8 - 11mpg...help...

[Indecisive]

Hey guys, I'm getting horrible fuel economy.

I changed the plugs only a little while ago with NGK BCPR7ES-11 plugs, and just checked them recently and there's no carbon buildup or anything.

The inside of my exhaust tip is very black though, so I'm running quite rich I'm assuming?

power Mods are:3" downpipe back straight-through exhaustFMIC

When I first got the motorset, the MAF was quite dirty, and I could clearly see dirt inside where the heating element was. I tried to clean it as best I could with carb cleaner.

Another thing I've read is that it could be a faulty/old O2 sensor causing my problems. I'm getting no fault codes from the ECU though.

Thoughts? If any more information is needed I can try to provide it.

[AWDB12wagon]

The ECU probably wont throw a code for bad O2 sensor, but the 7's are the wrong heat range, they're too cold. You need to look at the voltages of the O2 sensor see if its alternating regularly, I think its like more than 10 times in 30 seconds or 15 seconds or something. Usually when its bad it will not move at all, the voltages that is.

[Black on Gold]

Definately change the o2 sensor its only a $17 part at O'Reilys

[utemhsa]

Hey guys, I'm getting horrible fuel economy.

I feel your pain... my mileage isn't that bad, but according to my ecu, my knock sensor is bad (which is unfortunately NOT a part easily accessible)... do you have everything else set up stock though?

[Indecisive]

$17 O2 sensors? you americans are lucky heh.

AFAIK, everything is setup stock. I THINK I have a boost leak somewhere as well though.

I build up boost fairly easily, but it doesn't hold and the turbo is very loud(unusually loud for only a T25).

anyways, I changed the O2(it was very black), and the plugs yesterday(went with the 6 heat range instead). Haven't driven the car yet since I did it after work and was dead tired.

Hopefully today she'll be better.

[Black on Gold]

Lets hope

[ca18det240hatch]

how many K to a tank are you/were you getting?

mine, i see 150k to half a tank, which is around 30$......do you get better? worse?

im trying to get to the bottom of it. Oxy is fine, plugs are brand new. Im thinking the 255lph walbro is killing my FPR. car runs pretty rich, powerful, but rich. If im on the hiway and i have my window down, i can smell the rich mixture.

anyhoo, let me know what happened

[AWDB12wagon]

Ah, well, your stock regulator may be letting too much by. Test the fuel pressure and report back what it is. If its more than 43.5 at idle, then your regulator can't handle the fuel pressure, or its already focked. You can either get a nismo unit or a universal one, as long as it raises the fuel pressure 1:1 with boost.

P.S....why do you have the 7 heat range plugs??? You having detonation problems? It seems like they would exacerbate the problem of running too rich.

[Indecisive]

I'm getting around 38 - 40psi at idle which I thought was normal.

as far as the 7 heat range...I didn't know it was suggested for highly modified ca's til a while after I got them.

Seems to run better, but I wont' know for sure until I give it some more long term testing.

I am finding that I'm idling very high now though. Up at 1200 - 1400rpm. But while installing the O2, I noticed one of the plugs on the IACV system was unplugged. I don't know if I unplugged it during my install or if it was like that for a while or not.

I was getting about 125kms - 150kms per half a tank before I changed out the O2 and plugs. I'm running in an S12 though. It's a 53litre tank.

That boost problem is a lot more apparent now. Anybody know how to find a boost leak and not just a vacuum leak?

[mod_mastaz]

http://www.vfaq.com/mods/ICtester.html

boost leak detector. Did it in my friend's car, we found a boost leak about the size of my thumb. We didn't know he had a boost leak on his DSM til months later because the big16g still held boost all the way to redline.

[Indecisive]

wow...that's brilliant. I'd have never thought of something so simple.

Thanks a lot mod_mastaz. Hopefully that'll do the trick for me.