Can anyone help with this? Went on a trip last week, when I reached about 5500' above sea level the 2f turned into a dog wouldn't rev much past 2k rpm.
Help Please High Altitude Power loss
- Thread starter walnut
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high altitude with attitude lame dog FJ60
First it is normal as you climb higher as the air gets thinner so does the comptession ratio.
However, there are factor that contribute to amplify this effect.
Foremost check you ingnition system and vacuum hosing for leaks and proper routing. .
Set BTC to more than 7 degrees e.g. 10-12 degrees or more. It'll make quit a difference. You'll be amazed!
Check your vacuum hosing and disconnect and plug the retard hose. (The one that goes to the diaphragm closer to the distributor housing.)
But caution this will cause engine knock at low altitudes and you will have to use premium if you not set the timing back.
First it is normal as you climb higher as the air gets thinner so does the comptession ratio.
However, there are factor that contribute to amplify this effect.
Foremost check you ingnition system and vacuum hosing for leaks and proper routing. .
Set BTC to more than 7 degrees e.g. 10-12 degrees or more. It'll make quit a difference. You'll be amazed!
Check your vacuum hosing and disconnect and plug the retard hose. (The one that goes to the diaphragm closer to the distributor housing.)
But caution this will cause engine knock at low altitudes and you will have to use premium if you not set the timing back.
The FJ60 has a High Altitude Compensation circuit that is supposed to automatically the timing 7 or so degrees when at "high" altitude (above 4000ft or so). Do a search for HAC. A description of the system and troubleshooting are explained in the 2F emissions manual. I've taken my truck up to 8000ft and beyond and while it does lose some power, it never goes completely gutless...
x2 on what 2MBB is saying.....
I drive my stock fj60 at levels of 10,000-12,000 feet here in the rockies and uinta mountains of Utah and yeah it looses a bit of power, but never gutless.
I drive my stock fj60 at levels of 10,000-12,000 feet here in the rockies and uinta mountains of Utah and yeah it looses a bit of power, but never gutless.
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Only on 1978 2F.
All 79-later US-spec 2F dissys have dual vac advance. Main advance is nearest dissy body. Second high-altitude advancer is the outer fitting.
I'm a Utah lifer. A 2F with the smog junk is almost intolerable here. It's much better with a desmog, carb and header. It helped immensly, so did setting static timing at 10 to 12 degrees instead of 7 as has already been mentioned.
You will see a noticeable drop of power at 5500 feet however it should still run and rev OK. At 5500 feet you only have about 80% of air available as you do at sea level (11.7 PSIA vs. 14.6 PSIA) so you can assume an approximate 20% loss in power given everything else the same.
Assuming your engine isn't worn out, to optimize performance the following should be done, advance the ignition timing (rule of thumb 1 degree per 1500 ft), and put smaller main jets in the carburetor (rule of thumb is one jet size per 2000 ft elevation). Obviously, changing jets is something you would not want to do unless you were planning an extended stay. But if you are already running rich at lower elevations, things could get ugly as you get up a ways.
Also, because of the lower total pressure of the combustion mixture the octane requirement decreases with increase in altitude, the very reason gas stations at higher altitudes sell gasoline with lower octane numbers than stations at sea level.
Assuming your engine isn't worn out, to optimize performance the following should be done, advance the ignition timing (rule of thumb 1 degree per 1500 ft), and put smaller main jets in the carburetor (rule of thumb is one jet size per 2000 ft elevation). Obviously, changing jets is something you would not want to do unless you were planning an extended stay. But if you are already running rich at lower elevations, things could get ugly as you get up a ways.
Also, because of the lower total pressure of the combustion mixture the octane requirement decreases with increase in altitude, the very reason gas stations at higher altitudes sell gasoline with lower octane numbers than stations at sea level.
I had the same problem as you at 9,000 ft elevation. I connected a few hoses wrong.
Look at you vacuum lines and hosed near you distributor. There is one that plugs into/under the air filter housing. Make sure everything is connected properly. Make sure you VSV valves (the green and blue ones) are not installed backwards.
Once I connected the hoses correctly, mine it ran as good as it gets at 9,000ft elevation.
Look at you vacuum lines and hosed near you distributor. There is one that plugs into/under the air filter housing. Make sure everything is connected properly. Make sure you VSV valves (the green and blue ones) are not installed backwards.
Once I connected the hoses correctly, mine it ran as good as it gets at 9,000ft elevation.
I guess it's what you're used to but my stock '83 runs fine here at 7,000'. Revs to 4K & goes up & downhill on the interstate at 75 on stock tires.
There's something else wrong
There's something else wrong
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Thanks for the replies. I guess I need to look closer at the vacuum routing, then pack a timing light next trip.
Maybe yours is running as good as anybody elses at 5K feet, which is not well. If you have 32+inch tires and stock gearing your just gonna have to work the tranny to get over passes. In 1996 I had a 87 fj60 with very low miles..ran great in fort Worth but would barely pull the hat off your head above 5K feet, loaded with gear forgetaboutit..
I live at 4K feet here in Oregon now and get around pretty good but with 33" tires I stay in 3rd a lot.
the vacuum hoses on the carb, on the air rail side often get cooked. My rig was running crappy until I put all new vacuum hoses on. the ones on that (passenger/starboard) side of the carb were cracked and broken. Replaced them.... Idle problems solved. and it ran way better (still no v8).. might help you to check.
I live at 4K feet here in Oregon now and get around pretty good but with 33" tires I stay in 3rd a lot.
the vacuum hoses on the carb, on the air rail side often get cooked. My rig was running crappy until I put all new vacuum hoses on. the ones on that (passenger/starboard) side of the carb were cracked and broken. Replaced them.... Idle problems solved. and it ran way better (still no v8).. might help you to check.
