How do you diagnose a problem?

When you are faced with a problem on a car, what are the first few steps you take in diagnosing it? Just kinda doing a little survey of sorts. I typically try to duplicate the problem, verify the correct operation and isolate the effected system/circuit. Howzabout you?

Beer.

Get it so it fails consistently, then start isolating so you can identify just what's affected.

Of course, this is usually done over the phone and in that case I have to think of what the right question is. Usually it's "what did you do to the car right before this happened?"

I go straight into attempted duplication. If I can't duplicate it, I turn up the radio and ignore it.

DrBoost wrote: When you are faced with a problem on a car, what are the first few steps you take in diagnosing it? Just kinda doing a little survey of sorts. I typically try to duplicate the problem, verify the correct operation and isolate the effected system/circuit. Howzabout you?

What you said. Sometimes I use the mechanic dice when I am stumped.

Brian

I look for a VW logo then start praying it's not one of mine.

e28 = electrical - sensor, relay or component - maybe a connector - only question is where. bronco = ground issue (fiberglass body) everything else of mine is basic mechanical kind of stuff - fuel/spark/timing

If the problem is intermittant I try to note the conditions at the time of the problem. Air temp. humidity, engine speed, throttle position,oil press and temp, coolant temp etc. If possible I start to turn things off and see if the problem goes away. Then I will try different combinations of things on and off to get the most information that I can. This works better in an airplane where the instumentation is more complete and you can turn off and on more things than on a car but I use the same principle on a car.

Ignore it and hope it goes away.

John Brown wrote: I look for a VW logo then point them to a Japanese car dealership.

Fixeded it for you.

I start working it down (or up) the logic tree. Follow the clues and it will almost always take you to the problem.

So grab a tweed cap, smoke a pipe, and do your best Sherlock Holmes impressions.

Consult the internet. On 20 year old cars, you're pretty f-ing special if your problem hasn't been referenced online before.

paanta wrote: Consult the internet. On 20 year old cars, you're pretty f-ing special if your problem hasn't been referenced online before.

This most of the time.

I don't agree about the internet, actually. Not until you've narrowed down the problem somewhat. Otherwise you get a lot of noise from sources of highly variable quality.

For example, my M5 has a clunk in the back over certain types of bumps. Googling it leads me to believe that every bushing in the rear of the car has to be replaced. But more inspection on my part revealed an absolutely massive battery (which seems to be a little smaller than stock, this thing would suit a Cummins!) that is mostly-but-not-quite restrained. So I'm going to search to find out how the battery is supposed to be tied down, because I can't figure it out on my own.

Second example - we had a Miata come in on the hook yesterday. It had a freshly installed engine that had never run properly. It would fire up (sometimes) and die. The usual Googles on something like this would tell you the fuel lines were hooked up backwards or the wires in the AFM were damaged. I don't know how you'd ever use the internet to find out the owner had installed the cam gears incorrectly so they were both about 120 crank degrees off...

"Anyone have a hammer?"

In reply to Keith:

I guess i should have added "after looking at said problem to see if I can narrow it down". You are exactly right, but the web can give you a direction to look, a place to start if you are totally baffled.

DrBoost wrote: When you are faced with a problem on a car, what are the first few steps you take in diagnosing it?

1) Ask the owner for money. 2) ? 3) Profit

I just throw parts at it until it's fixed.

Or.... i ask on here.

I go by 3 or 4 things..

What does it feel like?( handling, power loss, etc) What does it sound like?( chirping, grinding, squealing) What does it look like? ( black, green, white, smoke, steam, fire) What does it smell like? ( burnt, eggs, etc)

Once any of those are determined, then you can usually narrow it down by when the problem occurs.