High BLM


I have been putting the car back together after being apart for many years. Engine is fresh......109 block, Champion irons, 206/206 roller, 60lb injectors, Translator with new plastic style GM 3.5 mass air sensor, Turbo Tweak chip, Racetronix 340 pump, adjustable regulator. Scanmaster to read data.
I followed Turbo Tweak instructions and have the fuel pressure at 43 (vacuum off). The car has been run in the garage only as it is not road worthy yet.
Originally the AF was at 4 and the idle BLMS at 137 . The Integrator stays at 128. I had a lot of issues getting the IAC numbers to stay put even after doing the procedure. The exhaust stinks. I have tried several GM oxygen sensors and they come out black and sooty. I pulled the spark plugs (CR43TS gapped at .030) and they are black as well. I have been checking for vacuum leaks and the only one I found was for the climate control head so I plugged that line off. I have not had much change in the BLMs. I noted that the AF was 4. I tried richening up the mass air on the dial in the Translator box and it went up to 6 but the BLM's didn't change.
I then tried increasing the fuel pressure up to 50 (using a rail mounted gauge which I dont know how accurate it is) and blms dropped to 134. I tried to increase fuel pressure more up to 60 psi and BLMs dropped to 132. I turned the pressure back to 50 and installed a new GM AFS 81 oxygen sensor (early 2000's vintage). After running for 5 minutes the BLMs went back up to 137 with the new sensor. I also noticed that the AF switches between 5 and 6. I pulled the number 1 and 3 spark plugs after all of this and they were wet. I am kind of at a loss as there is definitely something up with the black spark plugs and yet the high BLM numbers are indicative of it being lean and the computer adding fuel. I am not sure what else to try. I just dont want to wash out cylinders in a new engine.
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I would run and drive the car with 140 BLM's before I drove it with wet plugs and high fuel pressure.
I would put the fuel pressure back to normal, recheck the numbers and idle it for 15 minutes or so and check the sensor and plugs hopefully they look normal (dry and tan) regardless of the blm's.
Once on the road see where they go, mileage driven (computer learning) may change the numbers as well, hopefully back towards 128.
A wideband O2 with that setup is almost a must I would think and would give you better data.
If your BLM's are at 137 with the engine warmed up in Park...and your fuel pressure is set to 43 line off...then you have pre-turbo exhaust leaks/vacuum leaks.
I got the blms down to 134-135. Fuel pressure is 43psi. I had been in touch with Eric at Turbo Tweak. He said +/- 10 numbers is ok. I found a small vacuum leak at the HVAC control line. I plugged off all the vacuum lines at the throttle body and sprayed around the throttle body and intake. I am convinced it doesn't have any leaks. My header flanges have been flycut. There are no exhaust leaks. It's slightly lean at idle. My next step is to send the injectors out for service as they were last run back in 2011-2012
There is a chance that they are partially restricted. We shall see....
I was chasing very high(150) BLM's on my low mileage car and having the stock injectors flowed/ultra sonic cleaned dropped the BLM's to 124. I will try to load before/after cleaning pics, the difference was drastic.
injectors before.jpg
injectors after.jpg
I had my injectors cleaned and flowed and they were not bad to begin with and were within specifications. I was told by Eric to drive it and see. He says 135 isn't bad.
I would spend a little time tinkering with the translator. Look up the manual online if you don't have one. Here is a snip: