AFR and Boost suddenly in the toilet, WTF???

[SpeedViktm]

*** FIXED ***



Two logs attached, one when life was good and one now that life isn't. Except for AFR and Boost they look very similar.

Full Stage 2 goodies, 50/50 E85/93 mix, tuned by Dizzy. Been running great, suddenly started running like shit Fri night. Fueled up at my normal place on Thurs night. Saw that I wasn't getting over ~15.6 pounds of boost (usually in the 20-21 range) and AFR's were dropping into the 9's. Popped a P0234 CEL. Bucking and jerking like crazy, then settling down above ~4500 RPM but still sluggish. Air intake sounded odd, more like a hiss than the usual whoosh. Start thinking boost leak.

Checked boost path as best I can, tubes and hoses secure. Boost solenoid visually looks OK, everything attached. Disassembled BPV, inspected, cleaned and re-installed. Ends of the spring look a bit worn but I don't know what they look like new. No improvement.

Removed neg battery cable, pumped brakes, let sit. Reflashed tune. No improvement.

Removed filter from CAI just in case it was dirty (old, but I clean it). No improvement.

Cleaned MAF, put stock BPV back on. Noticed the spring on the stocker is a LOT stiffer than the Cobb. No Improvement.

What else to check?

[GODspeed7]

O2 sensor would be my best guess if you are SURE there isn't a boost leak


Tapatalk LIKE A BOSS!

[ASHMS3]

That is definately a boost leak. WGDC way higher, can't hold boost and AFR's are fucked. Keep looking, look for Joe Isuzu's boost leak finder vid if you cannot find something on further inspection.

[SpeedViktm]

Originally Posted by GODspeed7 O2 sensor would be my best guess if you are SURE there isn't a boost leak

Thanks. 2nd O2 Sensor has complained in the past, not currently throwing a CEL though. DP is catted. Kind of ignored the past P0139's since I know the wires on the 2nd sensor are stretched kinda tight. Probably should fix that some time.....

Originally Posted by ASHMS3 That is definately a boost leak. WGDC way higher, can't hold boost and AFR's are fucked. Keep looking, look for Joe Isuzu's boost leak finder vid if you cannot find something on further inspection.

Thanks, I'll do a more thorough inspection. Cursory glance looks good, but might be a hole in a boost tube or on the bottom of the IC that I can't see without disassembly.

Cleaning MAF and changing BPV didn't help, not that I was holding much hope they would....

[Fatguy729]

How-To NATOR A Boost Leak Tester for $15

[SpeedViktm]

Thanks to all. Cold boost tube at throttle body was loose, tube came off when I was pulling the IC off and it shouldn't have done that. Clamp was a little far back on the tube and might have been riding on the lip of the TB and eventually slipped down...

So the take-aways of this thread are:

1. OP is a dumbass.
2. Don't assume that since the hose was tight when you put it on 6 months ago, and it appears to be where you left it, that it still is tightened.

I'm still gonna build one of those testers though, like the shit outta that!!

[ASHMS3]

Shit happens, you got it worked out so chalk it up as a W.