Poor fuel economy. 5.7 Gsi

[cdavisdb]

I have a 1999 5.7 volvo gsi, fuel injected engine, throttle body injection, 600 hours. It appears to run perfectly, goes right up to redline, very smooth, perfect compression,no obvious problem except my fuel economy is getting very poor. It should be about 2.5/gallon or more and is now less than 2 and dropping. Measured 2.7 when I got the boat. Plugs are sooty black(not oily) and the discharge water dripping over the prop leaves a black deposit when running on the trailer. Smokes a little. I don't think it was doing this when I bought it. Looks like its running rich to me. ECM is recording no errors. The engine manual calls for 93 octane. I burn 90 octane, no alcohol, raised to 92+ with octane booster and have since buying the boat. I'm considering replacing the injectors and, if that doesn't work, trying ethanol 93 octane.

A sensor bad? which one? Anybody have any other ideas?

 

[Tahorover]

Re: Poor fuel economy. 5.7 Gsi

Check your fuel pressure.

 

[Don S]

Re: Poor fuel economy. 5.7 Gsi

You may have checked the ECM for codes, but did you check to see things like ECT values? If the coolant temp shows cold, even with a warm engine, the engine will run much richer than normal for a warm engine. It doesn't know if the engine is really cold or warm, and a cold engine does not throw a code.

 

[cdavisdb]

Re: Poor fuel economy. 5.7 Gsi

Fuel pressure is fine,

I will check for values out of engine temp sensor

Any other ideas?


Thanks a lot!

 

[Don S]

Re: Poor fuel economy. 5.7 Gsi

Check all the values, and make sure everything is working as it should be. Impossible to say what exact one is causing your problem.