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Rough Idle & Low /Unstable RPMs
What's been done: Rebuilt Supercharger due to blow-by; oil going into the throttle body/intake Sprayed 2 full cans SeaFoam (different times) into intake. Result: Driver (LHD) side blows out lots of smoke after, clears up. Both Cats removed trying to chase the issue. Pulled plugs on bank 2, inspected, cleaned and replaced. MAF has been cleaned as well as air filter. New coils. __________________________________________________ __ Code: 20 | Lambda code probe 2 rear cat | may be bad wire When I view it in INPA it says running rough, but if RPMs are increased by 100-200 it goes to 100% clear/perfect. Running low on ideas. Was thinking MAF maybe, but its not tossing a code. If I unplug the MAF it cuts off - meaning its a good part. Possible throttle body issue? Thanks for any suggestions!
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740iLDUKE 01' DINAN 7 S62 Swap - Stratus Grau (1587 produced in SG 440) 02' 4.6is DINAN X5 S2 Supercharged 833/3258 produced | 1/27 Dinan X5's |
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#2
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Does it settle down if you spray starter fluid in the intake? Caution here!!!
Had 3 bad injectors on a motor once and an independent shop used this method to determine a fuel issue. I'd also check fuel pressure to be sure there was enough and not fluctuating. |
#3
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Rough Idle & Low /Unstable RPMs
Idle control valve if idle sucks and you can make it run nice manually. MAF is very indeterminate but if you unplug and conditions improve it's likely the fault.
Car should run without maf but not sure if you unplug while running what happenes or if engine is warm already.
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2011 E70 • N55 (me) 2012 E70 • N63 (wife) |
#4
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Quote:
I will source a gauge and check the fuel pressure. Im sure it's due for a fuel filter as well.
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740iLDUKE 01' DINAN 7 S62 Swap - Stratus Grau (1587 produced in SG 440) 02' 4.6is DINAN X5 S2 Supercharged 833/3258 produced | 1/27 Dinan X5's |
#5
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Quote:
Update: with engine at operating temp, it shuts off immediately if MAF unplugged.
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740iLDUKE 01' DINAN 7 S62 Swap - Stratus Grau (1587 produced in SG 440) 02' 4.6is DINAN X5 S2 Supercharged 833/3258 produced | 1/27 Dinan X5's Last edited by 740ilDuke; 07-14-2019 at 07:34 PM. |
#6
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Pretty sure MAF is faulty. somebody on the forum recently did this same test. Borrowed MAF from wife's car (had to apollo 13 the thing in there with duct tape) same exact happened. When cold the car uses lookup tables to meter air fuel mix. When warm relies on MAF and O2.
You can look at live reading on MAF or even back probe and measure the voltage for some common sense values to confirm.
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2011 E70 • N55 (me) 2012 E70 • N63 (wife) |
#7
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Quote:
Just use tire pressure gauge. Also: not likely on fuel filter. They are "lifetime" filters and can last half a million miles. The pressure regulator can fail though. I'n the 100s of threads I've read on fuel system I've never seen a case of fuel filter being a problem source. Since it's combined with the regulator sometimes that part needs to be replaced but the filter is maybe 100-200x the size of the tiny filters of olde that needed periodic replacement.
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2011 E70 • N55 (me) 2012 E70 • N63 (wife) |
#8
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Sprayed starter fluid all around the intake, throttle body etc - no evidence of RPM change.
Have not checked fuel pressure yet. Continually running seafoam in the tank. It came from Montana and had a lot of dusty dirty in all the fun places.
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740iLDUKE 01' DINAN 7 S62 Swap - Stratus Grau (1587 produced in SG 440) 02' 4.6is DINAN X5 S2 Supercharged 833/3258 produced | 1/27 Dinan X5's |
#9
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Have you done a compression test on all cylinders to determine the health of the engine. A misfiring cylinder will smooth out and be masked if you run the rpm high enough. Low compression in one cylinder could be the cause of the problem and racing the engine just mask the problem.
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2006 Infiniti G35 2001 BMW 3.0I E53 X5 Build date 08/2000 SOLD Lotus Europa 1970 Destroyed by fire Lotus Europa 1970 S2 Renault Powered Lotus Type 52 1970 Twincam Webers Powered PORSCHE 911 Targa 1982 The Garage Queen Audi Avant donated to Kars for Kids BMW 525IT Sold Audi 4000CS Quattro Sold Jensen Healey Lotus Powered Sold Opel 1900 Sold Triumph Spitfire 1971 Sold Triumph Spitfire 1968 Sold Plymouth "Cuda" 340 Six pack SOLD |
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