akingzkid

My car is a 2006 A6 3.2. I've been having random misfires on all cylinders for several months. They were driving me crazy and after doing LOTS of research on this site I have counted around 14 things that could contribute to misfires and saw lots of guys throwing money away replacing stuff to only report back that they still had misfires. Two months ago I removed my existing plugs (Bosch PFGR7KQE0) and checked them and they didn't look horrible. Well, obviously you can't go by the looks of them. This past week I replaced them with OEM NGK PFR7W-TG (5592) plugs ($62 Amazon). The plugs were last replaced by the PO at the 55K mark and now the car has 115K so they were due to be replaced. I had intended to get to it but was distracted by other "needs" (all diff fluids replaced, tires, tint, etc). I had finally had enough of the misfires so I figured I would start with the logical choice, the plugs....especially since they were overdue. Instantly got rid of the misfires!! So, if you are having misfires and are running plugs other than these, may I recommend that you give these a try. Something interesting below that a friend figured out.

- Comparing specs from the OEM (NGK) plugs and the existing (Bosch) plugs, he discovered that they had different resistor values (looking at the manufacturer sites).
- The NGK plugs have a resistor value of 1K ohm and the Bosch have a resistor value of 5K ohm.
- The Current/Watt drop across the difference of 4K ohm is pretty significant and alone is probably enough to cause misfires.

Using Ohm's Law:

Calculating Ohm's Law with OEM (NGK) plug values:
Volts (V) = 12
Resistance in Ohms (R) = 1000
Results:
Calculating Current in Amps with formula (I = V / R)
Amps (I) = 0.012
Calculating Power in Watts with formula (P = (V * V) / R)
Watts (P) = 0.144



Calculating Ohm's Law with existing (Bosch) plug values:
Volts (V) = 12
Resistance in Ohms (R) = 5000
Results:
Calculating Current in Amps with formula (I = V / R)
Amps (I) = 0.0024
Calculating Power in Watts with formula (P = (V * V) / R)
Watts (P) = 0.0288


Hope this info may be helpful to someone.

Sverige

akingzkid

Sverige,
I believe my friend just used the battery voltage a an example to be able to do the formula. It allowed him to show the difference between the two plugs (Bosch vs. NGK) and it showed a big difference between the two. Difference would still be the same if using whatever voltage is supplied by the coil packs. But I get your point. Thanks.

UCLABB

uberwgn

akingz, was that BOSCH plug recommended by Audi ?? An alternate to the NGK?

akingzkid

Glad I could help. Are you having misfires?

akingzkid

uberwgn,
No clue. I have had the car for 8 months. That's what was in there when I got it. Misfires started about 3 months ago. They are gone now with the NGK plugs.

UCLABB

akingzkid

Ok. Gotcha.

kelisko

I'm glad replacing the spark plugs fixed your problem.