23 votes
Accepted

What possible causes for the "check engine" light can I check for myself?

You've come to the right place. There's a lot that you can do on your own. Even if all you end up doing is gathering more information for the mechanic who ends up working on the car, they never mind ...
user avatar
  • 24.3k
20 votes
Accepted

Can I confirm clutch slippage by shifting without disengaging the clutch (while stopped)?

It could possibly work, but the better question is why would you want to test it this way? You'd be "grinding the gears" for no reason (even though it's the synchros you'd actually be grinding). This ...
user avatar
16 votes

What exactly are fuel trims?

Motivation Fuel trims are a neat mechanism employed by auto manufacturers to reduce the sensitivity of fuel management to operational deviations. Modern-day fuel-injection systems rely on inputs ...
user avatar
  • 39k
16 votes

How can I detect vacuum leaks without access to a smoke machine?

There are several methods to detect vacuum leaks of unmetered air into the fuel delivery system One method is to use soapy water in a spray gun. The real issue here is how are you going to detect a ...
user avatar
  • 32.8k
15 votes

How can I tell if I have bad cats?

Cats can stop functioning in a couple of ways: physical deformation due to high temperatures According to this article, the catalyst melts at temperatures above 2100 °F (1200 °C). In the event of a ...
user avatar
  • 39k
14 votes

How can I detect vacuum leaks without access to a smoke machine?

One tool overlooked here is an ultrasonic leak detector. They work by listening to the noise of a leak. Obviously they would be better used in a totally quiet environment, but it's a possibility. ...
user avatar
  • 6,479
13 votes

How can I tell if I have bad cats?

Even before a cat plugs, you can test your cat using a laser thermometer. You are looking to compare the inlet and outlet temps on your cat. Do the following: Run the engine up to operating ...
user avatar
11 votes

What is the "propane test" and how is it carried out?

The propane test is used to find vacuum/air leaks in the intake of an ICE I used to use this test until I lost my eyebrows. You use propane to find vacuum leaks by applying the propane to suspected ...
user avatar
  • 32.8k
11 votes

Technique to test an alternator - fact or fiction?

To directly answer this question, no it won't work and you run the risk of damaging your alternator if it is good while doing so. The test you are asking about was used quite successfully with ...
user avatar
10 votes

How can I test my thermostat?

Failure Modes Mechanical thermostats fail in one of two ways: Stuck-closed The pintle/spring doesn't retract to permit flow at the set-point temperature that is usually stamped on the thermostat ...
user avatar
  • 39k
10 votes
Accepted

What can I do with an Inline Spark Tester?

First, think of the possible failure modes: Spark plug is clogged with carbon or has an isolation error - it conducts current, but doesn't generate sparks, because the current flows through the ...
user avatar
  • 6,997
10 votes
Accepted

Can I use a digital multimeter in resistance mode on a "no-load" circuit?

In "measure resistance" mode, the DMM (Digital Multi Meter) uses an op-amp (Operational Amplifier) to put a constant current across the probes. It then measures the voltage drop that results, and by ...
user avatar
  • 9,286
10 votes

How can I detect vacuum leaks without access to a smoke machine?

Some people have stated listening for a vacuum leak noise and if located within a vicinity disconnect and add a new line of the same diameter and get a cigar and blow smoke from the cigar in the line. ...
user avatar
9 votes
Accepted

Why are the spark plugs from the same 2 cylinders corroding faster than the others?

What you see could very well be burned coolant as well as oil. As the glycerin burns in the combustion process it can take on corrosive properties that degrade the electrodes. Typically with oil in ...
user avatar
  • 32.8k
9 votes

Can I confirm clutch slippage by shifting without disengaging the clutch (while stopped)?

I would not recommend it: Most likely something will experience excessive wear or damage. There are some other advices on various "tests" around, mostly they test if the engine stalls while pushing ...
user avatar
  • 7,828
8 votes
Accepted

What is the "dollar bill" test?

The dollar bill test is quite simply using a dollar bill (any denomination ... doesn't have to be American currency, even) and placing it against the exhaust tip while the vehicle is idling. You are ...
user avatar
8 votes

OBDII ELM 327 Bluetooth adapter - is it reliable?

The ELM327 is (almost?) as powerful as any other diagnostics solution. That's simply because it only translates the low level OBD protocols to some other format. Bluetooth connections on mobile phones ...
user avatar
  • 297
8 votes
Accepted

What is a smoke test and what kind of tools do I need to do it?

A smoke test is used to find leaks in any hollow body like the exhaust system, evaporative emission system or intake manifold. The smoke test works like finding a leak in a bucket. Fill the bucket ...
user avatar
  • 15.9k
8 votes
Accepted

Firing a Coil on Plug

You would follow these simple steps. Remove plug from engine Place plug into coil wire Make sure threads of the sparkplug are grounded to a metal surface. Validate metal surface goes to ground by ...
user avatar
  • 32.8k
8 votes

How can I detect vacuum leaks without access to a smoke machine?

One other way to look at this, sort of from a different direction. As I get older I really like being able to do more with less and do so safely. I think its sometimes awesome that an old guy with ...
user avatar
  • 6,479
8 votes

How can I detect vacuum leaks without access to a smoke machine?

@DucatiKiller gives a very good assessment of how to look for leaks. Using these same efforts, you can also use gas from a propane torch around the same areas described. When the gas finds a vacuum ...
user avatar
8 votes

How can I detect vacuum leaks without access to a smoke machine?

This is how I diagnosed a vacuum leak in my car. I removed the air filter from the intake pipe (mine was a turbocharged lancer evolution with an after market intake pipe) started the car. (Make sure ...
user avatar
  • 576
7 votes

What possible causes for the "check engine" light can I check for myself?

I think you may have mistaken a service interval indicator for a check engine light. Modern cars will ask to be serviced at regular intervals, even if no fault exists. There indicators can usually be ...
user avatar
7 votes

How can I detect vacuum leaks without access to a smoke machine?

Another way that has not yet been mentioned is artificially creating a vacuum or pressure in the intake. Vacuum is naturally there when the engine is working, but often the iconic hissing sound a leak ...
user avatar
7 votes
Accepted

How to check if spark plugs are firing? Coil-on plugs

You should have 2 coil packs on the back side of the engine near the throttle body. Wires run to individual cylinders. I don't know how easy it would be to find locally but you can use an inductance ...
user avatar
  • 10.7k
6 votes

Is this the correct procedure for a stator test?

Testing Your Stator There are three yellow wires that come from your stator. They come out of the left side crankshaft cover and route into your sprocket cover and out along the cast bottom portion ...
user avatar
  • 32.8k
6 votes

Are there any plans to update OBD-II?

Your question need answered with another question. What diagnostic capability do you want? While the generic side of OBD-II leaves something to be desired and has been stagnant since it's inception, ...
user avatar
  • 15.9k
6 votes

How to Test an Ignition Coil with a Multimeter

There are three tests that can be preformed using a multi meter. A DIS type coil that services two cylinders works like a transformer. The primary windings are controller by the ECU. The secondary ...
user avatar
  • 15.9k
6 votes

How can I detect vacuum leaks without access to a smoke machine?

If it's a vacuum leak, it will be sucking in air, and you'll probably be able to hear it. With the rest of the engine making noise, using something to pinpoint the sound would help: Take a piece of ...
user avatar
  • 678
6 votes

How can I detect vacuum leaks without access to a smoke machine?

There are usually two parts to this diagnosis: Establish that you have a vacuum leak If confirmed, find out the source of the malaise Confirming the presence of a leak My favorite trick to ...
user avatar
  • 39k

Only top scored, non community-wiki answers of a minimum length are eligible