Time for a new Temp Sensor I?
 

I posted earlier on a "hunting idle" but I think I have narrowed it down. After starting the engine cold, my idle speed is very low. When I unplug the intake air temperature sensor on the top of the intake plenum -- AKA Temp Sensor I (thanks to DD for the clarification) the idle is more normal. Does this sound like my Temp Sensor I has gone over to the dark side and needs replacement?

I am having the same symptoms and am interested in any ideas that the BBS might have.

I checked Temp Senson I and it was in spec as far as resistance goes. Currently, I have the sensor unplugged and a potentiometer inline with the CHT (set at about 500 ohms) and engine is running OK.

Would like to know what could be causing engine to be so lean at idle.

Thanks

Pritchard

[This message has been edited by Pritchard (edited 10-13-2000).]

Well guys, you may have this info already but I'll take the chance that you don't.

The temp sensor 1 (used to fine tune the mixture according to Kjell Nelin) can be tested as follows. Kjell says that "even if faulty, it has little effect on the running of the system".

Measured across the terminals:

(per RES systems test chart)
@14 degrees (F?) = 860-1200 ohms
@68 degrees F = 300 ohms
@68 degrees F = 260-340 ohms
@122 degrees F = 90-130 ohms

(per Kjell Nelins article)
@50 degrees F = 400-500 ohms
@100 degrees F = 150-200 ohms

BTW,

The idle hunting conditions I've had resulted from vacuum leaks or lean mixture conditions, maybe this TS1 is casuing one or both conditions, maybe not.

Have you had the CO checked at the exhaust pipe and checked alll possible vacuum leaks spots?

Thanks for your posts, Jeff. I went ahead and replaced the sensor anyway (piece of cake) but gained no noticeable improvement. So, it's back to the ol' drawing board. When the car reaches only 120 degrees or so, the idle returns to normal so the problem definitely seems temperature-related.

So its lean when its cold?

How cold?...it hasn't been cold enough locally lately to activate the cold start valve..it needs to be 40~50 degrees ambient air temp before that kicks in.

Have you checked the TS2 (CHT) sensor on the right cyl head?

I don't think any other sensors are temp sensitive. I'd look further for vacuum leaks if you haven;t checked everything yet. All vacuum hoses, throttle body gasket, injector seals, phenolic gaskets at head/runners, mainfold hoses, air plenum seams...use carb cleaner...

happy hunting...no pun intended 8^)

Does the Temp Sensor II (CHT) have any effect on fuel mixture when the motor is cold, or just when it's warm? I do know that when I unplug it, the engine dies immediately but I have not checked it for resistance.

Without checking the manuals before this response, the CHT sensor richens the mixture when the head is cold, and leans it out as it gets hotter. Its the more important of the 2 sensors.