Cold weather start but won't stay running...CTS ?

Post by **SonicAdventure** » 14 Nov 2019, 07:15

The past two days have been pretty cold here in PA, low 20’s. Coldest temps I’ve tried to operate the 850 I bought this summer.

Last night and this AM, it would start up and immediately stop. Last night it was in the 30’s but it eventually stayed running after a few tries and didn’t give any more problems.

This AM it would start right up but immediately stall after reaching 1,000 rpms. It’s 21 degrees right now.

The fact that there has been such a temperature drop and the immediate presence of this start but not stay running issue leads me to believe it’s probably CTS related as that is the only sensor that could cause a no spark condition strictly by temperate readings, right?

I have an older CTS (maybe two) from other cars which I’ve tested resistance on. However, I’m inclined to just buy a new one. What is the acceptable resistance for these anyway? I’m not getting a check engine light for CTS...would it throw one if this was for sure the issue?

It’s supposed to go up into the 40’s today, so I’m going to try again later.

Thanks

Post by **RickHaleParker** » 14 Nov 2019, 07:31

Engine Coolant Temperature sensor (ECT).

My '98 C70 did the same a few years back. It was a Altitude sensor that crapped out when it got cold. Any sensor the the ECM uses to make Air/Fuel calculations can do the same.

Try pulling DTC codes now when the problem is active.

Leaks in the Air induction that gets worst when it is cold can do the same.

Post by **Chuck W** » 14 Nov 2019, 07:51

Have you checked the CTS plug for corrosion? That could be causing a false reading also.

Had this issue with my '97 T5 last winter.

Post by **abscate** » 14 Nov 2019, 08:37

Pull the connector and check for corrosion per Chuck

Then search the forum using the part number (invented by the Mongols in 850 BC) to find the resistance chart

viewtopic.php?f=1&t=79330&p=427389&hili ... 86#p427389

I believe its 9186486 for the -1998 (for reference its 9125463 from 1999-end of P80 line)

Did you nab the one from the 1998 or do I have it? PM if you want it back

Its free

Part free
7.99 USPS small box
25 Shipping Handling
49.95 Shop supplies
7.37 Environmental Fee
$99 Core charge

Post by **erikv11** » 14 Nov 2019, 08:40

+1 on the ECT dirty connector idea. Had it on my 95 about 3 winters ago, it's a pretty common problem.

Post by **E Showell** » 14 Nov 2019, 08:45

Spray contact cleaner followed by a very small dab of dielectric grease could be your friend under those circumstances.

Post by **scot850** » 14 Nov 2019, 10:08

Is your car an NA or turbo? There may be another issue in relation to turbo cars and cold temperatures.

Turbo engines can have an issue with the intercooler freezing.

Neil.

Post by **SonicAdventure** » 19 Dec 2019, 03:50

So I got a new ECT sensor from FCP and installed it last week. Followed by a coolant flush and oil change. I put some wiring connector spray on a q-tip and cleaned the plug before putting the new ECT unit on. Also, I tested the new sensor with a multi-meter against the old one which seemed to be on the fritz (not displaying consistent readings in below freezing temps).

Car has been running fine, but it’s 16 degrees here this AM and it’s doing the same thing it was before - starts up and suddenly dies.

Not sure what to try next. I thought I had this sorted out, but it’s obviously something else. Any other clues? Also, I looked up front behind the passenger side headlight and I didn’t see a barometric sensor or the plug for one...

No CEL whatsoever for any of this, however, I know the CEL works because it indicated misfires this summer before I did my tune up.

Any thoughts?

Post by **abscate** » 19 Dec 2019, 05:15

Sonic, try unplugging the MAF and running the car on the default air fuel rpm map to see if that helps. That will help rule out a vacuum leak.

Are your ignition parts all new and good? Peek under the distributor cap for moisture, dirt, and other detritus.

Finally, a fuel relay can fail on a temperature change, so that’s worth investigating

Does it eventually start and run ok or are you stuck?

Post by **SonicAdventure** » 19 Dec 2019, 05:53

abscate wrote: ↑19 Dec 2019, 05:15 Sonic, try unplugging the MAF and running the car on the default air fuel rpm map to see if that helps. That will help rule out a vacuum leak.

Are your ignition parts all new and good? Peek under the distributor cap for moisture, dirt, and other detritus.

Finally, a fuel relay can fail on a temperature change, so that’s worth investigating

Does it eventually start and run ok or are you stuck?

Will try the MAF test. Full tune up this summer including cap rotor wires plugs and igniter so we’re good there. When you say fuel relay do you mean fuel pump relay? I have some extras sitting around I can test with. Technically not stuck (other than my driveway) but luckily I work from home...yes once the temp gets above 30 or so, it starts fine and runs with no issues.