Coolant Temp Sensor - what EXACTLY does it do?

[boondocksaint]

Other than the obvious thing of controlling the needle on the gauge?

Anyone know for sure if the ECU adjusts fuel parameters based on coolant temp? The reason for the question is this - cold start is rough and I get the feeling the car is running rich. I do NOT think I have a leaky injector (although I'll revisit if nothing else turns up). No CELs have been thrown, but the car is old and it does have a lot of miles on it. I wondered if the ECU adjusts the fuel mixture based on coolant temp or something, and may be causing it to run rich on cold start. Since I'm not an engineer, I'm fairly sure the theory is bollocks, but nothing ventured...

Once it warms up, it's running fine but it idles a bit high (~1k RPM). I'm going to remove/clean up/replace the ICV in the next few days (I've gotten lazy, should have done it by now). The problems may be mutually exclusive.

Thoughts, theories, answers, and ridicule welcome.

[zubbie]

yes. the temp input to the DME will be used to adjust fuel / air metering, cold start injection and idle. If you think your's is toasted, unplug it and compare engine reaction. You can also remove it, put it into a pot of water on the stove, heat it and measure the resistance along the way with a meter.

[boondocksaint]

10-4. Will unplug before next cold start to see if it makes a difference.

Duh. Should've just done that. Brain inoperative. Someone do a stomp test on it.

[M Quick]

Remember that you got two coolant temp sensors, one is for the gauge cluster and the other is for the dme input to control air/fuel mixture according to temp etc.

[5mall5nail5]

If unplugged I think the open circuit is like... over 250 degrees F... it won't run well. Hopefully the ECU detects open circuit and just blankets a safe compensation.

[boondocksaint]

Remember that you got two coolant temp sensors, one is for the gauge cluster and the other is for the dme input to control air/fuel mixture according to temp etc.

Any idea which one is which offhand or do I need to find my glasses and scour the Bentley?

[LouieD]

Blue one is for DME, black one is for the gauge. Both are mounted onto the thermostat housing on the m30. And yes, when the blue temp sensor is out of whack, the DME goes full rich and will flood the car on cold start-up. Sometimes to the point of wet plugs and no start unless you hold the throttle partially open to compensate for the extra fuel.

[TheStigg]

the blue one nearest the head is the dme. should read 2100 ohms when cold, 70f, and btween 250 to 400 ohms at operating temp, 176f, which are typical values for all thermistors. you could insert the leads of a 270 ohm resistor (red violet black) into the socket to feed it a static resistance, 1/4 or 1/2 watt should be sufficient. the idle will stumble if the sensor falls below 120 ohms.

[boondocksaint]

Thanks for the knowledge. I'll be giving it a whirl in the morning. Also, the sensor is way cheap. I looked at the part itself and it appears to be quite long in the tooth. I may simply replace it on general principles.

Part Number: 13-62-1-709-966-M14

Right? That's the Bosch. ~$20

[PiRX]

Remember that you got two coolant temp sensors, one is for the gauge cluster and the other is for the dme input to control air/fuel mixture according to temp etc.

And you have got third one, if your car is equipped with EML

[whiskychaser]

Ok, its from a VX site but you might find it useful:

http://www.migweb.co.uk/forums/engin...t-sensors.html

[boondocksaint]

Thanks.

[5mall5nail5]

The coolant sensor likes to just chill there and be a bawce

[whiskychaser]

The coolant sensor likes to just chill there and be a bawce

You never stop learning. I dont know what a bawce is

[5mall5nail5]

You never stop learning. I dont know what a bawce is

When you want to go to the store to Get some new peanut chews you have to ask the bawce

[Inv3ctiv3]

I replaced mine this weekend and it did make a difference but I still think I may have a leaky injector cause it does still run rough but not nearly as rough! It takes 10 minutes to replace and is super cheap so you might as well replace it.

[AHenry014]

just replace it, dont worry about testing it. autozone, 10 bucks, lifetime warranty

[boondocksaint]

Did I get the right part number? F'in local parts stores don't carry ANYTHING in stock.

"I can order it."

So can I, Jethro, and for a ****load less than you sell it for.

[dantheman67]

Did I get the right part number? F'in local parts stores don't carry ANYTHING in stock.

"I can order it."

So can I, Jethro, and for a boatload less than you sell it for.

Haha.. Oh, and fixed that for ya xD

[moots]

When you want to go to the store to Get some new peanut chews you have to ask the bawce

a ha ha....bawce = boss......i like how it's spelt......

[attack eagle]

F'in local parts stores don't carry ANYTHING in stock.

"I can order it."

So can I, Jethro, and for a ****load less than you sell it for.

sig worthy

[boondocksaint]

Lol