Skip the auto shop - Our mechanics make house calls

Q: #1 cylinder is misfiring.

asked by on

My #1 cylinder is misfiring fairly consistent (occasionally #5)...primarily at idle. im pulling code 0172 suggesting a faulty fuel pressure regulator. I have replaced all ignition parts with factory brand (plugs, wires, cap &a rotor). I am leaning more towards a faulty injector rather than a regulator. What are your thought? Can a regulator cause a misfire? By the way the plugs are not fouling out ... they look fresh as the day I put them in.

My car has 225000 miles.
My car has an automatic transmission.

Hello - I think your diagnostic skills are working well on this one. If the misfire is consistently a particular cylinder, that plug, wire or injector is certainly more suspect than anything else. A faulty fuel pressure regulator would have other symptoms, misfiring is possible, but less isolated and more random. Given your mileage, check the distributor for slop in the shaft that could cause "wobble" and misfiring as well. For additional technical expertise on this one, I would recommend having a Engine is Misfiring Inspection completed by a mobile, professional mechanic, such as one from YourMechanic, to diagnose this problem, get an accurate assessment of damage and cost estimate for repairs.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: My Ford Expedition shuts off while driving and theft light comes on and beeping sound

Hello, It sounds like something has triggered your theft control system. This system is designed to cut off power to the vehicle when it is triggered which is why it cuts out as you try to accelerate. This can happen...

Q: Truck isn't engaging into 4 Hi, but will go into 4 Low.

Hi there. Sounds like the shifter module motor or shifter rail is not working properly. Check the wiring on the shifter module motor on the transfer case and see if the wires are split or damaged. If the wires are...

Q: Not starting when moisture in air

When you do get your vehicle to start, open up the hood while your engine is idling and get a spray bottle with water in it. Spray the spark plugs and wires to see if you start getting misfires and...

Related articles

P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.