Unstable idle

[DannysBTW]

I got a 09 STI
1. Engine is throwing a System rich code
2. At idle it struggles to stay stable at 800rpm, every 30 secs it goes down almost to a complete choke, revs back to to 1200 and goes back to 800.
3. At slow driving 1st/2nd gear between 1000-3000 rpm the car is jerking.
4. These symptoms go away when i floor it and let the engine work hard, but come back when im in traffic.
5. Plugs get sooted. Need to clean them every 2 month - could depend on how long i keep driving in traffic.
6. Accelerating from a stop is mostly not easy, when I initially feather the gas peddle the response is a little delayed and weak.

My suspicion is the fuel regulator, how do i diagnose this?
Thanks.

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[Elbert Bass]

Originally Posted by DannysBTW

I got a 09 STI
1. Engine is throwing a System rich code
2. At idle it struggles to stay stable at 800rpm, every 30 secs it goes down almost to a complete choke, revs back to to 1200 and goes back to 800.
3. At slow driving 1st/2nd gear between 1000-3000 rpm the car is jerking.
4. These symptoms go away when i floor it and let the engine work hard, but come back when im in traffic.
5. Plugs get sooted. Need to clean them every 2 month - could depend on how long i keep driving in traffic.
6. Accelerating from a stop is mostly not easy, when I initially feather the gas peddle the response is a little delayed and weak.

My suspicion is the fuel regulator, how do i diagnose this?
Thanks.

With a fuel pressure gauge and the specification for fuel pressure printed in the FSM.


Sounds like your symptoms go away at WOT. A fuel pressure issue would still be an issue at WOT. I would be looking at a faulty AF sensor issue or leak in the exhaust upstream of the AF sensor. What is your coolant temp sensor reading in the ECM PIDs?

[Elbert Bass]

Originally Posted by Elbert Bass

With a fuel pressure gauge and the specification for fuel pressure printed in the FSM.


Sounds like your symptoms go away at WOT. A fuel pressure issue would still be an issue at WOT. I would be looking at a faulty AF sensor issue or leak in the exhaust upstream of the AF sensor. What is your coolant temp sensor reading in the ECM PIDs?

Also how is idle/run when you unplug the MAF?

[DannysBTW]

Originally Posted by Elbert Bass

With a fuel pressure gauge and the specification for fuel pressure printed in the FSM.


Sounds like your symptoms go away at WOT. A fuel pressure issue would still be an issue at WOT. I would be looking at a faulty AF sensor issue or leak in the exhaust upstream of the AF sensor. What is your coolant temp sensor reading in the ECM PIDs?

Oh thought i'd get some kind of a notification, sorry im new here.
I'll test next time i drive and post the data. For the record i do have an external wastegate, could that affect the AF sensor?
And what is the 'FSM'

Originally Posted by Elbert Bass

Also how is idle/run when you unplug the MAF?

Gonna try that too..

[DannysBTW]

Originally Posted by Elbert Bass

With a fuel pressure gauge and the specification for fuel pressure printed in the FSM.


Sounds like your symptoms go away at WOT. A fuel pressure issue would still be an issue at WOT. I would be looking at a faulty AF sensor issue or leak in the exhaust upstream of the AF sensor. What is your coolant temp sensor reading in the ECM PIDs?

I started the car today with unplugging the MAF, I noticed the rpm stays higher when the car still warms up than when the MAF is plugged - 950 instead of 800.
The ride was a little smoother but sometimes rarely its also smooth with it plugged.. I drove 20km, with no MAF, did a small stop, turn the car back on and it went bad again, Enginestart was weak, and jerking at low speed (I didn't film after the stop). Plugged it back in and started driving good again.

https://drive.google.com/file/d/1wSC...ew?usp=sharing
MAF Plugged Warmup(Forgot to film the unplugged warmup, but it was more stable, RPMs didnt drop beflow 950 when i was letting go of the gas peddle)

https://drive.google.com/file/d/1ipi...ew?usp=sharing
Drove unplugged 20km, this is plugged before the stop..

https://drive.google.com/file/d/1NAc...ew?usp=sharing
Unplugged before the stop

I noticed today my car started emitting a different smell kinda like a weird gasoline smell instead of oil vapor like it ususally smells from the cabin, checked my dipstick and the oil now has in fact a gasoline smell.. something's is going down..

[DannysBTW]

Hey i'm still trying to figure out why my plugs keep getting sooted
Any help?

[Thabias]

Here are some ideas

1.Faulty Oxygen Sensor (O2 Sensor): The O2 sensor monitors the amount of oxygen in the exhaust gases and sends this data to the ECU (engine control unit). If the sensor is malfunctioning or providing inaccurate readings, it can cause the engine to run rich. Use a multimeter in Ohms and check for 10-20ohms across the pins.

2.Mass Air Flow Sensor (MAF): If the MAF sensor, which measures the amount of air entering the engine, is dirty or faulty, it can cause incorrect fuel delivery, resulting in a rich mixture. Use something like https://a.co/d/0fVmflK to clean it.

3.Fuel Pressure Regulator: A malfunctioning fuel pressure regulator can cause excessive fuel to be delivered to the engine, leading to richness.

4.Stuck or Leaking Fuel Injectors: If the fuel injectors are leaking or sticking open, they may dump too much fuel into the engine, causing it to run rich intermittently. Try using: https://a.co/d/9pczPzd to check the spray pattern and clean them if need be.

5.Vacuum Leaks: A vacuum leak could cause an imbalance in the air-fuel mixture, leading to a rich running condition under certain conditions. Smoke machine: https://a.co/d/dwjym7b

6.Coolant Temperature Sensor: If the coolant temperature sensor is providing incorrect information to the ECU (such as reading the engine as cooler than it actually is), the ECU may enrich the mixture unnecessarily.

7.Aftermarket Modifications (Tuning, Intake, Exhaust): If the vehicle has been modified, incorrect tuning could cause an intermittent rich condition, especially if the modifications are not properly accounted for in the ECU.

8.ECU or Wiring Issues: Intermittent issues with the ECU or related wiring can cause the air-fuel ratio to fluctuate, leading to richness.