For a few weeks now my car has been experiencing a loss of power, most noticable at low rpms/off boost performance. It also experiences occassional rough idle (today dermined to be very rich, approx 9.0afr and injectors at 1.0-1.3ms), high knock count (seems to be caused by a super rich condition, and 100% injector duty (very rich again).

It is a v2 sti with basic upgrades and a power fc originally tuned on a dyno. I am running 15.5 psi of boost. I originally discovered a leaking intake manifold gasket so I replaced that as well as the maf as I had access to one. The car still ran the same. Today we did a compression test (passed), examined the coil packs- ok, and spark plugs (looked great). After that we ran it on the dyno and it is making about 30hp less than the last time it was tuned.

The strange thing is sometimes it will run good (still seems down on power), but other times it will be experiencing the above systems noticeably. After the dyno we hooked up wideband to it and did some rolling road runs and again it seems to either run ok, or just be way off. This is without making any adjustments to the power fc.

Does anyone have any suggestions of things I can look for? Mechanically the motor runs good and seems fine, except when it decides to go rich. We are out of ideas and spent a ton of time in this car trying to figure it out.

 

if you still have the original ecu I would maybe swap back to that to check for sensor faults. Something cannot be right if your injector duty is running 100%

 

Do you have a walboro pump and the OE fuel regulator? Could it be the FPR being over powered and intermittantly starting to fail?

 

Whats weird is it intermittently will go 100%, other times it hangs right at 80% with the exact same boost levels. I gave my original ecu to a friend, I might see if he still has it.

I am running a v8 sti fuel pump and stock regulator. We did do a fuel pressure test and it seemed to be ok on the gauge. I was originally thinking this route too but it just doesn't make sense with the readings we had on the gauge. I would think I would see some fluctuations. One time it was running **** poor and I shut it off and turned it back on and it started to run ok. Last night I was playing with the overall correction on ignition, pulling timing because it was getting high knock counts on the interstate (which we tuned out on the dyno earlier that day) and didn't notice a difference. The strange part is when I got into town I set it back to 0 correction and it felt real strong, lower knock count, and 85% duty cycle.

 

I would check the sensor outputs on the commander and post them up. I dont see how a FRP or uprated fuel pump would show your injectors on the commander as being 100%, if anything it would be lower. Could possibly be a problem with the power fc itself

 

I will record everything down tonight when I get home.

 

So here is what I got:

Idle, car warm and just started:

AF-1: 1.04v
THRO: 4.77v
BST1: 1.25v
BST2: .03v
WTRT:1.10v
o2-1: .20 steady (after moving car began to fluctuate 0-.74ish)
EXTM: 5.10v

Switches with circles solid:
IGN
IDL
NTR
FPC
--------------------------------
2nd Gear Pull, WOT @ 6300 rpms

AF-1: 4.61v
THRO: .83v
BST1: 4.07v
BST2: .10v
WTRT: 1.10v
o2-1: .88v
EXTM: 5.10v

Switches with circles solid:
IGN
FPC

I am running an mbc and have the boost control turned off in the pfc. I also tried to run with the o2 control turned off and noticed same if not worse performance and had a bad low rpm stumble when driving around.

 

So today my car is right back to hitting high knock counts in 5th and 4th gear above 10psi. I have been able to reduce it by adding fuel to 1.2 on the overall correction or by reducing timing by 6 degrees on the overall correction. Either of these methods rids me of the high knock count at wot but makes the car run poor. When I added fuel it had a knock count graph really high and spikey just when running at 3k rpm which I did not like but it smoothed out at wot, however the motor felt like it did not want to rev easily. With the timing reduced it didn't knock up top but was waaay down on power. With it set at 1.0, where it should be, I was seeing quick spikes of 78 on the knock count! I would expect to be out of injector but duty cycles were between 50 and 85% depending on throttle position.

 

kbahus did you get anywhere with your power loss and rough idle? my MY97WRX has similar issues and I too have noticed a constant WTRT reading of 1.10v.

Thanks.

 

Whats WTRT? water temp? Would a fault coolant temp sensor cause it? i.e. firing in too much fuel. Or does that not work on the PFC like the stock ecu?

 

Its water temperature, but my dashboard gauge reads middle ish as normal and the Commander show the temperature rising and the fans coming on also as per normal, but the WTRT sensor reading in the sensor check screen shows a constant 1.10V, my car is running very very rich as well, so sounds like it could be the temp sensor if it wasnt for the dash gauge and rad fans working.

 

the dash board temp gauge uses a different sensor..

Sounds like you might have found the problem!

Simon