Car is an 88 S4 TII.
I've been chasing my tail here and coming up with nothing. Last week I went for a short drive, was driving the car fairly hard and everything was running great. I literally turn around to go home and as soon as I hit 4k rpm the car sort of stutters and and makes no power (in comparison to how it was running before). This is not the 3800 rpm hesitation, I would compare it more to how the car behaves when there's a large boost leak. With that being said, I spent a solid day pressurizing the engine in various locations (@ AFM, @ intercooler inlet, @ throttle body, etc. to eliminate one variable at a time) with a DIY boost leak tester and an air compressor. At this time there are no leaks I am aware of that I have not attended to.

I have had my friend/tuner ride along with me and monitor the ECU parameters, what we have found is that:
-The car is still building boost, gets very near normal peak boost of 8 psi.
-AFR goes rich once approximately 3 psi of boost is reached, IIRC AFR was in the low 11's.

Car was tuned and AFR was spot on before this problem occurred. I pulled, checked, and cleaned the plugs and they looked very normal. I find it very strange that literally within the same drive the car could immediately start performing so differently. The car runs absolutely normal under normal driving conditions in lower rpm. Below I will list mods and any relevant information to the cars maintenance.

Does anyone have any ideas or advice? When can I go from here as far as troubleshooting and elimination? Could this be an ignition/coil problem? I would GREATLY appreciate it, I just want to enjoy my 7 again....

Mods:
-Rtek 2.1 ECU
-AEM UEGO wideband
-ID 725/1000 injectors
-**supposed Walbro 255, claimed by previous owner, not verified**
-BNR stage 3 turbo w/ upgraded wastegate actuators set at approximately 8 pis
-Corksport TID
-Racing Beat 3" downpipe to test pipe
-HKS hi power single exit exhaust
-Rat' nest delete

Maintenance (all performed within 100 miles):
-new OEM recommended plugs and NGK wires
-AFM rotated to sit properly and level (originally was sitting rotated @ 45* due to clearance issues, was tuned in this incorrect orientation but ran fine for few days before this issue occurred)
-new fuel filter
-new injectors
-OEM thermostat and coolant flush
-Oil

 

rewire the fuel pump yet?
How are you regulating fuel?.stock regulator?

 

Styx, I have not done the rewire as of yet, and unfortunately I am on the stock regulator...I know both are things that eventually needed to be attended to. For argument's sake, if the fuel pump not being rewired were to blame we would be experiencing a lean condition at WOT. If the regulator were to blame, would I not be having starting issues and also be rich at idle? What are your thoughts? Thank you for the ideas!

 

does it drive fine in normal conditions going up the rpm band past 4krpm?

I know you said it went rich before it cuts off but just to be sure, check to see if the secondaries came on when it is suppose to.

 

sure sounds like an injector issue to me, if its right at 4K. are you setup to have the secondarys come on right at 3800 still?? ( tach can be slightly off)


I had one secondary injector come unplugged once and it would run great to 3800 then run like total ***.

 

I visually checked the injectors to ensure that nothing has come loose. If an injector had come unplugged I believe I would be running lean.

I've looked into the FPR and this is not a cheap venture....considering metric-barb fittings in the sizes required don't exist, I need to convert to all -AN lines or use like 2 adapters on each fitting to work with hose...

 

did you try a post in the RTEK section yet?

 

Not relating to this issue, no. I just don't see how it could be Rtek related. I mean anything is possible, but the sudden change leads me to believe it's something of a physical nature. I'm going to do a TPS sweep tomorrow, does the car need to be warm to just check for dead spots? I know it needs to be at operating temperature to set proper voltage.

 

check your grounds!

 

Brian, recently went over the entire engine harness and at the time cleaned and improved nearly all ground. The only one that now comes to mind that is missing is the small one from the center of the firewall to the top of the UIM. I'll be sure to replace that.