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.

A: Hello - I think your diagnostic skills are ...

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: I have a 1998 ford ranger(AT) its shifting roughly, when i come to a stop, the truck wants to keep going, and as a result, the truck stalls out.

The torque converter clutch is not releasing as the transmission is shifting. Try pulling the fuse to the torque converter labeled as TCC and see if the symptoms change. If the vehicle stops acting up, then the torque converter clutch...

Q: Car shaking

Hello. This vehicle uses a center driveshaft support bearing (carrier bearing) on the rear driveshaft. This is a commonly known issue that I have seen go bad and cause vibrations around that speed. To confirm this, I recommend having a...

Q: My truck surges at low and idol speeds. Cold or hot. Sometimes quits when put in gear. Very low speed has a miss.

Hello and thank you for contacting YouMechanic. When you unplug the temperature sending unit the problem goes away but the engine light comes on. Check the plug to the sending unit for any corrosion or debris. Look at the pins...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
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.