Lean Idle
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From: Way ahead...
Lean Idle
I figured I should post this here, although I'm not really certain it's an ECU issue, but if anyone has encountered this or has any ideas - I'd be greatful.
So we got a car in that came with a blown motor and overall the car is in terrible condition. Everything just seems to be destroyed or blown that I put in my hands...
The car has a new built engine now - just regular forged stuff, 2.0, 9:1 CR.. China intercooler 3", HKS 280 cams (the old ones) and a random K&N small cone filter - on the stock rubber tube and MAF location. Evo metal dump valve. Fuel system is still stock by the looks of it - we didn't check the fuel pump if it's stock or not tho, injectors are however...
Running the stock map - it's lean at low rpm and idle. Idles at 18ish AFR and stutters. Touching the gas raises rpm and reduces the condition but still nowhere near the 14.7. At ~1300 rpm the afr is at 16 or so... However when going out for a cruise and driving slowly the cruise afr bounces from 14.4-15.0 so that seems normal.
The car does not have the rear o2 sensor at all - just chopped wires hanging there.
I haven't pushed the car yet so can't comment on anything wot related, the new motor has 5 miles on it or so now.
Things checked:
- no boost leaks
- no exhaust leaks
- front o2 sensor replaced with a working one
I can't log fuel trims - just 0's on all trims. Injector latency, scaling etc is stock.
Anyone has an idea what could the reason for the lean running be? What can I do to log fuel trims without the rear o2?
Cheers in advance!
The car has a new built engine now - just regular forged stuff, 2.0, 9:1 CR.. China intercooler 3", HKS 280 cams (the old ones) and a random K&N small cone filter - on the stock rubber tube and MAF location. Evo metal dump valve. Fuel system is still stock by the looks of it - we didn't check the fuel pump if it's stock or not tho, injectors are however...
Running the stock map - it's lean at low rpm and idle. Idles at 18ish AFR and stutters. Touching the gas raises rpm and reduces the condition but still nowhere near the 14.7. At ~1300 rpm the afr is at 16 or so... However when going out for a cruise and driving slowly the cruise afr bounces from 14.4-15.0 so that seems normal.
The car does not have the rear o2 sensor at all - just chopped wires hanging there.
I haven't pushed the car yet so can't comment on anything wot related, the new motor has 5 miles on it or so now.
Things checked:
- no boost leaks
- no exhaust leaks
- front o2 sensor replaced with a working one
I can't log fuel trims - just 0's on all trims. Injector latency, scaling etc is stock.
Anyone has an idea what could the reason for the lean running be? What can I do to log fuel trims without the rear o2?
Cheers in advance!
Thread Starter
Evolved Member
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From: Way ahead...
94170715(tephra) and 94170015. Both same thing.
I would believe the car doesn't go in to closed loop right away at cold start - but even warmed up it does the same thing so again - seems to be both. I'll do some more testing right now...
I would believe the car doesn't go in to closed loop right away at cold start - but even warmed up it does the same thing so again - seems to be both. I'll do some more testing right now...
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From: Ottawa, Ontario, Canada
Without the rear O2, the trims won't update.
If you run the Tephra rom, make sure the rear O2 sim is on, and the heater CELs are '0'd. The periphery bit for the rear O2 has to be set to '1' for the sim to work though. Then you can log trims
.
If you run the Tephra rom, make sure the rear O2 sim is on, and the heater CELs are '0'd. The periphery bit for the rear O2 has to be set to '1' for the sim to work though. Then you can log trims
.
Once you can log your O2 feedback and see what your trims are up to, scale your injectors correctly and then set your latencies. The K&N will upset your MAF and so you may also need to adjust your MAF compensation table to add fuel at idle and low RPM.
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From: Way ahead...
I managed to fix the o2 and I'm getting fuel trims logged etc. They're within 5% all the time.
I bumped up the idle to 1000rpm and it's idling around 15,7ish afr now and low rpm cruise around 15,2.. I'll have to play with the MAF a bit I guess now.
I was guessing it could be the cams overlap causing this?
I bumped up the idle to 1000rpm and it's idling around 15,7ish afr now and low rpm cruise around 15,2.. I'll have to play with the MAF a bit I guess now.
I was guessing it could be the cams overlap causing this?
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