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Discussion Starter · #1 ·
2002 Taurus DOHC misfiring on CYL 1 and sometimes CYL 3. Appears to do this only when idling and with a load (stopped but in drive). Causes CEL and P0301 sometimes P0316 misfire on startup first 1000 revolutions.. Changed Ignition Coil Pack, PCV valve and replaced IAC valve (was also getting P1506 IAC overspeed malfunction, but not anymore).
Engine swapped a year ago with one that had about 60K miles on it. At that time put in new Autolite Iridium plugs.
Have another set of OEM plug wires which either came with the other engine or was on the original one (not sure which set went on the car as I didn't do the swap).
Plug wires I have are OEM and have the numbers on each wire, cable management plastic clips and flexible plastic "hoses" over the wires and OEM long plug rubber connectors and right angle rubber coil connectors.

Measurements and resistances for each wire shown below. I measured from the place where the wire enters the rubber connector at each end with a DVM on Ohms scale.

#1 5.60 K Ohms 12 1/2"
#2 5.42 K Ohms 10 1/2"
#3 5.75 K Ohms 13"
#4 8.79 K Ohms 25 1/2"
#5 11.20 K Ohms 30 1/2"
#6 11.28 K Ohms 32"

I want to change out the wires but have to remove the cowling as I did to replace the coil.

1. Do the resistances look right for these wires.
2. If changing the wires doesn't stop the misfiring what should I do next?
 

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Resistance numbers look good, Kudos for posting wire length also, many people here don't realize that is part of the equation. Have you started the car in total darkness and looked under the hood for spark bleed? New coils can be NFG. For #2, check injectors next.

Edit: "flexible plastic "hoses"...it's called "wire loom"...
 

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Wire R

2002 Taurus DOHC misfiring on CYL 1 and sometimes CYL 3. Appears to do this only when idling and with a load (stopped but in drive). Causes CEL and P0301 sometimes P0316 misfire on startup first 1000 revolutions.. Changed Ignition Coil Pack, PCV valve and replaced IAC valve (was also getting P1506 IAC overspeed malfunction, but not anymore).
Engine swapped a year ago with one that had about 60K miles on it. At that time put in new Autolite Iridium plugs.
Have another set of OEM plug wires which either came with the other engine or was on the original one (not sure which set went on the car as I didn't do the swap).
Plug wires I have are OEM and have the numbers on each wire, cable management plastic clips and flexible plastic "hoses" over the wires and OEM long plug rubber connectors and right angle rubber coil connectors.

Measurements and resistances for each wire shown below. I measured from the place where the wire enters the rubber connector at each end with a DVM on Ohms scale.

#1 5.60 K Ohms 12 1/2"
#2 5.42 K Ohms 10 1/2"
#3 5.75 K Ohms 13"
#4 8.79 K Ohms 25 1/2"
#5 11.20 K Ohms 30 1/2"
#6 11.28 K Ohms 32"

I want to change out the wires but have to remove the cowling as I did to replace the coil.

1. Do the resistances look right for these wires.
2. If changing the wires doesn't stop the misfiring what should I do next?
I read mine yesterday and replaced the coil. (one on there was not Ford)

Resistance is not a critical thing as to value, the wire is normally made with a nominal 3,000 ohms per foot, +/- about 30%. Problem comes when one is open circuit. It may run ok but there is a spark gap and the spark between two pieces of string with carbon in them will soon make the gap larger and larger until misfire at speed.

Factory wires are numbered and have the looms around them. Good for abrasion protection. If you replace the wires, the looms should be reused as they came from the factory. I take a picture of things for reference. Helps when I forget where things go. I prefer to take the upper intake off and that gives me a chance to evaluate vacuum hoses and any other issues. I wipe off the matching surfaces of the upper and lower intake and inspect the gaskets.

I would not replace my wires. I did not write mine down as it is not important, but I do believe lowest (shorest) was less than 5K and highest around 10K. If I needed to replace them, I would ohm the new ones as they sometimes are open. Good practice to put spark plug silicone on the boots on both ends. I use a Q-Tip rather than a screw driver.

good luck.

If you find your source of misfire, share it here please.

-chart-
 

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2002 Taurus DOHC misfiring on CYL 1 and sometimes CYL 3.
I think they are sharing the same coil (follow the wires). I would suspect that coil first. Check the low voltage connector, clean it with electronic contacts claner.
If that doesn't work, get one from a junkyard.
 

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Discussion Starter · #5 ·
Its a NEW coil I Know NEW in not equal to good but I suspect something else

I think they are sharing the same coil (follow the wires). I would suspect that coil first. Check the low voltage connector, clean it with electronic contacts claner.
If that doesn't work, get one from a junkyard.
Old coil is Ford OEM part and LOOKS good. No cracks etc. But when the car got wet it would misfire a lot. Its now a non Ford new coil. Did this about 3 weeks ago. I will go for the wires next since I have a set that look like they are fine. Do I have to take the coil pack off to get to the rear plug wires especially #2 which is right below the coil pack? Too rainy today or I would have tried it. What about changing or at least removing #1 plug and seeing what it looks like?
 

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rain sensitive

Old coil is Ford OEM part and LOOKS good. No cracks etc. But when the car got wet it would misfire a lot. Its now a non Ford new coil. Did this about 3 weeks ago. I will go for the wires next since I have a set that look like they are fine. Do I have to take the coil pack off to get to the rear plug wires especially #2 which is right below the coil pack? Too rainy today or I would have tried it. What about changing or at least removing #1 plug and seeing what it looks like?
"..when the car got wet it would misfire a lot.."

This is a big clue. Likely insulation breakdown for that.

As for me, getting to the wires by removing the cowl is possible. Have to be careful which wire is which, and replace one at a time. Maybe just the offending ones, (pair) .

If you pull the cowl and replace only the pair in question, then try spraying water on the wires and coil and see if it misses. It would take quite a bit of insulation breakdwon to cause a water sensitive system. Possible one wire is rubbing something and exposed the core.

-chart-
 

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If I recall correctly anything more than 10K ohm per foot is bad. Your numbers look good with the length. Wire Looms - if you look at most ignition cables you will notice they don't touch anything. And this is the way it ought to be considering they transfer high voltage, wire looms helps transfer. If you get a weak ignition cable the spark will start jumping from the cable to ground causing a misfire. Probably a CEL number as well.

Your car is the perfect test platform for troubleshoot something like this. If you think about it takes fuel, compression and ignition to fire a cylinder. Anything to upset this balance and you'll have a miss.

If you can grantee you have spark and compression, that leaves the fuel to the cylinder that is the issue. As there may not be the correct air/fuel mixture in the cylinder. This can be anything from a clogged injector to leaky intake manifold gaskets. And when I had a miss on my Duratec it was leaky manifold gaskets.

Monsoon
 

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Fwiw, cyls. 1&5 share a coil. 2&6 share a coil. 3&4 share a coil. Same applies to vulcan and duratec. Firing order for both engs. is: 1-4-2-5-3-6.
 
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