Warbling idle after repair...no codes?!

[Brit-Car-Nut]

I can't see the switches clearly and I don't remember which is which without seeing the connector.

This is the CTS:

CTS.jpg

[Brit-Car-Nut]

I think I am with you now, in order to photograph those I will have to move the coolant header tank to one side or bleed it and remove it (it was one of the few parts I didn't document when I removed everything). From memory, the insides did not look corroded which may have been why I didn't photograph them but worth a check

While I am here, can i confirm which is the CTS from the diagram you linked earlier...in my photo I think it is (#1) but (#2) also has 2 wires although it is perpendicular to the Rad Fan thermal switch (#3) rather than beside

No need to get better access, the connections look OK once I enlarged and brightened the picture.

I think the CTS is #1, but it is late and my eyes are tired...

[GeoffSmith]

Check out WikiLEC for lots of useful information!

[Brit-Car-Nut]

Already provided in earlier post...

[GeoffSmith]

Indeed, but presumably the link was not followed otherwise he would have found the picture I posted.

[Simon_P]

You mention "after repair" but not what the repair was for.

[lotusflasherman]

OEM plug leads were in red. At least, otn his side of the Atlantic

From memory the OEM's were NipponDenso, as per the alternator

Correct ... and still red, not grey.

[ATCO99]

Thanks Guys, appreciate all your suggestions and guidance...bear with the Rookie as he learns his engine...this is new territory for me.

Brit-Car-Nut: I purchased 1 x GM 8153263860 from AutoZone and ordered another which comes with a new connector & replacement wires.

Before I switch out the one I have, I decided to test it with a multi-meter (Gardner Bender GDT-3190). Below you can see 1 pic of the lower housing (doesn't look corroded to me but experts might know better) and 2 pics of the connector (Again, doesnt look corroded but until the new ones arrive I have no comparison)

How I performed the test

Setting: 20k Ohms
OAT: 80F
Humidity: 58%
Method: Black test lead of multi-meter placed onto each terminal in turn, Red test lead touched to known earth on the engine block

Results:

Terminal 1
1st test: 4.27
2nd test: 4.27
3rd test: 4.27
4th test: 4.27

Terminal 2
1st test: -1.30 momentarily then reduced to zero (0)
2nd test: -1.92 " " " " zero (0)
3rd test: 3.05 " " " " zero (0)
4th test: 8.86 " " " " zero (0)

The wikiLEC shows the range of ohm values by temperature. I did not take the temp of the engine block but the OAT was 80F=27C which would put it somewhere between these values 20C/3400 & 38C/1800...which, if the graduation is linear would mean that 27C is approx 27C/2780 ... none of my test results seem to be close to this and terminal 2 was all over the place in values...does this mean its broken? or my test was bad?

[Brit-Car-Nut]

The resistance is measured BETWEEN the two terminals, not between the housing and a terminal. The housing would always be at 0 (zero) when installed in the thermostat housing.

[ATCO99]

Hi Simon_P

Repair was for the intermittent rough running of the engine described at the start of my thread, I took the car into Chicago (45 miles, longest journey yet, longest duration at speeds over 55mph) and about half way there the engine started occasionally losing power and the engine light would flicker on/off...returned to normal...then would run rough again a short while later...it also stalled at stop lights with the clutch in...on the way home from work it got steadily more frequent and more severe ...which got rather hairy when it stalled on top of this really tall steel bridge! (pic) ...the rest of the investigations and repairs are in this thread.

[ATCO99]

Brit-Car-Nut,

Removed the CTS again and measured resistance across the terminals this time. With multi-meter set to the 20k ohms range, the screen showed 4.27 consistently. Doing the math, 20,000 x 4.27 = 85,400
Comparing 85,400 to the scale in WikiLEC, my sensor is giving a resistance reading as if the temp is -35 celsius when in fact it is +26 celsius. Of the several side effects listed, 2 manifested.

1. Poor fuel economy = no
2. Black smoke from exhaust = no
3. Hot engine = initially yes but on later tests, no
4. CEL = yes, though intermittent not sustained

Temp(°C) / Resistance(ohms)

100 / 185
70 / 450
38 / 1800
20 / 3400
4 / 7500
-7 / 13500
-18 / 25000
-35 / 85,400 <--my reading
-40 / 100700

[GeoffSmith]

4.27 is 4.27kΩ (on the 20kΩ range) or 18°C.

[ATCO99]

Thanks Geof ... my learning curve continues. So that reading doesn't seem that far off normal now. Maybe the CTS is not the cause.