cars s4 chassis s5 engine and ecu. replaced fuel filter, fuel pump, replaced secondaries injectors, they are all clean. free rev it will go up WOT no prob. but underload wot its done no matter what rpm high or low. seems to be at almost halfway down on the pedal when this happens. i checked the TPS for bad spots both of them showed no sign. the only thing i can think of is pressure sensor or afm? idk guys gimmie some help here. thx in advance

 

First off, check the timing. My car was doing something similar to this, and the timing was way off.
Second, pull the codes. There are directions here: http://fc3spro.com/TECH/HOWTO/ERRORC...KI/zerror.html
You have to make a tester, but the parts listed aren't available anymore. You can still get similar ones, though. I used the "Red LED Assembly" part # 276-0270 from radio shack. You find it in the parts bin in the back of the store (the place with all of the relays and other electrical components.) That piece looks similar to the one in the writeup. You can get the spade terminals anywhere, I got a whole pack of them at wal-mart.

 

you think timing it would free rev high but not under load? about the codes im assuming they are retrieved from the ecu?

 

it does it after half throttle no matter what rpm.

 

That sounds like it could be a malfunctioning sensor. So since I noticed that you have an s5 ECU, that changes things. Does your car have the check engine light? If it does then it should on if the ECU detects a problem. If not, then I'm not really sure how to check the codes since its a non-stock configuration. You could still try the stuff listed in the link I posted. It shows you exactrly how to build the code reader and where to connect it. It costs maybe $9-10 in parts.

 

i got the parts laying around im pretty sure. i will check and mess with timing a bit. would afm cause it?

 

My guess is probably not, but I'm not totally sure about it. Another thing to do is check and clean the connections to the sensors and make sure your grounds are good. Bad grounds can cause all sorts of weird symptoms, possibly including this.
My car is actually doings something like this but to a lesser degree right now, and I think its from a bad connection on the pressure sensor.
Do you have an A/F meter? That would be helpful in chasing down the problem.

 

im swapping pressure sensors just 2 do it. i dont have a spare s5 afm. grounds are all there and then some....i think im gonna put a new ground in at the fuel pump. the CAS nut is about a 1/4 inch from the from im assuming advanced?

 

check the oil

 

Is this a TURBO engine and ECU? And the boost/pressure sensor is what number? N???

 

sry hailers S5 NA ecu and engine pressure sensor is an N350.

 

ok here well it appears that the secondaries are not kicking in......got 12v to the plugs so the ecu isnt sending a signal....where now?

 

unplugged the secondaries and no diff in rev........

 

could it be the afm? ive heard if u dont have it plugged in the secondaries wont fire? could it be that its bad and its not sensing the afm is there? do the secondaries kick on at full throttle? i know around 3500 rpm they kick on but do they at full throttle? thx guys

 

where does the signal come from to kick the secondaries on?