90/90Qs

My 90Q20v gets like 15.2 - 15.4 mpg now and it idles like I use beer swill for fuel. So I've replaced plugs, cap, rotor, wires, O2 sensor and knock sensor, and I use 93 octane fuel. Can't find any obvious vacuum leaks although that does not guarantee one does not exist, cat = N/A...
That's all I can think of for now; I've unplugged my O2 sensor while the engine was hot and running to see if anything happened and there was absolutely no change in the engine tone, does this make sense?
Also it runs even worse when cold and even backfired this morning on the way to work.

1)any diagnostic guesses?

2) Why is it bad to solder in the O2 sensor? - Mine is currently soldered.

3)Is here a way run a full vacuum system test?

4) If the O2 I just put in is bad, shouldn't it only be obvious(running like @#$) when it's running in open loop and the engine is warm? The O2 is bypassed when cold isn't it?

-been wrestling this prob for months now...
Thanks,
Marty

Joe Sixpack

ISV?

teabagger

Do you see any fuel leaks? Pull your injectors out and look at them.

90/90Qs

It always runs like *** lately : /

90/90Qs

except #1, (semi)wet plug and slightly low value on the injector coil.
would a leak around the seals cause these symptoms?

connell

i have the same issues with mine right now and have done exactly the same as you in terms of replacement parts. i also cleaned my MAF yesterday (experience with a POS jetta last year made me think of it) it's not back together yet but i doubt it'll do much good considering the luck i've had so far. i'll be getting some more experienced advice in the near future and will report my results.....worst comes to worst i'll spend the big bucks and give it to my mechanic for a few days.

i'm just hoping it's purely an air/fuel mixture thing cuz the computer's gettin the wrong info.

90/90Qs

Let me know what you find though. Tomorrow I'm going to recheck the O2 and do some further testing.