Losing Performance

[GDL]

Hope someone out there can help

I own a 97 celica GT and have had it for nearly a year.

It seems to lose power quite badly in the following conditions:

hot weather, or humid weather

long journeys, i.e. longer than 20 miles

When everything heats up there is a definite power loss.

On a cool night it goes very well indeed but again on a long journey the power drops off badly.

I have had the spark plugs changed to irridium ones, air, fuel filters changed, exhaust checked out from front to back and a basic diagnostics check done by Toyota. All seems ok. I have spoken to lots of people and one mechanic told me it could be a sensor problem.

how can I check this out, and is it likely to be a lambda sensor prob?

The brakes are fine, nothing is restricting the rolling of the car in that way.

also, when flooring the throtlle at 2-3000 rpm, there is a flat note from the exhaust almost like a blockage (thats what made me get the exhaust checked)

my mpg is quite poor also, maybe 25ish no matter how easy I drive.

please advise as its fairly annoying

[GT4 BOOSTER]

may well be the lambda as you say , try here for advice www.justlambda.co.uk

may well be the air temperature sensor going into the air filter box is faulty also , try disconnecting it for a while.if its miss behaving in hot weather. also take out the efi fuse for 30 seconds to clear the ecu.

you havent by any chance got 1 of those horsepower gainers from eBay on it have you. ???

[Lexus2192]

Gotta be the O2 sensor dude.

Have the same prob with my Levin, runs great when it is cool but that tropical sun does a number on her. And oh yes, when driven on the heavy side she gets really thirsty at the gas pump.