Temp II Sensor Again, Or Something Else?

[Silverghost500]

Thursday I took Von Westy to work, and she made it there and back again on the 60 mile round trip just fine. Ran great. Got home after driving in a thunderstorm and parked her in the basement, and she was still running great. Switched her off for the evening.

Yesterday I was packed and ready to go to Volksjam show at Tannehill. Go to start and she starts at first then the engine dies. Try cranking again. Engine will turn over but refuses to run. Unpack everything and open the engine bay. I don’t see anything out of the ordinary.

I go about checking spark plug connectors, distributor cap, coil connections, Idle stabilizer, etc. She still would not stay running. Fuel is between 1/4 and 1/2 tank. Check vacuum connections, and don’t see anything out of place.

Went through disconnecting electrical components like idle stabilizer, O2 sensor, etc. (not all at the same time…one by one). Got to the Temp II sensor and unplugged it. Engine fired right up and idled a bit high, like around 1,300 RPM where it’s usually around 900. Plug Temp II sensor electrical connector back in, engine will not start. Unplug, engine fires up. I let it run to get it up to temp. Turn the ignition key off, plug the Temp II connector back in with the engine hot and the engine fires right up.

With all that I’m thinking the Temp II sensor I replaced last year has already failed. This morning I tried a cold start of the engine with everything connected and she fired right up and idled where she usually does.

I’m wondering if water got into an electrical connection during the storm, or if the Temp II sensor really is going out. I’m going to order one just in case to have as a spare.
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1986 Volkswagen Vanagon Westfalia "Von Westy"
Honda K24A converversion-Road Testing Phase
3-Speed Automatic

Von Westy YouTube Channel
https://www.youtube.com/channel/UCbhyZYxJEQrUuLnMbLleeIA

[E1]

I do think you've nailed it as Temp II failure.

I carry two new ones as spares (in the parts truck ).
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‘84 Westy, 2.1L with Digijet, 5.43 R+P, GT Gears
"Adding power makes you faster on the straights.
Subtracting weight makes you faster everywhere."
— Colin Chapman

[oceanair]

Seems strange. Isn't the Temp II out of the loop and ignored by the ECU until a few minutes of running? Or is it used by the ECU to know when to stop ignoring it?
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84 Vanagon Pop Top Conversion from Tin Top, 1970 Ghia - all sweet rides! Love em!
Previous: Green 72 Tin Top, White 72 Westy, Blue 64 Beetle, Yellow 71 Squareback, 2014 Jetta TDI Wagon - wish I could have them all back!

[Ahwahnee]

I suspect the T2 got wet enough that it sorted across the leads.

As I recall, a short would be telling the ECU that the engine is hot (when it is cold) and disconnecting it would be like telling the ECU that the engine is cold.

As it has since started well when hot it may have simply dried out.

In any case, this is one of those parts (cheap, small and failure prone) that you should always have a good spare handy.

[E1]

[crazyvwvanman]

It is the O2 sensor that gets ignored at each startup. The ECU uses the Temp2 reading to decide how long to ignore the O2 reading.

Mark

[E1]

Vaulted.

Thanks, Mark! 👍🏼
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‘84 Westy, 2.1L with Digijet, 5.43 R+P, GT Gears
"Adding power makes you faster on the straights.
Subtracting weight makes you faster everywhere."
— Colin Chapman

[Wildthings]

Spray the TSII and its plug with some WD40 to dry it out. You could also use some Vasoline, dielectric grease, or other to try to keep the plug contacts dry. In addition, remove you distributor cap and dry it out well.

[Silverghost500]

I did put some dielectric grease in the plug this morning before starting her up. Turned the key, she fires right up to her usual cold start lumpy butt idle.
_________________
1986 Volkswagen Vanagon Westfalia "Von Westy"
Honda K24A converversion-Road Testing Phase
3-Speed Automatic

Von Westy YouTube Channel
https://www.youtube.com/channel/UCbhyZYxJEQrUuLnMbLleeIA

[bjrogers86auto]

I chased my tail on an issue this year that ended at Temp II sensor. After discussing it with my local van guy he said he'd bet it was the connection as opposed to the sensor. The plug on the new sensor was tight and loose on the old. I replaced the plug as well.

My point is, maybe change the plug to the sensor. That may be the issue.

Brian
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86 Vanagon GL Westfalia 2.1
18 Nissan Frontier Pro 4X
19 Honda Civic Hatchback

A little rudeness and disrespect can elevate a meaningless interaction to a battle of wills and add drama to an otherwise dull day. Calvin and Hobbes.

[AtlasShrugged]

I would suggest going to VW and getting an OEM new part. I have had disappointing results with aftermarket FI sensors.

Part number 025906041A about $27 from Jim Ellis here in Atlanta. The quality of these parts is very good.

[Silverghost500]

Thanks for the suggestion AtlasShrugged. I'll give them a call and see if they can get me a replacement.
_________________
1986 Volkswagen Vanagon Westfalia "Von Westy"
Honda K24A converversion-Road Testing Phase
3-Speed Automatic

Von Westy YouTube Channel
https://www.youtube.com/channel/UCbhyZYxJEQrUuLnMbLleeIA

[Steve M.]

What are your ohmmeter readings across the terminals of the ECU connector?
_________________
This free advice is worth exactly what you paid for it.

There are seven days in a week. Someday is not one of them.

[Silverghost500]

I didn't get a chance to test with the ohmmeter.
_________________
1986 Volkswagen Vanagon Westfalia "Von Westy"
Honda K24A converversion-Road Testing Phase
3-Speed Automatic

Von Westy YouTube Channel
https://www.youtube.com/channel/UCbhyZYxJEQrUuLnMbLleeIA