Long Crank Starting Issue 4.7

Having an intermittent issue with very long cranks. Seems to be worse during hot weather. Then i drove down to sea level and it didn't happen at all. Resumed having long crank issues as soon as I got back home to 4,000 ft elevation. Seems like AFR calculation is off while attempting to start maybe? Should I be looking at MAF and O2 sensors? No codes and like I said, truck started great 100% at sea level. Truck runs fine once it does finally start though.

 

Have it recalibrated at the stealership.. I think they still do it free99.. When I lived in Reno, I remember thwm saying something about recalibrating the ECU for altitude. I'd call ahead referencing that issue.

 

I'll look into that tomorrow. It's just strange that the truck has been at altitude its whole life of 180k miles and just recently started doing this. I just noticed the issue went away at sea level.

 

Food for thought. The age of your 2008 truck would qualify for this reminder.

Keep in mind that the truck has an immobilizer system (aka: anti-theft). The chip in the key, or FOB, must perform a handshake with the immobilizer system before it (the immobilizer system) will authorize the spark to make the engine go BANG. If the battery that runs the chip in the key, or FOB, gets low on juice, the key will turn (or button push) and the engine will crank and crank and crank but not fire. The immobilizer system believing the car is being stolen and therefore shutting down spark.

 

My truck started with 100% reliability at sea-level. Why would the immobilizer/ key fob be an issue at 4k feet and not sea level?

 

Posting incase this helps someone in the future. The issue with long cranking at start up was the MAF sensor. Cleaning it didn't help so I replaced it. Truck starts 100% now.