Hi all, I've been having an issue with missing boost and extra fuel being consumed as well as a loss of power lately. The car is an 06 MCS with a 17% pulley, 550cc injectors, and a tune from Adriancl. Has a CAI and exhaust as well also no cat. It seems to run normally at idle but smells a little rich, when driving I get roughly 15 mpg and my scan gauge reads 65 kpa at max (9.5 psi) so something is definitely up.

Did a smoke test today and found no leaks in the boost or vacuum systems. Everything else seems to be in good condition and I can't identify any other issues that might be causing this. Is it possible the supercharger is bad? Also tested the BPV recently and that is working properly so it's not that. Tried searching it on the forums as well but could not find anything quite the same as my issue.

Any help would be greatly appreciated.

 

Could be bad O2 sensors.
The ECU adjusts fuel according to their readings.

 

I'll test my O2 sensors and see if it could be them but that still wouldn't explain my low boost.

 

I'd be more suspicious of the MAP sensor than the O2 sensor.
The boost pressure reading you're getting from the scan tool comes from the MAP. If it's giving erroneous readings then the engine will not run right and it could be fooling you into thinking you're not building boost pressure.

 

I can check those as well but the readings seem accurate and the map sensor readings are consistent and mostly normal.

 

failed pressure regulator...

Put a fuel pressure gauge on the shrader valve, vacuum pump on the regulator, fire it up and monitor the pressure... apply vacuum to it and the pressure should change (no idea what they should be)

If you pull the O2 sensors get some CRC electronic components cleaner and spray the crap out of the tip. Could be the sensors are getting "lazy" meaning slow to respond. I've seen this in the past and cleaning it was a short term fix while new ones were on order. I dont recall how long I ran it that way (bmw 325is) before I swapped them but they were behaving the same at the time of the swap.

 

I've got a spare fuel pressure regulator so I'll swap that out and see if that fixes anything and if that doesn't change anything I'll test it with vacuum pump like you suggested. I'll also check out the O2 sensors like I was saying before and I have some pairs of those so I'll try switching them around as well.
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Look at the vacuum line that goes to the fuel pressure regulator, and replace it with some quality silicone with clamps

 

Checked out the FPR today and swapped it with a spare as well as checked out it's vacuum line. The line checked out and sealed good, FPR I took our seemed ok and the one I put in didn't make any noticable difference. Checked out the O2 sensors as well and all seems good there, they checked out normal but I might pick up a some new ones and swap them to be sure.

 

vacuum lines are cheap, just swap it. when I pulled mine and tested it, it sealed fine however when I took it for a spin with the new vacuum line the change in performance was noticeable. I expected no change was surprised... I figure it was running a tad bit rich.

 

Hmm fair point I suppose I'll swap it later or tomorrow and see if it helps

 

Another point eliminated How do the fuel trims look?

 

Swapped the fpr for a better one and replaced the brittle old line. No real performance difference but I am glad I replaced that line. It was super brittle. I'm trying to get my diagnostic laptop up and running, once I do I'll check the fuel trims.

 

Just wanted to say thank you to everyone for helping out so far. This problem has been super weird and everyone I've talked to about it so far has been stumped by it. I'm going to try to work on it regularly and I will do my best to update this until it's fixed. Never heard of anyone with this issue before but I hope this helps anyone else who might.

 

Go put some miles on it or clear the adaptations (?) and let it relearn... Also (not sure if you mentioned this) look at the BPV for proper operation.

I had inconsistent performance out of mine, springed the BPV arm so it had help to close and performance changed with the spring install. It would not build boost similar to yours and behaved inconsistently. Finally got a DT BPV in there and now its consistent. Was in the middle of doing a sea foam treatment on the motor and found I had an exhaust leak with smoke exiting behind the motor some place... (still not looked at the exhaust to find the source) But... it now does run consistently, even with the first compression check numbers being all out of wack (140, 90, 120~130, 130... iirc) the first time I did them 3 months back. I suspect carbon on the valve seats, thus the sea foam treatment. When done with the sea foam, will recheck compression #'s.

 

Tested the BPV about a week ago and it's good as far as I can tell. Gonna be renting a compression tester soon as well to test compression, just to check. I did a seafoam treatment recently too but noticed no difference. It's my daily so I'll be sure to keep an eye on things and post updates as I drive it.

 

Replaced split intake tube today with a better one. I also replaced the alta intercooler boots with new stock replacements. Did not notice a significant or noticable difference in performance and my gauges indicated no increase in boost. I have an analog boost gauge on the way that'll help me more accurately record boost and diagnose. I was also thinking about possibly doing a compression test today. If I do I'll post the results here. Does anyone think low compression or a bad ring may be the problem?

 

Played around with inpa and stuff today a bit, attached are some photos of what I found. 

 

Installed a boost gauge today too and found out that I am making around 20 pounds of boost, at least according to the cheap boost gauge I got to test pressures. I also picked up a cheap o2 sensor just to try and rule those out of the mix. I'll install that tomorrow or Wednesday if I have time.

Although this means my superchargers functioning properly and that is a weight off my mind it makes me worry about doing a compression test even more. I know my car has been down on power lately and slowly been getting worse. Got my fingers crossed that I don't have bent or dirty valves or worse.

 

This sounds like exactly what I just went through and turned out to be a plugged catalytic converter.

 

If only I wasn't already catless

 

well that rules that out.... map sensor and the mapt can cause those issues as well

 

why is your intake temperature 230*f?

 

Good eye, didn't even notice that. Maybe my tmap sensor is shot, I'll look into it.

 

fire it up cold while monitoring the sensors, if it never changes then look for an open sense wire off the sensor back to the ECU.