Hi guys, I have a 1985 Corvette with a Miniram Intake, flat tappet version of ZZ409 camshaft, Hedman Long Tube Headers, 3.75s, Cut Air Filter Lid, K&N Air Filter, 58MM Throttle Body, EGR Delete, Catalytic Converter Delete, AIR Delete, TB Coolant Bypass, Descreen MAF Sensor, Heated O2 Sensor Conversion, Timing set at 10* BTDC, MSD 8.5MM ignition wires, a few other small modifications and an AFR Gauge and Wideband O2 Sensor.

My problem is, when I first start the car, it idles at around 14.7:1 AFR, then slowly goes lean all the way up to 19:1. When it goes into closed loop, it idles at 14.7:1, and slowly goes lean all the way up to 19:1 again. It is very, very strange, you would think that especially in closed loop mode, the computer would be able to fix it and get it back to 14.7:1, but it doesn't. If I rev it up a few times, it will settle down to 14.7:1, and then slowly go lean to about 19:1.

I'm very confused. I just adjusted the valves the way that I found in All Data, and instead of going a whole turn, I went 3/4 of a turn as some other people suggested.

My MAT sensor is new, my CTS sensor is new, O2 Sensor is new, MAF sensor was swapped with one from an 86 and there was no change in engine response. The injectors are all new, cap and rotor were done less than 5k miles ago. Just repaired an exhaust leak at the collector, I really don't understand.

I had my computer tuned by lt1pcmtuning.com.

Is this normal? I'm really annoyed with this car and often think about swapping out to a carburetor.

I don't get how everyone else's build was so simple and mine keeps having one problem after another. Thanks for any help!

 

Nevermind, I found out what it was. My speedometer wasn't working and I did a diagnosis on my vehicle speed sensor and speedometer calibrator. My speedometer calibrator uses the same ground as my heated O2 sensor, the splice connector area was producing a resistance of 67-70 ohms. I swapped it and and fixed up the wires and everything is working perfect now. The O2 sensor couldn't get hot enough and would stay in open loop, which is why it was running lean. I'm assuming because the open loop mode was tuned for lower temperatures, and as the temperature got higher it threw it off or something. Don't really care about it too much.

 

Where did you get the idea everyone else's builds were simple? I've been trying to get my 396 tuned right for 2 years. Problems and performance go together.

 

I would prefer to say tuning is never ending and we all work together too help each other. Don't give up Daniel, and you'll get what you deserve eventually.

 

Well I'm going to be getting AFR 195s and MSD 6AL2 and MSD Ignition Coil, that'll be it for engine mods, and hopefully everything will work out okay, especially since my MiniRam is a 1204 gasket... :/

After that the modding fever will be over.. Until I blow the motor.