# 1986.5 HB TBI high idle



## NOWEFG (Nov 19, 2008)

My 86.5 D21 has an ongoing way-too-high idle problem, getting worse lately.

The thermo element may be shot, as it never moved the mechanical Fast Idle Cam to the low idle position. I locked the cam back, but found the idle ramping up again, after a 1-2 second purr at reasonable idle speed.

This seems to indicate trouble with the FICD and Idle-up soleniods. I'm going to test and clean these, but would appreciate an forum member suggestions, experience, advice.

I love my truck; at 377K and still going strong, I'm determined to resolve the problem, and go another 200K at least.


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## zanegrey (Dec 5, 2005)

try reading the codes..


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## MarcOfMaccTown (Aug 22, 2007)

I don't think the 86.5's had the self diagnostic ECM. I think they started that in the 87 model.

I may be wrong but I drive an 86.5 and I've yet to be able to get codes from my ECM. I also read somewhere on alldata that they didn't have the self diagnostic ECM until 87 and later.

Sometimes "Check the codes..." just doesn't work.


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## zanegrey (Dec 5, 2005)

well you are right ...about being wrong...


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## MarcOfMaccTown (Aug 22, 2007)

Not the first time I've put my foot in my mouth and probably won't be the last.

But it's good news in a way I guess.. Maybe I can check my codes after all. I've read the How To Check Your ECU Error Codes, 87-95 HB pickups several times but never get the results that the sticky says I should.

Anyway before I hijack your thread any further, NOWEFG if you manage to pull the codes from your 86.5 please post back with your results.


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## NOWEFG (Nov 19, 2008)

*Will do*

:also, nissan4wheelers.com also contains a thread on the codes, as well as info, with photos, on getting them.


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## zanegrey (Dec 5, 2005)

my method of reading codes..

with access to the ecm turn the key to the run positon but do not start the engine.

flip the ecm switch.

when it blinks 3 times turn the switch off and record following blips of light...


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## NOWEFG (Nov 19, 2008)

*codes - 23 & 24*

I checked the codes this weekend and got 23 & 24.

23 is the idle switch, and I hesitated to remove it, not knowing if it's something I can clean, or fix somehow. Chilton's says it's short or open...

A quick price check on new idle switches left me in shock, $300+, which I don't have.

Anyone have experience with idle switch repair/clean/fix ?


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## zanegrey (Dec 5, 2005)

check the codes again ..but this time hit the gas pedal once and then move the gear shift around the gears..
this might get rid of those codes..


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## NOWEFG (Nov 19, 2008)

*Your point...*

I'm having to guess, here, about your point, which seems to be that the codes I got were incorrect, and that taking the action you recommend will get me to accurate codes. Yes? Any information to support that?

There's also a possibility that solid information, without guesswork, may not be available for less-experienced DIY folks on this forum.


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## zanegrey (Dec 5, 2005)

not incorrect ..

it just actuates the sensors so they read correctly..


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## NOWEFG (Nov 19, 2008)

*high idle resolution - mechanical and simple*

Just to let everyone know,

after replacing the Thermo Element and still idling at 3K+, a friend noticed that the throttle linkage wasn't reaching the adjustment screw. I'd noted that, but thought the cause was internal to the TBI.

Turns out that the coarse adjustment linkage for the fast idle cam was deformed and had apparently crept out of position relative to the throttle linkage, preventing the throttle from bottoming against the adjustment screw. Resolution was as simple as loosening the linkage nut, reforming the fast idle linkage piece, aligning the two linkages, and presto, idle sweet and low.

Still have to replace the linkage arms, and I don't think I'd have caught the slippage if not for replacing the Thermo Element. Tips on that, and on locating an affordable parts vender, were found here at the forum.



Thanks to all repondents, and anyone else who gave the problem a thought.


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## zanegrey (Dec 5, 2005)

bravisimo....


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