Want to diagnose the Buick?? - Page 2

Originally Posted by Scrappah

It's a good thought but the tool is useless without the knowledge of how to use it. That's why you put your car in the shop and pay the money. You're paying for the mechanic's "know how".

They're training the automotive techs differently these days. They're taught NOT to try and diagnose because that only leads to confusion. Instead ... they're taught to follow a step by step troubleshooting procedure from a book that was written by the engineers that designed the vehicle. What you do is download the trouble code. Next, you look it up in the book. Next, you follow the prescribed troubleshooting procedure for that particular code.

The main problem is that the fuel injection systems are so complicated your average mechanic can't wrap his head around how it all works. If he tries the old skool approach he's like a blind squirrel searching for an acorn. He might get lucky and find the source problem but the odds are against him.

It would be better not to hollow out the cat. It's hard to accept but the cat is every bit as important as the crank, alternator,or water pump. It's an integrated part of the engine & transmission. It's not something they just bolted on as an afterthought to meet emissions standards.

If you sabotage the cat it will throw off the readings that the O2 sensor is picking up. If the ECU isn't getting a reading that is within range from the 02 sensor it will go into default mode. That will cause the air/fuel mix in the fuel injection system to run either too rich -or- too lean.

Too rich .... you get balls to the wall power but terrible gas mileage.

Too lean .... you end up in "limp home mode" and can barely climb a hill.

It's so much easier (and cheaper) to do things the right way.

Engine technology may have changed with all the addition of electronics and sensors, my father advice still holds true, No spark no fuel no run.

Of course there are a multitude of other problems that can cause an engine to run badly, not enough or to much fuel then to top it off the ECU unit originally desighned to control the engine is now tied into other components such as transmission, water, air intake and exhaust, sensors, door locks, GPS and probably even the AC.

The ECU being the central component also trouble shoots the system keep a record of codes, the code reader allows the mechanic or home enthusiast to retrieve these codes from the ECU you dont have to be a brain surgeon to decipher the codes returned to the reader, each auto manufacturer publishes the trouble codes. You can google for them

Originally Posted by Scrappah

I don't know about GM products but on some of the Fords you can just jumper two of the pins on the diagnostic connector with a paper clip. Your trouble codes will flash up on the check engine light. ( Paper clips don't cost much. )

The main problem is that it's too easy to end up chasing your tail with just a little bit of knowledge.

I've known people that have spent hundreds on blindly replacing sensors and electrically operated valves only to have the problem get worse.

You really need a good ohm meter and a vacuum gauge to test the different parts & pieces before replacing them. Sometimes it's in the wiring that runs from the sensor to the ECU. Sometimes the aftermarket parts are inferior to the OEM parts and they'll give you a bad reading.

Lotta ways to run into problems if you're trying to do the DIY thing.

ETA: As a guy that's just a shade tree mechanic i found this link to be super helpful. It breaks it down to the basics and explains fuel injection in a way that i could understand.

Fuel Injection Technical Library

No pain no gain,

I take little comfort leaving my vehicle at a dealership with a signed blank work order.

Ohh ... i hear ya !

If the vehicle is over ten years old they don't even want to bother with it. They'll write up a work order that costs more than the vehicle is even worth.

You're really out in no man's land when you're running older gear like i am. You have only yourself to depend upon.

A Chilton's or a Haynes can be helpful ... though not always complete.

Best source of info is a manufacturer's shop manual if you can get your hands on one.