Good thread, I can’t remember all of mine at once. Might have more.
-First thing I do with a test light, put it on the battery to make sure it works. Otherwise you potentially waste a lot of time.
-To test weak spark caused by either weak plug or coil pack, I take the spark plug out and put it in the coil pack if I can (in bolt the coil back) and use a jumper cable to put a ground from the battery (-) to the body (wrench flat) of the spark plug. I position the spark plug such that I can see it from the drivers seat between the cowl and hood. Wait until night time and look at the spark. Depending on the car, I can test more than one at a time and can tell which one is weak. Swap plugs and you know if the plug or coil pack is the problem. Friend took a minivan to an independent shop, and then dealer, neither could find the running a little rough sometimes condition. Thats because the spark plug was still sparking but weak, so it never threw a code. Yes you can use a spark gap tester, but the method I mention can test more at one time (depending on the car) and I’m looking for the delta in spark quality anyway.
-Removing rear axle housing bearing on a GM, remove axles and spider gears, and get a long 1/2” rod that goes all the way from the opposite side to the bearing you want to remove. Take a pry bar to hold the end of the 1/2” rod on the back of the bearing and have friend hit the other end. Remove pry bar and reposition pry bar 180 degrees from the last hit, tell friend to hit it. This is the fastest way I’ve found to remove those axle tube bearings.
-For replacing distributor gears, put the distributor in the freezer and the gear in the oven before assembly. Makes assembly easier.
-For a floppy u-joint (the tool, not the car part) you want to stiffen, wrap it in tape.
-Basics, basics, basics-don’t forget mechanical troubleshooting on newer cars. Gas engine has to have compression, fuel, and spark at the right timing. Diesel has to have compression and fuel at the right timing. If you don’t have that, forget the computer stuff. Example: Friend’s wife’s car running so rough, won’t get out of its own way. Exhaust stinky. (This should already be telling you something.) He takes it to dealer, they run codes and they tell him the codes, he buys a mass air flow sensor. Still running rough. I run the codes, idle air control circuit, mass air flow, and oxygen sensor popped up. I told him, you can try the mass air flow sensor but be prepared to take it back. Too many codes, something else is going on. I will be out of town for work for a couple days, I’ll look at it more this weekend. He takes it back to the dealer, this time they tell him it’s throwing the codes because of the non-OEM parts he put on it. I trailer it to my shop, took out all 4 plugs. 2 are wet 2 are not. Compression test showed dry plug cylinders have normal compression, wet plug cylinders do not. Was going to pull the valve cover, but oil cap was in the middle. With oil cap removed, and engine running, with a flashlight, I could look in the valve cover and see one rocker arm moving and the other side of the cap rocker arm not moving. The cam shaft was broke in the middle! Well of course the mass air flow threw a code, not because the sensor is bad, because it is out of limit, only flowing half what it should. Of course the idle air circuit threw a code, and of course the oxygen sensor threw a code - unburned fuel, ratio was off. Of course that’s the rotten egg smell, because the catalytic converter was working extra due to the unburned fuel........ Basics, basics, basics.
