87 - 258 Altitude jumper ground - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 10-24-2002, 05:15 PM
bchiker
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87 - 258 Altitude jumper ground

I've been trouble shooting my engine with the Tech notebook wow full of information. My question, they show a picture of an altitude ground jumper wire. It runs in a harness down the firewall between the battery and engine. It's ground is on the engine behind the coil. On my engine I have 2 lugs grounded at that grounding point. One lug has 2 wire crimped to it and the other has just 1. Is the one with 1 wire the high altitude jumper? How many do you have grounded to that point? What does the high altitude jumper do? How can I tell if thats it? I can't find one not hooked up like the picture shows. Did they put the jumper in all jeeps?
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post #2 of (permalink) Old 10-24-2002, 06:01 PM
 
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Re: 87 - 258 Altitude jumper ground

You don't need it unless you're running above 4000 feet and you still have the stock computer hooked up. Check out this article on off-road.com for some good info on this.
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post #3 of (permalink) Old 10-24-2002, 06:13 PM
bchiker
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Re: 87 - 258 Altitude jumper ground

I understand that, but my jeep has 3 wires = 2 lugs on it now. I don't know if one of them is that jumper. How many are on your jeep?
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post #4 of (permalink) Old 10-25-2002, 06:54 AM
 
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Re: 87 - 258 Altitude jumper ground

I've got a big rats nest of wires under my hood that I'm still trying to pick through so comparing mine won't help you. The guy I bought mine from considered himself a mechanic and made quite a mess of it.

All I can suggest is trying to follow it back to it's source.
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post #5 of (permalink) Old 10-25-2002, 07:56 AM
85Jeepny
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Re: 87 - 258 Altitude jumper ground

On my old engine the 258 in the CJ, I hooked up the "high altitude" wire because I live at 4,200 feet and saw ZERO change with this wire.....I'm not sure it did anything at all....I fixed that though with the help of Fuel Injection in the form of 4.0 Litres...hehe [img]images/graemlins/cool.gif[/img]
post #6 of (permalink) Old 10-25-2002, 12:00 PM
Mudman
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Re: 87 - 258 Altitude jumper ground

if I recall right my jumper wire was up near the battery, was in a harness that ran near the fire wall. it is supposed to change some setting in the computer.
try this jeep tech jumper
post #7 of (permalink) Old 10-28-2002, 08:06 PM
**DONOTDELETE**
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Re: 87 - 258 Altitude jumper ground

Though we spoke on the phone , I felt that my experience re : high altitude wire was worth sharing . The double wire grounded to the engine block near the coil correponds with the 2 ground wires from the MCU/PCM/ ECU . These 2 black wires originate at the MCU wire harness terminals #20 and #60 . They are part of the MCU wires that pass through the firewall above the gas pedal . The altitude wire also is part of this bunch of wires . It has its origin at MCU harness pin # 11. Below 4000 ft.altitude , you do not want this wire grounded. I encased mine within a rubber hose so that it would not ground .

There was an Information Service bulletin number 7E issued Sept 1987 for the 87 YJ Wrangler with 4.2 and the 2.46 TBI for vehicles which were built for one altitude , yet operate at another . The bulletin describes how to get better performance and is to be offered at no charge to the public. Any vehicle undergoing this change should have an updated VECI label. In a nutshell, the procedure either places or removes a metal U- shaped jumper connector in the duo-terminal connector located near the MCU wiring harness. Set the timing to 16 degrees BTDC above 4000 ft or to 9 degrees BTDC below 4000 ft altitude . When traveling below 4000, reset timing to 9 degrees BTDC , above 4000 reset to 16.
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