rough start and low MPG, is it tune-up time?

[justinarm]

I have a 2000 GTP with 75K miles. The engine will start fine on some days, and then start rough on others(mostly humid days). Is it tune-up time? I will be replacing my spark plugs soon. What else do I need to look for?

Also, my MPG is roughly 18.5-20 on the highway when I am babying the car. Is this normal MPG?

After I get this straightened out I am looking for a DHP and a 3.4 pulley. How do you guys like the combo?

[Ripn12s]

Plugs/Wires/Air Filter/Fuel Filter

That MPG isnt very good for a stock car. I see that MPG from my car w/ mods in sig.

3.4/DHP is a good combo

[GTPgirl]

I'd say it's time for a tune up, my 99 GTP gets 19-21 MPG when I'm NOT babying it. Babying it and using cruise control on the interstate on the way to Panama City, I got like 24-25 MPG.

[justinarm]

19-21 MPG is as good as my car can possibly get at this time with premium fuel. I baby it to death! I will check the service manual out also and see what it says about tuning up. My car is 100% stock at this time also!
Thanks again.

[GTPgirl]

I run Plus fuel, drive with performance shift all the time, and occasionally race a few third and fourth gen F-bodies and some 'stangs, and STILL get 19-21 MPG. I'm totally stock too.

[BIG-L]

I have a 2000 GTP with 75K miles.

Becareful....with that many miles it might not hurt to change the wires also,lots of us have problems with miss-fires after changing plugs with the old wires since they are old and hard to come off.Most of the time the miss-fire will happen around 4 grand and above @ wot.

Another thing to replace would be fuel filter and PCV.Im getting 19/20 in town and 26/28 highway.......~Larry~

[kilroypr]

Well, I have always achieved 22mpg and never been babying the car. Now I am getting around 20. Big-L. Now my rear looks like yours, painted my spoiler this weekend.

You should replace plugs, cables, filters, oils(tranny and engine).

[hardywang]

my 97 GTP, original park plugs and wires, I can get 30 MPG on high way, crusing at 106 KM/H.

For rough starting at humid days, I heard somebody else said, it might be distributor?

[BIG-L]

I heard somebody else said, it might be distributor

but we dont have a distributor