poor mpg...14mpg combined...no codes.

Smkn600ctd

Registered User
100% highway 20mpg. Combined 14mpg. There are no codes. If you short trip the car, it will sometimes have a long crank. Only once did I have to floor the pedal to get it to start. The car runs like a bat out of hell when you floor it.

The O2 sensors have been changed. (One after the new engine, the other maybe 5k miles). The maf has been cleaned. I am going broke keeping the gas station owners rich.

I threw in a whole bottle of seafoam in the gas tank to be sure the injectors are cleaned out.
1995 SC Auto.....stock.
 
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Maybe check fuel pressure, and see if the regulator is bad, and is causing high fuel pressure, or if you've got leaking injectors. If the latter, I would think you'd see fuel pressure drop fairly quickly after shutting down the car.
 
The new motor has lower compression than stock so it might benefit from a chip calibrated for that. Also depending on who built the motor and what parts they used it might not have an SC camshaft anymore and it might have even lower than stock 89 compression, but it sure doesn't have 95SC compression if the motor has been rebuilt.
 
I second with Dave. If it doesn't have any codes then the O2s are good. Other than that you would have to tune it to get the mileage out of it. That costs you about $350 for the equipment so you have to figure how long it would take you to benefit from having that. Unless, of course, if you need it for the future anyways.
 
The engine was is a Ford reman. It was built in 2005 and was sitting in a warehouse for the last 7 years (going from the build tag that's was in the crate).

It runs way better (power) than the old engine. We threw it onto a 5 gas analyzer and it was clean (10 hc, 0.02 co, 14.5 Co2)
 
The engine was is a Ford reman. It was built in 2005 and was sitting in a warehouse for the last 7 years (going from the build tag that's was in the crate).

It runs way better (power) than the old engine. We threw it onto a 5 gas analyzer and it was clean (10 hc, 0.02 co, 14.5 Co2)

Ok, so it's a low compression reman and it probably doesn't have an SC cam in it. There's your answer more or less.
 
Another fill up...169 miles with 12.1 gallons=13.96mpg. All highway, minimal idle time.

One thing I do notice is at cold start up, it is not at it's smoothest idle. Once warm, it may or may not have a long crank to start. Either need to find the cause, or this sc is gonna be up for sale
 
Might want to test the BAP sensor. You can do it with a frequency reading multimeter. It can give wrong data that still is within the possible range of outputs, so no code will be set.

Also try cleaning the MAF (very gently, search for instructions).
 
Think the timing/cam synch was off.

I pulled the cam sensor off and the "u" notch was parallel to the front of the block (6 o'clock position)

Using the pictures from a thread on it here that showed the relationship of the "u" to the front of the manifold and a page from the factory service manual.

I moved it from the 6 o'clock position to about the 4:30-5 o'clock position (30 degrees)

Well it starts up faster, the idle quality is better, and the idle vacuum is higher. Its way more responsive at lite pedal.

While I was at it, I sprayed all of the intercooler tube connections, back of the SC, and throttle body with carb cleaner and the idle stayed put, so no vaccum leaks.

Topped it off with gas, drive it all week...and see where we at :)
 
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