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Ask Chris (aka- Moose) Your Own Question
Chris (aka- Moose)
Chris (aka- Moose), Technician
Category: Ford
Satisfied Customers: 47956
Experience:  16 years experience
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I have a 2005 ford taurus 3.0 it idles rough and check engine

Resolved Question:

I have a 2005 ford taurus 3.0 it idles rough and check engine light comes on and has a 300 code a misfire in cylinders. seems to run good just idles bad. has new plugs wires fuel filter.
Submitted: 7 years ago.
Category: Ford
Expert:  Chris (aka- Moose) replied 7 years ago.

Was that a P0300 code or was it another code?

How many miles on the vehicle?

Does it miss at idle or does it just idle up and down?


Customer: replied 7 years ago.
the code they said was 300 misfire in cylinders. the car has 132000 miles and it seems to be missing only at idle.
Expert:  Chris (aka- Moose) replied 7 years ago.

Hello Customer


Thanks for visiting us Technicians here at Just Answer. I will do all I can to answer your question fully and understandable. If you need more assistance on this matter please just hit reply and do so, you can even reply after hitting accept. If this has solved or helped you understand the fix then my efforts can only be rewarded by hitting the GREEN ACCEPT BUTTON. I strive to maintain good feedback so do reply with any form of results.


Thanks Chris


Your next tasks are to check fuel pressure with the key on---engine running at idle----engine running at 2500 rpm. If its low at any point then the pump and or filter or regulator are faulty.


Next you need to use a sophisticated scan tool and monitor power balance and see if its one cylinder or all of them misfiring.


You then need to run a compression test on each cylinder to see if any are low from valve train fatigue or headgaskets or engine wear.

Customer: replied 7 years ago.
if it had bad fuel pressure it wouldn't have plunty of power at high rpm? which it does, if u have worked on lots of fords could the coil cause this or another sensor? it dosn't smoke runs supuberb.
Expert:  Chris (aka- Moose) replied 7 years ago.

Fuel pressure changes up and down at different rpms. Yes you can have low pressure issues at idle. This may not be the problem but it is one check which must be done.


Coils usually cause a misfire around 45 on hills while lugging. This is when weakness starts to show up first. If you feel its the coil causing this then replacing it is a cheap option to try rather than performing other diagnosis steps.

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