Heya, the forum is finally back! *whew*
Anyway, the past few days my car went from running like sh*t, to running like she was brand new, and here's why...
Have you ever had a hesitation problem with your M50, but it wasn't your DME, plugs, vaccum/air leaks, water, o2 sensor, etc etc etc? Do you have stumbling accelleration, like your car is bucking forward during lower rpms? Then you've probably got what I had, shoddy ignition coils!
Before I go any further, lemme say, if you haven't forked over the $70 or so for a Bentley Repair Manual, GO DO IT NOW! Stop reading! Goto amazon's website and order a copy because you're soooooo missing out!
That aside, my first crack at repairing my shoddy coil problem was, the home mechanic's method of, "let's buy a good coil, and swap it with coil #1, and see how she runs, still the same? Let's try #2 now..." etc etc etc. This is a pain in the arse, and actually doesn't solve anything if you've got the dreaded "multiple shoddy coil syndrome"
What do you do now? You've got more than one coil bad, and you can't visually tell which ones they are!
OMG, TIME TO GOTO THE DEALER RIGHT? .... NO!
WTF? BUY 6 NEW COILS AND SPEND $250?? .... NO!
So you pick up your bentley manual (because you bought one right? Hey, it's free shipping from amazon, what have you got to lose!?)
After much reading, and drooling
, over all it's wonderful information, you find yourself reading the section on testing coils.
So....what do you do?? Well, you grab your multimeter, (or ohm meter if you're a geek and have a seperate device for everything like myself), and proceed to remove all of your coils from the car.
Once removed, you can set your multimeter to the OHMS setting, and then take the red and black terminals and touch the two outer prongs on the clip part of each coil. You'll see the numbers fluctuate a little, but what you're looking for is a magic range of numbers.
If your coil is good, you will get a reading of 0.4 to 0.8 ohms
If your coil is bad, then you will get much higher numbers of 0.9 to even 1.4!
You might even have a totally screwed up one that will display numbers that rise and fall, but that probably means there is corrosion on the prongs so clean then with some steel wool or electrical contact cleaner. If it still does that, well, better safe than sorry, put it aside and mark it bad.
So....now that you've found your bad coils, and saved a bundle of time, effort, and money (debatable
), you can proceed to purchase new coils to replace the bad ones. I highly suggest getting coils made by the same manufacturer as it's probably not good to mix/match. I also highly suggest AVOIDING at all costs, any used coils made in 1992, or that came from a '92 e36. The '92 coils are very bad, and often malfunction, especially after 12 years (from what I've read anyway).
Thankfully for myself however, I buy coils from ebay whenever I see em, and I'm glad I did now because I have 18 spares with only 3 of them known bad (which I just removed from my car). Oh, and the best part is, your car will run like you've NEVER felt it run before (or at least not in a long time I bet), and you'll be kicking yourself for not doing this beforehand!
p.s. using the stock OEM $6 plugs from crappy tire also made a HUGE HUGE HUGE difference with my car. I will never use 'designer' plugs again, especially after reading so much on ignition lately, a lot of tuners out there will agree with that statement.
now get out there and start turning the 10mm socket wrench!