Q: Hesitation occasional misfire and poor mpg

asked by on

Had a very long cranking time to start idled very rough and had poor power/acceleration. occasionally when I first start the car there is almost zero power even with the peddle to the floor and it will backfire a few times. But not a normal back fire it sounds a lot quieter, and comes from the front of the vehicle inside the engine bay. After a few pumps of the peddle it's like it never happened and the rest of the drive the car runs normally. I changed the fuel filter and it smoothed out the idle. I opened to intake plenum, back two cylanders we're washed clean, so I replaced the fuel pressure regulator. solved the long cranking. Now the hesitation/power/poor fuel economy problem. So far replaced worn dist cap and rotorand map sensor also plugs and wires. Got a touch better. Then unplugged the maf and got a little power and acceleration back. So bad maf? Or something else being masked running in open loop?

My car has 150000 miles.
My car has an automatic transmission.

The MAF is a possibility. I think it is also possible that one or more injectors are clogged or malfunctioning as the symptoms you describe sound like that of a fuel system issue. I would recommend having the fuel injectors and mass air flow sensor tested with a digital multimeter to determine if they are within the manufacturer’s specifications. If not, replace any parts that fail to meet specifications.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. Hesitation occasional misfire and poor mpg

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: How many air bags does my car have?

Your vehicle has 10 air bags: frontal air bags for both the driver and the front seat passenger; knee air bags for both the driver and front seat passenger; seat-mounted side impact air bags for the driver, the front seat...

Q: Truck idling higher than normal.

I would recommend taking the vehicle back to the facility that replaced your TPS and ensure that the throttle body gasket was replaced as well. If the gasket was not replaced a vacuum leak may exist near your throttle body...

Q: Service engine light is on and blinking when started?

The check engine may be blinking due to computer sensor or misfire issue. Have the computer scanned to get the failure codes and then have the codes diagnosed. You may have a lean injection system causing misfire when first started...

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...
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...
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...