Severe engine hesitation or stumble

  • 4.0L
  • 6 CYL
  • 2WD
  • 115,000 MILES
Recently my step son was driving his car when it began to stumble or hesitate very severely to the point that he had to pull over and have us come get him. The car will start and idle fairly well but when you attempt to give it gas, the engine will not accelerate and will stumble and many times stall. I cleaned the throttle body and MAF with appropriate cleaners, changed the fuel filter, the spark plugs and wires but the problem persisted. I also added fresh gas thinking he might have gotten some bad gas, but did not drain the tank. Still no change in how the car runs. The check engine light has not come on and when I check with my OBDII tool, no codes are indicated. I wondered about the fuel pump being the culprit but the OBD tool showed fuel rail pressure of about 40-50 psi with no big drop when I try to give more throttle. I also wondered if the MAF or ECM could be bad, but with no trouble codes to guide me, I am at a loss. Any suggestions on further diagnostic work-up I can preform or is it time to get a mechanic involved who has more specialized diagnostic tools?
Thank you
Do you
have the same problem?
Wednesday, March 29th, 2017 AT 3:10 PM

1 Reply

Check fuel pressure with a gauge auto parts rent it. It should be 35-70 with key on only which yours does not sound bad. Then check for vacuum leaks like a hose off etc. Sounds like this has been the 16yr old test and he is not telling you everything.
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Thursday, March 30th, 2017 AT 6:37 AM

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