to dealer for diagnostics

[jamesmetairie]

2003 vibe (base0,automatic, with 17 inch stock wheels and about 85,000 miles on it only getting about 17 mpg,s in the city with a/c on. when would you guys change wires and plugs on it ? would you get it checked on a computer to see if thgere,s a bad plug or something else causing the low mpg,s ?

[Raven]

It's probably time for plugs soon but this would not cause such terrible mileage. I would suspect a messed up catalytic converter. If you have no check engine light, it's hard to tell. A bad plug or injector would cause a misfire and the CEL to come on. Cat problems are common on Vibes.

[DavidPIL]

Hi James,I changed mine near 60,000 though they're supposed to be good for up to 100,000. I would still change them out with the recommended Denso or NGK plugs. Also look at the PCV. That should be changed as well. Consider a Fuel Injector cleaner. There is a process with stuff called Seafoam which is supposed to do good work to the injectors. I use about 1/3rd of the bottle through the same line that the PCV is (following instructions on the bottle) then pour the rest in the tank on the next fill-up.You can use the Techron stuff from Chevron or I have also tried Redline Injector Cleaner. These all should be able to be purchased at Auto Zone.Since doing my plug change at 60,000, I will now change them out every 2 years. I do the Seafoam treatment and PCV change once a year.Also, check your tire pressure. Check it early in the morning before the day warms up. Make sure you're at least at 32 psi and all the same on each tire. Make sure you're changing your Oil every 3-5,000 and maybe it's time to flush the Tranny fluid?Only a few suggestions but I think these are the first things to consider, especially with the miles you have on your Vibe. So... I hope this helps some.Dave

[Petrucci914]

Ya, I have like the exact same car as you with very similar miles. The lowest mpg I ever got was like 24, and that was in sub-zero temperatures and warming up for extended periods of time. I've gotten 34 at the highest. The last post has some very good things to go about doing.

[jamesmetairie]

bad cat coverter = ? i already put the vibe up on ramps and tapped the converter and stuff . no rattling anywhere. i remember a good muffler shop telling me they could check for a bad cat with some gadget. if it is bad is it possible to replace it with a straight pipe without any problem "CEL" or "SES" light appearing ? is it possible to cut it open and clear the guts out ?

[Petrucci914]

You can bust the insides out of it, yes. If you do that to the first one you'll get a CEL. It's fine to do the second one. If you do have a bad cat I'd just recommend getting them replaced. You can get high-flow magnaflow cats on ebay for around $60. It wouldn't cost much to have a shop do it either. Save a tree and some lungs.

[Raven]

Quote, originally posted by Petrucci914 » If you do have a bad cat I'd just recommend getting them replaced. You can get high-flow magnaflow cats on ebay for around $60. It wouldn't cost much to have a shop do it either. Save a tree and some lungs.I agree. Are you down on power too? This is also a symptom of a blocked cat problem.

[jamesmetairie]

not down on power. maybe just worrying too much because of the low mpg,s. the 17 inch wheels don,t help city mpg,s either.

[coldmm803]

unless the rims and tires are a bit heavier it shouldnt matter

[jamesmetairie]

taller tires or rims turn less so at highway speeds you usually get a better mpg. but in the city worst mpg,s . on another thought = this stuff is all factory so the speedometer is calibrated. on some of my old cars if i installed taller tires to get better mpg,s for highway commuting it would throw the speedometer reading off. i got more than 1 speeding ticket doing about 65 when the dash said 60 mph.

[Petrucci914]

If you have bigger rims then you have smaller tires, if you have small rims you just have bigger tires. Usually the complete size stays about the same, you just have less rubber. I know you can get really huge rims and that'll change.

[ragingfish]

Quote, originally posted by jamesmetairie »bad cat coverter = ? i already put the vibe up on ramps and tapped the converter and stuff . no rattling anywhere. i remember a good muffler shop telling me they could check for a bad cat with some gadget. if it is bad is it possible to replace it with a straight pipe without any problem "CEL" or "SES" light appearing ? is it possible to cut it open and clear the guts out ?just be careful, if your state has stringent emissions testing programs, gutting a CAT could cause your car to fail a state inspection.I know in Jersey we have some of the strictest emissions tests in the country...I don't know if removing the second CC here would let that car pass inspections...Just something to keep in mind...

[Lancer]

What is your mpg with your a/c OFF?If yo check your plugs yourself, there's a lot that they can tell you. Running lean, rich, burning oil, fouled from short distance driving, if your engine is detonating, or just if there're worn out.About the cats, you'd be suprised at how much louder your exhaust is without just one of them!

[goodvibe]

Quote, originally posted by jamesmetairie »taller tires or rims turn less so at highway speeds you usually get a better mpg. but in the city worst mpg,s . on another thought = this stuff is all factory so the speedometer is calibrated. on some of my old cars if i installed taller tires to get better mpg,s for highway commuting it would throw the speedometer reading off. i got more than 1 speeding ticket doing about 65 when the dash said 60 mph.You know that since the speedo is off, your calculated mileage is also. It's higher than than you think because you're traveling further than your odometer indicates. If your speedo is off 5% add 1 mpg at 20mpg.