Chevy Tracker will not hot restart.

I have a 2000 Chevy Tracker 4x4 with a 1.6 Liter 4 cylinder. It has developed a problem, and there are no associated error codes from the computer. It runs perfectly, but if taken on a long highway run, especially when the weather in warm (Alaska), as in never in winter, if the engine is shut off it will not hot start until you wait about 20 minutes. Then it starts and runs fine. In warm weather it will occasionally stall when idling in traffic for too long, or going at slower speed up a steep hill after a highway run. I replaced spark plugs and wires (needed after 101,000 miles) and did other tune up chores. No difference. A GMC dealer was convinced that it was due to both catalytic converters being plugged—I was skeptical but had them replace them. No difference. I was able to catch the engine when it wouldn't start and pulled a plug and attached a spark tester and there was no spark. I replaced both coils (no distributor in this model) thinking it may be a coil pack failure. No change. The only other think I can think of is a malfunctioning control unit (computer). Anyone have any thoughts?
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thecardoc3 Member Posts: 5,842
The most likely suspects are going to be the crankshaft position sensor and the camshaft position sensor. Usually when the camshaft sensor fails the car will be a hard start long crank but it will start. When the crank sensor isn't sending a signal you wont get spark until it starts working again.
The crank sensor is an AC voltage, you could measure it when it works and get a reference for when the car is acting up. Make sure to use a cranking signal, even if you have to disable the engine to catch the value.
The camshaft position sensor is a hall effect and outputs a square wave a scope is the best choice to measure it's signal.5
Answers
ECT engine coolant temp sensor itself could be bad, or maybe just a wiring problem to the sensor.
The other was a unit the Tracker doesn't have and that was a small computer unit that received the signals from the CPS and generated the spark in the 3 coils sitting on top of it. Those also could fail and yet test okay at the parts stores. Called ISC, ignition spark control, IIRC. I don't see that in a Rockauto.com parts list for ignition.
So I'm hoping you can isolate it to your CPS.
There used to be some instructions on the net for isolating the ISC units by checking for the signals from the CPS when the engine was cranking to see if the CPS was sending electrical pulses. I believe there were two lines actually and if they were both carrying pulses, then the ISC was bad.
Cardoc3's symptoms of cps versus camshaft position sensor match what usually happened on the 3800s in H-bodies with which I'm reasonably familiar. The occurrence in hot weather because cold weather has more air cooling on lower engine, the higher temp of engine block with climbing hill or sitting and idling..., all make me think the CPS needs checking FIRST.
Removing the harmonic balancer to get to it is not a difficult task for a fast garage tech.
2014 Malibu 2LT, 2015 Cruze 2LT,
The CPS testing is not necessarily static testing. It's dynamic. This video talks about the testing
to see if the CPS is generating the AC currents that the module or computer needs to synthesize
the timing for a spark to a plug.
There are some empirical tests at the end using a soldering gun and it's magnetic field to see if
a magnetic field generates an AC current from the CPS.
https://www.youtube.com/watch?time_continue=5&v=Exz4f4RfBFY
Usually testing the CPS for proper output when engine cranking, even when generating no spark from the modules, was a way of seeing if it was working.
The CPS uses a magnetic field and the disturbance of that magnetic field as each tooth of the harmonic balancer moves past to generate the AC current signal. The aging and weakening of the magnetic field form heat causes that AC signal to fail. That was the usual weakening pattern. Cooling the engine makes the magnetic field more effective again to generate the signal from the Hall Effect.
2014 Malibu 2LT, 2015 Cruze 2LT,
I would love to know if you have done any other repairs or if you decided to junk the car. And your last post you suspected it was a computer problem did that pan out well?
Noticed I'm loosing coolant *head smack*