Code 25 lean condition running ~12psi

EvilStig

New member
Hi folks,

so the wideband I installed is a PoS and doesn't work, so I can't get an accurate reading... with the stock o2 sensor, the ECU throws a code 25 after ~60 miles of driving. I'm running ~12psi on a CT27 (stock turbo with upgraded turbine and compressor impellers) using a greddy profec EBC. My boost gauge is also apparently shit though so I don't really know how accurate that is either...

Anyway, shop tells me vacuum leak which I know it's not, since the manifold holds pressure. Too much venting from BoV would read rich, I would assume, so that leaves... the injectors? Is it possible I just need to upgrade my injectors to support the extra boost? Has anyone else run into this?

Thanks.
 

underscore

Well-known member
If it's at the same-ish distance every time maybe the O2 sensor is just crapping out when things fully heat up? Or alternatively something is leaking when fully heated up. Is the code coming up under boost or when cruising?
 

EvilStig

New member
underscore":2ul6frha said:
If it's at the same-ish distance every time maybe the O2 sensor is just crapping out when things fully heat up? Or alternatively something is leaking when fully heated up. Is the code coming up under boost or when cruising?

milage before it throws code seems to vary. It usually seems to throw it while cruising at or around freeway speeds.

I've already replaced the o2 sensor so I doubt that's it unless I was sold a bad one.
 

Gert

Active member
EvilStig":kphwkj0k said:
Has anyone else run into this?
Probably. But you are very brave that you try to tackle a problem without knowing the most important data like: A/F ratio and boost level.
 

EvilStig

New member
Gert":3hktfvxf said:
EvilStig":3hktfvxf said:
Has anyone else run into this?
Probably. But you are very brave that you try to tackle a problem without knowing the most important data like: A/F ratio and boost level.

hey not my fault everything is shit. Gotta start somewhere to get this shit working again.
 

underscore

Well-known member
If it's happening while cruising you should be under vacuum so a leaky BOV would make it run lean. Definitely get a known good boost gauge on there along with a wideband should cut the potential causes in half, since you'll know whether the problem is that you're actually running lean or it's an error in the engine management somewhere.
 

EvilStig

New member
silverarrow":38q3wrjr said:
Can you dial down the boost or is the wastegate set at 12 psi? Clogged cats if you still have them both?

Using a pro-fec EBC, have to reprogram it anyway after leaving the battery unplugged overnight to clear the codes, I'll dial it down a bit to around 10 and see what that does. Although the pro-fec isn't smart enough to meter boost by MAP, I still trust its boost reading a lot more than the stock or aftermarket boost gauges I have installed. I've only ever seen the glowshift gauge hit 8 PSI when I know it's been up around 14, and it consistently reads a vacuum with the engine off or even under moderate boost (so did the Bosch gauge it was a replacement for).

underscore":38q3wrjr said:
a leaky BOV would make it run lean

I don't believe it's leaking under vacuum, my concern was if it was dumping too much to atmo when letting off under boost (It's a partially recirculating system). But that would cause a rich condition.

It took me half a week to run the current boost gauge and wideband into the cabin, and the manufacturers have been less than helpful in supporting their products. I'd have to start from scratch with new, different branded equipment to install trustworthy gauges, and that's time consuming and expensive... plus I have only one upstream o2 port so I'd need to find another all in one gauge and sensor kit that includes a narrow band emulator to plug into the ecu.
 

underscore

Well-known member
Don't get fancy with the gauge, just run a piece of vacuum tube out the hood near the windshield and back in the window and put a mechanical gauge on the end of it. Borrow one you know is good off a buddy or grab a cheap one, it doesn't even have to be made for a car. If it's something new test if against a known good gauge to see how off it is.
 

silverarrow

New member
Curious...what wideband are you using and I'm guessing you're putting the o2 sensor in the stock o2 location? As for the boost gauge issue, bum one off a buddy to test. Reading off your ebc should be quite close or as accurate as a boost gauge too though. I've never been a fan of the Greddy boost controllers...had boost spikes and boost creep often with them. I'm a fanboy of the APexi AVCR if I had to have a boost controller.
 
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