Recently I had a rough idle during a cold start--the whole truck would shimmy when I started it. Plus the fuel mixture smelled a little rich on initial start up. Figured it was the IAC that was going bad, so I replaced it. Once replaced it the throttle body had a rattling/ticking sound that could be heard from inside the cab. Drove the blazer around the block to see if it just needed to run for a bit for the rattle to go away. No dice. Thinking it could be a defective IAC, went and got a new one and installed a 2nd new IAC. The rattle/tick didn't go away after I installed the 2nd new IAC, so I reinstalled the original IAC. Rattle/tick was still there. I ensured there weren't any loose wires/components when I installed the IACs, so what could have caused the rattle/tick? I did not remove the throttle body and clean it, so could that be what's causing the noise?


I'm new at performing maintenance on my blazer, so please be patient if you recommend something and I don't understand right away. Thanks.

 

Normal for the IAC to make noise. When the PCM adjusts it, the motor inside moves in "steps" not a smooth motion. Some IAC's you can hear, some you can't.


The IAC will not cause a rich fuel mixture or cause the engine to run rough. Is the check engine light on? If so, have the DTC's retrieved and post them here in the order they are retrieved.

 

engine light is not on.

 

If the light works, (comes on and goes off with the bulb check) the problem is something that the PCM does not monitor. Next step would be to check fuel pressure and leakdown. This link explains how to check it: https://blazerforum.com/forum/2nd-ge...eakdown-88305/

 

ok. i'll try that and let you know how it goes. appreciate the help.