I am still trying to figure out the rough idle in my 308 GTSi. Last night I did the dark garage test. What I saw amazed me. There seemed to be dim blue tracers running along the outside of the spark plug wires for the rear bank, which is the one running rough. Where the wires passed near a ground, the blue sparks would leap to the ground. I carefully pulled the wires apart, but I could not find the origin of the blue sparks. Where the plug wires touched, the sparks seemed to dance between them. The strange thing about all this is that in my experience, a leaking high tension wire usually emits a white spark at the site on the hole and you can see the white spark leap to a ground each time that plug fires. But this was nothing like that. When I moved a spark plug wire near a good ground, the blue light would just sort of flow over to it. The engine would not run any different. It was almost like a static charge running along the outside of the whole ignition system. Has anyone seen this effect before? I plan to take the distributor cap off and start there, but I am really baffeled how this electric charge is leaking out and around the wires.
The reason for this (your) observation is that the 308 uses an "inductive coil" wire construction for interference suppression. Surrounding the conductor (carries the voltage to the plug), is a separate, thin gauge, wire which is "spirally wound". This "coil", if you will, does not carry any current or voltage, directly. But, when the high voltage charge passes through the center conductor, an electric field is induced in the outer spiral wire ---- the purpose of this is to provide for noise suppression and signal isolation of the ignition circuitry. What you are observing is the sporadic leakage and dissipation of the static charge built up in the outer spiral wire (not the main conductor charge arcing / leaking). It is similar to a mild plasma discharge ----- so it will appear "bluish" and widely dispersed. This charge is able to escape through micro cracks and tiny porosities in the outer insulation, and indicates that your plug wires are wearing out. Even though the main spark plug charge has not been able to leak out yet, it will very soon. Replace them .
I had/have this effect (and it is beautiful) with BRAND NEW WIRES, caps and rotors all made within the past 3 or 4 years. What is next to check? What else could cause this?
The reality is that the escape of the static charge through the outer insulation does NOT actually pose a problem ---- the primary ignition signal is still getting to the plug electrode effectively. The construction of and materials used in the original Cavis brand wires are simply poor compared to modern standards ---- so, even "fresh" Cavis wires may still leak. However, the leaking will get progressively worse, and sooner or later, transmission of the primary signal will be compromised. I don't recommend using the original Cavis wires to anyone unless they are wanting to show their cars at concours events where original equipment is important. Instead, I suggest using aftermarket Taylor brand (some other, good quality options exist as well) plug wires. They make a higher quality, wire-wound suppression, plug wire that does not leak ---- and, it is much less expensive than the 30-year old technology Cavis garbage Alternatively, you can wrap your leaking wires with silicone tape or cover them with snug-fitting silicone tubing to provide additional insulation from the discharge --- of, course you will sacrifice the "original look" of the Cavis wires if you do so.
So, do you think this effect is related to the misfire I seem to be experiencing, or should I look elsewhere?
What you did was the standard old spark plug wire test among "hot rodders" years ago and it's still a good one. If you saw a light show you replaced the wires. To make it an even more critical test, folks would spray the wires with water beforehand!
Sorry if I'm going off topic but I just installed new wires and in testing (the old fashioned way - plug and extender out and ground plug on engine) I'm getting what to my eye is a very weak spark. I am running Iridium plugs with teeny tiny pin type electrodes but I would expect to see a very healthy spark as you would on an old style plug. Is this normal? Going out now to see what the inaccessable front bank is getting. steve
It very well could be related. Once the amount of leaking and discharge gets large enough, it will interfere with primary transmission. Trouble is that is not really possible to determine the criticality of the leakage by mere visual inspection. As I mentioned before, although it is "normal" for the OEM Cavis wires to discharge, that does NOT mean that it is desirable for plug wires to do so. I would replace them regardless. As an inexpensive, albeit a bit time consuming, test you could temporarily cover your wires with silicone tubing, and see if that corrects the "misfiring" problem. Although, silicone tubing is not real cheap either. Frankly, if it were my car, I would just go ahead and put on a new set of Taylor wires. As I said, the Cavis wires are crap right out of the box, IMHO
All the fine, wire-tip electrode type plugs (NGK, platinum, iridium, etc.) generate a very small spark width compared to the older, broad, flat-tip electrode type plugs ---- this spark does not look too impressive to the naked eye, but that does not necessarily mean that it is too weak. The true test of the quality and sufficiency of the spark is to measure its voltage. You can do this with an oscilloscope or an inductive clamp-on type voltage probe and a high quality multi-meter. Any of this equipment is not cheap, and often not feasible for the DIY'er...... But, any decent repair shop should have a scope or SUN diagnostic / test console which they can use to verify your sparking voltage.
BTW, even Ferrari eventually realized the Cavis wires were crappy..... This is why they added the "condom" rubber sheath covering on the plug wires for the 308QV and the 328. Of course, this was another typical "Ferrari-half-assed" fix --- the proper solution would have been to resource better quality wires. But, then again, Ferrari has always been loyal-to-a-fault to many of their suppliers --- Cavis hoses and wires have been used by Ferrari for a long, long time.
Thanks for all the replies. It actually does look just like St. Elmo's. I'll try changine the wires out with an older set I have lying around and see if that makes a difference. I know that one bank is misfiring because I can smell the gas in the exhaust and feel the miss when I put my hand in front of the tailpipe. The tailpipe for the front bank is steady as a clock, with no gasoline odor. It is a K-jet car, so both banks get the same fuel mixture. Likewise a vacuum leak would effect both sides. When I pull the plugs, they look okay, so I think the missed spark is moving around, thus the St. Elmo's fire. It seems to run clean at higher RPM, so maybe the leak is drawing off just enough juice that it misfires at lower voltages, but not when the alternator revs up. I have not ruled out the Diz cap, the multiplexs and wiringing, or the flywheel sensor. The juice could be leaking out the diz cap and jumping to the wires then running all over the loom until it finds a ground. I did swap out the coils to no avail, then I did the darkness check and saw the dancing colors and figured that must be the problem. I guess I will see what the new plug wires do and post the results.
Dave H sells wire sets. I also got a great set from Magnecor the guy there was very cool and let me pic ewhich plugs to match my oem ones. Daves wire has the proper OHM though. Rob
Great advice! Without a doubt...absolutley crap! If the wire "quality" doesn't bite you in the butt where first installed, the loose crimps will do you in shortly thereafter! And many owners (and shops) have been chasing misfires and other related ignition problems for a long time, as well!
Do any of you have a part number for say the taylor wires? or the other aftermarkets because I need to change my wires as well. I haven't bee able to find anything yet so a little help would be appreciated. I have a US 2 valve injected car.
If you desire a ready-made kit, contact SR (Dave Helms), otherwise Taylor does not make a "kit" (last time I checked) for the Ferrari 308 application. But, you can order bulk, 7mm OD, coil-wound, stock wire (with compliant to OEM specification, resistance & inductance / unit length) --- and cut the pieces to fit. There are many sources for Taylor in the aftermarket... or you can order from them directly. Just go to their website, call them up, tell them your application ---they will, help you.
oh I know they don't have a kit for the car just wondering what some have used but that helps ill see what I can dig up, Im sure I will still need to have the extenders and that sucks.
Take a look at Magnecor wires. They are high quality and reasonably priced for what you get. No more blue flashes at night, and a much smoother running car. I think a set for the 308 is around $149. I'll let them do their own explaining: www.magnecor.com
Yes, you do need to use the OEM extenders. In the past, I have purchased partial spools (about 16-18 feet is required, IIRC) of 7mm wire directly from Taylor. They also sell the crimp-on clips. Then, I just match lengths to the original wire set, install the clips, and go. Taylor will make a "custom" wire set for you to whatever configuration you request. If you give the folks at Taylor specific lengths, quantities, and clip styles, they will (for a an extra charge) cut the individual pieces and install the clips for you --- that way you do get sort of a "kit". You will, of course, have to put on the boots and pin them into the distributor caps yourself --- but, you have to do that anyway with whatever wire set you use.
Just a note: I didn't think it good for the later ignition modules to run them with the "spark plug out"??? Is that correct, or am I confused on that.....
It's certainly not recommended. It also ain't great to have a cylinder (the one which you've removed the spark plug) washing in unburnt fuel for an extended length of time, either It washes away the oil from the cylinder wall and causes excessive wear on the rings, pistons, and cylinder bore. The safest (and also the easiest) way to check for spark is to use an inductive (clamp-over-wire style) timing light. You can get a "no-frills" one at Wally-World for under $20 ---- it will pay for itself the first time you use it
OK, here is what I created. see attached images. I also wanted to do away with the extenders and as you can see on my images I have done so. I ordered these parts from Kingsborne and they have a huge selection of wire and accessories.(Less than $100) Wires are red 7mm spiral and I reused the red sleeves from the old set. I numbered all the pieces and hopefully everything should be self explantory. The extenders are eliminated and the black tubes take their place. After completion it looks completely original, plus with these new tubes, it is much easier to push the connectors into the plug and you don't have to play around trying to catch the treaded connector right on. Just remember to put the treaded cap back on top of the plug before you install the spark plugs. These treaded caps usually comes in the box with NGK plugs. Car runs very strong but I still haven't solved my 3000 rpm misfire, but at least I know it's not the plugs and wires and no more extenders. I belive Birdman was looking for something like this and here it is. Joe Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
So, I found this thread and wanted to know how it's all holding together. Any problems or is this still the way to go? FWIW most of those parts are no longer at Kingsborne and they instead have Ferrari specific parts. Thanks, Lester
