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Discussion Starter · #1 ·
I have a 99 Accord ULEV 4 cyl 170k miles automatic that had started running rough and gave me cyl 4 misfire and multiple misfire codes. EDIT: A little quick history:

It started with a code of random misfire but seemed to run fine so I ignored it. I noticed it wasnt getting the mpg it used to. It also shut completely down twice on me while I was driving and I had to coast to the side of the road. I sat for a few minutes and it cranked right back up like nothing ever happened each time. Weird. We drove it on a 2.5 hour trip and on the way back it strted running rough with horrible idle. It would drive ok when at 55-65 but idled really rough. THen it had the multiple/random misfire and cyl 4 misfire codes. Thats when I started replacing things.

Going with the advice of the master mechanic at Autozone I replaced the cap, rotor, wires and plugs. Cranked her up and....still extremely rough and smells like fuel. I went back and he suggested I unplug each fuel injector to test them. I did and cylinder 3 did nothing when I unplugged it. So I bought a new injector, installed it, cranked her up and....frick, still running like crap. What the french toast?! What sends a signal to each injector and what would make an injector not work?

I know, I should have just paid the $70 to the local mechaninc for the official diagnosis!
 

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So you have replaced, the wires, cap, rotor and plugs, and that made no change. So unplugging the injector on #3 made no difference in how the engine ran so you replaced the #3 injector, is the new #3 injector releasing fuel? You can use a long wooden dowel (you can also use a long screwdriver) and place it on each fuel injector and put the other end to your ear to listen for the pintle valve opening and closing. If the fuel injector is working then you should hear the clicking sound if not then the issue is most likely the wiring since you have already replaced the fuel injector. The issue is most likely the connector at the fuel injector, the connector is not that expensive and easy to replace. There is a tool to check fuel injectors that works on the same principle called EFI quick probe, but it cost around $100. As long as all 4 spark plugs are firing, all 4 injectors are releasing fuel, the misfires should go away. The only thing else that can cause a misfire is valve clearance being way off or oil fouling the plugs.
 

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Discussion Starter · #3 ·
I actually did adjust the valves but forgot to list that. Funny thing is that although it still idled horrible, it did seem to idle horribly smoother lol if that makes any sense.

I will check the wiring and see what happens. Thanks!
 

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Do a compression test next to see if there is a mechanical problem with any of the cylinders. Low compression on any cylinder could cause your misfire problem.

Check the new #3 plug as it could be fouled by the old injector before it was replaced.

What codes are you getting now?
 
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