I have a rx300 1999 that runs great parked at idle Its when I put it in drive is where i notice a problem bad hp loss! All car maintenance is up to date, I just replaced the flange right before the cat convt because i noticed a slight hissss when i step on the gas. I have noticed a loss in hp slowly getting worse and then the leak at the exhaust flange happened. Something tells me its the cat? Can you guys give me some ideas on how to T-shoot this prob? oh and give me your ideas on cost?

 

Whack the cat off. Replace with pipe, and enjoy. Don't forget to turn in the old Cat for some $'s at the local scrap yard.

 

try resetting the ecm,it might help.is your check engine light on?

 

If you have a hole in exhaust that will do it. If putting a modified exhaust on a car can gain HP one with a hole can lose HP just as quick.

 

With the car at idle do you have a good exhaust flow at the tailpipe or is it a very low flow. A restricted exhaust flow will be the result of a plugged cat.

 

The bigger picture is:

Air intake, fuel, spark, ECU (control) and exhaust and drag.

Some of these can be eliminated by stepping on the gas pedal in Park @idle.

Just pushing the RX in neutral; Flinstone style. [to check the drag]

Air filter examination and in the right conditions running without filter.

Salim

 

Ok guys thanx for your t-shooting tips and it looks like its the cat. the one before the muffler. Im only doing this one time so what is the best upgrade? Also what will keep this from happening again?

 

oh and my "save the planet from global warming" test is due in January!

 

Are there any engine-related modifications we should know about? Any engine repairs done in the past?

 

no no mods its stock.

 

A couple of years ago I had a leak in the flange before the rear catalytic converter. I ignored it until finally I got a cat failed code. I took it to the dealer to replace the gasket.

The dealer wanted to replace the converter too (for about $1100!!) because the code said it was bad. They acknowledged that a leaking gasket could fake out the oxygen sensors before and after the converter. I told them to just reset the code.

The code came on a couple more times over the course of the next week or two. I cleared it repeatedly. Haven't seen it since, and the car runs fine.

 

Well its been 2 days now with the new Hi flow Cat and WOW! My RX has made huge HP gains. Shifting has smoothed out, greater towing and best of all my MPG has jumped 2-3 more MPG.

 

I don't understand how reducing exhaust back pressure can increase both power and gas mileage. Can anyone explain the mechanics of it?

 

Well i can try: When you see cars like 6 cylinder skylines with 4 inch exhausts within the tip the exhaust itself is actually rotating air so a 4 inch outlet has its own air curtain as the gases circle it is actually reducing itself to about 2.5 inches therefor creating back pressure giving the motor more power.