Ok especially with selling the car I am determined to fix the intermittent starting problem. and I come armed with some information, I need a little bit of help on how to fix it though

Outside air temp today in PA is mid-high 20's maybe low 30's. My car has been sitting since 10:30 this morning, so even though I havent stuck a thermometer in my coolant (dont have one) it should be around 30-40 degrees, maybe even cooler.

ok, so I find this chart pictured below in my service manual, and go check the ohm, before i started it, it was 2.5k ohms, 2,500 which according to that chart would put my coolant at about 85 degrees, start it up a time or two (not running between start ups) trying to make it no start like it does sometimes and now I am getting 1.7k ohm which is like 110-120 degrees.

What could be making it read so high, its not the sensor, its the 2nd sensor.

Cut wire? Bad ground to the remote T-stat housing, any ideas.


...I'll upload the pic in a minutes, Im scanning it now.

 

here it is

 

I dont know if this isolates the problem, or throws a wrench into it, But I Found the above quote in a post by Vader and checked that stuff. Got 0 from ground wire to battery ground, and got 4.99 across the two while ignition was on, Doesnt that say that the

Im gonna go let the car run for a few minutes, shut it off start it, shut it off and see if the problem is back, and take the readings again.

 

I see both of these listed, these are actually for a '92, ya think some parts guy could be giving me the wrong sensor, for an '86 it only lists the WT-300 one.

Engine Coolant Temperature Sensor, At Intake Manifold, Interfaces w/ECM, Used For Cluster s w/Oil Gauge & Light Combination, Use w/{12101899} Connector Formula, Trans Am Listing
• Usually ships in 7 - 10 business days. AC DELCO 213-310 $9.96 $6.87 $0.00 Each


Coolant Temperature Sensor, Formula, Trans Am Listing
• Usually ships in 7 - 10 business days. BORG WARNER WT3000 $37.40 $20.93

 

Ran it for a few minutes, shut it off, restarted and shut off rite away and as I suspected, problem occured, ground and 5v were still good, resistance was now reading .82kh so its 820 ohms which puts it at around 120-140, is that good after running for like 5 minutes.


...ever get the feeling your just talking to yourself?

 

At some point, you're just going to have to break down and find someone with a laptop to really see what the ECM is doing. For all you know the problem might have nothing to do with the CTS. I had a bad IAC make me run in circles for 9 months. Was convinced i had an ignition problem, and i could consistently make my bad idle go away just by cleaning my distributor cap. That was just a red herring though, cleaning the cap had nothing to do with it, the car just pretended it did.

BTW, AFAIK, all GM temp sensors have exactly the same transfer curve. IAT and CTS both have the same R @ T values, even across generations. For example, thirdgen MAT is the exact same part as the CTS. A 4th gen plastic IAT is interchangeable.

 

You never said when the problem occurs..? Is it just sometimes when its cold? Sometimes when it's warm? Sometimes after you drove it 20 minutes ago? After you go to the store? I'd hate to hunt down a problem that was completely random.

 

It does it when its was running for some time, or driven around, parked, then run for a short time.

Like if Im out, go home, park it, go rite back out and start it up again like if I had to move it or something, ...only if its run for a real short period of time and turned off when its warm.

 

I'm really trying to help you here. You NEED to get a scan tool on it to diagnose something so flaky.

The problem may not even be the sensor, could be a section of wire thats partially broken and changes resistance when hot. Could even be completely unrelated to the CTS, could be the IAC getting goofy with heat soak or something, or getting stuck. Likewise with any other electric part on the car. Something flaky in the dizzy even.

Concentrating on the CTS is apparently not getting you anywhere IMO. Just checking resistance isn't going to rule it out conclusively though since there are several feet of wire also in the loop. Only a scan tool during a no-start will tell you what the ECM is thinking.

 

You don't happen to have an aftermarket chip or a reprogrammed one, do you?

 

yeah, I got one that John M. from LT1intake.com burnt to get rid of the EGR