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Dan, Technician
Category: Chevy
Satisfied Customers: 23943
Experience:  Independent Shop Experience, 2 Year Automotive Diploma, & Access to Information Database
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Chevy trailblazer: i have a 2005 trailblazer 4.2 4x4. When

Customer Question

i have a 2005 trailblazer 4.2 4x4. When i come to a stop light and i sit there for a minute the cars rpms will drop then rebound and sometimes will kill the car and i feel like the car has really bad hp if i gas it and its reving up when it hits around 5k rpms something seems to kick in and then it really takes off
Submitted: 2 years ago.
Category: Chevy
Expert:  Dan replied 2 years ago.
Hello, my name is ***** ***** I'm here to help get your problem solved. It sounds like your catalytic converter may be starting to clog up, possibly a failing mass airflow sensor. Try to disconnect mass airflow sensor to see if that helps, if so replace. If not then next step I'd recommend is a exhaust pressure test, if pressure goes over a few psi during problem while reving engine then replace the converter. If exhaust pressure test is good then move onto fuel pressure test. Let me know how it goes or if you have more questions, thanks.
Customer: replied 2 years ago.
it does not have a mas it has a map sensor and when i unplug it nothing changes at idle i have not drove with it unpluged i feel like it is the iac but that is a one piece to the throttle body and dont want to spend 400 on a new one yet till i know for 100% that is the problem
Expert:  Dan replied 2 years ago.
If you unplug the throttle body, does that prevent idle issue from happening?
Customer: replied 2 years ago.
i unplugged the iac on the throttle body and the car runs like crap when i do
Expert:  Dan replied 2 years ago.
Check engine light on?
Customer: replied 2 years ago.
when i unplug it yes but not any other time
Expert:  Dan replied 2 years ago.
I agree the throttle body has most likely failed. To know for sure a scan tool with capability to monitor pedal position sensor and PCM command to throttle body. If everything else was working properly during problem but not throttle body response that would prove throttle body is the problem. These are common to fail but cleaning does often help. Let me know how it goes or if you have more questions, thanks.

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