92 metro ruff idle, gas smell

[russ2u]

My 92 geo metro idles badly, the gas milege has gone down, and theres a faint smell of gas after i drive for awhile. A local shop told me it's probadly a sensor, but this model cant be hooked up to the computer. What could be the problem?

[Johnny Mullet]

The very first hing I would do is perform a compression test on all cylinders. These cars have a known issue of having burnt exhaust valves causing low compression. If you do have low compression, it's not the end of the world. These engines are easily rebuilt without removing from the car and will continue to save you gas money and pay you back when you are done.

Let us know, we can help. Post those compression test results.

[Woodie83]

Originally Posted by russ2u

A local shop told me it's probadly a sensor, but this model cant be hooked up to the computer.

Well, can't be hooked to a computer, might as well throw it away. What happened to the concept of troubleshooting? Are there no real mechanics left any more? (except maybe one with a funny hairdo in Ohio somewhere, I've heard rumours of this guy around the Internets)

[Johnny Mullet]

Compression test................

In order to determine if a rough running engine has internal issues, then a compression test is highly recommended. This is a very simple test and you can usually rent or borrow a compression tester to get your readings. You could also purchase a tester fairly cheap if you shop around. Here is what a typical compression tester looks like..........



To do this test, you will need an assistant to help you. It is best to perform this test with the engine warm, but if it will not start, then you have no choice but to test it cold. First off, you need to remove the coil wire and then remove all the spark plugs. Be sure to mark your wires so you do not get confused. Find the appropriate adapter in your compression test kit to match the spark plug thread and insert it into the #1 cylinder. You just thread it right into the cylinder by hand until it's snug.

After you have the tester inserted, make sure your car is out of gear or in Park (Auto trans) and the parking brake is set. Have your assistant hold the gas pedal all the way to the floor (WOT - Wide Open Throttle) and begin cranking the engine over for a count of 5 to 7 seconds. Record your reading from the gauge and repeat this on all cylinders..............

Now add one teaspoon of engine oil into the cylinders and repeat the compression test one cylinder at a time. This will give you the "wet" readings and determine if you have worn rings.

The compression readings should be no less than 156 PSI on all cylinders and they should not vary much between the others. Here is an example of a low compression reading.........



A healthy reading would look like this............



A really healthy engine will have around 200 PSI of compression. Please note that these engines will run with lower compression numbers, but will not run correctly or get the expected fuel mileage.

[Colt1911]

A good place to start might be to check the MAP first, as it is quick and simple. It will also cause some of the symptoms described.