MazdaRx7Power

ok whenever the car is still cool it accerlates pretty good. but after driving it some distance it like tightens up and doesnt accerlerate that good. anyone have a problem like this. its an 87 na with an intake and hollowed cats and 5th & 6th ports tied down.

Marco

I have the same problem and thought a lot about it. I concluded that there can be various reasons. First is the air-fuel ratio, this is probably to lean when the engine is hot. (When the engine is cold the computer makes the air-fuel richer) Air-fuel ratio is (among others) controlled by the O2 sensor and TPS (so replace the O2-sensor and adjust you're TPS). I've did that but didn't notice much difference

- Another reason could be bad compression which could be worse on a hot engine than a cold engine (because of the heat the parts differ in size) Just today I bought a bottle ATF and I got a set of old spark-plugs ready so I'm gonna give the ATF-trick a try soon. ( Just waiting for a foggy day to keep the neighbours from complaning)

- Yet an other reason could be clogged cats, i don't know why but I notice the differ in acceleration much less now I have gutted my pre-cats. I did notice an overall performance gain though.

- Vacuum leak. I sprayed varnish-based anti-moist all over the intake and tubing hoping to cure vacuum-leaks (not sure if there were any, but just in case) and this also seemed to make a big difference in power.

( All this is why I like my car so much, I can experiment with it and I understand what I'm doing and how it works. )

Marco.