Thread: Unstable combustion troubleshooting

Hey forum, I need to some feedback on what to troubleshoot next.

The issue: Unstable combustion, AFR deviating 1.X whole AFR from 14.7 in closed loop AND open loop. Only occurs at idle and low load.

Here's a video of the MTX-L readout. 1 year old LSU 4.9 sensor. You can see AFR jumping between 13.0->16.3, this was filmed with closed loop.


Current setup:
SR20VE, temporarily N/A for inspection
Nismotronic ECU
259cc DE injectors. Rock stable 3ms injection, no dips/table corrections whatsoever. Same behavior with 850cc injectors.

Major suspects I have changed:
-Distributor
-Spark plug wires
-New spark plugs
-New ignition coil
-Injectors

Things I have checked/tested:
-No leaking injectors. Rail is bone dry after priming.
-Power balance test reveals all cylinders create equal power.
-Converting from turbo->N/A did nothing.
-Spark is not a prime suspect, since issue is only at low load, and all spark related components have been replaced.
-Only fuel components still suspected are fuel pressure regulator and damper. Could these cause issues?

I need to smog check the car within 24h, and I am sure it's gonna fail. I will post the exact results to this thread when I get them.

I feel lost...

Dala

I also have a MTX-L, and have many friends that do as well.

Your o2 sensor is worn out and in need of replacement. I have seen this exact issue many times.

Innovate recommends sensor replacement every 3 months on turbo applications.

I'd say sensor as well as ive had the same issue.

Go with a newer Bosch LSU 4.9 sensor. I'm converting all my cars over to them. The new AEM setups are very reasonable.

Bosch LSU 4.9 vs LSU 4.2 - efiHacks Wiki

Been running the AEM with LSU 4.9 in my Z31 Turbo and Juke Nismo RS and love them. Pretty much hassle free and don't have to calibrate them in free air like alot of the Innovative series.

Dala, I installed my ecb-1. 4.9 sensor and everything integrated into nemu flawlessly.

Alright, thanks for the feedback guys! LSU 4.9 wideband sensor ordered.

Strange thing, I had already upgraded to 4.9 last year. These sensors seem to break way faster than I'd like. My first 4.2 sensor only lasted 2 years, this 4.9 only lasted 11 months!

I went and smogged it, these were the results

Idle
CO 0.3 max 0.5 %
HC 105 max 100 ppm
02 3 max 5 %
Lambda -

Fast Idle
CO 0.7 max 0.5 %
HC 135 max 100 ppm
02 3.7 max 5 %
Lambda 1.10

So, safe to say I have an exhaust leak that I've already welded up, so now I just gotta wait for the new sensor. I'll bump this thread once everything shows up.

What is the distance between your o2 sensor and your turbo outlet?

5 inches... this might have contributed to the early sensor failure...

Im glad i grabbed mine at orailys i told them it was for wideband use they told me lifetime warranty i can exchange after it goes bad , same here got mine right about 5 inches after turbo since i know i can replace anytime, mine is innovative brand and i like to calibratre since im on mile high above sea level really wanna be sure im zeroed at my elevation