when modern cars don't run well, or at all

In My Humble Opinion
1

I have a 96 Saturn SW2 (that’s the ultra cool station wagon), it’s got the twin cam eingine, and mine is a 5-speed. I’ve had it for not quite two years and it’s been a fine car, until recently. I have started and posted in a few threads about it, both complimentary and otherwise.

For some time I’ve thought it was running oddly, there was a little stutter or stumble and the power kind of came and went, independent of the throttle position. Last year I got new plugs and a new fuel filter, and in the past few months a couple temperature sensors have been replaced. Currently, the temp gauge acts weirdly, registering a temperature not connected to the motor, and also independently of the temp sensor, as well as the weird power fluctuations.

Last night driving home, it stopped running, just turned itself off. It would crank, and would start if I floored the pedal but would not run. No matter the throttle, it would die immediately. It took a couple hours for AAA to tow me to the shop, and, once there, the car started and ran fine, well, fine as can be expected lately. The mechanic is a decent fellow, and is honest and hasn’t charged me for things that other shops might have, but the car still isn’t running “optimally”, IMO.

The current problem is something electrical or electronic, it has to be. And given that the car stalled shouldn’t there be some kind of code stored ina chip comewhere? Isn’t that what the OBD or OMB or whatever that damn electronic code stuff is calledall about? And I wonder if this shop has the right tools to examine such things? Can any modern repair shop not have such tools? Perhaps this guy isn’t tenacious or stubborn enough t sit with my car and try and get it to stall, or fail or whatever.

This is kind of a rant to vent my frustration, but also a question relating to modern car electronics and such. But I’m asking for opinions, so I chose IMHO.

<sigh> Thanks!

2

There’s a large list of possible causes for the symptoms you describe. Some of them, but by no means all of them, are normally monitored by the electronic control system (“computer”). Not every problem will set a code.

The poor running, temp gauge behavior, and dying are not necessarily related. You may well have three different problems.

Electrical and electronic devices often act up intermittently when they start to fail. This can be terribly frustrating to both the owner of the car and the mechanic trying to fix it. Many such things must be caught in the act to be definitively tested – when they work, they test normal. The next failure of a given item may occur in 5 minutes, 5 hours, 5 days, or 5 months, and there’s generally no way to predict it.

I will venture a guess on the dying/failing to restart. I interpret this: [it] would start if I floored the pedal but would not run. No matter the throttle, it would die immediately. to mean that the engine would run when the key was in the “start” position but immediately die when it was released to the “on” position. That suggests a faulty ignition switch.

3

The car stalled for the mechanic during a test drive. Teh coolant sensor was reading -40F, on a day when the high is 88F.It’s probably a computer problem, and this guy isn’t giving me a lot of hope that he can do what needs to be done, but I also believe he’s not trying to screw me or anything. But at least we have an inkling as to what the problem is!

4

This sounds exactly like the problems my 1995 Saturn SC2 was having. It turned out it was the EGR valve was broken and exhaust was getting backed up into the engine and the water pump had gone bad (it was trying to mug the fuse box…haha). The temp gauge would be reading fairly high (this was in January so the weather was not hot or even warm) Hope this helps narrow down your problem.

Don’t you hate that… it is so embarrasing, especially for a woman- they think you are just imaging problems or some other BS (My Cavalier did this to me forever- it turned out it was the transmission going out)

5

This one I can answer. The temp sensor is of the NTC (negative temp coefficent) type in other words as the temp gets colder the resistance gets higher. A scan tool reading of -40 is the same as an open circuit. So either the ECT (engine coolant temp) sensor has gone belly up (they do that sometimes) or there is a bad connection (corrosion), or a wire has broken the harness. The hard part is knowing which.
Start by taking an ohm reading on the sensor itself. Then work your way back to the computer checking ohm reading along the way. Inspcet the harness for chaffed spots along the way. Have fun.
Don’t forget power must be off, or the ohmmeter reading will be wrong.

6

Also, when the coolant temp sensor starts reading colder than it really is, or has an open circuit as Rick says, sometimes the ECU will interpret this as the engine being really cold and so it might dump fuel or run richer than suspected. Make sure your mechanic rechecks the condition of the plugs, as they might be fuel-fouled ( they will have a black sootiness to it).

You haven’t said the mileage you got it at, what it’s at now, and what else has been done…does this have plug wires, or is it direct ignition? You might want to check the plug wires for the stutter/stumbling problem. Also, I’ve seen engine based electronics crap out when hot and then start up when cooler…such as engine mounted ECUs (like in the early to mid 90s Oldsmobile Cutlass Supremes) and also control modules.

Your mechanic sounds like he has a scan tool due to the reading he got from the CTS. If he isn’t charging you, you’re lucky. You might want to give him (or her :smiley: ) a few days to hang onto the car to give them time to properly test drive and run the car long enough to give them a window of time for the car to fail. Intermittents aren’t easy to diagnose. S/he can’t fix what ain’t broken. Can you give them the car for a few days?

7

Also, a bad ground = high resistance

And this high resistance goes even higher when the engine is hot. So if the car ran fine when cool, because the resistances are acceptable…when the car gets hot it could make it high enough where it isn’t acceptable. Hope that made sense.

8

Rick, the mechanic is in agreement with you. He’s replacing a wiring connector, I hope to get it back today. Except, now LolaBaby tells me to let him keep it. Hmmmm. Lola, the mechanic told me I should replace the plug wires too, to fix that stutter/stumble problem. I like the outside verification. :wink:

And, although it’s past being important, I’ve owned the car for almost 2 years, bought it with @75K miles, now it has 85K.

9

How’s it going?

I was just wondering how the car has been since you’ve gotten it back. Also, I wanted to know the mileage, as it could indicate whether or not the first owner (or if YOU were the first owner) took care of it, by what sort of maintenance items may or may not have been replaced. Or rather, SHOULD have been replaced by a certain mileage. :slight_smile:

10

I reported the mileage in the post right above yours, LolaBaby! :wink:

It obviously ran better on the way home Friday. It’a amazing what one gets used to! Still need to get the plug wires changed, but I went on an overnight trip yesterday and just got back, haven’t had time. If it hadn’t crapped out on me we would have driven it on our trip instead our van, 'cause of the better mileage. But I didn’t want to get stuck again. I’m sure it’s fine, but the risk was enough to turn me off. I’m trying to do more of this stuff myself, but my lack of knowledge and experience/skill with tools makes it a daunting task.

I’ll be able to handle the plug wires , and it needs front brake pads, I think. I’ll try that too. We’ll see how it goes.

11

Yeah, I saw it, I was just explaining why, I asked, cause it seemed that you thought it didn’t matter. Mileage is a good indicator of certain things. Anyway, change the plug wires, and see…also, did he check the plugs? If they are fuel fouled (IF the faulty reading was causing the injectors to dump fuel), they CAN be cleaned.

12

Ah, yes, mileage is a good indicator of such things. I don’t know why I didn’t report the mileage along with all the other particulars. :smack: Thanks for your advice! Oh, and I didn’t mention the plugs, I was going to check those myself when I swapped out the wires. I’m feeling “lucky”. Or stupid, I can’t tell these things any more…

13

Good luck, then! Keep us (or me) updated. Since becoming a full-time mommy I live vicariously through others’ car repair attempts. :smiley:

14

Since you asked to be updated, I’ll ask a question…the idle zooms up to 2000RPM. It takes maybe 20 seconds for it to slowly get back to normal, just under 1000. I’m just wondering if this is connected to the other problem, is there another bad wire? Is this another symptom of an underlying problem that has yet to be identified? Or is just some kind of electronic adjustment needed?

<sigh> This car is not making me happy. It is supposed to be reliable, practical transportation, and with a 5-speed, let me pretend every now and then. :smiley: It’s starting to make me not like it. :frowning:

15

When does it do that? If it’s when you start up, and the engine is cold, I don’t see any problem as many vehicles have a “warm-up” period. If it’s during any other time it might possibly be a idle air control valve problem, but usually when IACs go bad they are stuck in one position or another.

16

The idle thing happens intermittently as well, and not frequently, maybe a couple times in the past month. Which helps not all, I know. Even after the car warms up though, the car will idle much higher than normal, and then slowly go back to normal. Work is about a 10 mile drive and it doesn’t act normally on that drive. We’ll see what happens on the way home today.