My Legacy, when I hit the gas hard it tends to hesitate and knock and ping, it feels almost as if it were running out of gas. This happens especially when the engine is cold. Could it be the octane rating or the fuel pump?. Thanks...

Knocking, pinging that running out of gas feeling may be exactly what's happening. When an engine is cold it needs more fuel.

 

I'd start cheap & easy with a fuel filter. If that doesn't help it may be more serious/ expensive. It may be the fuel pump. While you're replacing the filter, look over the lines to be sure none of them are pinched, or kinked.

[...]Could it be the octane rating or the fuel pump?.

Yes, or the fuel filter, as has been mentioned, or some other possibilities. What is the octane rating of the fuel? Are you using an ethanol/gasoline blend, and if so, what is the ratio?

Just out of curisosity, when exactly this start happening. When was the timing belt last changed. Check the knock sensor. Change the fuel filter, and invest in a tank of preimum name brand fuel and tell us what happens.

 

 

nipper

Yup, the regular gasoline here now comes with 10% ethanol. I don't normally fill it up with premium gasoline (not mixed) since it is very expensive. I haven't changed the fuel filter yet, ever since I bought the car. Timing belt & sensors seem to be OK or so appears in the scanner. On the other hand, the fuel pump was replaced almost a year ago. I will implement your suggestions and let you know what happens... Thanks...

Mom's 98 L does this when they run regular, 87 octane, in it. Whenever I get ahold of it I run a tank full of either 89 or 93 through it and it does great for a while. More than likely thats the main cause of the problem

10% Ethanol has been around since the 1980's (in other parts of the country), so no its not the fuel. Cars have been designed to run on them all across the board. There is something else wrong. Start off with a tuneup.

 

nipper

Yup, the regular gasoline here now comes with 10% ethanol. I don't normally fill it up with premium gasoline (not mixed) since it is very expensive.

I asked because I know that certain parts of South America are using high percentages of ethanol fuel blend. Ethanol has a higher vaporization heat than gasoline. When the engine is cold (running open loop, with the ECU unable to compensate) ethanol effectively leans the mixture at a time when the engine needs it richer. However, 10% ethanol isn't excessive; if higher, it might have explained all or part of the problem.

 

 

I haven't changed the fuel filter yet, ever since I bought the car.[...]

Since you can't know for sure when the fuel filter was last replaced, and a partially obstructed one could cause the mixture to lean during high demand (cold engine or hard acceleration), changing the filter is a reasonable starting point. Please let us know if that resolves the problem.

A new fuel filter is a good idea. You also might want to replace the engine coolant temperature sensor.

 

Good luck.

Just start with a tune-up and see what happens. i'm nt a big fan at throwing parts of the car untill the basics are covered.

 

nipper

Just start with a tune-up and see what happens. i'm nt a big fan at throwing parts of the car untill the basics are covered.

 

nipper

 

Nor am I. But I think in this case the coolant temp sensor could be considered a basic.

Nor am I. But I think in this case the coolant temp sensor could be considered a basic.

 

Not necassarily, i would be suspicous of a knock sensor or an o2 sensor as well, so lets get new plugs and filters in there first to have a good baseline.

 

nipper