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Discussion Starter · #1 · (Edited)
Bad fuel economy with no obvious issues on '97 base

Hey all,

First time poster here.

I have owned my '97 prelude for 6 years now and absolutely love it!
I recently had all the engine gaskets/seals replaced, new timing belt, water pump etc. But over the years I have noticed the fuel economy continue to degrade. I remember getting 500km per fill back when I bought it and now I barely get 400.

One other thing I have noticed is that time when I dont drive it for a few days (business trip out of town) that tank last fewer km than usual (think 380km vs the 400 i have been getting). This is strange because there is no visible leak on the ground and no smell of gas.

A friend has recommended changing the O2 sensor, but I don't have any check engine lights on. I have also heard about cleaning the EGR valves and ports.

Anyone else have any suggestions?

Thanks!
 

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How many kilometers did the car have when you got it? How many Km now? Have recently done any maintenance right before the issue started? Have you done any maintenance at all?

May be a good idea to change air filter, plug wires, spark pluds, distributor cap, distributor rotor, PCV valve, and maybe even a fuel filter. Not saying any of those will fix the issue but if none have been replaced in over 150,000 km then its good to so. Same thing with adjusting the valves.

Check tire pressure. Make sure brakes arent dragging too..
 

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any cels? burnign smoke? loss of power? like you need to describe allot more than you have.

any nosies? valve adjsutments, and the like?

waht kind of trans you have? are your tyres filled with correct amoutn of air?

do your wheel bearings get hot or make noise?
 

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Discussion Starter · #4 ·
Thanks for the quick reply's.

I just had a full tune-up done that include spark plugs, cap, air & fuel filters etc. Not sure about PCV valve, but I will check.

There are not CEL's, but I would say there is some power loss and hesitation of a second or two when I gas it. There are no noises and it is not burning oil. I can see the exhaust (white) at times, when idling. Idle feels smooth most of the time, some few dips in RPM at standstill. I have a 5sp manual base model (not SH) and the transmission is pretty good. A little shudder accelerating past 50km, but nothing major at all.

The car has 240k km on it now and it had about 175k km when I bought it. Tires are well filed and maintained properly. I live in Canada (snow!) so every 6 months I do the change over neither tire seems to impact fuel economy. All tires are on the same stock rims.

I will look into bearings being hot and brakes dragging as well. Thanks for those suggestions.

Does this sound like it could be O2 sensor problem? That was going to be my next attempt to resolve.

cheers!
 

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Vrooom PSHHHH
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The only way you could check the O2 sensors is to plug in an OBD2 scanner to look at the voltage readings. If you are still on your original sensors though, it wouldn't be a bad idea to change them anyways. It takes quite a bit before you will throw an O2 code, they can be "bad" long before that
 

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Thanks for the quick reply's.

I just had a full tune-up done that include spark plugs, cap, air & fuel filters etc. Not sure about PCV valve, but I will check.

There are not CEL's, but I would say there is some power loss and hesitation of a second or two when I gas it. There are no noises and it is not burning oil. I can see the exhaust (white) at times, when idling. Idle feels smooth most of the time, some few dips in RPM at standstill. I have a 5sp manual base model (not SH) and the transmission is pretty good. A little shudder accelerating past 50km, but nothing major at all.

The car has 240k km on it now and it had about 175k km when I bought it. Tires are well filed and maintained properly. I live in Canada (snow!) so every 6 months I do the change over neither tire seems to impact fuel economy. All tires are on the same stock rims.

I will look into bearings being hot and brakes dragging as well. Thanks for those suggestions.

Does this sound like it could be O2 sensor problem? That was going to be my next attempt to resolve.

cheers!
I'd clean out the egr ports/valve/iacv/tb/im runners and if your cat is original it could be starting to clog.
 

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Opinionated Bastard
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Just a thought: could you be losing economy due to weather?

I get less out of a tank once the temperatures start to drop in late fall (as in, now) because it takes the car longer to warm up, and at some point, they start using "winter gas" with more ethanol in it.

I usually get ~350 miles to a tank in the summer, now I'm only getting ~300.
 

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Just a thought: could you be losing economy due to weather?

I get less out of a tank once the temperatures start to drop in late fall (as in, now) because it takes the car longer to warm up, and at some point, they start using "winter gas" with more ethanol in it.
That is probably because of the winter mix in the gas they use...

it could be starting to clog.
I'd try this to see if you have the downtime for your car...

http://www.preludepower.com/forums/showthread.php?t=336400
 
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