I had a local guy over at my house yesterday with a bad misfire on his 2000 2.5L TJ. He had spent way too much time trying to get the #1 spark plug out, the one behind the a/c compressor and I said to come on over. Between a 3/8" wobble joint and my impact wrench on its lowest power setting we finally got it out and the new spark plug in but it was still misfiring badly, actually worse at one point. I thought maybe his one or two of his Duralast ignition wires might have pulled apart inside and got my multimeter out.
They normally measure no less than 500 ohms per foot but I was getting an infinite/open connection with the meter on its X10 scale which would have put it at mid-scale with 500 ohms. Nothing. Nothing with any of the other range scales either, it showed open on the #2 and #1 plug wires I checked. And yes I have measured ignition wiring many times over many years... and never had one measure open/no ohms at all no matter what the scale. Yes it swung over to 0 ohms when touching the probes together. We zoomed up to O Reillys auto parts to buy a new set of ignition wires. I asked to use their meter to see if the new wires showed the expected 500 ohms or anything close. Nothing, their meter read open too!
I KNOW how to use a multimeter, have been using them since the 60's. I am mystified. It's running well now after he drove it home. About the only other thing I did was tighten the exhaust manifold bolts closest to the #1 plug since they were a little loose and might have been letting air in since the codes said both #1 misfire and #1 fuel mixture too lean. Maybe that was the fix, hard to say at this point.
So he said it's running well now after driving it home but my question is why did two different meters show an open between the two ends of two ignition wires. On the X1, X10, X1000 scales even though the X10 would have been the best scale with it supposed to being 500 ohms per foot and these two particular ignition wires were about a foot long. New battery in my multimeter too.
They normally measure no less than 500 ohms per foot but I was getting an infinite/open connection with the meter on its X10 scale which would have put it at mid-scale with 500 ohms. Nothing. Nothing with any of the other range scales either, it showed open on the #2 and #1 plug wires I checked. And yes I have measured ignition wiring many times over many years... and never had one measure open/no ohms at all no matter what the scale. Yes it swung over to 0 ohms when touching the probes together. We zoomed up to O Reillys auto parts to buy a new set of ignition wires. I asked to use their meter to see if the new wires showed the expected 500 ohms or anything close. Nothing, their meter read open too!
I KNOW how to use a multimeter, have been using them since the 60's. I am mystified. It's running well now after he drove it home. About the only other thing I did was tighten the exhaust manifold bolts closest to the #1 plug since they were a little loose and might have been letting air in since the codes said both #1 misfire and #1 fuel mixture too lean. Maybe that was the fix, hard to say at this point.
So he said it's running well now after driving it home but my question is why did two different meters show an open between the two ends of two ignition wires. On the X1, X10, X1000 scales even though the X10 would have been the best scale with it supposed to being 500 ohms per foot and these two particular ignition wires were about a foot long. New battery in my multimeter too.
