P0305 Code (misfire code) Topic is solved

[MadeInJapan]

I just looked at a car today with the #5 random misfire code. The crank wire was to close to #5 cylinder spark plug wire. Moved the wire and the misfire stopped.

Oh yeah- I remember that phenomena- we're talking "old school" This dates us Robert!!
There was also some info about tying up (with a zip tie) the wires away from the crank position sensor...remember that? I believe that was it? And the MAF wire, away from the edge of the fuse box!! There are certain electrical currents that are just not compatible under the hood on these cars!

[songzunhuang]

I just looked at a car today with the #5 random misfire code. The crank wire was to close to #5 cylinder spark plug wire. Moved the wire and the misfire stopped.

Can you clarify more here? What is the crank wire?
My misfire began when I had the Bosch wires on there. When I changed to NGK wires, I routed them in exactly the same paths. I don't think I saw any other wires to interfere, but who knows. Please explain in more detail. Thank you.

[erikv11]

Thought you already checked this, too! For details scroll back up to the top of page 5 and links therein, Robert is talking about this:

Also, consider sleddriver's comment here about the coil wire, it's a real stretch for what you are seeing but it doesn't hurt to just check it https://www.matthewsvolvosite.com/forums ... 61#p401661

You want to check the routing of the crank sensor and cam sensor wiring, and make sure they are not too close to any ignition wires. It's a fairly common problem.

[sleddriver]

I just looked at a car today with the #5 random misfire code. The crank wire was to close to #5 cylinder spark plug wire. Moved the wire and the misfire stopped.

Can you clarify more here? What is the crank wire?
My misfire began when I had the Bosch wires on there. When I changed to NGK wires, I routed them in exactly the same paths. I don't think I saw any other wires to interfere, but who knows. Please explain in more detail. Thank you.

Crank wire = signal wire from crankshaft position sensor.

Song, here's my original post erik if referring to:

I wonder if it could be the lead from the coil to distributor, being too close to the crank position sensor, just below the distributor? Seem to recall reading somewhere that this can cause problems. You might want to temporarily route it on top, over the air filter box, to get it as far as possible and see if the misfire codes cease.

You don't want any high-voltage ignition wire in close proximity to any sensor (crank and cam position) wiring, nor running parallel to it. The HV pulses will be coupled to the sensor wire and lead to a corrupted signal that will possibly confuse the engine management controller, thus leading to misfires.

Given the above, I strongly suggest you re-route your HV lead from the ignition coil to the distributer and see if your misfire problem is solved.

[songzunhuang]

I just looked at a car today with the #5 random misfire code. The crank wire was to close to #5 cylinder spark plug wire. Moved the wire and the misfire stopped.

Can you clarify more here? What is the crank wire?
My misfire began when I had the Bosch wires on there. When I changed to NGK wires, I routed them in exactly the same paths. I don't think I saw any other wires to interfere, but who knows. Please explain in more detail. Thank you.

Crank wire = signal wire from crankshaft position sensor.

Song, here's my original post erik if referring to:

I wonder if it could be the lead from the coil to distributor, being too close to the crank position sensor, just below the distributor? Seem to recall reading somewhere that this can cause problems. You might want to temporarily route it on top, over the air filter box, to get it as far as possible and see if the misfire codes cease.

You don't want any high-voltage ignition wire in close proximity to any sensor (crank and cam position) wiring, nor running parallel to it. The HV pulses will be coupled to the sensor wire and lead to a corrupted signal that will possibly confuse the engine management controller, thus leading to misfires.

Given the above, I strongly suggest you re-route your HV lead from the ignition coil to the distributer and see if your misfire problem is solved.

Allright, thank you for the clarification. If I recall correctly the camshaft sensor is just under the cover for the rear camshaft seal (nearest to the firewall). Your explanation of the possible cause make sense. I'll re-route this evening and see what happens.

[erikv11]

You've got the cam sensor location correct.

Also check the crank sensor wiring, they are separate sensors: crank sensor plugs into the top of the transmission, just aft (toward the firewall) of the distributor.

Both the cam sensor and the crank sensor plugs are held on a little bracket down low on the head, midway between the cams. Stuff will be in the way, notably the snorkel tube from the MAF to the turbo and the SAS plumbing if your car still has that.



You also don't want the MAF wiring any closer to the leads than necessary.

[sleddriver]

Nice photo there Erik! Clearly shows these two connections & wiring just below the distributor. That bottom plug wire could also cause problems if it's too close.

[rspi]

Great picture indeed. This is the wire I moved. In this pic it is close to the coil wire.

Volvo 850 crank sensor wire to close to coil wire.

IMG_20160507_033447.jpg (37.45 KiB) Viewed 2472 times

[songzunhuang]

Huh, that's much more informative thanks. I moved the main wire from the coil to the distributor routing it above the air duct and it didn't make much difference. I was in the process of setting up an appointment with a Volvo specialists for Tuesday next week.

Now with this information, I'll go out and give it another try to see what I can affect.

[songzunhuang]

Checking on the various wires and connectors after the last post, I discovered that my CAM position sensor connector was in bad shape. If you see the photo below, the housing on the white connector basically crumbled when I was disconnecting it. I also saw a bit of corrosion on the blades of the connector. So I used a steel brush and a liberal blast from some electronics parts cleaner to remove the corrosion. I got some electrical tape and protected the exposed terminals and wiring and plugged it back in to check it out.

Well, it didn't fix the problem of the rough idling. However, I am sure that I could use a new CAM sensor at this point. That crumbling connector can't be a good thing, although I don't think it was preventing a signal from the sensor from reaching the ECU. The wires, although exposed, were still intact.

In any case, I have another CAM position sensor on order and the parts store said they'd have it this afternoon. The adventure continues.

The connector on my sensor has seen better days. It's getting replaced.