2001 SL1 hesitation, stumbling (almost anti-knock-like)
 

How much of this old thread holds true for me? (See the link and a partial quote, below, but whose answers can be found following, here: )

1. I don’t think I have NGK plugs in it, although they are a year old.
2. My engine coolant temperature sensor has a brass tipped version from four years ago. I have been getting a low voltage confirmed code for the ECTS. Low voltage means broken? Registering always cold? I’m not sure on this. There’s also no corrosion on the connector.
3. EGR valve was cleaned three months ago. 200,000 miles on the odometer. My guess is it’s the same for the exhaust gas recirculation valve, too.
4. The throttle body was removed and cleaned very well two months ago. I do go through a LOT of oil. I have to top it off about every four or five fillups.

For the suddenly appearing hesitation, similar to what used to happen with anti-knock sensor before I switched to premium fuel, stumbling, (not so much lurching), and odd and seemingly unusual upshifts and downshifts that seem to be regularly but randomly happening at unneeded times, should I still go for another set of plugs and a new ECTS?

Here’s the old link:

https://www.saturnforum.com/forum/sa...ty-tach-11939/

And here’s DERF’s quote in question, answered above.

Having the correct plugs and a properly functioning correct ECTS for the s cars, along with the correct and functioning front O2 sensor, are the three most important aspects of these engines running smoothly. Yes, there are many other parts of the systems that must work correctly, but without proper ignition of the proper air fuel mix, you're not going to have a chance for the engine to run as designed.

Before I jump on that, there were several years of the third gym SOHCs that had an incorrectly installed intake manifold gasket. I believe it partially blocked the intake to the head on that cylinder, causing no end of problems. However, usually this would show itself as a cylinder one misfire, which you do not mention as a symptom. Just keep in mind that it doesn't take much of a leak at the intake manifold to really mess with these engines.

Okay, back to the regular stuff

Based on the amount of oil you are going through, one or more of your plugs may be getting oil fouled. Usually this will show is a random misfire in these engines. If there seems to be a knock issue, inspect each of the plugs very carefully for signs of detonation.

Ultimately, as part of troubleshooting, replace the plugs with the OEM plugs.
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​​​​​​ECTS is a temperature dependent resistive device that sits in the court flow in the head. The PCM measures the voltage drop across the ECTS and uses a lookup table to determine resistance of the ECTS and, from its calibration, the court temperature in the head.

If the resistance of the ECTS circuit is not representative of the actual coolant temperature (sensor Plus connector plus wiring), The PCM infers a bogus temperature from the reading.

Post ECTS s fail open circuit. This creates an infinite resistance situation. The PCM interprets this scenario as the vehicle being at -40 and remaining at -40........ This causes the air fuel mixture to be too rich and to stay too rich as the engine runs. This will cause everything from sluggishness to hesitation to no start conditions. You're confirmed low voltage code for the ECTS sounds like it is open circuit.

I recommend you You check the entire circuit for continuity. If the ECTS is open, you will see it . The other point of failure is the contacts on the squeeze connector. They have corrosion that builds up on them which increases the resistance of the circuit and tells the PCM the coolant is colder than actually is. Failure of the ECTS connector wiring where the wires meet the connector pins is also common. Sometimes you will not see this immediately with your meter until you wiggle them around

Damaged wiring between the ECTS and the PCM also occurs.

If you find the ECTS itself has failed, replace the ECTS and the pigtail with the connector. The original connector is 23 years old. And you've gotten your money's worth.

Do not purchase from a chain store. These are often generic ECTS's that behave differently with temperature than the ones in the Saturns. I don't know who makes them these days, but in the past AC Delco or Delphi did the trick.

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When was the last time you changed the front 02 sensor?
These tend to have a lifetime of about 100 to 125K miles. And with all the oil you are burning, these will get poisoned quicker than that. O2 sensor provides direct feedback to the PCM as to weather the engine is running too rich, too lean, etc. a poisoned sensor will usually read lower than the correct O2 levels, causing the PCM to richen the mixture.

Would suggest inspecting and replacing front O2 sensor with the denso equivalent of the OEM sensor. It is cheaper than the OEM sensor and happens to be the identical part.
Do not purchase a Bosch front O2 sensor for an s car.

PLEASE DO THESE REPLACEMENTS ONE AT A TIME AND CHECK VEHICLE PERFORMANCE IN BETWEEN THEM. If you do multiple changes at the same time and the issue is addressed, you will never know with the original problem was.

You are going to have to continue cleaning the EGR and throttle body regularly, but you already know that. Make sure you EGR gasket is not leaking.

As far as the shifts are concerned, this sounds more like an emerging transmission issue for which the s cars are well known with respect to the automatics.

I would change filter and fluid and see if the shifts improve. There are a few common points of failure on these transmissions. We can get to that after the other stuff unless it becomes impossible to drive the vehicle.

​​​​​​More detail than you ever never didn't not ask for

Intake manifold, plugs, no-start predicted
 

That intake manifold gasket was replaced 3 years ago.

I'm going to be buying a new set of plugs - the appropriate set of plugs - and replacing them today.

This morning, you predicted the "no-start condition." That has never happened to me in the 4 years I've used the car.

When you talk about "checking for continuity on the whole system," I hear the sound of crickets chirping. Where do the ends of the wires go that come out of the engine temperature engine coolant temperature sensor?

I think more importantly, how do I, where do I go to to, find the wiring diagram for this? Then how do I translate the wiring diagram on paper to the actual ends of the wire underneath the hood in practice? I've got a mental block on this at the moment.
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Late edit: I’m not changing the plugs until I do a replacement of the ECTS and its wiring connector first to address what I hope is the no-start condition, first. The plugs will come next—one thing at a time, after all.

On this very forum I was told about the CHARM project. Give it a look; it's real handy for diagrams.
charm.li/Saturn

The ECTS wires go directly to the PCM.
The wiring diagram will give you wire colors and the pin connector as well as the PIN numbers for each. There are multiple connectors that attached to the PCM.

I don't like to tell people to back probe the ECTS wires because when done incorrectly it leaves shall we say bare spots that may later cause problems. However you can back probe the ECTS wires and measure the resistance of the circuit to ensure you have a resistance that is approximately reasonable. I posted a resistance versus temperature chart for the ECTS about 15 years ago. It's here somewhere. It's also out on the web.

The okay resistance range for the ECTS circuit is about 2,700 ohms low temp to about 300 ohms high temp. Anything outside that range in either direction means something is not quite right.

Even small amounts of corrosion can add resistance to the circuit. Damaged wiring can increase resistance by having effectively less conductive material available for current to flow.

Once the engine is at operating temperature, we're talking about maybe a thousand ohms, so it doesn't take much to throw the circuit resistance off and with it the temperature that the PCM infers from the circuit. And it is definitely not a linear relationship.

Make sure you pull the ECTS wiring diagrams from the correct year and model. Many share the same, many share the same across generations. Some just don't.

I found this for the wiring diagram: https://portal-diagnostov.com/en/202...sl-2001-model/ I can see more clearly now, but now I have to go back and see if I can actually see where it enters the PCM. Black 48 452, and yellow 54 410. Never having looked at this before, I’m not sure what has to happen to replace the wire, but I’ll figure it out. It’s probably best to replace the whole thing, to NOT cut midway and solder because of the possibility of introducing some additional resistance through the solder joints.

By “probing” you mean “carefully pushing a pin through the wire’s insulation?

Since you said they fail OPEN, I’m thinking of simply disconnecting the connector and checking its resistance while it’s still in the engine block. An open would means it’s time for a new one.

What is meant by “court” when you’re taking about “court temperature in the head?” I’ve never heard the term “court” used in this manner in 60+ years! :-D (…wondering if it’s an autocorrect of ‘coolant’)

Do I have to get the newly run, replacement wires inside the same wiring harness, or can it parallel it and be wrapped by… something, I don’t know what, maybe some larger pieces of flex tubing to keep it close to the bundle, keep it from flapping, and keep it secure?

Pull the squeeze plug connector off the ECTS and measure the resistance across it. They MOSTLY fail OPEN but some do fail SHORTED. If your fan doesn't turn on when it should and the car overheats, provided everything else is working properly, the ECTS if failed has failed open circuit or close to it. If it doesn't fail completely you will read resistences higher than approximately 3,000 ohms. APPROXIMATELY. Pulling numbers out of my arse right now.

There is no reason not to solder and shrink wrap. A proper solder connection adds negligible resistance. A crappy solder connection creates problems. You can use b u t t connectors but in my experience they suck. Maybe I'm not crimping them properly, but they always seem to pull out and you must be sure that you use the correct size for the gauge of wire. It's all stranded copper wire which also sucks for trying to crimp. Trust me. Solder and shrink wrap.

There is no point in re running all of the wire back to the PCM unless the wiring is sufficiently damaged to warrant it. You will know after checking the circuit if the ECTS, the wiring, the connector, some of them, all of them, etc are part of the problem. Replace only what you need to..

Court was supposed to be coolant. Apologies. I voice dictate submit and then go back and fix the typos. Sometimes I get interrupted. It's a bad system but it works for me most of the time.

Like I said, there's no point to running new wires from the PCM connector to the ECTS. You are more likely to damage the PCM connector for the PCM trying to insert newly pinned wires if they are not the same gauge as what was in there before. And if you don't get them in straight, then they bend when you try to attach say a 48 pin harness. When those bend, the new pins, it can lead to other pins bending because the alignment of the whole thing gets effed up. If you've been working on cars that long, 60 years, please for the love of Saturn I know you know how to solder.

There's nothing wrong with being a perfectionist.

I still can't reel mine in on a lot of my posts. Part of me is trying to leave as much detail behind as possible for when I'm dead.

I replaced the ECTS with a brass tipped model without changing the connector, and it’s still not starting. I measured the resistance across the old, brass tipped ECTS and it was open.

Do the “black 48 452, and yellow 54 410” numbers correspond to fuse box locations to do the continuity testing of the wiring? Since I’m not going to be pulling the connector on the power control module PCM that’s the only place I can think of to go to to match up the number with something tangible. I haven’t looked, but I think I remember seeing numbers molded into the fuse box.

The next step is to solder in the new ECTS connector. It surprises me that it costs $30.

“For the love of Saturn…” I love that!

One other symptom I noticed before this “not starting” phase started is that the engine seemed to be running fast. I’ve read others posting the same thing in the past—now it’s my turn. I haven’t gone back to read those accounts over yet. I had sprayed engine cleaner near different vacuum hoses while idling but I never detected any RPM increases, so for the time being it doesn’t appear to be a vacuum hose leak. I’m not chasing down the high RPMs at the moment, I’m focusing on the non-running and ECTS-related stuff for now.

Interesting tip: opening the petcock on the radiator to slowly drain the fluid provided enough back pressure to keep the radiator fluid from coming out of the ECTS mounting hole. Leave the cap on the overflow reservoir. Maybe it was the crown of the street I was parked on. Maybe it was the small amount of fluid I’d already drained below the opening. I dunno. Anyway, I got no leakage and felt proud to be the master mechanic for about 90 seconds. (-: