# What's wrong with my truck (loss of power)? **URL:** \ **Category:** Factual Questions\ **Created:** [March 7, 2008, 11:53pm UTC](https://boards.straightdope.com/t/whats-wrong-with-my-truck-loss-of-power/440535 "2008-03-07T23:53:52Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![St.Urho](https://avatars.discourse-cdn.com/v4/letter/s/8e7dd6/32.png) [@St.Urho](https://boards.straightdope.com/u/St.Urho)\ **Post date:** [March 7, 2008, 11:53pm UTC](https://boards.straightdope.com/t/whats-wrong-with-my-truck-loss-of-power/440535/1 "2008-03-07T23:53:52Z")
I have a 2004 Ford Ranger that I just bought 2 months ago. It has 50,000 miles, the 4.0 L V6 and four-wheel drive. I drove it up I-70 into the mountains today, and a couple things happened. First of all- it has absolutely NO power over 4000 rpm. I had my foot to the floor, and I was only going about 50 mph- the fully loaded semi’s were passing me! While this was going on, it shifted very awkwardly- it’s an automatic and shifts fine othewise. It also had a misfire at one point- I pulled right over and turned the truck off, it hasn’t happened since. Any thoughts? ---
**Author:** ![CynicalGabe](https://avatars.discourse-cdn.com/v4/letter/c/3e96dc/32.png) [@CynicalGabe](https://boards.straightdope.com/u/CynicalGabe)\ **Post date:** [March 8, 2008, 12:35am UTC](https://boards.straightdope.com/t/whats-wrong-with-my-truck-loss-of-power/440535/2 "2008-03-08T00:35:09Z")
Putting cheap gas in it by any chance? 😕 ---
**Author:** ![St.Urho](https://avatars.discourse-cdn.com/v4/letter/s/8e7dd6/32.png) [@St.Urho](https://boards.straightdope.com/u/St.Urho)\ **Post date:** [March 8, 2008, 3:18am UTC](https://boards.straightdope.com/t/whats-wrong-with-my-truck-loss-of-power/440535/3 "2008-03-08T03:18:45Z")
Unfortunately, no- I always get either Conoco or Phillips. ---
**Author:** ![Yeah](https://avatars.discourse-cdn.com/v4/letter/y/dbc845/32.png) [@Yeah](https://boards.straightdope.com/u/Yeah)\ **Post date:** [March 8, 2008, 6:07am UTC](https://boards.straightdope.com/t/whats-wrong-with-my-truck-loss-of-power/440535/4 "2008-03-08T06:07:54Z")
What was the elevation change? You have some kind of air mass sensor that is supposed to cut back on gas as the air becomes thinner at altitude. If it doesn’t work you will lose power and misfire. ---
**Author:** ![St.Urho](https://avatars.discourse-cdn.com/v4/letter/s/8e7dd6/32.png) [@St.Urho](https://boards.straightdope.com/u/St.Urho)\ **Post date:** [March 8, 2008, 7:44am UTC](https://boards.straightdope.com/t/whats-wrong-with-my-truck-loss-of-power/440535/5 "2008-03-08T07:44:46Z")
[QUOTE=Yeah] What was the elevation change? You have some kind of air mass sensor that is supposed to cut back on gas as the air becomes thinner at altitude. If it doesn’t work you will lose power and misfire. [/QUOTE] I’d estimate it started happening at 8500 feet. I live at 5400, for what it’s worth. ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [March 8, 2008, 8:08am UTC](https://boards.straightdope.com/t/whats-wrong-with-my-truck-loss-of-power/440535/6 "2008-03-08T08:08:03Z")
A severe lack of oxygen is probably the cause. 8500 feet is a long way up for a normally aspirated engine. Semis have turbochargers which are more immune to the effects of altitude. ---
**Author:** ![St.Urho](https://avatars.discourse-cdn.com/v4/letter/s/8e7dd6/32.png) [@St.Urho](https://boards.straightdope.com/u/St.Urho)\ **Post date:** [March 8, 2008, 8:23am UTC](https://boards.straightdope.com/t/whats-wrong-with-my-truck-loss-of-power/440535/7 "2008-03-08T08:23:14Z")
[QUOTE=Rick] A severe lack of oxygen is probably the cause. 8500 feet is a long way up for a normally aspirated engine. Semis have turbochargers which are more immune to the effects of altitude. [/QUOTE] It just seems odd that every other car on the road can go the speed limit but me. We have a Focus with the 2.0 L 4-cylinder engine and it can do the speed limit just fine on that same stretch of road. ETA: I also have to point out that the OP was my Norman Conquest post (1066)! ---
**Author:** ![enipla](https://avatars.discourse-cdn.com/v4/letter/e/54ee81/32.png) [@enipla](https://boards.straightdope.com/u/enipla)\ **Post date:** [March 8, 2008, 5:02pm UTC](https://boards.straightdope.com/t/whats-wrong-with-my-truck-loss-of-power/440535/8 "2008-03-08T17:02:19Z")
You bougt it used? Check your air filter. You never know. It may be the original. Other than that I would suspect an air/gas computer sensor problem.