Auto repair brainstorming needed: car dying unexpectedly

Factual Questions
1

I am currently at wits’ end with my car (a 1997 Nissan Sentra with 56k miles on it)– I’ve now spent $1300 on it in the past 3 months, only $300 of which was expected routine maintenance. I’ve had the ignition assembly replaced, the muffler and exhaust pipe replaced (muffler was under warranty, at least, but pipe wasn’t covered), a tune-up, and most recently, this week I had a complete front brake job.

So last night, 2 days after bringing the car home from getting the brake job, I started the car to run some errands, and it just died in the middle of the street. I tried to start it again several times, and it wouldn’t start. I was about to call my mechanic again, hoping I could catch him before the shop closed up for the night, when it occurred to me to try starting the car without the AC or fan running at all. It worked, but barely – the car really didn’t sound happy about starting. That was when my boyfriend mentioned the same thing had happened to him several times, minus the AC issue, even since I had the ignition assembly replaced (which would have been nice to know before I took the car in to the mechanic the last time, but nevermind).

So we ran our errands, and I decided to run a test as we arrived home – I turned on the AC. As I somehow expected, the car immediately died. I managed to start it again, sans AC, but obviously I’d like to be able to use the AC without the car dying. Oh well - at least I wasa on a side street, not the expressway or something.

I’m no automotive genius, but to me the symptoms suggest some sort of electrical problem. Am I on the right track here? It shouldn’t be the battery, which is only a couple of years old, but what else could it be, and how much of a financial shock am I in for when I do take it in to my mechanic?

2

It sure sounds like you don’t have the required cranking power with the accessories all turned on. The battery may in fact be on its last legs, but that may also be due to a bad alternator. Most places can test the alternator fairly cheaply.

3

It’s not the battery.
It’s probably not electrical (it’s unlikely to be the act of turning on the AC that causes the problem, it’s more likely to be the load caused by the AC).
Does this happen only at idle, or will the car stall if you are driving it, and turn the AC on?

If the car is running rough, it could be:
Timing.
Fuel injection problems.
Computer or sensor problems.
Clogged air filter.
Bad ignition assembly or distributor (or Cam position sensor, if this car has one).

You need to get the codes read.

4

Hard to pinpoint, but I have a few questions:

  1. When you tried your test, was the car moving, or just sitting idling when you turned on the A/C ?
    If you were just idling when you turned on the A/C, then it sounds more like an engine power issue. The A/C adds additional load to the engine, and I’m thinking when it drags the engine’s RPMs down low enough, the car dies. This might point to something in the fuel system - maybe dirty fuel filter or bad fuel pump.

  2. If you only turn on the fan (without the A/C), does the car also die ?
    If so, then this is more likely something in the electrical. Using only the fan adds only another electrical device. Usually if your car is able to run, it is generating enough electrical power to keep going. So there could be a short or something.

Hope this helps.

Given that you can easily re-create the problem it shoudn’t be too tough for a mechanic to determine the problem.

5

It could be that your battery is not getting a full charge. Perhaps the alternator system is not charging the battery fully. Have it checked out.

6

It also stalled while I was driving it, as soon as I turned the AC on.

7

I tried it both ways (idling and moving), and it died both ways. A couple of times it never fully turned over at all.

I haven’t tried it with just the fan - maybe I’ll do that next.

8

Two possibilities:

  1. You have a bad (intermittent) battery cable 9might be corroded under the plastic insulation). When you check it with a meter, wiggle it
  2. partially plugged catalytic converter. garage can check this for you (with a bypass pipe).
    If #1, you are looking at $35-$50
    If #2, perhaps $300-$400
9

Bad idle air controller? Doesn’t it open when the AC is on in order to deal with the load?

10

Let’s start with some definition of terms, and clarification of the symptom.

In order to start, the engine first must be cranked by the starter. Normally it starts within a second of turning the key to “start,” but if the starter cranks and the engine doesn’t catch and run, you’ll hear a rhythmic “ruh-ruh-ruh” sound. This is the starter cranking the engine. Cranking is also called “turning over” - a term which is often misused and which should be avoided to eliminate confusion.

My understanding is that the starter cranks normally (~3-5 “ruhs” per second) in this case. If that’s so, you can pretty well eliminate any thought of battery, battery cable connections, and alternator.

While it appears irrelevant here, I’d like to know what is meant by “ignition assembly” (a term not used in the auto repair field). Distributor? Ignition switch? Something else?

Okay, so the car first died suddenly without the A/C controls having been manipulated just prior to dying, is that right? Then it would crank but not catch and run with the A/C left on, then would catch and run (poorly at first) with the A/C turned off? And now it will start reliably with the A/C off, but will die when the A/C is turned on, even if you’re rolling down the road?

Critical question - does it die, either sitting still or rolling down the road, if you have the accelerator pedal partly depressed (so as to rev up the engine)? If it dies even when revved up some, it’s not in the idle control system. An electrical problem related to the A/C and/or blower would be first on the suspect list.

If it won’t die when revved, but dies as soon as your foot is off the pedal, it’s an idle problem. A faulty idle up control valve would be first on the list, especially if it idles normally with the A/C off.

Another critical question - does it in any way run poorly with the A/C off? If so, there’s very likely a relationship between that and the dying. There are many possible causes of poor running, ranging from a ruptured vacuum hose to problems with the electronic engine controls (computer/sensors).

11

I think so, but frankly I don’t remember exactly which sounds it was making - I was hot, sweaty, and aggravatted. I may try again later tonight, with a clearer head. (I probably won’t take the car in until Monday at the earliest, or I’ll be stuck with no car all weekend and a lot of errands to run.)

I’m using my memory of the term the mechanic used when explaining why I now have 2 car keys: one for the door, and one for the ignition (his explanation is that I could have a locksmith re-key the ignition to match the door, but once the ignition is taken apart, it’s never quite the same). I may very well not have gotten the term quite right. Like I said, I’m no automotive genius.

Not really - at first it wouldn’t start at all. (I think the AC had been left on when the car was last turned off, so it was still on, albeit not at full blast, when I started it up again.) Then after a few tries, it started, but died within a few yards. That was when I had the idea to try starting it with the AC totally off, which worked.

[quote]
And now it will start reliably with the A/C off, but will die when the A/C is turned on, even if you’re rolling down the road?
[/quote

Yep.

[quote]
Critical question - does it die, either sitting still or rolling down the road, if you have the accelerator pedal partly depressed (so as to rev up the engine)?

[quote]

Yep. My test of the AC on the way home was with the car in motion (slowly, maybe 5 mph). As soon as I turned on the AC, the engine died.

I’ll have to test that a bit more.

12

Gary T: My understanding is that the starter cranks normally (~3-5 “ruhs” per second) in this case.
Eva Luna: I think so, but frankly I don’t remember exactly which sounds it was making…

We don’t have to precisely describe the sounds, I was just giving a guide. The point is that it presumably was cranking, as opposed to the type of no-start where you turn the key to the “start” position and nothing happens, or it just clicks, or it cranks very slowly (< 1 “ruh” per second).

Eva Luna: I’m using my memory of the term the mechanic used when explaining why I now have 2 car keys: one for the door, and one for the ignition…

Okay, that means it was the ignition lock cylinder that was replaced. No bearing on this problem.

Gary T: Critical question - does it die, either sitting still or rolling down the road, if you have the accelerator pedal partly depressed (so as to rev up the engine)?
Eva Luna: Yep. My test of the AC on the way home was with the car in motion (slowly, maybe 5 mph). As soon as I turned on the AC, the engine died.

Let me clarify, because often at 5 mph the accelerator is not depressed, one is merely coasting. Was the pedal indeed pressed down some?

13

At work I was once directed to help some guy with a Cadillac get a jump-start.

Turns out the reason his motor would not crank/turn over was because the AC compressor had internally seized.

Perhaps your compressor has too much internal friction? I believe you can still purchase a recharge canister of R134-A which includes the new refridgerant, flourescent leak dye, and compressor oil.

14

UPDATE: I was procrastinating on taking the car back to the mechanic, partly because I was in denial, and partly because I’ve spent too damn much money on repairs in the past 3 - 4 months and was wondering whether it made any sense to throw more than half the car’s book value into repairs.

So Sunday it died again - why is it always in the rain, with a full load of groceries? My boyfriend managed to start it by gunning the gas a bit, and we got it home. He took it in to the shop yesterday, and said once he told the mechanic that the idle was too low, the mechanic exclaimed “that explains everything!” and that he might need a part, but that it might just be a matter of a minor adjustment.

The mechanic told me he’d adjusted the idle (no charge). So I went to pick it up, having been promised that it was All Better Now, but I should give it a spin around the block to be sure.

So yeah, it died. Repeatedly. Even though the mechanics had run it “for hours.” The shop owner was annoyed, and took it home last night to monkey around with it himself (still at no charge). Have I mentioned I love my mechanic?

I just talked to him, and he said he spent a long time fooling around with it last night, that it will run forever as long as he keeps one foot on the accelerator, and so he is almost positive the problem is the idle air control valve, which is apparently some little valve on the engine that communicates with the computer to control the idle speed. It’s about a $180 part - I told him to go ahead and order the part.

Sigh…so it sounds like about a $200 repair, more or less. I sure as hell hope that’s the end of it for a loooooong while.

15

A cable with worn insulation caused my girlfriend’s car to short out the entire electrical system and just die while heavy traffic in the fast lane of the motorway, about ten minutes drive from Charles De Gaulle airport, from which I was due to fly back to the UK fairly shortly. Fortunately it was not raining, and we had very few groceries :smiley:

16

Well, I suppose it could have been worse - my real nightmare is havig it die on a back road in semi-rural Indiana, with my friend with cerebral palsy and his 6-year-old daughter in the car, at 2 a.m. (I actually have a trip coming up soon which will involve that scenario. Hopefully without the car dying.)

17

Hmm. Take multiple cellphones, leave itineraries/route maps with several people and agree checkpoint calls etc. so that if anything goes iffy resce will arrive soon?

18

That’s basically the plan - it’s about a 2-hour drive, and there are people at either end who would come pick us up if needed. But I picked up the car last night,and it sounds much happer now, and I have almost a month to test-drive before I have to worry about it.

19

Dump it.

The Nissan Sentra is a mediocre car. It was rated by Consumer Reports as only average up to about 2004, and since then has dropped to worse than average and much worse in 2006.

An eleven-year-old car, that was only average in reliability to begin with, and is now beginning to have several expensive problems? I wouldn’t pour any more money into this. It’s only worth $4000-5200 anyway; you’ve spent 1/3 of it’s value in just the last 3 months. Invest your money in a newer car instead.

20

I’m not interested in dumping it. Until 3 months ago, every single bit of work I’d had done on the car in 11 years was routine maintenance. Even now, except for the valve just now and replacing the ignition lock, most of it has been maintenance-type work; it’s just unfortunate that it all came up basically at the same time.

For example, let’s face it; after 11 years, any car is going to need brakes done. And if I can spend this $180 (my mechanic did the labor for free, partly because he was annoyed that his employee hadn’t diagnosed it correctly the first time) and avoid spending thousands more to buy a new or newer car, in this economic environment, that’s what I’m going to do. If the car had 110k miles on it, or if I needed it to commute to work, it might be a different story, but for now I’m going to stick with it. I really don’t want to take on a car payment unless I absolutely have to.