COP Harness

[Eastcoast SHO]

So this is what I'm thinking the problem is. Chris suggested my harness was no good and I'm starting to think he is right.

I had a misfire on 3 then it moved to 4 then to 1 now it is on 1 and 2. I didn't see any damage on the harness where I reinsulated it with high temp tape.

So here comes the questions:

1. is it possible the harness is shot further back to cause these problems?
2. Where does the harnes actually start?
3. How does one go about replacing them correctly?
4. Does anyone have a good one?

Fyi the things that were done in the past, before I get these questions again:

New spark plugs
New coil packs
Checked vaccumm leaks,none were found
Cleaned maf/tb
Reinsulated rear cop wires with high temp tape
Compression test, good
No signs of blown head gasket

Thank you guys again

 

[CanadianSniper]

Eastcoast...........in IMO I don't beleive it is your harness, and that the problem is more complicated than this. I assumes you are pulling misfire codes. And after resetting, they are recurring at a different location.

Please read this link .......http://www.fordscorpio.co.uk/misfiremonitor.htm......


I will try and help you all that I can. I believe you have another flaky component in the OBDII circuit. This info is from an English site, however the principal is the same.

 

[CanadianSniper]

So I was reading back to understand your history. Only to find you had original codes of;
P0171,0172,0304. Is this correct? Have you checked all your vacuum hoses, as Chris said all your wiring and connections? Looking at your codes have you checked the fuel pressure?



Engine running rough or misfiring can be cause by the following-inspect and test all the following listed below:
1.Defective spark plug.
2.Inadequate spark/coil,defective spark plug wire.
3.Lack of compression
4.False air leakage.
5.Faulty fuel injectors.
6.Insufficient fuel pressure.
7.Contaminated fuel.
8.EGR valve that is leaking.
9.Oxygen sensors.
10.Throttle position sensor.

 

[Izzmo]

The harness is just wiring.. so there must be a big defect in the wires themselves for it to be a bad wiring harness, IMHO. Such as a big tear in a wire, or bare wire is being shown (and thus the wire could start coroding, which would cause problems).

 

[Eastcoast SHO]

is there any way to test them before replacing them?

 

[SHOZ123]

Yes with an ohm meter. You would need the pinout of the PCM connector to find the wire colors. One COP wire is always hot and the other wire is grounded by the PCM to fire them.

 

[Izzmo]

As Paul and many others has said before, testing the resistance of a COP can not always mean it's bad.

I think, more or less, you should test it right after you turn off the car at optimum temperature. If you test it cold, it probably won't give an honest reading.

 

[SHOZ123]

I thought he was talking about testing the harness.

 

[Eastcoast SHO]

I thought he was talking about testing the harness.

yes the harness itself, dont know what else to do, im stumped

 

[wymjym]

I second the harness assumption

yes the harness itself, dont know what else to do, im stumped

I have trouble shot my 97 for several years. (if your bored just check my posting history and read my stories of woe)

Basically I've tested or had tested everything that has been mentioned, whispered, written about...several times. I still have an idle miss and the ecm pulls fuel out of the back bank in order to try to keep the fuel ratio inline. I believe that the resistance that has come with years of heat cycles, moisture, vibration and who knows what else has added enough resistance to one or many of the wires within the harness and this is leading to the issue.
I bought a used harness but have yet to cut it apart, check for abrasions, test the continuity, put it back together and them swap it out. WHY? after all of my efforts this idle is the only issue I have and it doesn't surge very much nor does it throw a code unless I drive in city traffic for some time and let it idle. I live in the country so this isn't my typical drive.
I also bought a used ecm with semi high hopes...plugged it in (after cleaning all contacts in the harness and the replacement ecm...it ran exactly the same....so no joy on my part.
and lastly....I had all those issues with the wipers/washers and other weird things...finally all was (and still is) resolved because I cleaned the plug and socket contacts.
So, my vote is the harness. If there is added resistance in one of the wires and there is a high energy source anywhere near this wire, that wire is even more susceptible to noise and all you need to do is throw some random noise into the harness and the ecm doesn't know if the sensor input it is reading is valid or not (assuming it is within some parameters)..oh yeh, ask toyota about there unexplained acceleration or lack of braking.....there is no DIRECT mechanical actuation or control taking place, rather a potentiometer tells the ecm something and then the ecm relates that to a certain demand and then tells something else (fuel/throttle/brakes) to act appropriately.
I'm done for now.
wj