skizix Posted June 28, 2006 Share Posted June 28, 2006 Ok, so: recently acquired an '02 OBW, 2.5l, 5MT. Has had some driveability issues, and some attempts to resolve it, with mixed results, as chronicled HERE: Well, I was just about to bring it in to my regular mechanic, in the hopes of a pro wrench driving/riding in it, with a probe attached, to see what might be screwy, in runtime. In the meantime, I'd gotten to thinking it was maybe a coil, so I decided to check the terminals for deposits (recently did new plugs and wires, and cleaned significant deposits off of one terminal). Well, when I went to pull the wires off the coil, I noticed that the plug wires were crossed (on the correct terminals, but touching, maybe 4" from the coil) on both sides. See, when I put in new plug wires, one on each side seemed very tight, like I had to really stretch it to get it into all the little clips/holders. I guess over time the heat stretched 'em out a bit, and they'd popped out of the holders, and on both sides, one wire was sitting on top of the other, touching. Coil terminals clean, BTW. So, the question is: would having wires laying on one another have been causing my intermittent misfires (at least that's what it felt like -- CEL never lit, and haven't pulled codes since)? Other question: is this likely to have fried my new wires (likely less than 2000 miles in this state)? Still have some lesser oddness, and looking into an ECU flash/software upgrade from dealer as a TSB-repair (at the suggestion of my "real" mechanic). But uncrossing the wires seems to have smoothed things out considerably. Or is it likely all in my head (the improvement, that is -- intermittent problems can get pretty psychological)? Can crossed plug wires (in new condition) cause misfires/driveability issues? Quote Link to comment Share on other sites More sharing options...
skizix Posted June 28, 2006 Author Share Posted June 28, 2006 Bump. What, nobody? Opinions, theories? What I can confirm is this: while the plug wires are of course insulated...the voltage is high enough that the current can easily cross said insulation. Try touching a plug wire on a running engine some time -- it is not entirely unlike being kicked by a horse (I confirmed this for myself as a kid, with a lawnmower; and then last year, **after** warning him it would happen, watched my friend get shocked in this very manner by his Forrester, not once, but twice in a row ) So I'm guessing that having the plug wires touching each other could cause the spark impulse to take the wrong path. Anybody else think this might cause an occasional miss? Quote Link to comment Share on other sites More sharing options...
nipper Posted June 28, 2006 Share Posted June 28, 2006 Ok, so: recently acquired an '02 OBW, 2.5l, 5MT. Has had some driveability issues, and some attempts to resolve it, with mixed results, as chronicled HERE: Well, I was just about to bring it in to my regular mechanic, in the hopes of a pro wrench driving/riding in it, with a probe attached, to see what might be screwy, in runtime. In the meantime, I'd gotten to thinking it was maybe a coil, so I decided to check the terminals for deposits (recently did new plugs and wires, and cleaned significant deposits off of one terminal). Well, when I went to pull the wires off the coil, I noticed that the plug wires were crossed (on the correct terminals, but touching, maybe 4" from the coil) on both sides. See, when I put in new plug wires, one on each side seemed very tight, like I had to really stretch it to get it into all the little clips/holders. I guess over time the heat stretched 'em out a bit, and they'd popped out of the holders, and on both sides, one wire was sitting on top of the other, touching. Coil terminals clean, BTW. So, the question is: would having wires laying on one another have been causing my intermittent misfires (at least that's what it felt like -- CEL never lit, and haven't pulled codes since)? Other question: is this likely to have fried my new wires (likely less than 2000 miles in this state)? Still have some lesser oddness, and looking into an ECU flash/software upgrade from dealer as a TSB-repair (at the suggestion of my "real" mechanic). But uncrossing the wires seems to have smoothed things out considerably. Or is it likely all in my head (the improvement, that is -- intermittent problems can get pretty psychological)? Can crossed plug wires (in new condition) cause misfires/driveability issues? yes. There is electrical theory behind this that i will post later, i have to go to PT soon and not one of my better days.. There is a reason why there are things called wire trees. Its to keep the wires seperated and induce a current in an opposing wire. nipper Quote Link to comment Share on other sites More sharing options...
skizix Posted June 28, 2006 Author Share Posted June 28, 2006 Cool. As I type, I'm getting the CEL flash. TSB myass, it's going to be $98 (only free up to 80000 miles, which I'm past). Damn dealer. Whatever, it is supposed to address hesitation and surge issues, of which I do have some remaining. So with the crossed-wire miss and the flash, hopefully I'm getting there now. I sold off my '90 legacy (235,000 miles) the other day. After driving only my '02 OBW for three months, it was truly depressing to realize that my super beat-up '90 drove way smoother, better, etc. Getting close w/ the new one now though. So anyway...think I ruined my plug wires? They look ok. Quote Link to comment Share on other sites More sharing options...
nipper Posted June 28, 2006 Share Posted June 28, 2006 Cool. As I type, I'm getting the CEL flash. TSB myass, it's going to be $98 (only free up to 80000 miles, which I'm past). Damn dealer. Whatever, it is supposed to address hesitation and surge issues, of which I do have some remaining. So with the crossed-wire miss and the flash, hopefully I'm getting there now. I sold off my '90 legacy (235,000 miles) the other day. After driving only my '02 OBW for three months, it was truly depressing to realize that my super beat-up '90 drove way smoother, better, etc. Getting close w/ the new one now though. So anyway...think I ruined my plug wires? They look ok. nope its a magnetic thing, not an physical thing. Google basic electricty or right hand rule, that ill explain it more Quote Link to comment Share on other sites More sharing options...
idosubaru Posted June 28, 2006 Share Posted June 28, 2006 then once you get that down, google guassian surfaces, real fun stuff.....NOT! are these OEM subaru plug wires? if they are aftermarket off the autoparts store shelf then they need to go. Quote Link to comment Share on other sites More sharing options...
skizix Posted June 28, 2006 Author Share Posted June 28, 2006 are these OEM subaru plug wires? if they are aftermarket off the autoparts store shelf then they need to go. OEM plugs and wires. Being OEM, I was surprised the wires were such a tight fit (they were stretched so tight, I thought they were going to pull off the coil). And especially because it was only two of the four that were tight. I thought I might have gotten the wrong wires. But like I said, a couple of months of under-hood heat seems to have relaxed them -- they fit like I'd expect now. I put 'em back in the clips, and pulled the slack down towards the heads, where they can't cross. Quote Link to comment Share on other sites More sharing options...
OB99W Posted June 28, 2006 Share Posted June 28, 2006 What I can confirm is this: while the plug wires are of course insulated...the voltage is high enough that the current can easily cross said insulation. If there is actually a flow of electrons through the insulation, then the insulation is inadequate or defective. However... Try touching a plug wire on a running engine some time -- it is not entirely unlike being kicked by a horse (I confirmed this for myself as a kid, with a lawnmower; and then last year, **after** warning him it would happen, watched my friend get shocked in this very manner by his Forrester, not once, but twice in a row ) So I'm guessing that having the plug wires touching each other could cause the spark impulse to take the wrong path. The rapidly rising and falling current flowing through the plug wires creates a pulsating magnetic field around the wires. That changing magnetism will induce a current to flow in any nearby conductor. Conductors that are close enough and parallel for a sufficient distance could be cutting across enough "magnetic lines" to have quite a bit of energy induced. This can happen even if the insulation is flawless. Anybody else think this might cause an occasional miss?Usually spark crossfire doesn't occur unless the plug wires are close and parallel for at least several inches. (If the insulated wires just touch for a short distance, especially if at a significant angle to each other, crossfire usually isn't a problem.) Since misfire can be caused by a weakening of the spark or one occuring at the wrong time, if the spark wires are misrouted it could lead to misfire. Quote Link to comment Share on other sites More sharing options...
skizix Posted June 28, 2006 Author Share Posted June 28, 2006 If there is actually a flow of electrons through the insulation, then the insulation is inadequate or defective. However... The rapidly rising and falling current flowing through the plug wires creates a pulsating magnetic field around the wires. That changing magnetism will induce a current to flow in any nearby conductor. Conductors that are close enough and parallel for a sufficient distance could be cutting across enough "magnetic lines" to have quite a bit of energy induced. This can happen even if the insulation is flawless. Usually spark crossfire doesn't occur unless the plug wires are close and parallel for at least several inches. (If the insulated wires just touch for a short distance, especially if at a significant angle to each other, crossfire usually isn't a problem.) Since misfire can be caused by a weakening of the spark or one occuring at the wrong time, if the spark wires are misrouted it could lead to misfire. Thanks for clarification. I'd always wondered how plug wire insulation could be adequate for anything, given how easy it is to get zapped. Anyway, on one side, one wire was laying on the other (i.e. all but parallel) for a good 4 inches, and in direct contact in 2 places. It was only an occasional miss, and never stored a code (my ECU memory was clean as of this morning). No backfires or anything. But it seemed to have caused some low-speed driveability problems. In any case...I hope the crossed wires were causing problems, 'cause otherwise I've got other problems! Can't wait to see if the ECU flash does anything noticable. Quote Link to comment Share on other sites More sharing options...
nipper Posted June 28, 2006 Share Posted June 28, 2006 If there is actually a flow of electrons through the insulation, then the insulation is inadequate or defective. However... The rapidly rising and falling current flowing through the plug wires creates a pulsating magnetic field around the wires. That changing magnetism will induce a current to flow in any nearby conductor. Conductors that are close enough and parallel for a sufficient distance could be cutting across enough "magnetic lines" to have quite a bit of energy induced. This can happen even if the insulation is flawless. Usually spark crossfire doesn't occur unless the plug wires are close and parallel for at least several inches. (If the insulated wires just touch for a short distance, especially if at a significant angle to each other, crossfire usually isn't a problem.) Since misfire can be caused by a weakening of the spark or one occuring at the wrong time, if the spark wires are misrouted it could lead to misfire. thanks for explaining it. It doesnt have to be just high voltage to get mutual inductance. http://www.ndt-ed.org/EducationResources/CommunityCollege/EddyCurrents/Physics/inductance.htm Inductance is how your coil and transformers work. ONce my boss bought a used 100 ton h frame press. It had a handel on top the change the height of the press. The press had a 240 volt heater on it. Instead of wiring this porperly, he taped into a box and coiled all the extra wire on the handle on top the press. I started blowing out solid state relays and other control items. Then we started getting zapped. I fioinally figured out that coil of wire was inducing a charge in the press. Once we moved the coil it stoped (and i wired it properly ... bosses shouldnt be allowed to play with tools). High Voltage Electricity can do really weird things. nipper Quote Link to comment Share on other sites More sharing options...
wallaceg Posted June 29, 2006 Share Posted June 29, 2006 High Voltage Electricity can do really weird things. nipper Mutual inductance has nothing to do with voltage. It's all about a change in magnetic flux, generally caused by a change in current through or geometry of a wire loop. Quote Link to comment Share on other sites More sharing options...
nipper Posted June 29, 2006 Share Posted June 29, 2006 Mutual inductance has nothing to do with voltage. It's all about a change in magnetic flux, generally caused by a change in current through or geometry of a wire loop. http://mightyautoparts.com/pdf/articles/tt72.pdf sigh, its common knowledge that high voltage can do really weird things you wont get inductance at 1 volt as you would with 10000 volts in the stated condition of ignition wires. Also there are far more things out there then cars with high voltage, maybe i should have clarified that, as i was making a general statement and not a car specific statement. I worked for a military contractor making helicopter towed mine sweepers and sonar systems. We have had mine sweepers set off mines stored on land (not the design plan) and screw up LGA radar in heavy fog conditions (when the airport was closed). I have worked on 600 volt DC Transit cars where the amperage is unlimited. I have witnessd it all and stand by my comment. nipper Quote Link to comment Share on other sites More sharing options...
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