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4Jb1-T idle too high

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4Jb1-T idle too high

Postby SamMu93 » Sat Aug 22, 2015 3:29 pm

hi guys,

This has been bugging me since I tweaked the fuel pump - the idle is now sitting at 1500/1600 and the idle screw has no adjustment left. You could remove it and the idle would be the same!
Is there any other adjustment (aside from lowering the fuel rate back down) to lower the idle when the idle has increased as a result of 1.5turns of the fuel screw?

Main concern is the small amount of run on i am starting to get now...(when engine is shut off)
SamMu93
Isuzu Junior
 
Posts: 148
Joined: Sun Jan 18, 2015 3:22 pm
Age: 29
Country: New Zealand
City: Wellington
Vehicle: 93 Isuzu Mu 2.8 TD
Rodeo 3" dump pipe off turbo
2.5" Exhaust to tip
Bighorn intercooler
Tweaked fuel pump
Boost tap (15psi)
Egt monitor installed
Rear: 2" lifted leaf springs
Front: Wound torsion bars, dropped front diff, flipped ball joints, cut upper bump stop

Re: 4Jb1-T idle too high

Postby isuzurob » Sat Aug 22, 2015 4:43 pm

1 1/2 turns is nothing on the fuel screw, you should be able to back off the stop enough, only thing that will stop that is if someone has had the top off the injector pump and put the throttle plate in the incorrect place
isuzurob
Global Moderator
 
Posts: 1775
Joined: Mon Jun 07, 2010 6:12 pm
Age: 25
Country: New Zealand
City: Taupo
Vehicle: 1990 Isuzu Bighorn 2.8t/d, 3" extended shackles, 2" body lift, 33" silverstone extreme tyres, Front+rear bars, winch with 40m dyneex rope, 21/2 inch exhaust, lokka's front+rear, custom turbo, emissions removed, injector pump modified and more

Re: 4Jb1-T idle too high

Postby SamMu93 » Sat Aug 22, 2015 5:10 pm

Seems unlikely- I am the first to adjust the fuel rate (had the cap still on the screw/ unviolated).
SamMu93
Isuzu Junior
 
Posts: 148
Joined: Sun Jan 18, 2015 3:22 pm
Age: 29
Country: New Zealand
City: Wellington
Vehicle: 93 Isuzu Mu 2.8 TD
Rodeo 3" dump pipe off turbo
2.5" Exhaust to tip
Bighorn intercooler
Tweaked fuel pump
Boost tap (15psi)
Egt monitor installed
Rear: 2" lifted leaf springs
Front: Wound torsion bars, dropped front diff, flipped ball joints, cut upper bump stop

Re: 4Jb1-T idle too high

Postby isuzurob » Sat Aug 22, 2015 6:12 pm

i would say the tops been off at some stage by now as they all leak diesel, just sounds like the throttle plate is on the wrong spline
isuzurob
Global Moderator
 
Posts: 1775
Joined: Mon Jun 07, 2010 6:12 pm
Age: 25
Country: New Zealand
City: Taupo
Vehicle: 1990 Isuzu Bighorn 2.8t/d, 3" extended shackles, 2" body lift, 33" silverstone extreme tyres, Front+rear bars, winch with 40m dyneex rope, 21/2 inch exhaust, lokka's front+rear, custom turbo, emissions removed, injector pump modified and more

Re: 4Jb1-T idle too high

Postby SamMu93 » Sat Aug 22, 2015 6:41 pm

isuzurob wrote:i would say the tops been off at some stage by now as they all leak diesel, just sounds like the throttle plate is on the wrong spline


Oh so is it straight forward to adjust? Just a case of taking lid off and adjusting it a few splines back clockwise direction?
SamMu93
Isuzu Junior
 
Posts: 148
Joined: Sun Jan 18, 2015 3:22 pm
Age: 29
Country: New Zealand
City: Wellington
Vehicle: 93 Isuzu Mu 2.8 TD
Rodeo 3" dump pipe off turbo
2.5" Exhaust to tip
Bighorn intercooler
Tweaked fuel pump
Boost tap (15psi)
Egt monitor installed
Rear: 2" lifted leaf springs
Front: Wound torsion bars, dropped front diff, flipped ball joints, cut upper bump stop


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