Help with P0305 diagnosis...wire harness looks good (1 Viewer)

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Joined
Mar 25, 2012
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Location
Hannibal, MO
Hey all.

‘97 popped a p0305 code while on Highway with all the usual symptoms...engine vibration, loss of power, etc. I had this happen once before and jiggling the injector connector fixed issue for another 3 yrs.

I figured it was the wire harness near the EGR pipe. So today I started tearing down to where I could inspect the loom by removing throttle body and EGR valves. Along the way I...
-tested plug wire @ 25k ohms. Good.
-inspected spark plug. A little black, but I did drive it ~200 miles without detonation. Otherwise looked good.
-measured resistance on injector @ 13.7 ohms. Within FSM specs.

So I proceeded to tear into the wire loom and it looked.......perfect.

I’m at a standstill.

Anything I’m missing?

I’ve thought of biting the bullet and just getting a new harness. I don’t have a lot of time to waste on diagnosis. In my head, the wires next to the EGR would be toast and it would be a simple splice and dice and done. Grrr.

Thoughts??

-Jared
 
Make sure it’s not a headgasket issue. Pull no 5 plug and pressurize the cooling system.
 
There is a spot under the glove box where the wire harness goes into the ecu. Mine rubbed through there and caused a cylinder 6 misfire.
 
There is a spot under the glove box where the wire harness goes into the ecu. Mine rubbed through there and caused a cylinder 6 misfire.

Where it passes through the firewall? Or near where it plugs into the ecu?
 
Remove the glove box, cant miss the spot in question. The harness has black plastic cover in that area, but can fail.
 
Yeah, I checked there. It wasn’t touching the metal.

I’ll try these things once throttle body is back on:

-check for 12v at injector plug, then

-swap new spark plug in, then

-try different plug wire, then

-buy new injector, then

-buy new wire harness

Cheapest to most $$$.
 
Check continuity on the grounding wire for that injector. It runs all the way to the ECU as the trigger for the injector.
 

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