Coolant Temp Sensor: are these replacements the same?

[Lenny D.]

Absolutely.


And this is how to do it with a cheap DVM.

[Adam Gravois]

Thanks, Lenny. That is awesome information.

Today I had some time for the car so I clipped, trimmed, retwisted, resoldered and reclamped the CTS/ECU ground. Made me awful nervous as screwing this up=buying new wiring harness, but it seemed to come out ok. Still no improvement in cold start.

I also tested the old CTS at cold & hot temperatures and it returned the resistance values you would expect. So that was not the problem originally.

Next steps: replace shattered Bosch connectors at CTS & cold start valve, just in case weak connection there is causing problems. Remove and test new CTS to verify it is ranged correctly. Try to check voltage drops along that path properly. Hope that answer is in there somewhere.

[Adam Gravois]

Replaced bosch connectors on cold start valve, coolant temp sensor, and temp time switch, as they had all shattered due to my clumsiness. Gave the contacts a sandpapering. Thoroughly sandpapered CTS/ECU ground contact on intake: it was quite dirty/oxidized, and looked much happier for the polishing.

The first start, the engine caught after cranking for a little bit (but with no throttle input) and idled low and steady (maybe 300-350rpm). It only stalled when I tapped the throttle and it crashed back down to zero.

Second and subsequent starts, it would crank and crank but never get ignition, whether I was hitting the throttle or not.

Hmm. Where to look next? Back to the ol' firstfives Google search...

[anthony]

I had similar problem maybe ten years ago.

In the distributor there is a coil, the pulse generator. You don't need to replace the distributor just the coil. Just like any coil the wire can break or work intermittently. If you had a distributor available to swap real quick that would be great. I'm not sure how you could static test the coil.

I would hate to send you on a wild goose chase. Maybe someone can help.

Part 12111273287

[Adam Gravois]

In the distributor there is a coil, the pulse generator. ...I'm not sure how you could static test the coil.

Appreciate the suggestion. I'm not inclined to suspect the distributor as the car was running fine except for warmup, but heck if I know.

The distinguishing characteristic of my problem was weak cold performance (idle very low, hesitation and surging throttle response) BUT only at higher ambient temperatures. Last summer it showed up in the afternoons, then went away with the fall weather. When warm weather returned in the spring, so did the weak cold performance. Seemed like, based on what I've read here, quite likely a coolant temp sensor/aux air valve issue.

Thinking about it now, I wonder if this is what's happening:
A) the CTS/ECU ground contact is much cleaner than it was.
B) the CTS microvoltage signal to the ECU is experiencing LESS artificial resistance
C) causing the ECU to think the engine is much WARMER than it is
D) thus thinning the mix to the point where the engine won't start?

and if that's the case, then I need to recalibrate the air flow meter, per Lenny's post? Although I can't do that if I can't start the car... slowly, slowly the gears in my head turn...