
With the original valve, I had to hold my foot on the throttle while starting as it was the only way to keep it going until it warmed up.
Upon startup, I believe the DME determines just how much enrichment is required based upon the little temp sensor closest to the front of the engine. This sensor provides a varying resistance based upon coolant (block temperature). The ICV also plays a part in this, it *should be* close to - if not full open - when the car is cold.
With the engine at 50 degrees fahrenheit, I measured around 3.5 kohm at the DME temp sensor terminals with my Fluke 87III multimeter. This resistance value is inversely proportional to the engine temp - the colder it is, the greater the resistance across the two terminals.
I had found a temp sensor at a local NAPA to compare. My original sensor was fine.
After some poking around and the car idling oddly, I gave that ICV a good whack with a screwdriver..sure enough, the idle speed changed.
I doubt cleaning it would have helped, look at the area where the motor brushes made contact.
Also, in my Bosch Engine management book, it mentioned this test:
When the car is cold, you should be able to clamp the ICV hose and kill the car. When the engine is warm, clamping the hose should make no difference.
In may case, the ICV was opening, but not enough. Take that FWIW.
The only issue was when the engine was cold. It ran perfectly otherwise, with the DME dithering around 14.7:1 at warm idle.
Regarding your turbo sound, you may want to check your diverter valve, aka blow off, cut off or recirculation valve! None of the ports should pass a vacuum to the other (put your mouth to it and suck!).
Sorry for the novel, but I hope it helps you.
With the original valve, I had to hold my foot on the throttle while starting as it was the only way to keep it going until it warmed up.
Upon startup, I believe the DME determines just how much enrichment is required based upon the little temp sensor closest to the front of the engine. This sensor provides a varying resistance based upon coolant (block temperature). The ICV also plays a part in this, it *should be* close to - if not full open - when the car is cold.
With the engine at 50 degrees fahrenheit, I measured around 3.5 kohm at the DME temp sensor terminals with my Fluke 87III multimeter. This resistance value is inversely proportional to the engine temp - the colder it is, the greater the resistance across the two terminals.
I had found a temp sensor at a local NAPA to compare. My original sensor was fine.
After some poking around and the car idling oddly, I gave that ICV a good whack with a screwdriver..sure enough, the idle speed changed.
I doubt cleaning it would have helped, look at the area where the motor brushes made contact.
Also, in my Bosch Engine management book, it mentioned this test:
When the car is cold, you should be able to clamp the ICV hose and kill the car. When the engine is warm, clamping the hose should make no difference.
In may case, the ICV was opening, but not enough. Take that FWIW.
The only issue was when the engine was cold. It ran perfectly otherwise, with the DME dithering around 14.7:1 at warm idle.
Regarding your turbo sound, you may want to check your diverter valve, aka blow off, cut off or recirculation valve! None of the ports should pass a vacuum to the other (put your mouth to it and suck!).
Sorry for the novel, but I hope it helps you.
04-03-2007, 05:55 PM
#17
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Interesting. In my case the car doesn't actually want to stall, although it drops low enough to give the car that near stall shake. As it shoots the RPMs back up the Turbo makes a small squeel, but I don't think it implies there is a problem with that part of the car - it drives fine and the turbo spools perfectly when the car is warm and ideling normally. I'll have my mech. check the ICV, and if that isn't the case I'll go from there. Thanks for your help, I'll let you know what the results are!
