03 fiesta HT leads

jimmyw

Noticed a misfire the other day while driving on the level, but when I reached a hill it got really bad and the car just barely got up and the EML was flashing, not staying on, while going up.This problem occured before so I practically knew it was the plugs.

I changed these when I got home and waited until today to drive as someone else was going to use the car then.When he came home he said there was still some missing, but not as bad, but still there.I decided to remove the plugs to regap them only to see on the plug makers site (NGK) that they are pre gapped :mad:.

I then checked the HT lead resistance to find that 2 of them had a value, but the other two had zero.From this you would think that those two plugs that they are connected to are not firing, but they seem to be.It does not sound that she is only firing on 2 cylinders.

So, after all that long winded statement:P, the leads will probably need changing, but how can they still be providing a spark to the plugs with zero resistance, ie "1" on my meter

dooroy

If the plugs are single electrode you can check the gap - just in case one of them fell etc and narrowed the gap .
If they have more than one electrode you can't really check them .
As regards the leads - a lead with no resistance would give a very good spark.
Plug leads have a resistance - varies depending on length etc .
Not sure what you mean by a reading of '1' on your meter .
What scale etc are you using ?

jimmyw

The plugs only have a single side electrode, but the website says they are pre gapped.What i mean about the lead is that to check continuity, you put the meter on the ohm setting, and touch each of the probes together and you get a "000" on the display and when putting the meter probes on whatever you want to check, in my case, the leads, and you get a value.

But on two of the leads, I am checking, the display is not going to "000" or the value of that lead, just the "1", meaning there is no continuity, but they are still sending the volts to the plugs. Am I reading it wrong?

dooroy

Not sure really .
When you switch to ohms are there a few possibilities e.g 100/200/1000 etc .
If there was no continuity in a lead then that plug should not be firing. Maybe the resistance is very high (outside the range you have it set to ) and the meter then reads it as 1 ?
If the resistance was say 15K and you had set the meter to the 10K setting then it could , I think , read as 1 .

jimmyw

dooroy wrote: »

Not sure really .
When you switch to ohms are there a few possibilities e.g 100/200/1000 etc .
If there was no continuity in a lead then that plug should not be firing. Maybe the resistance is very high (outside the range you have it set to ) and the meter then reads it as 1 ?
If the resistance was say 15K and you had set the meter to the 10K setting then it could , I think , read as 1 .

Yeah I was thinking along the same lines too, because there is no way the plugs can still be firing if there is no connection on the lead, so the resistance must be up in the sky, me thinks. They must be fecked then.

The other two leads are giving me 6.23k and 85-90k on number 2 and 4 lead but on number 1 and 3, its the "1" on the display.I believe these coils use the "wasted spark" setup for the plugs.

whizbang

Your meter is probably reading -1, meaning out of range, or greater than 999, 1999, etc.

The meter will read resistance of the leads, but if there is even the tiniest break in the conductor, the meter will then be out of range.

The spark can jump gaps of >1mm in the plugs; on a good system it will jump up to 10mm, so any small gap in the lead is small enough to jump over, so often a broken lead can still spark ok.
But gaps cause weak spark, and misfiring.
Also the spark will burn away the conductor inside where the break is very quickly, so any tiny crack soon becomes a big gap.

You have only 1 good lead out of 4. Change all 4

jimmyw

whizbang wrote: »

Your meter is probably reading -1, meaning out of range, or greater than 999, 1999, etc.

The meter will read resistance of the leads, but if there is even the tiniest break in the conductor, the meter will then be out of range.

The spark can jump gaps of >1mm in the plugs; on a good system it will jump up to 10mm, so any small gap in the lead is small enough to jump over, so often a broken lead can still spark ok.
But gaps cause weak spark, and misfiring.
Also the spark will burn away the conductor inside where the break is very quickly, so any tiny crack soon becomes a big gap.

You have only 1 good lead out of 4. Change all 4

No, I dont think its minus 1, but its still must be what you say because I would know if the two leads that are giving the different readings, or non readings, were not working at all.

No, I wouldn't be changing just the two leads, that would be stupid.