[SMORGAN]

I have 2003 Nissan Frontier w/ 4cyl. Auto. The engine shudders under light acceleration at low rpm. If I press the pedal on down or let off completely it seems to smooth out. I am getting a code for " cylinder # 1 misfire". I replaced plugs, wires, cap and rotor with no noticeable improvement. My mileage has went from 26mpg to 19 and I noticed the tail pipe is sooty black. Any hints would be appreciated. Thanks.

[CaptainRich]

I have 2003 Nissan Frontier w/ 4cyl. auto. The engine shudders under light acceleration at low rpm. If I press the pedal on down or let off completely it seems to smooth out. I am getting a code for " cylinder # 1 misfire". I replaced plugs, wires, cap and rotor with no noticeable improvement. My mileage has went from 26mpg to 19 and I noticed the tail pipe is sooty black. Any hints would be appreciated. Thanks.

Misfire on Cylinder # 1. You've addressed the secondary ignition system.

I'm going to say the # 1 fuel injector is sticking open. This will need to be verified by whoever is going to do the repair(s).

If the fuel injector doesn't fully close, more fuel will be allowed into the engine, resulting in a ruff-run/misfire. And the unburned excess fuel will show up as soot at the tailpipe.

A good professional cleaner, properly done, may free up the injector. Don't try to use the stuff that goes into the tank. The only thing that cleans is wallets.

If the injector is sticking, and it doesn't come clean, it would need replaced.