Help, MPG problem, 02 Censer Maybe?? - Honda Prelude Forum

Musicman2k · 03-14-2010, 11:25 AM

Hello guys and gals!

Ive been having a problem with my 1998 2.0 prelude, since i picked it up over 3k miles ago now, there has been an issue with the temp gauge. Once the car gets up to temp and gauge never will show this heat and nun of it comes through the blowers when driving along,

When in town and the car is not moving fast at all, the heat quickly begins to show on the temp gauge and the blowers start kicking out some heat!! soon as the car gets to about 30-40 the temp gauge falls all the way back down and the heat goes!!

I was thinking maybe because the temp gauge is low its tellin the ECU the car is cold and making it run rich?? been racking my brain about why im getting 15-18 mpg even when driving like a proper granny!

Any help would be great!!

dontbuyprelude · 03-14-2010, 08:06 PM

1. you probably have a bad thermostat and as a result, your engine doesnt have a chance to fully warm up so your ecu is still in "warmup" mode. this is why your getting poor mpg. the temp gauge is just for you to moniter your engines heat. the gauge itself doesnt have any influence on the ecu.

changing your o2 sensor probably wouldnt hurt as well since you probably have high mileage by this time. a reputable source is sparkplugs.com. they offer direct plug and play sensors that you dont have to splice or solder into the existing factory wiring.

indylude18 · 03-14-2010, 09:35 PM

Quote:

Originally Posted by Musicman2k

Ive been having a problem with my 1998 2.0 prelude

I take it you are not from the U.S. then?

I agree your thermostat is probably stuck open, so whenever you are driving and air is passing through the radiator your engine is going to be running cold. It's only like $25 for a new t-stat, and it shouldn't take more that an hour or two to swap out.

Kronn 98SH · 03-14-2010, 11:34 PM

1) I definitely agree with thermostat.
2) That could be anything, however, shifting before the powerband actually reduces fuel efficiency.

Musicman2k · 03-15-2010, 06:06 AM

Quote:

Originally Posted by indylude18

I take it you are not from the U.S. then?

Im in the UK, love the car, dont want to sell it,but its driving me mad getting like 25miles from £10!!!

ive phoned about the T-Stat! £17 so ill give that a go in a few days!! maybe ill for once be warm in my car when motoring along!!

Cheers fellas,

Any other tips on how to save fuel or what could be wrong?

dontbuyprelude · 03-15-2010, 04:18 PM

Quote:

Originally Posted by Kronn 98SH

1) I definitely agree with thermostat.
2) That could be anything, however, shifting before the powerband actually reduces fuel efficiency.

doesnt the prelude make the most horsepower at ~7k rpms? and most torque at 5250 rpms? explain how shifting before powerband reduces efficiency? what rpm do you personally shift at?

indylude18 · 03-15-2010, 04:32 PM

^Search "engine load"

Kronn 98SH · 03-15-2010, 04:40 PM

Quote:

Originally Posted by dontbuyprelude

doesnt the prelude make the most horsepower at ~7k rpms? and most torque at 5250 rpms? explain how shifting before powerband reduces efficiency? what rpm do you personally shift at?

The powerband doesn't start at 5250. I shift around 4000 typically.

dontbuyprelude · 03-15-2010, 04:58 PM

Quote:

Originally Posted by Kronn 98SH

The powerband doesn't start at 5250. I shift around 4000 typically.

4000? isnt that a tad high? the owners manual states 3500. when i feel like saving gas i shift at 2500. but im very light on the throttle when i do so i dont "bog" the engine.

dont you have a tuned vafc that increases mpg bc it leans your fuel up a bit?

darn sh's...

Kronn 98SH · 03-15-2010, 06:32 PM

yes, no, yes

commandokock · 03-16-2010, 11:38 AM

Quote:

Originally Posted by dontbuyprelude

doesnt the prelude make the most horsepower at ~7k rpms? and most torque at 5250 rpms? explain how shifting before powerband reduces efficiency? what rpm do you personally shift at?

those are just the rpms where hp and tq are at their peak. the powerband is the entire range of rpms where the prelude makes power. it starts pretty low. i know when i drive in granny mode, i shift at between 2k and 2500 rpms and the tach goes as low as 17 or 1800 rpms while still making relatively low power so i think thats within the powerband. when the car kinda gets 'shaky', for lack of a better word, thats when i consider it below the powerband

Glaucus · 03-16-2010, 01:20 PM

I've read that the most efficient rpm is 3K, and that keeping the car between 2500 & 3500 is the best for fuel efficiency. I try to shift at around 3500 when trying to save fuel, but typically shift at 4K cause I'm a bad ass.

Kronn 98SH · 03-16-2010, 02:22 PM

Quote:

Originally Posted by commandokock

i know when i drive in granny mode, i shift at between 2k and 2500 rpms and the tach goes as low as 17 or 1800 rpms while still making relatively low power so i think thats within the powerband.

Not really. Shifting at 3000-3500 is ideal. I shift later cuz I drive faster than most all of you.

KraserK · 03-16-2010, 11:50 PM

Quote:

Originally Posted by Kronn 98SH

Not really. Shifting at 3000-3500 is ideal. I shift later cuz I drive faster than most all of you.

Lol! Yeap 4000rpm is a beautiful place to change her at car sounds way more gruntier + I love the sound our preludes make at around that range and I still get 32mpg no matter what or more. Kronn is badass it's normal for him hehe. I notice I get power at around 2500rpm+

+1 for thermostat too