Editing Forums/Z31P/z31-repairs-forums engine-mechanical/85NA Auto in limp home mode

{{ForumImport
|op_user=dbruce
|op_date=2018-07-02 23:42:36
|post_count=9
|archive_url=/Z31performance_archive/forum/z31-repairs-forums/engine-mechanical/540070-85na_auto-in-limp-home-mode.html
}}

'''dbruce:''' <small>(2018-07-02 23:42:36)</small>

starts fine, idles and warms up fine … but no rev beyond 2K

ECU reference: [[Z31/ECUcodes php|https://dev.z31library.com/xenonzcar_archive/z31/ECUcodes.html]]

So long story short .. I ran ECU diagnostics and have two codes

23 - throttle valve switch (idle switch ) circuit

31 - load signal switch

After checking the Auxiliary driving lamps aren't working at all so that is probably the 31 . I'm going to try swappin in another relay and see if that helps the fuse was OK … hmmm

I have a spare TPS so I'm going to try that tomorrow ( Its not perfect , it has a dead spot on the throttle rheostat deal )

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'''Z_Karma:''' <small>(2018-07-03 01:11:42)</small>

I seem to remember that the limp mode 2K limit was more often than not, caused by a faulty AFM.

Might unplug it and try to start it to see if anything changes or at least throws that code. Just purely a guess.

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'''dbruce:''' <small>(2018-07-03 02:13:42)</small>

Thanks for the ideas .. I've seen lots of variations of this problem and right, bad wiring connections and bad power can make all this happen . Sometimes it is a bad component . When things go back and forth between working and not, I tend to think its a bad connection. I remember once I had a bad coil wire that was arcing and it acted just like this … so it's not my first rodeo … It's always the last place you look where you find the problem .

I'm checking fuses and connections and I've got some spare pieces to swap …

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'''dbruce:''' <small>(2018-07-03 18:48:51)</small>

So today it rev'ed fine … took it for a drive and now waiting to see if it survives a thermal cycle … hmmm … bizarre

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'''dbruce:''' <small>(2018-07-05 19:36:18)</small>

So today it's reving fine and I've started the engine multiple times and heat cycled the car …

So I must of cleaned the bad connection ( wish I knew which one )

Now of course is the question of reliability, repeatably … dependability

I've got more new parts on the way … and i'll check more bits …

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'''dbruce:''' <small>(2018-07-08 20:32:05)</small>

She lives … again

[https://www.youtube.com/watch?v=tSukMQHQLIs https://www.youtube.com/watch?v=tSukMQHQLIs] '''The Sword Has Been Drawn'''

[archived image: 1985NA300zx_20180708.jpg]

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'''dbruce:''' <small>(2018-07-16 15:20:43)</small>

So far it seems to be fixed .... installed a new coil and TPS ,,, may have been water condensation around the spark plugs? Whatever … Got new tires put on last week ( man the mich pilots were great 80K+ miles) and I'm proceeding with the tuneup …

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'''dbruce:''' <small>(2018-07-22 03:40:59)</small>

Today I put in a new fuel filter , dist cap and rotor , and added an auto trans inline filter … Adding in some Auto-rx to the auto trans to see if it un-stick the solenoids ( temp sensor, kickdown, lockup inhibit switch aren't working consistently see: [https://www.auto-rx.com/for-dirt-contaminants-abrasives-sludge https://www.auto-rx.com/for-dirt-con…rasives-sludge] ) but shifts fine … so maybe its the wiring again

Last week I discarded the no tread Michelin Pilots ( 80K miles ) for these less expensive tires …

[https://www.tirerack.com/tires/tires.jsp?tireMake=Sumitomo&tireModel=HTR+A/S+P02+(H-+or+V-Speed+Rated)&partnum=16HR5HTRASP02&vehicleSearch=true&fromCompare1=yes&autoMake=Nissan&autoYear=1985&autoModel=300ZX&autoModClar= SUMITOMO HTR A/S P02 (H- OR V-SPEED RATED)][https://www.tirerack.com/tires/types/modalbox_perfcatdefinition.jsp?perfCat=HPAS High Performance All-Season]Size: 215/60R15 94H Serv. Desc: 94H

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'''dbruce:''' <small>(2018-08-03 21:38:40)</small>

FYI … Today the AT lockup inhibit switch started working again … E4N71B This takes you out of overdrive in all the gears 1-2-3 and out of TC lockup …

Also install the prw2 for the ignition yesterday

So I don't know why maybe the AUto-RX is working or just that I've been driving it ( I took a long drive just yesterday ,,, and it would not work for me.) … time will tell