Rodent chewed injector leads: misfire after repair
lgw1
03-31-2007, 10:13 AM
First time for me to post on a forum, although I appreciate that so many people take the time and are willing to share their knoweldge and experience, which is humbling to this long time do it yourselfer; I usually can figure it our or make it up as I go... I've done the light work maintaining numerous old cars, motorcycles and boats.
My son has a 2001 Nissan Altima. On a recent cold day he drove the car in the morning, then parked it. When he went out in the afternoon it ran very rough and the check engine light came on and blinked. He brought it to me to look at two days later.
A quick look under the hood showed both the lead wires to the #3 fuel injector, right above the intake manifold, were gone. Only short stubs at the injector connector and at the (fortunately substantial) plastic harness channel. Also one of the two leads on the #4 cylinder was severed. Not rocket sience to deduce a rodent got up on the warm engine and made space to curl up. There is no other evidence of the culprit; fur, droppings, nuts or twigs, etc. however the damage to four wires (one was chewed but not separated) were definitely not cut with a tool. He always locks the car.
I was able to solder lengths of wire back in place, using the short stubs that were exposed. It immediately ran better. I had the codes erased from the computer and had them read after a short run. Thanks for courtesy assistance by a local auto parts outlet. The check engine light started blinking after half a block. The new code shows a misfire on cylinder 3.
I checked the resistance on all injectors and the #3 is consistent with the others. A buddy (formere mechanic) loaned me a set of injector test lights. The #3 connector is dead. I am confident the solder connections are good. I coated the repairs with silicone (little room for tape) sealant and they are separated by enough space that they do not touch to short each other.
My questions to the AF community:
Is there another test port I can check to see if the computer is sending a signal? Do I need to invest in an analyzer (suggestions?) to do so?
Or should I:
Cave (I mean recognize the limitations of shade tree efforts) and take it to a shop (I have two I would trust with the problem) with the necessary diagnostic equipment?
Replace the ECM which was, in all likelhood toasted by driving (I routinely buy from a local auto parts recycler)?
Other suggestions?
Thanks
My son has a 2001 Nissan Altima. On a recent cold day he drove the car in the morning, then parked it. When he went out in the afternoon it ran very rough and the check engine light came on and blinked. He brought it to me to look at two days later.
A quick look under the hood showed both the lead wires to the #3 fuel injector, right above the intake manifold, were gone. Only short stubs at the injector connector and at the (fortunately substantial) plastic harness channel. Also one of the two leads on the #4 cylinder was severed. Not rocket sience to deduce a rodent got up on the warm engine and made space to curl up. There is no other evidence of the culprit; fur, droppings, nuts or twigs, etc. however the damage to four wires (one was chewed but not separated) were definitely not cut with a tool. He always locks the car.
I was able to solder lengths of wire back in place, using the short stubs that were exposed. It immediately ran better. I had the codes erased from the computer and had them read after a short run. Thanks for courtesy assistance by a local auto parts outlet. The check engine light started blinking after half a block. The new code shows a misfire on cylinder 3.
I checked the resistance on all injectors and the #3 is consistent with the others. A buddy (formere mechanic) loaned me a set of injector test lights. The #3 connector is dead. I am confident the solder connections are good. I coated the repairs with silicone (little room for tape) sealant and they are separated by enough space that they do not touch to short each other.
My questions to the AF community:
Is there another test port I can check to see if the computer is sending a signal? Do I need to invest in an analyzer (suggestions?) to do so?
Or should I:
Cave (I mean recognize the limitations of shade tree efforts) and take it to a shop (I have two I would trust with the problem) with the necessary diagnostic equipment?
Replace the ECM which was, in all likelhood toasted by driving (I routinely buy from a local auto parts recycler)?
Other suggestions?
Thanks
UncleBob
04-01-2007, 03:49 AM
its possible (but IMO unlikely) that the unattached wires grounded and took out a driver in the computer....but I've repaired many rat damaged wiring harness', especially injector harness' (they really like those and ignition wires) and I've never seen a computer have a problem from it
I would recommend double checking your work more thoroughly. Test for injector pulse before your solder job. If you don't have pulsing, you need to see what side of the signal is missing. One lead will have constant positive power, the other will have pulsing ground signal.
If you are missing the ground, that is fed from the computer, at that point I would test it at the computer. If you are missing the power side, that is most likely directly from the power distribution box
I would recommend double checking your work more thoroughly. Test for injector pulse before your solder job. If you don't have pulsing, you need to see what side of the signal is missing. One lead will have constant positive power, the other will have pulsing ground signal.
If you are missing the ground, that is fed from the computer, at that point I would test it at the computer. If you are missing the power side, that is most likely directly from the power distribution box
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