About 2 months ago, my car was running really rough and I pulled the CEL for Multiple Misfires. I changed all my spark plugs (with NGK OEM plugs) and narrowed it down to bad fuel injectors in banks #2 and #6.

Last night my car started to act up again. I pulled the CEL today and there is a misfire in Cylinder #1 now. I am sure it is the fuel injector, because the symptoms are the same. I bought some fuel injector cleaner and have put about 30 miles on since. Nothing has changed.

My question: What is causing these fuel injectors to go bad? Is it that my car is old and has 110,000 miles on it? Could something be causing them to go bad (perhaps upstream)?

 

What makes you think it's the injectors and not the coil packs? Do you not hear the ticking noise that they make or something? Especially if you are talking multiple failures, I would think about the coil packs first. Often, they will intermittently fail (ie. misfires) before they die completely.

 

The last time my car was misfiring (the 2months ago), it was 2 bad fuel injectors. I just tested all coil packs 2 months ago. They were all good.

The symptons are very similar to before. Rough and very shakey, hesitant before 2k RPM. A strong gasoline smell from the exhaust, with a lot of "fluid" coming out of the muffler. I have yet to test the fuel injector in bank #1 with a multimeter, but I am pretty certain its the cause.

 

i had a misfire on mine then i changed the spark plugs to new ngk plats, problem went away. then i started to feel my engine hiccup at red lights and stop signs. i have a 99 and coils are **** so i changed them to Mitsubishi coils (from Hanshin) i gained .2 secs in the 1/4 and now my engne purrs like a kitten with very linear acceleration.

do yourself a favor get a good multimeter and check the ignition coils (Haynes manual has the steps on how it's done)
i got my mitsu coils from courtesy nissan with maxima.org discount for $56-$58 each

and for fuel injectors, get 2 bottles of fuel injector cleaner and use it on your next 2 fillups, should clean them out. or get a complete fuel system cleaner from STP (about $6-$8 @ Autozone) it can't hurt but usually results in better throttle responce and easier revving after 4K+ rpms

 

Since you need gasoline, air and spark to generate power, and you have a strong gasoline smell from the exhaust. I'd be guessing that either either it doesn't have air, or spark, because if your injector was clogged the partial fuel would have been burned up before being pushed out the exhaust. And since there isn't many ways to block air, I'd be guessing that it's a bad ignition coil.

Also, since you had 2 injectors clog before... have you changed your fuel filter lately? If that sucker clogged up, it might feel like a bad injector.

 

Since coil packs are easier to test than the Bank #1 fuel injector, I'll check that first. If that comes out okay, I'll just assume its the fuel injector.

Fuel filter-Lately? No its about 6k old. I have a spare, I should just change it anyways.

 

6k should be fine, they should last about 30k at least. Unless your local gas station got a bunch of dirt or other junk in their tanks.

 

Testing coil packs with an ohm meter is unreliable. I've got a whole set in my garage which test pefectly, but place them in the car and they will missfire. I would suggest the following:

Switch the coil pack on the cylinder thats misfiring with the one next to it. If the misfire codes switchs to that cylinder, then you know its the coil pack. If the misfire code stays the same, then you have an injector problem. Good Luck

 

That has been my experience also.

 

A good suggestion. I'm getting code 0201 which relates to the primary iginition circuit. It may be a coilpack issue. Any suggestions on the best way to troubleshoot this problem if the code for the specific misfiring cyclinder is not given?

A friend offered me two suggestions:
1. Wait for the "proper" error code that indicates which cylinder is the problem.
2. Change all the coilpacks.