Misfire caused due to change in altitude and ambiance temperature

[Max Fernandez]

Greetings, I had to post this thread to see if anyone of you had a similar situation to what happened to me last week. I have an Expedition Eddie Bauer 2007.

I live in Bogota, Colombia. The city is at 2.600 meters above sea level (8.500 feet) and with a regular temperature of 12-14 Celsius (mid 50's Fahrenheit). I traveled to visit family in my expedition to a city at 1.000 feet above sea level and with temperatures of 95 Fahrenheit.

During my trip, my expedition started to misfire, once in this city, the failure was getting worst. No check engine light came up and I checked the truck with a scanner with no codes shown. We took out coil plugs and spark plugs and everything was perfect.

In the end, the technician told me that this could be caused due to the oxygen/fuel governor was not working ok and the setting of the truck was still for a high altitude environment. When I returned home yesterday, the truck is running smoothly again.

Any ideas of what could cause this and if there are any sensors I should be looking to change? This is the first time I see this happen and I plan to continue traveling other places with my truck, so all the help and advice you can provide will be much appreciatted.

Thanks and happy new year!

Max

 

[1955moose]

The fuel mixture is leaner up in the altitudes, at least that's what's ideal for the thinner air. Did a shop or you lean out fuel trim? The computer normally will adjust for different altitudes, that being said though, if you have anything that's not perfect, IE, exaust or intake leak, etc. Also unless you have X-ray vision, how can you know a sparkplug, or a coil, or coil boot are functional? These items need to be tested, or seen on a advanced scanner that can read KV readings. I'm thinking your running too rich down at sea level, and need to find out why.

Sent from my N9131 using Tapatalk

 

[TobyU]

I don't believe what the tech said.
These things adjust all the time and almost instantly. Short term and long term fuel trims etc.

I would lean more toward moisture or condensation (was it rainy) in a plug well.
It is amazing how much oily residue and condensation can collect in the plug well and on the boot.

You need a scan too that will show test results with misfire counts for each cyl.
A bad repeated misfire like completely no spark of fuel to that one will give a flashing check eng light quickly. A on and off can take a long time but the test results will show right now.
So you know which cyl to check.

 

[Max Fernandez]

Thank you both for your feedback. I had the coils tested on a bench for performance and they were working ok. The truck has been running perfectly since I returned home at the regular altitude. I think there is a fuel/oxygen sensor not working as this should adapt instantly to different environments. Does this make sense to you? Do you know any particular area I should be looking for?. I had a scanner during a run test looking for data in each cylinder and even when misfiring the data did not show anything irregular. Thanks again for all the support.

 

[TobyU]

If you have a scan tool that shows cylinder misfire counts it is going to show an increase number anytime you feel an engine misfire. Once you reset the codes you will lose this information. You have to rescan it to see it also.
You can watch the oxygen sensor in the monitor results to make sure it's working properly and switching low voltage to high voltage and back and forth every couple of seconds. You can also make sure that your fuel trims are not getting high. They should be low the most vehicles the long-terms being down 3% or less. The short terms bounce around a lot but if you're idling or rolling at a steady speed they should reduce down to lower.

 

[Mad Oshea]

I drive My XLT 5.4, at 5,000 ft to 11,000 foot above sea level. At the top elivation, at 15% humidity I use the lowest octain gas. When I drive in lower elevations, I burn a hi octain. The Pcu will take care of the rest. I do run with PLASMA plugs. Not split fire. PLASMA.