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: Car hard to start and idles rough

A rough idle will usually indicate that the engine isn't running at its peak efficiency, and needs some attention. The hard start condition will also suggest that the engine isn't running its best. The things I would look into would...

Q: Fuel gauge stopped working and now gas tank won't let me pump more than a few gallons at a time.

The refueling problem is due to the fill pipe in the tank. The fill pipe has a smaller hose inside of the larger pipe which keeps you from overfilling the tank. If someone tried to siphon fuel from your vehicle...

Q: Reverse gear not working

To rule out a hydraulic fault, you can check for adequate line pressure, using external gauges, while in the various gear positions. If pressure is out of spec. you would then look at the valve body for leaks but it...

Related articles

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...
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...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...