HT leads / Ignition wires whatever you call them...

[e34.535i.sport]

Could they be causing an INTERMITTENT misfire? Been getting a bit worse, particularly today the car even bucked when i went to accelerate at low speeds. Turned it on a couple of hours later and it was ok... Weird.

Took the spark plugs out today, all look absolutely fine... However, looked down the end of the leads and one looked different from the rest - here's some pic's (I apologise for the low quality could't ge the right focus!) one of them looks different (pictured right), all the others look the same.









They all have the red ring but there's only one where it is like cracked and sticking out over the other part... Could this be an 'iffy' lead?

Anyone seen this before? I would just order a new set but tbh they're fairly expensive so I didn't want to just throw money at it before consulting you guys...

Thanks for any input in advance...

[whiskychaser]

It may seem obvious but were the caps on top of the plugs screwed on tight? A loose one will make a poor connection and possible misfire. May be the pic but the odd plug lead seems to have the contact recessed deeper. Any chance the sleeve is bottoming out before the inside makes a proper connection? Of course if a PO has pulled on a lead instead of getting holding of the bit the plug goes into then it could be broken inside.

If you want to get your hands dirty again, I'd take off the dizzie cap and make sure its spotless inside and out, that the brush isnt worn and is free to move and the terminals arent blown away. Check the rotor arm too. You could wait till it gets dark and see if you can spot an arc on the HT leads or dizzie cap.

[Rus]

It may seem obvious but were the caps on top of the plugs screwed on tight? A loose one will make a poor connection and possible misfire. May be the pic but the odd plug lead seems to have the contact recessed deeper. Any chance the sleeve is bottoming out before the inside makes a proper connection? Of course if a PO has pulled on a lead instead of getting holding of the bit the plug goes into then it could be broken inside.

If you want to get your hands dirty again, I'd take off the dizzie cap and make sure its spotless inside and out, that the brush isnt worn and is free to move and the terminals arent blown away. Check the rotor arm too. You could wait till it gets dark and see if you can spot an arc on the HT leads or dizzie cap.

As far as I know, the M30 engines do not use the caps on the plugs. We just pop the ignition leads onto the threaded spark plug terminal. Unless I've been doing it wrong for the past 30K miles :-p

[e34.535i.sport]

Hey Colin - Thanks!

I'm wandering if the recession is a possibility but more likely to be my fault than PO's as the #4 wire wasn't like this a while ago??? Maybe I've pulled it by the wire. I might try to see if I can sort it out by having a mess with it, and if not see what prices I can find for a new set.

I was wandering about the dizzie and wanted to check it out but don't know much about it at all so didn't want to start messing incase I broke something! Is it a straightforward removal of the red cap thing and just have a look around then??! AnythingI need to consider first?

The cap situation is correct Rus - I found that my leads wouldn't fit over the plugs with the caps on so I took them off and hey presto. The m50 uses them though I know that for certain...

[tim eh?]

you have to take the caps off the plugs on the m20 too.
first time I changed them I took the plugs back to the supplier and told them they gave me the wrong ones oh the shame....

i have found a spray bottle filled with water to be a very useful diagnostic tool in situations like this. set it on mist and douse the wires (a good dozen squirts at least, really give it to it) - if the engine stumbles then they are cracked somewhere. same goes for the distributor cap, it will stumble or die if the cap is cracked or not sealed properly. it is also useful for finding corroded terminals eg at ignition coil. for the wires you can also measure resistance on each one individually. Inside the cap it should be pretty evident if you have a problem - you are looking for deposits like you would find on spark plugs, any evidence of of anything burning, etc, look closely at the rotor for cracks.

as you know i'm no expert but i have used this method to find all kinds of ignition problems on an old dodge van i used to drive, including finding a bad 'ballast resistor', cracked cap, bad wires, corroded terminals at ignition coil and it pointed to the problem like a forked stick points to water.

[whiskychaser]

Hey Colin - Thanks!

I'm wandering if the recession is a possibility but more likely to be my fault than PO's as the #4 wire wasn't like this a while ago??? Maybe I've pulled it by the wire. I might try to see if I can sort it out by having a mess with it, and if not see what prices I can find for a new set.

I was wandering about the dizzie and wanted to check it out but don't know much about it at all so didn't want to start messing incase I broke something! Is it a straightforward removal of the red cap thing and just have a look around then??! AnythingI need to consider first?

The cap situation is correct Rus - I found that my leads wouldn't fit over the plugs with the caps on so I took them off and hey presto. The m50 uses them though I know that for certain...

Must have been having a 'senior moment' regarding the plugs The (red) dizzie cap will come off if you undo the 3 screws. I think there should be a plastic cover over on top but but I dont recall seeing one on yours. Only real thing to remember is where each plug lead goes if you pull them out of the cap

[e34.535i.sport]

Must have been having a 'senior moment' regarding the plugs The (red) dizzie cap will come off if you undo the 3 screws. I think there should be a plastic cover over on top but but I dont recall seeing one on yours. Only real thing to remember is where each plug lead goes if you pull them out of the cap

Yeah no plastic cover on mine... I think I'll have a look at it for curiosity's sake!!! Thanks and will keep u informed!!

[e34.535i.sport]

Hey guys, wonder if someone can advise me on this one... Gonna get a set of leads as all my instincts are telling me this must be the problem.

There's two sets on ebay, one of the sets say they're COPPER wires and is double the price of the other set... Worth it??? Both same brand, same seller etc.

Thanks!

P.s Not had time to check out the dizzy yet, but *hopefully* over the weekend I will...

[whiskychaser]

All you ever wanted to know (or didnt really) about spark plug leads:

http://www.magnecor.com/magnecor1/truth.htm

[ahlem]

If you have a Harbor Freight or big box auto supply store near you, you can purchase a spark tester. Harbor freight was less than $10. It has a clear section that shows the arc. You can try it at a couple different locations to zero in on what's going on. I tried at the coil, then the coil wire at the distributor then each of the wires coming out of the distributor then the wires at the plugs. Be sure to get the kind that has the extender to reach down to plugs so it will give more options on other cars. My last one on a non-bmw turned out to be a rotor and cap from different manufacturers not liking each other.