MYSTERY SOUND

my 08 2.7 makes a strange sound on start up. it sounds like something being sucked closed and then my ideling drops down to normal. im pretty sure its nothing but im one of those guys who cant stand a noise and not know what it is. does anyone else have this sound.
thanks.

 

ok thanks man, thats one of the many great things about this forum there are not many unsolved problems.

 

It's an emissions related air injection pump. Look for a small electric motor located in the engine bay on the passengers in front of the engine. It pumps fresh air into the exhaust manifold during cold startups, which causes a sort of 'afterburn' effect and heats the catalytic converter up faster.

When I first got my truck I had a hard time finding info on this topic. It's not discussed on this forum very much, which means people either aren't aware of it (despite the 'shop vac' sound at startup), or people don't have many problems with the pump failing.

Anyway, don't worry, it's totally normal.

 

Ya it's like a pissing/whistling sound about 15-20 seconds after startup, after which the RPMs immediately begin to drop. It's normal, mine's been doing that on every cold start since I got it.