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High negative fuel trims and poor idle

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Old 08-26-2021, 10:40 AM
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MI High negative fuel trims and poor idle

Hi All,

I recently completed my rebuild, 05 6sp, resurfaced housings, reused irons and new Atkins seals all around, new Intermotor coils, NGK plugs and wires. Not too much trouble starting but refused to idle (tends to hunt a LOT) until it was running for 10 mins or so. Still hunts, but no longer dies. I've put about 50 miles on so far without any change (runs pretty smooth). STFTs started at around -20, LTFT's @ 0. Over time STFTs have transitioned to be closer to +/- around 0 and LTFTs have leveled off at around -20. It's guzzling gas and I definitely smell unburnt fuel while driving. Starts easily hot and cold. Next I tried a new MAF, cleaned the TB, new injectors (verified wiring was correct), new CAT (old one was gutted), new CPP switch. No change.

I fear I've reached the limit of my troubleshooting ability and need a fresh perspective from the accumulated wisdom here! Here's a typical snap of what things look like when it idles after a drive.


Old 08-26-2021, 11:07 AM
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You probably have your p1 and p2 injector plugs reversed. Common error.
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DocWalt (08-27-2021)
Old 08-27-2021, 05:38 PM
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Good call, turned out to be the case. Weird thing is I had marked all the connectors before the tear down, and when I installed the new injectors I verified I had kept that sequence. I bought this as a non-runner so maybe the previous owner messed with them. Seems unlikely the previous re-builder did it, but they left out the copper washers on the oil injectors which ended up deforming the housings and taking out the apex seals, so who knows! All is good now, thanks again.
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Brettus (08-27-2021)
Old 08-27-2021, 07:42 PM
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Originally Posted by cmolitor
Good call, turned out to be the case. Weird thing is I had marked all the connectors before the tear down, and when I installed the new injectors I verified I had kept that sequence. I bought this as a non-runner so maybe the previous owner messed with them. Seems unlikely the previous re-builder did it, but they left out the copper washers on the oil injectors which ended up deforming the housings and taking out the apex seals, so who knows! All is good now, thanks again.
Yeah , sounds like you inherited someone else's f...up . Glad you got it sorted !
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wcs (08-28-2021)
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