Sucking Gas

[TsiMiata]

My V-6 1.8 has a drinking problem :p I'm getting a whole 20mpg. Something is up. I checked the ECU codes and there was nothing. It does two things that seem odd that I'm sure are a sign of whats wrong.<p>#1- It will backfire when I shift. It's not a loud bang, just a small pop. It doesnt do it every time. I'd say about 30% of the time I shift.<p>#2- It will stumble when I accelerate from lower rpm's when the engine is cold. The original fil up I did was with 87 octane and I put in 93 this time to see if it helped that but no improvement.<p>I checked the timing(yes I jumpered the diagnostic plug) and that checks out fine. Cap, rotor, plugs & wires are all in good shape. I checked the plug holes for oil and no troubles there. I was thinking O2 sensors but when one went bad on my MX-6 V-6 it acted very differently and the ECU threw a code almost right away.<p>I've had the car for about two weeks. The previous owner had brought it in for service for the same problem about 3-4,000 miles previous. They adjusted the timing and replaced the plugs and wires. I think they may have smoothed out whatever it enough so that the PO(completely car illiterate) thought it was gone but didn't really fix the underlying problem.<p>Any ideas are appreciated.<p>[ August 24, 2003: Message edited by: TsiMiata ]</p>

[RayRay]

This sounds like the problem I had. My cat was clogged. My car would backfire when i shift hard near redline. I used to get about 20 mpg (around town) then i replaced the cat after i failed emissions. Afterwards i was getting atleast 23 mpg around town, and about 27 mpg highway. So i guess you should get a new cat or atleast get rid of the one on ur car. This might be a good excuse to get a testpipe since its alot cheaper than a new cat.

[TsiMiata]

I was actually trying to find where to buy a test pipe but couldn't find anything. So where can I get one?

[Sonicxtacy02]

any muffler shoo can make you one for around 50 bucks as its just a straight pipe.

[RayRay]

The guys on ProbeTalk and Mx6 forums are pros with this. I've read alot of their posts about em. Here's a useful one:<p>http://208.57.88.26/forums/showthread.php?s=&threadid=1701053865

[TsiMiata]

Another symptom I forgot to pint out is that I need to crank the car over longer than what should be normal. It takes ~5 seconds for it to start.<p>AS far as the test pipe goes if I could find where to buy the flanges I'd make my own.

[mitmaks]

i know guy on ebay that can get me test pipe for mx3, but wouldnt that make you fail emissions, i might have to do emissions soon and i thought about putting it on but dont wanna fail emissions.

[TsiMiata]

I just pulled the cat and the aft part of it is all broken up. Hopefully this is the problem! Thanks for the advice all!

[UoMDeacon]

What does everyone else get as standard mileage? I commute to work, and usually pull ~30mpg if I have mostly highway miles on the tank...which makes me think that maybe my tripmeter isn't that accurate.

[TsiMiata]

I've got the car back together. The backfiring is still there, It starts slightly quicker but still not right. Gas mileage is TBD since I've only done 20 miles since gutting the cat.

[pickinganame]

i got to the same gas problem and the noise shifting i thought cat also but then agian who knows?

[RayRay]

do you still have a stock muffler, cuz maybe thats clogged too?

[TsiMiata]

Stock right now, actually worse than stock. It has a Midas 1 7/8" OD crush bent exhaust. I have a pacesetter on order. I love the build to order setup JC whitney has on pacesetter I ordered it two weeks ago, they say it will ship 9/12. We'll see........

[TsiMiata]

Brough this back from the dead for a small update. I'm pretty sure this not O2 sensor related. I did an all highway trip and got 29mpg. In city driving I'm still getting 20mpg. I think it might be a problem with the fuel cut on deacceleration. Since it is backfiring in around town driving which is consistent with extra fuel being dumped.<p>Any thoughts with this new info.