Lean Misfires at 2700-2800 rpm

[outreach]

My car just startes doing this yesterday for the second time since i owned it. I gave it a nice clean air filter and some new vac lines and this is how it treats me . First time it was a combination of having old plugs in the rear bank and new in the front and a leaking bov. This time im not so sure. It drives prlerfect then epic lean missfires for no reason.

[levani041491]

anybody fixed this ?

[luvness018]

i think my problem may have something to do with a clogged injector. My car used to idle fine then miss when a load was put on it, then clear up around 3k rpms. I did the vacuum reduction, new fuel filter, new plugs. it eventually got worse and started missing at idle so i was able to pull the coil wires on by one to find the bad cylinder...my plug was jet black and i couldnt smell any gas on it. Going to test some more tonight and see if the ECU is grounding the circuit out to fire the injector.

[luvness018]

Just to update. I found that I had a bad injector. It progressively got worse that just low rpm missing and hesitation to missing all the time. The injector ohmed out and everything but must have been clogging up our just failing. Just got a new injector on and she has never run this good!

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[jaysmirage]

Sorry to bring this back but has anyone tried dissconecting the active aero comp ?

[DoctorDex]

Where is that one located again? Sorry it's been awhile since I've worked on my car.

[jaysmirage]

all data says Active AERO Control Unit: Rear LH Side Of Luggage Compartment

[jaysmirage]

THis may help


QUALITY MITSUBISHI
QUALITY MITSUB0000


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1991 Mitsubishi 3000GT AWD V6-2972cc 3.0L DOHC Turbo

Vehicle » Powertrain Management » Computers and Control Systems » Crankshaft Position Sensor » Specifications

•Specifications

Advanced Ignition Timing [2]




At idle

15°BTDC


Base Ignition Timing [1]




At idle

5°BTDC


Air Flow Sensor




At 750 RPM

20 - 50 Hz






At 2,000 RPM

70 - 100 Hz


Barometric Pressure Sensor Voltage
(W/ key on and engine off)




At sea level

Approximately 4.0 volts






At 2,000 ft.

Approximately 3.75 volts






At 4,000 ft.

Approximately 3.50 volts






At 6,000 ft.

Approximately 3.25 volts


Crank Angle Sensor




Approximate Voltage at idle

1.8 - 2.5v (needle fluctuates)


EGR Temperature Sensor Resistance [3]




At 122°F (50°C)

60 - 83 Kohms






At 212°F (100°C)

11 - 14 Kohms


EGR Control Solenoid Valve Resistance [3]




At 68°F (20°C)

36 - 44 Ohms


Engine Coolant Temperature Sensor Resistance




At 68°F (20°C)

2.5 Kohms






At 176°F (80°C)

300 Ohms


Fuel Pressure Control Solenoid Valve Resistance




At 68°F (20°C)

36 - 44 Ohms


Fuel Injector Coil Resistance




At 20°C (68°F)

2 - 3 ohms


Idle Speed Control Servo Resistance




At 20°C (68°F)

28 - 33 ohms


Intake Air Temperature Sensor Resistance




At 68°F (20°C)

2.7 Kohms






At 176°F (80°C)

300 Ohms


Primary Coil Resistance




At 20°C (68°F)

0.67 - 0.81 ohms


Secondary Coil Resistance




At 20°C (68°F)

Approx 11.3 - 15.3 Kohms


TDC Sensor




Approximate Voltage at idle

2.0 - 2.5v (needle fluctuates)


Throttle Position Sensor Adjustment Voltage




At curb Idle

0.4 - 0.1 Volts


Throttle Position Sensor Resistance




Varies between

3.5 - 6.5 Kohms


Wastegate Solenoid Valve Resistance




At 68°F (20°C)

36 - 44 Ohms


[1] Refer to ADJUSTMENT PROCEDURES .
[2] Not adjustable.
[3] California Only.

[DoctorDex]

I can't recall whether or not I disconnected the active aero or not.

With that being said, my lean misfire issued has resolved (and I still have the active aero hooked up). I'm not sure what fixed it as I changed so many variables at once, but I think it was likely related to an airflow issue possibly related to resonance in the intercooler piping system. The reason why I suspect this is because of the pressure fluctuations causing the BOV to blow off if I was to hold the rpms between 2700-3200 rpm.