Sunday, December 5, 2010

If it ain't broke....

Aimee has been complaining now for some weeks that the Camry is giving her starting problems. The first time she complained, I went out the next day and started the car and could find nothing wrong. This happened a couple more times.

Aimee said she thought the problem was occurring when the car was parked on the lawn instead of the driveway, intimating that damp grass and humidity in general might have something to do with it. This made sense. I've had any number of cars that had distributor cap problems that acted up like this, the problems going away once the engine was warm. I tried a couple of first stage diagnostic tests, such as spraying the engine with a mist of water and looking for the sparks that would mean there were ground leaks in the HT wires, to no avail.

Aimee is enough of a scientist to understand that diagnosis of intermittent problems requires time and patience and the good luck to have the problem occur when you have time, daylight, and other conditions are ripe. And the check engine light wasn't on, so there would be no computer diagnostic code to pull, even if I were to wire up my handy-dandy code-puller thingy.

Put simply, the car just wasn't helping at all with the diagnostic process. Poor starting and an intermittent idle can be caused by at least half a dozen common engine problems.

But the problem became less and less intermittent as the winter drew closer and my lovely wife more and more impatient with me. The problem became sufficiently consistent that almost each morning she would have trouble getting the car to idle until it was warmed up. It might even stall while being driven if the throttle was closed before the engine warmed up properly. I tried it myself a couple times and realized that the Camry could idle OK if the engine happened to catch before the throttle was touched. If you so much as tickled the throttle lever before the engine was fully warm, you would stall out.

So I set aside weekend time to diagnose it and read the Haynes manual, and the online user group list serves to determine what the problem was likely to be, narrowing it down by a process of study and elimination, without even looking at the car.

I also warned Aimee that we might find a problem that couldn't be fixed right away and so lose the use of the car for a time. Picking a weekend would give me more time, to be sure, but perhaps not enough.

We'll come back to this last point later.

This was of course all waaay too slow for Aimee's taste. She wanted her beloved Camry fixed, and fixed now! But the allotted Saturday came along and I ran the proper tests, in the right order, and everything fell into place like clockwork, albeit not on the proper wifely schedule.

The book suggested both the coolant temperature sensor or the idle air control valve could cause the symptoms we were seeing. But there were far more list serve posts on idle air control valve, and the symptoms more completely matched what we were seeing. At some point in the conversations with Aimee I had suggested the "cold start valve," an item of equipment that most fuel injected cars have. I'm still not sure if the Camry has one, but the idle air control valve has a similar kind of role, enriching the mixture for starting and also setting the starting idle speed a little higher than normal operating idle speed. So cold start valve was a good guess. The list serves confirmed it.

I can't sing the praises of these Internet Age innovations high enough. The user list serves, which can be found for almost every make and model of car, give backyard mechanics like me access to the kinds of specialized make-and-model specific knowledge that we used to have for older type cars. Take the old style British Leyland Mini, for example. When I was a kid, and an enthusiast for this great little car, there was all kinds of lore available to amateur Mini mechanics. Likewise when I came to the states and worked for the first time on popular American engines such as the old Ford "slant six" truck engine. Air-cooled Volkswagons were of course by far the best car for this kind of thing, the most accessible vehicles ever made from an amateur point of view.

But then computerized cars and trucks came along in the 1980s and 1990s and threatened to make the backyard mechanic obsolete. But these days, if you combine the online list serves with the availability of cheap code pullers, the position of the backyard mechanic is more or less restored, and possibly even better positioned than before. Of course, you have to be able to use a computer, so lots of older backyard mechanics were made obsolete, and you still hear that now-spurious compliant "I just can't understand these things any more."

But actually, "it ain't necessarily so."

The first test for a failed idle air control valve on the Camry is to short out two of the computer test plug connections to operate the valve out-of-sequence, and listen to see if the idle rises. I couldn't hear anything much in the engine note, so I asked Aimee to watch the tachometer, then, just to make sure, I asked her to short out the contacts while I watched the tacho. There was a tiny "blip" in the idle of less than 30 rpm, when a rise of a couple hundred rpm is normal.

So the valve failed the first test. Good going.

The second test is to check the resistance across the plug connection contacts of the idle air control valve. Like most solenoids, this resistance is supposed to be in the low tens of ohms. Try as I might, bent over and as low as I could, even using a flashlight, I couldn't actually see the contacts and operate the test leads at the same time.

The Haynes book is typically obtuse on this kind of thing. They just give the bare bones of each procedure and let the amateur mechanics figure it out, causing, I expect, no end of frustration and probably millions of dollars of damage and added repair bills to automobiles annually. I expect the dealers' technicians use an old connector for this, to bring the contacts that need to be tested out from within the confines of the engine compartment. But I already had enough data to go on with the first test, so I disconnected the throttle body from the engine and took it to my workbench to run the test.

This was, of course, the moment I had been trying to avoid, the point of no return. More of which later, but back to the plot.

The solenoid was showing the proper resistance of around 21 ohms.

But of course the book didn't tell you that this meant nothing much at all if the valve was stuck.

And by the time I had the whole thing on the bench I could see it was a fairly simple matter to dismantle it and see if it was or was not working. Which I did and found the valve stuck in the half-way position with a little of the kind of black sludge that builds up in fuel/air passageways. The photo above shows the idle air valve chamber dismantled, with the valve itself a tiny half-cylinder, just visible if you click on the photo to enlarge it, stuck half-way across the passageway. I was able to free the mechanics of the valve up, but, using a spare twelve volt battery I keep handy and charged up for such things, I couldn't get the solenoid to work. The coil must have burned up trying to operate the stuck valve.

So this was pretty good, I thought. Makes perfect sense, when you think about it. All aspects of data and theory lined up. Very scientific. I thought Aimee would be pleased. An almost certain diagnosis. Very little chance that any other item could be to blame.

I went shopping for the part.

Calling first the nearest Autozone ($150) then the dealer ($250), then looking on eBay for a salvaged unit ($35), I settled on having a new one shipped from an eBay vendor for $80, with free shipping, which turned out to be only a little more expensive than the secondhand one when shipping was taken into account.

Then I went to put everything back together so Aimee might use the car. And this is where my husbandly flag started to fall back down the mast a little.

I was pretty happy at this point. And why not? My guess was that I was at least $400 ahead over what a dealer might have charged us to fix this problem, never mind what might easily have been repeated trips to Brewer, Maine, where the dealership is located. I was definitely ahead on time and money.

And I doubt a non-dealer mechanic would have been able to diagnose such a tricky problem successfully at all. Using a private, non-dealership shop probably wasn't even an option.

This happy diagnosis was confirmed yet further when, having reassembled the whole thing again to the throttle body, and having refitted the throttle body to the engine, the car idled at 2,000 rpm.

If you think about it, this confirms the diagnosis yet further because now the idle air valve is still stuck, but stuck in the cold start position.

So I took it all apart again and set the valve to the opposite position. This time it wouldn't idle at all. Brilliant! Even more confirmation.

I was now 99% sure that I could get this car fixed completely for $80. Indeed the only thing that might reasonably go wrong would be that the new part could arrive broken or be the wrong part.

But then I made my mistake. I couldn't see the point of tinkering further to find a sweet spot in the valve setting where the car might just about run safely, when we have a spare vehicle, and the part would be here by Wednesday. I went and explained the whole thing to Aimee. I told her that she could have her choice of 1) driving the truck for a few days (I even offered to go gas up the truck) or 2) having me fiddle with the setting of the stuck cold start valve to try to find a point at which the car would idle, and continuing to drive the Camry. I explained that the Camry was now more likely to act up on her because my work to free the valve up meant that the symptoms would be even less consistent than previously. I recommended the truck, on the grounds that she would be pretty mad if stranded by the Camry.

All perfectly logical.

She agreed, but not before complaining that she wouldn't be able to drive her beloved Camry. And it was obvious that my certainty of diagnosis, which to me meant almost absolute certainty of success, as well as saved money, meant very little to her.

She was, shall we say, far less satisfied with the results of my labors than I expected her to be.

You can please some of the people some of the time.

I think this might be the difference between a scientist and an applied scientist.

Or between a wifely view of automotive misfortune and a husbandly one.

And it just goes to show you that the old American rural adage, "if it ain't broke, don't fix it," has very high value even in this era of computerized cars.

Did Aimee really want me to fix the Camry?

A very good question.

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