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The mkiv Supra Owners Club

NA-T help? UPDATE


WaLKeRR
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well what happend is theres an na-t local and ive been asked if i know what this problem could be but i have no idea...basically the car was running fine at .5 bar he manually upped the boost to .6-7 and it was running fine just a little bit leaner still in the 12s on afr. Then a couple of weeks after the car only boosts fully in 1st n 2nd gear 3rd 4th 5th run in the 16 plus area on boost anyone have any ideas hes using stock everything on e manage blue

Edited by WaLKeRR
updated (see edit history)
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Hi, there's lots of us running na-t if your running 16 s afr then your in the dangerous area for on boost and lean for even off boost, do not run this car without finding the issue.

Can you give us a spec list and any symptoms the ca is showing besides the afr, any modifications or changes.

Thanks

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the car boosts in 10 11 12s in 1st n 2nd gear and higher gears its leaning big time normal driving its fine 14.2 - 15.1 stock fuel pump stock injectors running .6-7 bar was running fine then on motorway all of a sudden was stuttering under boost...driving back under 3k revs perfect afr i was thinking possibly a boost pipe loose or leaking?

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I doubt it. The exhaust turbine will create positive pressure in the exhaust system, therefore creating less exhaust flow past the sensor but not sucking in air giving a false AFR.

 

The issue is most likely happening when there is more load. 1st and 2nd gear are very quick, therefore in 3rd gear it probably stays level AFR and then after a time (which would take you longer than 1/2nd gears) the car leans out.

 

A boost pipe leak would cause a misfire I don't think that's the answer.

 

Maybe there's a sensor problem, the first thing to check is fuel pressure, as 3rd gear onwards was where I had issues with on my old NA fuel pump. it could be leaning out due to not having enough fuel.

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If the fuel pump gave up completely your engine would die.

 

I think what could be happening is the fuel pump can't supply as much fuel as you need, therefore the increase of air leans the mixture out while injectors and pump work to their limitations.

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but thing is i think is odd. the car has been running fine no issues boost was upped to .6ish from .5 no difference obviously just a move in afr but still roch enough was being boosted about fine then a day later driving fine 5th gear overtake on motorway and its lean also been told its leaning off in 2nd gear now under boost and feels like its missing to me

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So Today......Started off first of all fixing this downpipe issue that was loose, no change!, got a smoke tester out to check for boost leaks in the system, no leaks!, Not going good so far, then i checked timing all lined up perfectly, next up the plugs! i thought id start at plug 6 and work towards myself plug 6 was a little white, 5 had small amount of oil, 4,3 and 2 were perfect, plug 1 was soaked in oil and i mean soaked! pot was pretty much filled with oil, so then we replaced plugs with new ones and closed the gap to 0.028 iirc, at a chance the oil was from it being so lean due to the plug gap, ran the car very smoky on idle. Took it for a quick run to see if it drove better, it idled slightly better went for a run 1st gear boost fine 2nd gear fine, 3rd gear would run lean if i throttled upto boost under 3k (obviously i let off) then top end of revs was perfects 11's on the afr same for 4th an 5th so the oil must be coming from the rings so a bit strip down on its way!

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