Hard Start/Rough Idle only in Florida Climate
 

My 06 E53/M54 has an odd problem.

When home in FL climate it struggles to start from cold, and once started I need to bring the RPM up a little for just a second and then the idle stabilizes.

Just did a road trip to Ontario for 2 weeks and the car had zero issues the entire trip. Started right up every. Single. Time.

We get down to around Georgia and now it's back to hard starts and poor idle. Every. Single. Time. (When cold. Once engine is hot it's good again)

New plugs. New CCV. New thermostat. New O2 sensors. New Intake Side Cam Position Sensor.

I'm wondering if the MAF could cause this? Or if there's something else I should look at?

It burns about a Qt of oil every 900 miles (now that the oil leak from the oil filter housing gasket has been fixed!) so initially I was wondering if it was just CCV leaving oil in the intake that needed to burn off before idling smoothly. But new CCV and no issues in cooler dryer climates for weeks. So thinking it's not an oil issue.

If the plugs weren't new and the problem didn't exist prior to changing the plugs I'd suspect those. But the problem has existed since owning the car. This trip up north just gave me more feedback to diagnose with in terms of climate and humidity.

It also continues to have an issue where it stalls (infrequently) at low rpm around corners. This issue also did not exist in the cooler climate.

Does e53 have IAC? I'm thinking it's an altitude thing and at higher altitude the mix is calculated better at start.

What scan tool are you using?

Mine will show me atmosphere pressure, MAP, throttle position sensor and (both). I also bumped my idle speed up 25-50 Rpm.

A cold engine starts in open loop. In open loop the ECM controls the air/fuel mixture reading input from sensors. Might be a bad MAF, coolant sensor or thermostat. Try cleaning the MAF with MAF cleaner. Spray liberally. Be sure to spray the wires that are kind of hidden. Doesn't always work but worth a try.

Good points. Read all the temp sensors and MAF realtime values. A week or two ago a few of us posted the MAF rate at idle for reference. Search MAF and g/sec I don't remember what thread.


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Don't you mean open loop controls the mixture from a look-up table and NOT from sensors...? Once the sensors are in play, the loop is closed.... ;)

ECM does use stored maps but also uses sensors such as temp sensor etc. When in open loop the 02 sensors are not in the equation.