Do you mean vwvortex.com? and what subforum? This one? http://forums.vwvortex.com/forumdisplay.php?510-VAG-COM-Diagnostic-Forum I broke my DSO. Never tried a usb DSO as you propose. Is the one you listed on ebay good and the source reliable? Hong Kong vendors scare me.
Yup, there's a lot of good VW/Audi info there. I'm not gonna vouch for the vendor of the scope on ebay. It was just a suggestion. I have a Tektronix 475 with 10X probes, but that's kinda pricey for simple auto scoping. Interesting the V in the cylinders is 65 deg. That must have a strange harmonic balancer or balance shaft in it. The 60 deg V12 is the smooth setup.
Thanks to everyone for the great information. Doc's detailed explanation was quite helpful. Now it is back to the independent mechanic to review everything and begin working to resolve the CEL. Since I started this thread, twice on starting the car the CEL did not come on. The first time there were two restarts with no CEL then on the freeway it reappeared. In total I traveled 46 miles with no CEL. Does this have any siginifance? Thanks again for your help. Keith Stephens
Not that I can think of. I will date myself horribly and say that in the olden days, a high speed misfire would be diagnosed as coil saturation. However, before anyone climbs all over me and laughs uproariously, I realize that this is probably not the case. Even though modern HEI systems demand a lot from a coil at high RPM, unless the coil is breaking down, it shouldn't be an issue.
Hi, Keith: Apologies on reviving this old thread but I'm haing the exact same CEL issue on bank 1 on my 1997 456 GT that you have described here. Were you ever able to determine what the root cause of the misfires was?? I have replaced MAFs, Fuel pumps, fuel filters, both sets of intake gaskets (Upper and lower), air filters and spark plugs... so as you can imagine, I would definitely like to hear anything input you have because this is driving my bananas!! Thanks! -Adam
Hi Taz, Which course of action would you suggest is best to do a comprehensive check on the wires? Resistance with an Ohm meter or swap the wires from bank to bank and see if the misfires migrate? I think my fear of having to shell out the cash for a new set of new wires has pushed this step down the ‘diagnoses list’ haha!
Great, so I used a VOM to measure the resistance of each of the 12 plug wires. Here's what I got: Bank 1 (misfiring bank...currently getting P300 through P0306) Plug Wire 1: 5900 Ohms (longest wire) Plug Wire 2: 5860 Ohms Plug Wire 3: 6090 Ohms (shortest wire) Plug Wire 4: 6090 Ohms (shortest wire) Plug Wire 5: 6200 Ohms Plug Wire 6: 6140 Ohms (longest wire) Bank 2 (no misfires other than occasionally getting a P0312 - cylinder 12 misfire) Plug Wire 7: 5930 Ohms (longest wire) Plug Wire 8: 5930 Ohms Plug Wire 9: 5830 Ohms (shortest wire) Plug Wire 10: 5980 Ohms (shortest wire) Plug Wire 11: 5910 Ohms Plug Wire 12: 5830 Ohms (longest wire) I understand the resistance number is usually measured per foot of wire. My question is could the numbers above be an indication that the plug wires going/are bad?? Any idea what the range of Ohms per foot are 'in spec' for the 456/500? Thanks, -Adam
Adam- Those numbers look consistent, so that does not sound like it is likely your problem. I am not sure what the absolute numbers should be. Maybe one of the pros can chime in.
Odd, I cant tell a thing from that. Most wire failures on modern engines are not a failure indicated by readings on a VOM. Most are a failure of insulation causing crossfires or short to ground. Can't see that on a VOM. Its the entire reason coil on plug has become so important. Spark plug wires were causing auto manufacturers fits and they needed to be gotten rid of. Propensity for crossfiring was THE REASON for changing the firing order on the 456. The European addiction to bundling spark plug wires sure doesn't help matters either. Evidently they have no understanding of electricity. If your wires are original, throw them away. They are way past their use by date. Make sure it has a set of the correct NGK plugs in it too. At that time Ferrari was still using Champions and they were awful.
And that is why you need a pro. Cribbj has coil on plug conversions for the 550 that are cheaper than buying a new set of OEM wires. Might check and see if he has done a 456. NGK makes an iridium spark plug for the 456, DCPR9EIX. I have iridium plugs in mine (575M) and they really work well.
Thanks for the feedback, guys. I really appreciate it. Yes, it's funny...changing the Champion plugs to the NKG DCPR9EIX was one of the first things I did after purchasing the car and have stuck with them ever since. I can only assume the wires are original. This assumption was given some validity last night too as I did the "spray bottle" test: With engine running and all the lights off, I lightly sprayed the wires and saw lots of little sparkles not just on bank 1 (where I'm getting the misfire codes) but on bank 2 so I can only assume that bank 2 misfires are not too far in the future. This morning, I pulled off the plastic wire cover and saw a few of the wire's insulation had given way and could see the bare metal. I'll definitely be looking into the COP conversion for the 456 though my searches so far haven't produced any hits. The cheapest set on OEM HT Wires I've found so far are for $1,100 from a shop in Italy (takes PayPal which would help me sleep at night).
Adam, you have a slightly different ignition setup on your early 456 than the later "M" and our 550's so my existing COP setup won't work for you. I'd like to develop a system for the older 456's but would prefer to work with someone locally (Houston) for S/N 001
To Kieth, no expert by any means but did you have any major services before the car started acting up? Reason I ask is Ive seen a few times where something gets either incorrectly connected or damaged during disassembly reassembly. My friend just bought a 456M that had a constant intermittent CEL. Would get reset then come back 60-120 miles later. The previous owner spent 10's of thousands trying to get it resolved, replaced ecu's, O2 sensors, etc. Turned out the previous owner had the timing belt replaced and when they reinstalled the components hooked a connector up backwards, so the ECU was getting feedback from the wrong bank and trying to correct throwing things off even more. I had an idle issue in my Murcielago after a service.. turned out the mechanic used the ECU in my car to diagnose another car (I didn't know) so I spent thousands diagnosing, replacing parts on it only to find it was a bent pin on the ECU connector. If you've had a service try and trace back the work. It may not apply but thought I would share in case it does.
