sputtering engine

[pulleye16]

My wife has a 2001 ford focus that when given gas hard, the car begins to shake and sputter. I replaced the 4 spark plugs and wiring harness, just throw in some sea foam in the gas. What would cause this? I'm thinking maybe the fuel filter? It runs ok, but when first starting and when given hard gas, she just doesn't want to go!

Thanks for any help!

[Scott K]

Is the check engine light on? Unplug the Mass Airflow sensor, see if it still does it. Unplug the connector to the Exhaust back pressure sensor (EBP) see if it still does it. Check the fuel pressure while it is happening.

[Jeremy airjer W]

Condensation in the spark plug tubes? May just need a set of wires.

[pulleye16]

check engine light was on. When first started sputtering, replaced all spark plugs and wiring harnesses, much improvement. Engine light is now off (or burnt out,LOL) but now just sputters during Hard excellerations...I'm going to start out cheap and just run some sea foam (maybe bad gas????) and replace the fuel filter. If that doesn't work, I'll check out the fuel pressure and maybe need to replace the pump. I know she likes to run this think on Empty alot so maybe she got some junk in there from the bottom of the tank.

[Powerstroke]

Had the same problem in my 2000 focus. Did the same diagnostics. Finally replaced the fuel filter and it fixed it immediately. I did have a couple bad plugs but it was from the lack of fuel. Engine code said too lean.

[Macgyver55]

I'm not all that familiar with that particular engine, but a cracked/bad coil pack seems a possibility.

[Jeremy airjer W]

I think I would at least see what code is stored in the computer. From your description I would have to say secondary ignition is a factor not fuel. The stored code will give you more insight into what direction to go.

[Glockwinger]

Possible fuel injector. Had a similar problem with a different engine. 2 new injectors and now running good.

[Jeremy airjer W]

You hardly ever see a Ford injectors go bad.

[pulleye16]

Update: After replacing the plugs, wires, and fuel filter, we are still seeing a problem. It keeps getting better, just slightly, every time we'd fix something. I'm going to check the fuel pump next and pressures. The coil pack will be next. I'll run some more sea foam through the injectors as that is how my f150 got cleaned out (and worked GREAT). Everything I've replaced so far should have been done anyways as it was time so I guess no money lost.

[pulleye16]

Macgyver was right! Just finally replaced the coil pack and the car runs like a champ!

[Jeremy airjer W]

Thanks for posting the Fix!