Nikom1

The video shows all the sensors while driving with the snap on computer connected, you will see the BLM numbers rising with the rpms, car goes 10mpg and lacks power, any thoughts will help. THanks

PatternDayTrader

So its adding fuel. Either because it's correcting for a lean condition or because it's erroneously enriching the mixture.

Go stick your finger in the tailpipe and see if there's heavy black soot present. If so then it's very likely running rich (which seems probable), and there could be several reasons for that, but step one is finding out where the mixture really is. Rich or lean.

Cliff Harris

Your O2 cross counts are increasing way too slowly. They should go up about one time per second.

I suggest a new O2 sensor.

Nikom1

There is nothing on the pipe, its clean.

This a motor with about 1300 miles on it and has had this problem since day 1.
All sensors have been replaced, injectors, MAF, Computer etc.
The intake has been smoked, sprayed with carb cleaner checking for leaks. None Found.

Nikom1

This is actually the third one installed and it is a 3 wire heated o2 sensor just to be sure that it is at the right operating temp, since it is installed on headers.

Kevova

Is engine stock or modded? If modded was ecm "tuned" for changes. Since screen says 87 trans am is this a 305 to 350 swap?

Nikom1

The only parts that are not original on this car is the exhaust from front to back.
It has the 5.7L

PatternDayTrader

Forget about the data stream for a minute and figure out how your going to figure out if its actually rich or lean. I suggest sticking your finger in the tailpipe and smear it around and see if there's heavy black soot coating everything. If not then stick a fuel pressure gage on it and see if your fuel pressure is dropping off .... You could be suffering from either a rich or lean condition. Step one is to determine which one.

Nikom1

As i have checked , its clean. Fuel pressure is holding with the engine off for an hour or so with the gauge on it , it is roughly 47 with vacuum off and 40 or so on, and rises while driving as it should. The INjectors had been replaced due to leaking with bosch 3's.

What could be causing to run lean and get 10mpg? the egr opening?

Kevova

INT/BLN will go up on accel and should fall back to the 125-140 range, which data streams seems to do. You post 1300 miles engine rebuilt? What is vacuum at idle? Is timing retarded? I would verify tdc on balancer is actually TDC of #1 cylinder.

Nikom1

The vacuum is holding a 18- 19 at idle, the timing is 6d before tdc.
I had double checked the timing marks on the crankshaft and balancer , just incase it would of been the wrong one and tdc would of been off. I have played with rotating the distributor and had no changes.

has been looked over many times and can not get to the problem.

Nikom1

also , where is the gas going? Gas has been measured by mileage and gallons used and averages 10-11 mpg.

PatternDayTrader

You grounded the est connector before setting base timing ????

PatternDayTrader

A lean engine can get bad mileage because you have the throttle open further to go the same speed. Ten to eleven is pretty bad though. I assume no codes or you would have said that. I guess I would verify base timing again, and check all ecm input sensors. You might try adding an auxiliary ground strap to the exhaust system. I have had to do that from time to time to get o2 sensor cross counts up where they belong. Don't ask me why cause I don't know.

Kevova

Does tcc or OD work?