CTS issues... which one does what?

[skeeters_keeper]

So there seem to be 3 coolant temp sensors, and they only one i can find in the haynes manual is the one on the intake manifold. I think this is the main sensor and controls the temp gauge as well as sends a signal to the ECM.

The second one is in the head, just on the head side of the tstat. I believe this is a simple on/off switch for the radiator fan.

The third is in the tstat housing, near the upper rad hose. it is a single "male" type spade connector, and the plastic surrounding mine is busted up a little. My question is: what does this one control?


Ever since my B6 swap my car has been running cold, and when its luke warm it cranks for a while before it fires (when its cold or real hot it fires on the first crank, and if i hold the gas in a little while its luke warm it fires better). I replaced the tstat (which was a dual-stage) with the dual-stage tstat that was in my B3 (ran at normal op temp) and now the B6 will heat up to 1/8" or so above the cold line, but it still has the weird starting problem. So i replaced the CTS that is in the intake manifold with the one that was on my B3, and no change. Thats why i'm wondering what the third temp sensor is for...

any ideas? thanks

[miami man]

i think it controls the gauge

[jglutz]

The two near/in the t'stat are the Instrument Gague and Cooling Fan...If you need to which is which...advise and I will look it up and repost.

The CTS in the intake manifold provides a signal to the ECA with the coolant temp of the block...There is one additional temp sensor you did not mention...it is located in the VAF...you can see it by removing the duct and looking into the VAF...its on the top of the housing below the electronics. This temp sensor signal is combined with the VAF paddle position to feed the ECA a mass flow signal.

At start up the ECA reads the CTS and initial VAF signal...since the VAF is not moved yet, the VAF signal represent the air temp. This is an example, there ar four various starting conditions...they are:
1) Cold Air (VAF) - Cold Block (CTS)
2) Cold Air (VAF) - Warm Block (CTS)
3) Warm Air (VAF) - Cold Block (CTS)
4) Warm Air (VAF) - Warm Block (CTS)

If the base VAF signal is off (temp sensor screwed up) the starting fuel mixture can get screwed up...First check all the grounds at the VAF...There are a couple of them.

HELP...does anyone have a FORD Powertrain Manual that has all the sensor data specifically the VAF? If so...do they publish any type of volt meter type test...output signal v. ambient temp.

[skeeters_keeper]

Correct me if i'm wrong, but if its the VAF temp sensor then it should give me hard start-ups all the time, since its the ambient air temp thats being measured, correct? whereas now if its running and i shut it off, then try to fire it up again it'll fire right up. If it sits for 1/2-2hrs or so is when it gives me the problems, which is why i figured it must be a coolant temp sensor problem. However if it gets up to like 60 or so out it will give me hard-startups all the time.

How does the temp sensor in the VAF work? is it a wire, or ?

Also, the only other noticeable problem (besides the hard startups) is the sukky mpgs, around 33 with mixed driving.

thanks so far!

[FB71]

Volume H / PCED does not publish VAF expected voltage against temp

[jglutz]

^^Thanks Jim.... ....I'm going to buy one (VAF) soon and test it at various temps before I install it....maybe I'll find something interesting.