ls1 really bad gas milage help

IT started around the time that i installed my k and n air filter into my car, i know with performance comes poorer gas milage but i had half a tank in my car and went 70 miles and i am on empty? Also i know it has something to do with my exhaust because it is gargling on the way down. Any idea about what is wrong with my car? I read up on my haynes manual and it says the timing is probably wrong, but it does not say how to put it in timing. I do have a little bit of engine experience with my truck but that is really out dated compared to this distributerless ignition system so bear with me. Also my engine light has not come on. thanks

You cannot adjust timing unless you have an ls1 edit program, I highly dought that is your problem, How many miles are on the car and when was the last complete tuneup. Any check engine lights on, could be a number of things.

i've got about 112,xxx miles and there are no check engine light's on. this help?
oh and last completer touneup was about 2 wks ago

How many miles are you getting per tank? I know my gas gauge needle drops like a stone between half a tank and empty.

around 20mpg i get about 300 to a full tank and my tank is 15 gallons (for a '99) , I also thought my needle was falling faster between half a tank and empty, now i know i am not crazy.

I get about 18 mpg driving around San Diego. Just a straight miles driven divided by gallons at fill up. 20 mpg sounds good depending on how many miles are highway or city. I am assuming your 20 mpg is after the K&N filter?

Possibly with more air coming in, your engine will run lean. The computer will compensate by using more fuel. But I don't think it would be that much more, actually minimal, with just a filter.

I would check your mileage on the next tank. See how it stands up to your mileage from before the filter.

Good point Mister Will but the 20mpg was before the k and n so that is proabably why i am getting poorer gas mileage, but what would account for my exhaust garguling when it is going back to idle?

OK, first, more performance DOES NOT always mean worse gas mileage.

In fact, usually when you install one of the aftermarekt air intakes the engine is able to breathe better and it will increase your mileage.

One thing you might want to check is if the K&N filter had too much oil on it. If it was too oiled, some of the oil might have been sucked through the MAF Sensor and screwed up the elements in it. If the MAF isn't reading quite right, then it will tank yor mileage.

The exhaust will gargle some when the engine coasts down to idle. So based on how you describe the sound I would say it sounds normal. Did you change the cat back recently? That may account for the change in sound. Has it been backfiring more lately? Do you notice the smell of unburned gasoline from the tail pipes? However, I'm beginning to get beyond my scope. I am hoping some other people will chime in who have had a similar problem.

Change your fuel filter....

Call me crazy, but is there a chance you forgot to plug the IAT sensor back in? :confused:

Originally posted by Mister Will
How many miles are you getting per tank? I know my gas gauge needle drops like a stone between half a tank and empty.

ditto, even when i keep my rpms below 2k. Just the way our cars are, they eat up gas.

I havn't done anything to my exhaust since i bought the car in June of last year, as far as i know it is stock except the original owner added chrome split tips to it.

I changed my fule filter the same time i had my injecters cleaned this past august. However, i just remembered that when i filled it to half a tank (when i added my k and n air filter, i added a complete fuel system cleaner by chevron when i put chevron gas (that is what i always use) WOuld that account for anything?

Also, I just filled it up for the first time since the addition of the filter and my gauge was completely on e, it took 13.5 gallons to fill up, don't i have a 15 gallon tank? my fuel gauge must be off right? And all my sensors are plugged in.

I might have oiled the k and n too much because it is still all oily as of last night. I recharged it about a week ago. So did i mess up my MAF for good?

Usually aftermarket mufflers have the company logo stamped into the outside shell. Take a look at your muffler. Also the stock muffler will be louder than an Impala ( duh!), but quiet and smooth for a 5.7 liter HPo V8. So if it is domesticly compatible, it is probably stock. But I can't hear it from So Cal.:p

I usually put about 13 to 13.5 gallons when I fill up. The needle is on empty. But it can go below empty. Do the math, if you have 1.5 gallons to go when the needle is on empty, then you should have about 25 miles before running dry. 25 mi. isn't much to drive here in San Diego. So when you're on E, I start looking for a gas station. I have never run out of gas in a FI vehicle, but I hear that it takes a shop to restart it. Something about priming the injectors. It would be a good topic for a thread.

There should not be any fresh oil on the filter. You probably have oil on the sensor and that could be the cause of your problems.
I have never recharged a K&N filter. However, I have heard, from this board, that a common mistake is to reinstall the filter before the oil has completely dried on the filter.

Your MAF is probably ok. But it needs to be cleaned. Problem is you could damage the sense while cleaning it. But very careful.

I just remembered. DO NOT RUN OUT OF GAS:eek: :eek: :no: If you do you will expose the fuel pump, which is in the tank. It will be fried. Then your car will not run until it is replaced.

So Do NOT run out of gas!

LOL... I get about 160 miles per tank right now and takes 12.7 gallons to fill it up. Getting about 12.5 MPG. I don't run it to the bottom. This is all around town driving and I do have somewhat of a heavy foot and the car isn't stock. I don't beat on it all the time though... get about the same mileage however I drive. Yeah, I'm still running RICH which is a MAF/O2 issue..

It's a MYTH... if you run out of gas , you dont have to take it to a shop to have the injectors primed. Fill er up and go.

But it's not good on the fuel pump to run it low. Since it's a submerged pump, the fuel actually keeps the pump cool. So running it low all the time, will most likely shorten the life out of it. It will NOT kill it instantly or anything like that..

Steve

Don't worry how many miles you get on a tank of gas. Fill it up,set trip meter to 0,drive till it shows 1/2 tank, fill up with gas and check mileage. That will tell you how many miles per gallon you are getting. I get 21-23 mpg runing around and 31 mpg on a trip.

You dont have to check at half a tank. Just reset the trip meter the next time you get gas. While the gas is pumping just reach in and press the button w/the key in the on possision. Now the next time after that, that you get gas, divide the milage by how many gallons you just pumped in. That willl tell you what your actual milage is.