Not_An_Abba_Fan
Exhaust Guru
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Well, after what has been a frustrating few months, I think I may have fixed my intermittent miss issue I was having. After dropping the nose into a rather large hole and sucking a substantial amount of water into the engine, it developed a miss where it would totally lose injector pulse on one cylinder. It did kill the resistor pack, as it filled that up with water as well, but it only lost one cylinder.
The 3.5L has an interesting setup whereby it runs power through a resistor pack to the injectors, then the ECU controls the earth to fire them. I lost power to one pin on the resistor pack rendering number two injector non functional. Replaced that and it went well for a bit. Then, while driving, it would develop a miss again. Coincidently, the miss was on the same cylinder, so at first I thought dead injector. But that was fine. The plug on that injector had some broken insulation on the wiring, so cross shorting the plug killing the fuel flow. Fixed that, but it still missed.
Testing the plug with a test light (yes, it's perfectly fine to do that on this engine), and initially there is nothing, but then after a second, it starts flashing dimly, then brightens. Plug it back on the injector and bingo, purring again. Only to develop the same miss a bit later in the day. Putting the test light in the plug obviously adds more resistance to the circuit and it starts working, so then it is safe to assume I have a dodgy connection somewhere. I proceded to pull every plug in the injection harness, spray a liberal amount of contact cleaner in both sides and put them all back together. On initial start up after a few minutes of being off, it would typically miss until the test lamp was inserted in the plug. This time it started and ran beautifully, a bit rich with a fuelly smelling exhaust, but it's always been like that.
Next was to try and solve the rich running, these things have a little injector type solenoid in the plenum that puts in extra fuel on cold starts, my thought was that it may be playing up. Disconnected the fuel line from this and ran it again, and hey presto, no more fuel smell. I'll be interested to see if this has fixed my problem on the next run, but it looks good so far.
The 3.5L has an interesting setup whereby it runs power through a resistor pack to the injectors, then the ECU controls the earth to fire them. I lost power to one pin on the resistor pack rendering number two injector non functional. Replaced that and it went well for a bit. Then, while driving, it would develop a miss again. Coincidently, the miss was on the same cylinder, so at first I thought dead injector. But that was fine. The plug on that injector had some broken insulation on the wiring, so cross shorting the plug killing the fuel flow. Fixed that, but it still missed.
Testing the plug with a test light (yes, it's perfectly fine to do that on this engine), and initially there is nothing, but then after a second, it starts flashing dimly, then brightens. Plug it back on the injector and bingo, purring again. Only to develop the same miss a bit later in the day. Putting the test light in the plug obviously adds more resistance to the circuit and it starts working, so then it is safe to assume I have a dodgy connection somewhere. I proceded to pull every plug in the injection harness, spray a liberal amount of contact cleaner in both sides and put them all back together. On initial start up after a few minutes of being off, it would typically miss until the test lamp was inserted in the plug. This time it started and ran beautifully, a bit rich with a fuelly smelling exhaust, but it's always been like that.
Next was to try and solve the rich running, these things have a little injector type solenoid in the plenum that puts in extra fuel on cold starts, my thought was that it may be playing up. Disconnected the fuel line from this and ran it again, and hey presto, no more fuel smell. I'll be interested to see if this has fixed my problem on the next run, but it looks good so far.
