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Dino, Technician
Category: Car
Satisfied Customers: 5716
Experience:  have lots of general auto exp in all cars over 24 yeas in this profession
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2000 chevrolet blazer surges, why?

Resolved Question:

2000 chevrolet blazer surges, why? at idol in nuetral rapidly and in drive every 30 seconds or so
Submitted: 6 years ago.
Category: Car
Expert:  Dino replied 6 years ago.

hello welcome to the site.

has the coolant level been checked ?

the iac control this but relies on temp readings from the engine coolant.

please check to see if its low or empty.

also is the check engine light on ?


Customer: replied 6 years ago.
no check engine light is on and it was just in for an oil change and no mention of low cooling fluid
Expert:  Dino replied 6 years ago.

ok i would double check just to be sure.

if the level is ok then a faulty idle air control valve will need to be tested to confirm its failing or failed.

also i would check the pcv valve and also spray some carb cleaner around the intake manifold to see if you have a vacuum leak.


here is a idle reset procedure to try before you start replacing parts.but first check for any vacuum leaks



The Vehicle Control Module (VCM) controls idle RPM with the Idle Air Control (IAC) valve. To increase idle RPM, the VCM retracts the IAC pintle from the seat, allowing more air to bypass the throttle plate. To decrease RPM, it extends the IAC pintle valve in towards the seat, reducing air flow through the IAC valve port in the throttle body. A scan tool will read the VCM commands to the IAC valve in counts. The higher the counts, the more air allowed (higher idle). The lower the counts, the less air allowed (lower idle).

IAC Valve Reset Procedure

Without Scan Tool

  1. Start the engine for 20 seconds .
  2. Turn OFF the ignition for 10 seconds .
  3. Start the engine.
  4. Check for the proper idle speed
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