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

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: Okay, my ignition is spinning loose and the car is stuck with the auxiliary on but wont start has no pressure.

Hi there. If the ignition switch is moving around, then the tabs that lock the switch in place on the switch are either broken or damaged. I recommend replacing the ignition switch. If you need further assistance with replacing the...

Q: Replacement AC compressor labor cost

The AC may have a leak somewhere that is causing the AC to cycle on and off. The compressors on these vehicles are known to go bad and contaminate the entire system with compressor internal parts. The system will need...

Q: Dies during idle or when put in gear.

Hello, and thank you for writing in. Everything you have done so far has been helped narrow down possible issues. You should check your vacuum supply at the intake, the intake air temperature sensor, your oxygen sensors, and the possibly...

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...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the P0052 code means This code is seen when the Engine Control Module (ECM) tries to control the...
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...