shimonmor Posted February 13, 2005 Share Posted February 13, 2005 Just bought some Napa "Belden Max" spark plug wires for my 99 OBW (2.5L) part number 700031. They look like the right ones but when I checked their resistance...they were all ~ 3.5k ohms. According to my book they should all be between ~4.9k-11.5k ohms (#4 being ~5.2k-12.3k ohms). I checked the Napa online site to see if maybe they gave me the wrong part number but it matches the 700031 Belden number. I checked my ohm readings with two meters (a Fluke and a Blue Point) and they come up the same. Is it ok to use these or should I get another brand? What brand? Thanks. Quote Link to comment Share on other sites More sharing options...
SlipSquad Posted February 13, 2005 Share Posted February 13, 2005 Just bought some Napa "Belden Max" spark plug wires for my 99 OBW (2.5L) part number 700031. They look like the right ones but when I checked their resistance...they were all ~ 3.5k ohms. According to my book they should all be between ~4.9k-11.5k ohms (#4 being ~5.2k-12.3k ohms). I checked the Napa online site to see if maybe they gave me the wrong part number but it matches the 700031 Belden number. I checked my ohm readings with two meters (a Fluke and a Blue Point) and they come up the same. Is it ok to use these or should I get another brand? What brand? Thanks. Try NGK wires.. I'm in the process of scoring some. Post up what you've found & where you found them. I figure NGK makes good plugs.. why not wires? Quote Link to comment Share on other sites More sharing options...
shimonmor Posted February 13, 2005 Author Share Posted February 13, 2005 Well, I decided to use the wires. I've got some nice weather and some time so I opted to be lazy and use what I have. I can't imagine that 1500 ohms can make that much difference (especially when it's lower than spec...of course that's just rationalizing on my part). Seems to run ok. No one in town carries the wires for this Sub so I had to special order these and I don't want to have to special order again. Too much of a hassle. Just put in new plugs too and didn't want to use the old wires since there was corrosion on #4 wire at the plug end (had a CEL #4 misfire). Anyway, if someone does see a reason why the resistance difference is critical...I would like to know. Quote Link to comment Share on other sites More sharing options...
frag Posted February 13, 2005 Share Posted February 13, 2005 Good question! I would like to know too, because if it does'nt matter what's the point of testing one's wires and finding them out of spec... Quote Link to comment Share on other sites More sharing options...
Nug Posted February 14, 2005 Share Posted February 14, 2005 3.5k ohms is better than 4.9-11.5k ohms, in my opinion. There are those that would argue that OEM is the only way to go. I say go with the NAPA wires. Quote Link to comment Share on other sites More sharing options...
SevenSisters Posted February 14, 2005 Share Posted February 14, 2005 Run 'em for another 100K, but next time get OE or NGK. I can't see how low is bad. Set your meter to a higher scale and see if you get a different reading. Quote Link to comment Share on other sites More sharing options...
Tiny Clark Posted February 14, 2005 Share Posted February 14, 2005 I believe the resistance is to keep EMI in check. The most that could happen is that you'll hear stratic on your AM radio... Quote Link to comment Share on other sites More sharing options...
frag Posted February 14, 2005 Share Posted February 14, 2005 3.5k ohms is better than 4.9-11.5k ohms, in my opinion. If the more easily the current pass the better, you're right and I would tend to agree with that. Then I ask myself, why do all manuals give a minimum value? What's the point in writing "4.9 - 11.5K" instead of "anything lower than 11.5K" ? Then I think there's likely a reason and but I dont Know what it is. Maybe Tiny Clark's explanation is the good one. Quote Link to comment Share on other sites More sharing options...
Nug Posted February 14, 2005 Share Posted February 14, 2005 My subaru doesn't even have a radio, so my answer may be biased. Quote Link to comment Share on other sites More sharing options...
frag Posted February 14, 2005 Share Posted February 14, 2005 Have a look at this. Very interesting. Specially the part about how EMI emitted by faulty ignition wires can send false info to the ECU thru the sensors that might explain some mysterious ailments like cylinder miss and hesitations. The fact that it's witten by and for Magnecor can cast a shadow on the article objectivity, but everything here seems to make sense. http://www.magnecor.com/magnecor1/truth.htm One quotation: «Although most new ignition wires will perform the function of conducting coil output to the spark plug, what is important to sophisticated race engine preparers and owners of production vehicles with exhaust emission controls is EMI suppression. All electronic devices can be effected by EMI emitted from ignition wires, and the problem is often exacerbated by installing a high-output ignition system. As production vehicles age, engine management sensors and wiring deteriorate and become more susceptible to EMI radiating from improperly suppressed ignition wires. To be truly effective, ignition wires need to be EMI suppressed for a reasonable time, while having the ability to maintain good conductance without overloading other ignition system components. Engine tuners should also take into account that most stock engines and some hi-tech aftermarket engine management systems use resistance in ignition wires to sense additional information needed by the computer. Quote Link to comment Share on other sites More sharing options...
idosubaru Posted February 14, 2005 Share Posted February 14, 2005 if your stock wires fall outside that range, something is electrically compromised in that wire, that's why they provide those numbers. those numbers are not applicable to other type/manufacture of wire and are not meant to apply to all wires ever made. the FSM doesn't say "the motor needs wires in this resistance range", it just tells you the spec's of the stock wires so you can determine if something is wrong with them. the engine does not care what resistance the wires are, so long as the air-fuel mixture is combusting properly. the resistance of the wires is transparent to the motor, only thing it may affect is the life span of the plugs due to different loads being applied to them. and i say this liberally, as i can't imagine it would actually be a quantitative difference that's even measurable without a scanning electron microscope. go with the NAPA, i use www.magnecor.com . they have extensive information (as unbiased as you'll find from a manufacturer) about wires there. Quote Link to comment Share on other sites More sharing options...
frag Posted February 14, 2005 Share Posted February 14, 2005 if your stock wires fall outside that range, something is electrically compromised in that wire, that's why they provide those numbers. those numbers are not applicable to other type/manufacture of wire and are not meant to apply to all wires ever made. the FSM doesn't say "the motor needs wires in this resistance range", it just tells you the spec's of the stock wires so you can determine if something is wrong with them. the engine does not care what resistance the wires are, so long as the air-fuel mixture is combusting properly. the resistance of the wires is transparent to the motor, only thing it may affect is the life span of the plugs due to different loads being applied to them. and i say this liberally, as i can't imagine it would actually be a quantitative difference that's even measurable without a scanning electron microscope. go with the NAPA, i use www.magnecor.com . they have extensive information (as unbiased as you'll find from a manufacturer) about wires there. Magnecor seems to imply to the contrary : «Engine tuners should also take into account that most stock engines and some hi-tech aftermarket engine management systems use resistance in ignition wires to sense additional information needed by the computer.» But I'm not sure what they mean by that exactly. Quote Link to comment Share on other sites More sharing options...
idosubaru Posted February 14, 2005 Share Posted February 14, 2005 i'm not sure what they're referring too either, but i'm skeptical that it's applicable for this thread in anyway. there are no "resistance sensors" that i'm aware of on subaru's. Quote Link to comment Share on other sites More sharing options...
NorthWet Posted February 14, 2005 Share Posted February 14, 2005 What the resistance in the high-voltage circuit does is affect the peak voltage, how quickly the voltage is reached, and how long a sparking voltage is achieved. The wire resistance, in series with the coil inductance forms an RL circuit; RL circuits have a time constant that causes the discharged energy to increase at a slower rate, peak at a lower value, decrease at a slower rate, and thus spread the discharged energy over a greater timespan. From an EMI point of view, what this does is make the radiated EMI of lesser strength, lesser "frequency", and spreads it over a longer period of time. No short, sharp shocks. (Sorry Pink Floyd.) From the spark plugs' point of view, the energy is potentially ( ) spread out over a greater time frame with a lower peak, which might make the plugs last longer... but the maximum firing power is also reduced, so they are more prone to misfire. Quote Link to comment Share on other sites More sharing options...
shimonmor Posted February 15, 2005 Author Share Posted February 15, 2005 Hmmm. This turned out to be an interesting thread. I appreciate the replies. The spec is there for a reason...what that reason is, I'm not sure. The EMI theory sounds plausible. Anyway, the car is running fine so I'll assume (yes, I know what happens when you assume) that I'm ok. Thanks again. Quote Link to comment Share on other sites More sharing options...
Tiny Clark Posted February 15, 2005 Share Posted February 15, 2005 If it's running good, leave 'em alone. I don't think the resistance is that far off to cause a problem. The variance in resistance readings is directly related to the length of the cable. Usually, resistance of a wire will not decrease, only increase. Quote Link to comment Share on other sites More sharing options...
NorthWet Posted February 16, 2005 Share Posted February 16, 2005 I agree that the FSM resistance specs are there to determine if OE wires are failing. The EMI issue has to do with FCC regulations. The real issue with the wires being good or not is how long before insulator breakdown, and how long before conductor failure. These are things that only time will tell. Quote Link to comment Share on other sites More sharing options...
chico00 Posted February 16, 2005 Share Posted February 16, 2005 I have been reading through this thread and a funny thing has just occured to me. I have been having problems with my CEL and getting the infamous "Misfire 4 code" for about month. First I changed the plugs, wires (belden from NAPA) and coil pack to no avail. Now in the past month I have put in a mass air flow sensor, fuel injector @ 4, cleaned the EGR and cleaned out the throttle body and all the vaccum tubes, (California emmisions crap) all to end up with the CEL flashing @ me. I think my problem might be the EGR solenoid but at this point it has become a full on parts toss. How much are OEM wires? This is getting expensive! Quote Link to comment Share on other sites More sharing options...
Tiny Clark Posted February 16, 2005 Share Posted February 16, 2005 You could always swap two plug wires around before you go spending more money. Just curious, do any other misfire codes come up besides 4? It seems to be a very popular number. Given that the engine uses one coil pack, I have a hard time believing the ECU can tell if one particular cylinder is misfiring, but stranger things have happened. I still miss setting the dwell for the points gap... :-\ Quote Link to comment Share on other sites More sharing options...
frag Posted February 16, 2005 Share Posted February 16, 2005 You could always swap two plug wires around before you go spending more money. Just curious, do any (1) other misfire codes come up besides 4? It seems to be a very popular number. (2) Given that the engine uses one coil pack, I have a hard time believing the ECU can tell if one particular cylinder is misfiring, but stranger things have happened. I still miss setting the dwell for the points gap... :-\ (1) I've had a «misfire on cyinder #2» that went away after a dose of fuel system cleaner. (2) I think the way the ECU «knows» that is that it detects a slight deceleration after a given cylinder is supposed to have fired and interprets this as a «misfire». That's why even a misfire caused by a mechanical component (valve for ex.) can be detected by the ECU. Quote Link to comment Share on other sites More sharing options...
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