Just some general info on testing my car.
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Just some general info on testing my car.
I tested a lot of things on my car recently using timing lights, compression tests, digital multimeters, oscilloscopes, microvats and handheld scanners. I'm just gonna post some results.
My car is a 1998 Honda Civic EX Coupe 5spd. The car has 111,600 miles. The engine is a stock D16y8. The engine has about 75,000 miles on it.
Basically everything I tested passed with a few things needing replaced.
I'll start off with the spark plug wires. OEM specs say no more than 25k Ohms. The longer the wire the more resistance as well. To test the resistance of the wires, just remove the wire completely. Set your Digital Multimeter to Ohms. Then just attach one lead to each end and note the reading.
Cylinder 1 = 11.8k Ohms
Cylinder 2 = 11.0k Ohms
Cylinder 3 = 8.9k Ohms
Cylinder 4 = 79.6k Ohms <-- really bad
High resistance in a spark plug wire will cause a number of things. It can cause misfires. It can cause your starter to draw more amperage than normal which can wear the starter out and drain your battery quicker.
Next thing is compression test. OEM specs say Standard is 184psi, minimum is 135psi and max variation between cylinders is 25psi.
To do the compression test, I unplugged all four injectors, unplugged the distributor and removed all four spark plugs. Screw the tube in 'just' until it makes contact and do NOT tighten it any more than that or you may regret it. Have someone inside the car hold down the clutch and throttle completely and crank the engine over five times. The needle on the guage should jump five times. Take the reading down immediately because it 'may' leak air. After you're done with that, press the button to relieve all the pressure, unscrew the tube and repeat for the rest of the cylinders.
These are my results...
Cylinder 1 = 190psi
Cylinder 2 = 187psi
Cylinder 3 = 186psi
Cylinder 4 = 190psi
Looks good to me. Low compression could mean that your piston rings are bad or your valve guide seals are bad or that your valves just dont seat properly.
On to timing. For my engine it says OEM specs is 12 degrees +/- 2 degrees. Connect the positive clamp to your positive post on your battery and then connect the negative clamp to the negative post. Clip the other wire around your spark plug wire from cylinder 1. Start the car. On the Left side of your engine bay shine the light down just to the side of the motor mount. There should be a tooth that kind of looks like |/\|. If you look on the belt there should be 3 lines that you'll see when the timing light flashes. Adjust the timing light degrees until the 3 lines match up with the tooth. The timing gun should tell you how many degrees you're at. If you're too low or too high you'll need to adjust your timing by loosening the three bolts for the distributor and either moving it forward or reverse.
My timing was at 14 degrees which is fine and within specs. (I thought that was pretty good because when I first set my timing I did it entirely by ear.)
I also tested my starter. It put out 149A which is just right below the max limit of 150A. I believe mine is that high because of my spark plug wire with high resistance. Other than that my starter was fine. For this test you would use the microvat. Pull the plugs for the injectors so the engine won't start. Connect the positive to the positive post, the negative to the negative post and clip the other wire to the wires coming off the negative post. It will instruct you what to do. It should just say to crank the engine over for 10 seconds or so.
My alternator tested just fine but the positive cable going between the alternator and the battery had too high of resistance. It should have had no more than 0.5 Ohms. My cable had 1.2 Ohms. I need to replace that cable. To test the output of the alternator, you use the microvat. Hook the positive to the postive post and the negative to the negative post. Connect the clip around the power cable of the alternator... then you start the car. the microvat will instruct you what to do... it basically just wants you to raise the rpms to about 2000 and hold it there for 15 seconds. It will tell you the low and high reading.
I tested all four of my injectors with an oscilloscope and all four shared the same pattern and looked good. To test this start the car. You use a backprobe to do this. A backprobe is just a pin really. You slide it in the back of the connector where the wire goes into. You do not disconnect the injectors. After the pin is in you put the positive clip lead on the pin and the negative lead to the negative post of the battery. You should pick up a reading. The oscilloscope I used had a reference graph for every test so you can get the general idea of what it's supposed to look like.
I did a voltage drop test on my battery. Touch one lead to the negative post and the positive lead just tap around on the top of the battery to see if there are any voltage drops. I had a 9.6V drop on one area of the battery. To clean the battery mix some water with some baking soda. A voltage drop on top of the battery may not hurt anything at the moment but over time it can drain the battery.
I hooked a handheld scantool up to my OBD connector and checked out all the various readings it gave me. Everything was within specification. It changed from open loop to closed loop fairly quick which is fine. Closed loop is based on coolant temperature, o2 sensor, and time. I know my car will heat up to operating temperature in about 1 minute flat (and it doesn't overheat.)
Throttle position was at 0.5V when closed and 4.7V fully open. In general it can be anywhere between 0V and 5V.
Basically everything on my car checked out fine with the exception of high resistance in a couple things and the voltage drop on my battery.
Hopefully this info can help some other people out with testing their cars or just to provide some decent info.
Modified by inane at 2:30 AM 8/7/2005
Modified by inane at 2:44 AM 8/7/2005
My car is a 1998 Honda Civic EX Coupe 5spd. The car has 111,600 miles. The engine is a stock D16y8. The engine has about 75,000 miles on it.
Basically everything I tested passed with a few things needing replaced.
I'll start off with the spark plug wires. OEM specs say no more than 25k Ohms. The longer the wire the more resistance as well. To test the resistance of the wires, just remove the wire completely. Set your Digital Multimeter to Ohms. Then just attach one lead to each end and note the reading.
Cylinder 1 = 11.8k Ohms
Cylinder 2 = 11.0k Ohms
Cylinder 3 = 8.9k Ohms
Cylinder 4 = 79.6k Ohms <-- really bad
High resistance in a spark plug wire will cause a number of things. It can cause misfires. It can cause your starter to draw more amperage than normal which can wear the starter out and drain your battery quicker.
Next thing is compression test. OEM specs say Standard is 184psi, minimum is 135psi and max variation between cylinders is 25psi.
To do the compression test, I unplugged all four injectors, unplugged the distributor and removed all four spark plugs. Screw the tube in 'just' until it makes contact and do NOT tighten it any more than that or you may regret it. Have someone inside the car hold down the clutch and throttle completely and crank the engine over five times. The needle on the guage should jump five times. Take the reading down immediately because it 'may' leak air. After you're done with that, press the button to relieve all the pressure, unscrew the tube and repeat for the rest of the cylinders.
These are my results...
Cylinder 1 = 190psi
Cylinder 2 = 187psi
Cylinder 3 = 186psi
Cylinder 4 = 190psi
Looks good to me. Low compression could mean that your piston rings are bad or your valve guide seals are bad or that your valves just dont seat properly.
On to timing. For my engine it says OEM specs is 12 degrees +/- 2 degrees. Connect the positive clamp to your positive post on your battery and then connect the negative clamp to the negative post. Clip the other wire around your spark plug wire from cylinder 1. Start the car. On the Left side of your engine bay shine the light down just to the side of the motor mount. There should be a tooth that kind of looks like |/\|. If you look on the belt there should be 3 lines that you'll see when the timing light flashes. Adjust the timing light degrees until the 3 lines match up with the tooth. The timing gun should tell you how many degrees you're at. If you're too low or too high you'll need to adjust your timing by loosening the three bolts for the distributor and either moving it forward or reverse.
My timing was at 14 degrees which is fine and within specs. (I thought that was pretty good because when I first set my timing I did it entirely by ear.)
I also tested my starter. It put out 149A which is just right below the max limit of 150A. I believe mine is that high because of my spark plug wire with high resistance. Other than that my starter was fine. For this test you would use the microvat. Pull the plugs for the injectors so the engine won't start. Connect the positive to the positive post, the negative to the negative post and clip the other wire to the wires coming off the negative post. It will instruct you what to do. It should just say to crank the engine over for 10 seconds or so.
My alternator tested just fine but the positive cable going between the alternator and the battery had too high of resistance. It should have had no more than 0.5 Ohms. My cable had 1.2 Ohms. I need to replace that cable. To test the output of the alternator, you use the microvat. Hook the positive to the postive post and the negative to the negative post. Connect the clip around the power cable of the alternator... then you start the car. the microvat will instruct you what to do... it basically just wants you to raise the rpms to about 2000 and hold it there for 15 seconds. It will tell you the low and high reading.
I tested all four of my injectors with an oscilloscope and all four shared the same pattern and looked good. To test this start the car. You use a backprobe to do this. A backprobe is just a pin really. You slide it in the back of the connector where the wire goes into. You do not disconnect the injectors. After the pin is in you put the positive clip lead on the pin and the negative lead to the negative post of the battery. You should pick up a reading. The oscilloscope I used had a reference graph for every test so you can get the general idea of what it's supposed to look like.
I did a voltage drop test on my battery. Touch one lead to the negative post and the positive lead just tap around on the top of the battery to see if there are any voltage drops. I had a 9.6V drop on one area of the battery. To clean the battery mix some water with some baking soda. A voltage drop on top of the battery may not hurt anything at the moment but over time it can drain the battery.
I hooked a handheld scantool up to my OBD connector and checked out all the various readings it gave me. Everything was within specification. It changed from open loop to closed loop fairly quick which is fine. Closed loop is based on coolant temperature, o2 sensor, and time. I know my car will heat up to operating temperature in about 1 minute flat (and it doesn't overheat.)
Throttle position was at 0.5V when closed and 4.7V fully open. In general it can be anywhere between 0V and 5V.
Basically everything on my car checked out fine with the exception of high resistance in a couple things and the voltage drop on my battery.
Hopefully this info can help some other people out with testing their cars or just to provide some decent info.
Modified by inane at 2:30 AM 8/7/2005
Modified by inane at 2:44 AM 8/7/2005
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