Small misfire issue

I have a 2003 2.7l and recently it has been slightly misfiring while idling and normal driving. It only shows it when it is warm. There is no check engine light and it is not overheating or any other sign of engine problems. The miss is very slight but interrupts the powerband while driving. My dad thinks it might be the fuel filter or water in the fuel. Any ideas?

 

How many miles on your truck?

Water in gas is very unlikely as the system is pretty well sealed and ethanol will hold a fair amount of water in suspension and generally burns with no noticeable effect. Maybe: fuel filter, dirty injectors, spark plugs, MAF (especially if you have an aftermarket air filter). A misfire should light the check eng. and leave you a code indicating which cylinder(s) are missing unless it's really brief. If you're overdue for any maintenance, handle it. I'd also feed it a bottle of Techron injector cleaner and see. It has cured MANY little issues for me and my customers.

 

About 174000. There is no check engine light at all which is what is puzzling me. I was going to run an injector cleaner through it as well as run a tank of premium gas. As well I bought a complete fuel system cleaner and an octane booster and was going to try that as well. If the plugs are black and such would it cause that issue?

 

Absolutely. I would also just change the plugs. Also.check your coilpacks for damage as well as any cracks in the spark plug wires.

 

Don't bother with premium or octane boost, they'll do nothing for you. Black plugs is an indication that something is wrong and it's running rich or burning oil, rich should have triggered the light. Were they black and wet, or dry when you pulled them?

 

I havent pulled the plugs as I replaced them about 2000 miles ago. I ran the injector cleaner and a fuel system cleaner this morning and will see how that goes when my tank is gone. I'm thinking I will replace the fuel filter on it next but if it is not that I have no idea what it is. Does anyone know where the fuel filter is on my model year/engine?

 

under the intake manifold. Its a full day project for sure. Took me 5 hours to do mine.

 

It ended up being an ignition coil in cylinder 4 causing the issue. Thanks for everyones help!

 

it took 5 hrs to change a fuel filter? i did mine in about 35-45 mins, used a 2 ft extension and universal joint with a deep well socket, went in through fender well for bottom bolt and manifold for top belt, theres a video on youtube somewhere, take it out as an assembly not just the filter, way easier.