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MagiLLa
06-27-2004, 02:31 PM
here's the deal.
(i live in Canada so im working in Kilometer's here, not Miles)

i used to get 400km's to a full tank. now i get 200-250km's.

i got my oil, fuel filter, spark plugs all replaced. even injector cleaner fluid.
after all this, i was getting ~400km's..

now im back to this terrible gas mileage and the car is just eating it :(....
why did it come back? it's only been like 2-3months since i got everything changed.

it's not a gas line leak, because there is never any on the ground.

help?

zerogman
06-27-2004, 05:56 PM
Does your vehicle have a V6? If it's the 3400 V6, they've had a LOT of problems with intake gaskets... and a really stupid thing is that there isn't a gasket between the part of the lower plenum (lower intake manifold) that touches the block, they just gob it up with black silicon.

I believe that this problem comes from them being REALLY lazy and using the same components as the 3100 for the 3400 except for the block. The crankshaft, rods, heads, intake and exhaust manifolds are all the same as the 3.1 for the 3.4. I can't tell if the camshaft is the same or not since I don't remember if the 3.1 had roller lifters.

Anyway, in an answer to your cry for help, at about 30k miles on the 3400 V6, you just totally lose performance due to wear. My guess? Check and maybe replace the intake gaskets if they are leaking...

If you have the 4 banger, there really isn't much I can do to help, I don't know I4's that well. However, I noticed you didn't mention your air filter, I hope you replaced that... Also, why worry about the oil filter when it SHOULD be replaced with every oil change? One thing that might help is to run the tank to less then 1/4 full and then fill it with premium at least once. Also, an easy way to check for carbon build-up is to pop off the valve cover(s) and take a peek, hopefully clean with the only things in there being your valves and oil.

I hope some of that helps!

BLACK99GT/ROB
06-27-2004, 06:16 PM
I was getting really bad gas mileage so I replaced the wires with MSD 8.5MM and replaced my plugs and already had a CAI and my gas mileage is still bad.........I have no idea why unless a coil pack maybe???

jaketuff
06-27-2004, 06:47 PM
Reset your PCM by unplugging the battery (neg. cable) for about a 1/2 hour and see if the MPG go back up.

OUT

BLACK99GT/ROB
06-27-2004, 06:52 PM
Reset your PCM by unplugging the battery (neg. cable) for about a 1/2 hour and see if the MPG go back up.

OUTI have tried that myself and it didn't help.I just noticed your avatar........has Bob seen it yet?

MagiLLa
06-27-2004, 06:58 PM
Reset your PCM by unplugging the battery (neg. cable) for about a 1/2 hour and see if the MPG go back up.

OUT
why would resetting the PCM (unplugging battery) increase my gas mileage??
that makes no sense.

98GrandAmSE
06-27-2004, 07:04 PM
new o2 sensors or egr valve. either or these 2 things should have thrown a code though. Try buying gas at a different gas station too, and sticking to just that one for a while.

nomojo
06-27-2004, 09:43 PM
.... here's the deal. .....
i used to get 400km's to a full tank. now i get 200-250km's. .....


This is gonna vary alot by how you drive it, but to give you an idea, I got 350 km's a tank (CITY) in my 99 GAM SE V6, i figured it out once and it was 19 MPG.

My '03 GT1 only gets 300 km's a tank (CITY), prolly in the neighborhood of 17-18 MPG's.

These things aren't the best on gas to begin with, but I'd say 250's trouble.

For @!^#'s & giggles, When its "empty" next time, pay attention to how many litres go into the tank. They're 55L tanks, and on mine, after driving it around for a bit with the light on, a "fill-up" is around 47 Litres.

If you're on "empty" and you only put like 30 L in to "fill" it up, maybe your fuel float in the tank is busted? Thats been another problem that GM has.

just a thought.
cheers.

AaronGAGT
06-27-2004, 11:51 PM
why would resetting the PCM (unplugging battery) increase my gas mileage??
that makes no sense.

It makes plenty sense. :rolleyes:

Hexx
06-28-2004, 05:28 AM
This is gonna vary alot by how you drive it, but to give you an idea, I got 350 km's a tank (CITY) in my 99 GAM SE V6, i figured it out once and it was 19 MPG.

My '03 GT1 only gets 300 km's a tank (CITY), prolly in the neighborhood of 17-18 MPG's.

These things aren't the best on gas to begin with, but I'd say 250's trouble.

For @!^#'s & giggles, When its "empty" next time, pay attention to how many litres go into the tank. They're 55L tanks, and on mine, after driving it around for a bit with the light on, a "fill-up" is around 47 Litres.

If you're on "empty" and you only put like 30 L in to "fill" it up, maybe your fuel float in the tank is busted? Thats been another problem that GM has.

just a thought.
cheers.

A little OT: Would that be the cause of my fuel gauge kinda sticking? Like yesterday, it was at 1/2 tank, I did a good amount of driving to my friends, then we sat in my car for a while with the A/C on...the car read just a tad under 1/2 at this point. Then we took off and as soon as I started driving it went down 1/8 a tank. I figured the driving I did would have used up that much fuel...but to be on topic here again...my MPG sucks too. When I first got my car it went just under 400 miles on a full tank of mid grade fuel. Now it will go just under 300 miles....these are highway miles, same weather conditions, same destination (friends live far when they are in college).

So yeah, could I be a suspect of this? Car goes in the shop tonight for the dealer to replace the LIM gasket tomorrow...and retorque my rockers (damn ticking noise).

mr03SCT
06-28-2004, 05:31 AM
my 03 has just over 70 000kms and I get about 540km a tank. You migh also have a faulty gas gauge.

nomojo
06-28-2004, 02:48 PM
A little OT: Would that be the cause of my fuel gauge kinda sticking? ....

Its the float in the tank, not the actual gauge on the dash itself. Dont know the hard-core details or whatever, but GM chooses to blame it on poor gas refinement wrecking the sensor.

Anyways, when its in at the dealer, if you describe the problem to them like you just did me, im certain they'll know what it is and be able to fix it for you.

Cheers.

Jagey
06-28-2004, 02:52 PM
My '03 GT1 only gets 300 km's a tank (CITY), prolly in the neighborhood of 17-18 MPG's.
.


FINALLY i have found another canadian GAGT that has fuel economy as horrible as mine in the city!

nomojo
06-28-2004, 03:12 PM
FINALLY i have found another canadian GAGT that has fuel economy as horrible as mine in the city!

Yeah. Its pretty poor. I thought the 330-350 i got in my 99 GA'SE V6 was bad. I guess the extra PCM adjustments and gear ratio in the GT's makes enough of a difference.

It does O.K. on the highway though, maybe 550 - 600 km's a tank.

cheers.

tammikm
06-28-2004, 04:42 PM
A little OT: Would that be the cause of my fuel gauge kinda sticking? Like yesterday, it was at 1/2 tank, I did a good amount of driving to my friends, then we sat in my car for a while with the A/C on...the car read just a tad under 1/2 at this point. Then we took off and as soon as I started driving it went down 1/8 a tank. I figured the driving I did would have used up that much fuel...but to be on topic here again...my MPG sucks too. When I first got my car it went just under 400 miles on a full tank of mid grade fuel. Now it will go just under 300 miles....these are highway miles, same weather conditions, same destination (friends live far when they are in college).

So yeah, could I be a suspect of this? Car goes in the shop tonight for the dealer to replace the LIM gasket tomorrow...and retorque my rockers (damn ticking noise).


hello, you said that retorqueing the rockers will get rid of the ticking? Is that a big job? what is involved?

mine ticks real bad

thanks

Hexx
06-28-2004, 05:47 PM
hello, you said that retorqueing the rockers will get rid of the ticking? Is that a big job? what is involved?

mine ticks real bad

thanks

A bit of stuff. The GM guy said that is part of the LIM replacement procedure (he made a note on the paper to have them make sure they retorque them). Basically you remove your upper manifold and I *think* lower. You will need new gaskets and bolts so this will run you around $100 (average price if you are changeing the LIM gasket yourself).

Then, while the upper half of the engine (well some of the upper half) is apart, just retorque. If you don't know what to tq down, I suggest you don't touch anything...get a mechanic or someone that knows what is going on to do.