Q: Hesitation occasional misfire and poor mpg

asked by on July 10, 2017

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.

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