So i have a 91 JDM FC with the following:
-new street ported 13B
-725cc secondaries
-RTek 1.7
-stock cleaned and tested 550cc primarys
-3" turbo back exhaust
-greddy blow-off valve
-stock intercooler
-Brand new OEM TPs sensor
-86 clock warning lights

So the problem ive been having is when im driving my AFR gauge reads 10.9 to 11.7 then it seems to switch over to 14.7-15.2 between 2000 RPM to 2700 RPM the engine then intermittently has a hesitation when i accelerate and the AFR gauge reads up to 15.7 until secondaries kick in and the AFR reads 12.8-13.6, as well whenever i let off the gas the engine boggs and AFR gauge always reads 16, when i press on the gas again it feels a little harsh getting it revving smoothly . i cannot code the ecu since i only have a 86 clock warning lights, i dont know what could be doing this!

 

Is this car a conversion or originally turbo? If a swap, be sure the AFM and MAP sensors are the correct part number for an S5 turbo.

Under what kind of throttle input does it go lean at 2-2.7k RPM? If you're at light throttle, you'll go into closed loop (O2 sensor input used) and meter around 14.7 AFR. That's normal.

If you get a lean hesitation on any kind of acceleration, it may well be a fuel issue. I would suggest correcting your warning light issue to get a check engine light. Otherwise, you can test individual sensors by multimeter per the FSM.

You could also have low fuel pressure, which could create a lean spot as the injectors would not flow as much. Testing fuel pressure involves tee-ing a gauge into the feed line. Pressure specs are in the FSM.

 

Forgot to say its a stock JDM 13B Turbo with airpump removed with all proper vaccum lines bocked, as well i added a FD fuel pump but it was used. it seems to do the hesitation when i accelerate medium to fast. as well when i let off the gas it makes a blurpppping sound (does not sound normal). when i press on the gas again it revs smooth again.

 

Are you using a JDM ECU or USDM?

 

Using N374 jdm Ecu and i have tried my stock ecu and the one with rtek 1.7 and the same problem presists.

 

The reason I asked is because a USDM version has the ability to read for error codes besides the Check Engine Light. I don't believe the JDM versions have this other way of checking for error codes. If there is a Green check connector w/four wires near the leading coil then three of these wires, Yellow based, are connected to the ECU and are for diagnostic purposes such as pulling codes.

 

it feels like its loosing power as i am accelerating faster and then it hesitates and goes lean, could this be a fuel pump problem, and this doesnt happen everytime i accelerate. and doesnt seem to happen at higher rpm just around 2.5k

 

could my fuel pump be going bad or does it just not work at all?? or is there somthing else in the fuel system that could be malfuntioning???

 

Clogged fuel filter?

 

Could my secondary throtlle plates be set slightly open?

 

Or maybe i need to take the throttle body apart an clean