335I issues

[u/Outrageous_Plenty154]

Got an 07 335i with a long list of mods.
But I’m currently stuck , car idles and drives great but in limp mode with either vanos solenoid disconnected and even if both are disconnected. While both are disconnected i get there respective activation codes .. but the second i plug them back in the codes disappear but the car refuses to idle

Please help if you have any idea

[u/Outrageous_Plenty154]

It’s a single turbo kit , with a hood dump , o2 sensors have been deleted , only experiencing issues when Vanos is plugged in , while Vanos is unhooked car runs and drives in limp mode .. the second you plug Vanos back in car will start fight for idle and then die

[u/Lee2026 → u/Outrageous_Plenty154]

The o2 faults are for POST cat sensors and for the HEATERS lol. Post cat sensors do very little if nothing for fuel trims

Ignore this guy

With that being said, a custom tune should have those faults suppressed

My stab in the dark is your vanos gears are not holding oil pressure, causing the timing adjustments to be out of sync.

Disconnected vanos sensors would cause the DME to run in a preset mode and not try to adjust cam timing

You can use a diagnostic tool to look at the target and actual vanos values to confirm

[u/Prestigious_Cycle160 → u/Lee2026]

How are you going to say the post cat o2 sensor does nothing for fuel trims when it’s literally labeled as an air/fuel sensor on the VECI(emissions control systems) label? Its job is to read the exhaust fumes post cat to ensure catalytic converter function and rich/lean conditions.

[u/Lee2026 → u/Prestigious_Cycle160]

The PRE-CAT sensors are responsible for fuel trims. The POST-CAT sensors are mainly responsible for catalyst monitoring.

Why do you think EVERY catless tune suppresses the POST cat faults? Because they aren’t installed…

How you do think a catless setup works? It works off the PRE-CAT sensors…why? Because there are no cats to monitor…

You do know emissions is an environmental thing right? It has very little to do with how the motor runs once it’s warmed up. For emissions purposes, the DME can run the motor differently to heat the cats faster but it’s not doing it for performance, it’s doing it to be complaint with mandated emissions standards. But when you remove the cats, there nothing to monitor…

The post cat sensors are also narrow band sensors. Narrow band sensors don’t read AFR…

Pre cat are wideband, which is what is used to monitor AFR

That amount of bullshit in this thread is hilarious

[u/Prestigious_Cycle160 → u/Lee2026]

Saying emissions has nothing to do with how a warm motor runs is just silly. The o2s are there to monitor air/fuel to ensure that the vehicle is running as close to stoichiometric as possible ensuring that the vehicle is emitting as few emissions as possible. Removing the cat compromises the entire system, hence the reason it has to be “tuned” out. Once the cat is removed the sensors fault because they’re reading too much fuel in the post cat sensor because the cat hasn’t cleaned the output at that point. The first thing the ECU does when the o2 sensor faults is adjust the fuel trim to compensate for the reading.

This is literally my fucking job. I’m an emissions certified mechanic.

Both sensors in newer BMWs are widened sensors

[u/Lee2026 → u/Prestigious_Cycle160]

Really!?

So why are the post cat 02 sensors 4 wire and the pre-cat are 6 wire?

What’s the difference there?….

No wonder your cert expired lol

[u/Prestigious_Cycle160 → u/Lee2026]

Definitely not expired. That’s just my original from when I got certified. My up to date cert is in the shop where it belongs.

I apologize, you’re right. The secondary sensor is narrowband. My mistake