engine speed hunting at hot idle

eastavin · Post by **eastavin** » Tue Jun 24, 2008 1:16 am

2007 model, auto. With a hot engine (a/c off) at idle I can watch the tach move between 800 and 1000 rpm every 15 seconds or so like someone throwing a switch. Is this normal in a vibe/matrix? I am used to a rock steady idle unless there is a vacuum problem of some kind with my GM cars. Is there anything to check for that might provide a clue if I hook up my neighbours live engine data reader?

joatmon · Post by **joatmon** » Tue Jun 24, 2008 1:18 am

I wonder if it might be the engine cooling fan cycling on and off. When the fan comes on, it puts a little more load on the engine, and the computer will kick up the RPMs a little to compensatewelcome to genvibe!

zionzr2 · Post by **zionzr2** » Tue Jun 24, 2008 4:43 am

Quote, originally posted by joatmon Â»I wonder if it might be the engine cooling fan cycling on and off. When the fan comes on, it puts a little more load on the engine, and the computer will kick up the RPMs a little to compensatewelcome to genvibe!That would be my thought as well!

ajconover · Post by **ajconover** » Tue Jun 24, 2008 1:08 pm

I find I get a bit of idle speed fluctuation as well, especially when stopped in hot weather and sitting in drive. I also find the idle a bit rough with the Vibe in gear, so if I'm stopped at a longer light, I generally shift into neutral, which seems to smooth out the idle.

Lancer · Post by **Lancer** » Fri Jun 27, 2008 5:31 am

You all have automatics, right?

engine speed hunting at hot idle

engine speed hunting at hot idle

Re: engine speed hunting at hot idle (eastavin)

Re: engine speed hunting at hot idle (joatmon)

Re: engine speed hunting at hot idle (eastavin)

Re: engine speed hunting at hot idle (ajconover)