Ericksd

Hi I have a 95 z28/lt1/t56 that is my son's car we bought with the clutch out. We have since got it running and on the road. It is running really good. With not knowing a lot about the car it looks like a remanufactured engine new wires and spark plugs 3 inch exhaust. All aftermarket suspension. Problem is it seems to be getting horrible gas mileage. We have not been driving it long to figure out the mileage yet. I do not know if there are any engine modifications the car really is running good. I did find a black box mounted in line with the computer It has the name Jet but the stickers with information are unreadable. Question are these just **** to have bad gas mileage. any suggestions. The injectors are black in color do not know if they have been changed or not it does smell like raw fuel once in a while but does not seem to miss. Thanks in advance for any information.

Injuneer

Wrong forum.... this is the V6 section. I'll copy this to LT1 Based Engine Tech for you.

Injuneer

The LT1 with T56 was factory rated at 15 city/24 highway. I had no problem achieving that with my 94. Average in extremely heavy, bumper-to-bumper traffic in overcrowded NJ dropped to 16-17 MPG, mixed city/highway in Los Angeles and suburbs averaged 21 MPG. Cruising long distances in 6th gear, at 70 MPH would produce 30 MPG.

First thing you need to do is calculate the MPG for several tanks. The post the results, along with the driving conditions - city, mixed, freeway, etc.

There is a JET module that inserts between the PCM and the harness connectors. Not very useful, doubt it would materially affect fuel mileage, just as it doesn't do much for performance.

Stock 24 #/HR injectors are black on the top 1/2 of the barrel, and gray on the bottom 1/2.

Fuel mileage can be negatively impacted by many thing, in addition to a heavy right foot, and an addiction to stop-light drags:

-faulty O2 sensors
-faulty coolant temp sensor
-exhaust leaks before the O2 sensors
-using low octane fuel
-leaking fuel injectors
-leaking fuel pressure regulator

sbellis

With 12 years on a 1995 LT1 Camaro I found the thermostat was the culprit.

The wax pellet had changed characterists and would no longer allow the thermostat to sufficiently open. The old in a boiling pot of water opened only 3mm whereas a new would open 10 or 12mm or so and flow more coolant into the engine.

An easy item to overlook and fortunately easy to change out. Should be considered a slowly worsening wear part.

IIRC the engine temp was only obviously way too warm and approaching the red area on the gauge after sufficient HW driving followed by stop and go traffic The known issue of the rad fans being programmed to only come on at too high a temperature would allow the temps to rise on the dash gauge. Otherwise sufficient speed and airflow allowed the gauge to read only a touch too warm.

However all along the computer in attempting to counter the higher engine temps and unknown to me could also start spraying more fuel to cool the engine and thus causing the lousy fuel economy. I would suspect anything that prevented the engine from extracting heat could also cause a similar problem.

Was stuck in rush hour traffic with a 1/4 tank of gas and swear I could see the fuel needle slowly falling.

97WS6SCharged

Do yourself a favor and invest in an ALDL cable and download TTS Datamaster or Freescan. Being able to datalog these cars will save you a fortune at the parts store.

Injuneer

Scan9495 Should also be considered, in my opinion. And we have active support of the Scan9495 author right here. I find the data logs easier to work with.

Proabably doesn't matter, since the OP hasn't signed into the site since November 10. Couldn't have been very important.