Hi,

My newly overhauled long block runs great; except that it's running lean- the plugs are white. I'll need to check the fuel pressure, but other than a vacuum leak from various gaskets/hoses, what all sensor based problems can arise causing a lean condition?

The o2 sensor is new, plugs, cap, wires, rotor, and the fuel pump are all relativity new. The only other sensors that I can think of that would cause a lean condition would be the coolant temprature sensor (new), the MAP, and the TPS. There are no vacuum leaks, although the motor pulls about 15 inches of mercury- it should be around 18 or 19, right? The psi on the cylinders seems a little low at 135 psi, but none of this explains why the plugs are white. the intake gasket gasket is new, and there is no hissing sound emiting from the engine, indicating that there is a vacuum leak. I'm at my whits end, and am pretty tired of working on it. Any help would be appreceiated.

 

135 psi is health...120-150 is factory spec.........how many miles are on the plugs? are you geting any codes?

 

The motor and the plugs have about 300 miles on them. I noticed the plugs were pretty white on the old motor as well. I'm a fan of autolite plugs, but perhaps I should run the champion p/n that is under the hood? Maybe the heat ranges are a little different? If it were REAL lean, I bet I'd hear a pinging/detonation, but I'm not.

There are no codes from the engine (the check engine light isn't on) but it comes on when you turn the key on. It's OBD1, so a lean condition wouldn't be monitored under the component perameters.

The only thing that I can think of is low fuel pressure, meaning low volume. At 200K+, it probably wouldn't hurt to change out the fuel pressure regulator, but before dropping 65 bucks on a parts swapping experiment, I'm going to check the fuel pressure.

Has anyone expericenced a lean condition due to a faulty MAP or TPS sensor? What about a bad computer not commanding the injectors on for a long enough duration?

 

OBD1 should be able to pick up a lean condition...........FYI to read plugs and be as acurate as possible you must do a WOT run then immediately shut the engine off......Thats why its just so much easier to use a Wide band.......