The engine will start but will not idle?

RTHDC35

MEMBER
2004 GMC SIERRA
6 CYL
2WD
AUTOMATIC
65,000 MILES

The engine will start but will not idle. I have replaced the fuel filter. I can keep the engine running by using the gas pedal but when I let off it tries to idle but it will die if I don`t give it more gas. The old filter was almost completely clogged. I can hear the pump running but don`t know how much pressure there is or if the new filter is partially clogged. I don`t have a fuel pressure gauge. Can I take a line apart someplace & check for fuel?

Thursday, May 6th, 2010 AT 12:35 AM

1 Reply

SQM

MECHANIC
6,383 POSTS

Hello,

You might have an issue with he mass air flow sensor. If the sensor is dirty it can trigger similar issues that you are having.
Many times servicing the mass air flow sensor by cleaning it can fix the issue.
The mass air flow sensor is located at the end of the air intake tubing just before the air box (see diagram).

You might find these articles helpful:

https://www.2carpros.com/articles/how-a-mass-air-flow-sensor-works-maf
https://www.2carpros.com/articles/mass-air-flow-service

Its likely not a fuel pressure issue. As if it was the fuel pressure that it is likely that the engine will not stay running regardless of throttle input.

I have attached diagrams for your reference.

Please let me know of any questions.
Thank you.

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