mazda5 RPM bounce between 500 and 1000 from a cold start(idle)

joe379

I want to get a mazda5(2010) through hertz rent2buy program. I tried out two cars. Both have issues with RPM sometimes bouncing between 500 and 1000 from a cold start(put in idle). Initially, I thought that there could be a leak somewhere which usually causes this bouncing RPM. But, after test driving two cars, two cars have the same symptom. I start wandering if this is a "feature" to this 2010 Mazda5. Thank you.

davicho

Someone probably disconnected the battery and did not do the "iddle learn" procedure. MZ5 have an electronic throttle body and requires iddle learn everytime the battery is disconnected.

1. Disconnect battery (once again)
2. Connect battery
3. Get in car and close doors wait for dome lights to go out
4. Turn ignition to ON (but do not start car) to where all dash lights come on
5. Leave it like that for 1- minute (time it)
6. Start car and let it iddle for 5 minutes

Voila!

joe379

Thanks. But, if that is the case, I should always see the RPM fluctuation happen every time it has a cold start. Sometimes, it looks perfect from a cold start.

davicho

Not necessarily! In cold starts it usually just jumps up to between 2000-2500 rpms and stay steady for a few seconds... which is high. Cold starts should be no more then 1800 rpms and quickly settle down to just about 1000 rpms.

You could also clean out the throttle body with some throttle body cleaner sprayed on a rag and wiping the inner bore and the butterfly. Then do a iddle learn procedure.

Just suggesting...

whobodym

thanks to you both for probably perfect answer to my mystery of what happened after putting in new Costco battery yesterday for our 2006 MZ5 5MT -- warm idle fluctuating erratically between 500-750 rpm, almost stalling. The above is certainly worth a try. I'm heading out to try it right after dinner.

PS -- the Mazda OEM positive battery cable end was shockingly weak, I completely ruined it overtightening trying to get a solid connection to the new battery. But a new connector, labeled "marine", costing less than $5 from O'Reilly's was an easy fit after some filing to enlarge the bolt-hole, and adding some washers.

whobodym

and the new "marine" battery cable connector is about 10 times stronger than the OEM one. I'll live with the few-ounces weight penalty sapping my gas mileage, thanks.