This just in

Wrx=\=Miata

More at 11

:giggle:

But srsly, no idea, never had that happen.

Oh yeah, I know. :) Its one of those things where I'm still calibrating my brain to a different platform where I'm not 100% familiar with its peculiarities quite yet so I figured I'd ask.

Interestingly enough, no CEL and no trouble codes stored or pending. I considered getting back on the highway so I could loop around and try to duplicate it, but I was already on the edge of being late.

I know N/A guys on E85 in the BURZ are having to stay above half a tank, or run a surge tank to avoid starvation on track.

now that you mention it, I think that applies to some (all?) wrx's too. at least pre-06 ones anyway. Friend of mine has a EJ hybrid swapped 01 RS, and had to go surge tank too cause he was constantly starving in hard corners

I've had my 05 at the limit of traction with the fuel light on and didn't have this issue. I'm on star specs too.

not sure if the STI and WRX have differences in the fuel tank.

My engine randomly shut off in stop and go traffic yesterday. It started back up and nothing was wrong so i don't know what that was about.

post 05 wrx's, no difference in fuel pumps/cradles from sti
pre 05 wrx's are different

What would be the symptoms of a slightly-out-of-spec maf sensor, and of a thermostat that doesn't close all the way? I have been struggling with minor rough-running for a while now and I suspect one or both of those conditions exist. I replaced a bad coil yesterday and that didn't fix it all. I get no misfire codes. Anything particular I can look for in ROM raider? Other things to check? What would be the symptoms of a mafunctioning VVT Control valve? Those seem easy to pull out and clean so I will likely give that a try for free.

I should mention: 05 OBXT, 5speed manual, stock everything, minor shaking at idle, and some bucking between 2000 and 2500rpm, as well as some other generally "off" behavior all the time.

I have the exact same driveline, and from my limited knowledge, I would agree with the MAF. Have you cleaned it yet? Its thuper easy.

if the tune is stock, and the sensor is stock, it can't really be "slightly off'.
it either works fine or it doesn't and you have noticeable problems.

vvt valves definitely go bad on those, log them and see if they both open/close properly. also boost/vac leaks are very common and would cause stumbling at idle as the car flips out trying to correct the fact that it's running crazy lean.

I'd check the inlet and intake for holes/tears before I'd suspect bad maf. but cleaning maf is super easy so might as well while you're in there

I have cleaned the MAF a few times, but it was a while ago (back when I first started noticing the problem). The car came with a K&N filter, so I replaced that with a paper one, cleaned the MAF, then cleaned it again in a few thousand miles. I don't recall whether there was improvement.
I did have a leak in my intercooler for a while, but I bought a new/used intercooler and braced it up with that "bulletproof mod" thing so it's got some aluminum u-channel and clamps on it.

I'll clean the MAF again, and try to do a boost leak test. Does anybody know what size coupler I need to buy at lowes to make the tester? Not having to measure it myself would save me a special trip to lowes.

pretty sure it's 65mm
google it. there's 4 billion threads about it and lots of walk thru's.

boost leak tester on a high mile Subaru is mandatory at this point. I rage hard when people say "no leaks" when all they've done is look at engine bay and somehow magically visually tested it.

and check inlet. might be torn, usually right near turbo on the accordion

I want to check the whole intake tract, from right after the MAF onward. I'll look it up.

From my experience on the BURZ, that's not entirely true. Your LTFT can point to an out of cal MAF. There are guys having luck getting the car running better my rescaling the MAF, even with everything completely stock.

If you're consistently seeing +/- 5% on your LTFT, it may be worth it to rescale the MAF. From what I gather, a really solidly running tune shouldn't be seeing more than 2-3% on LTFT.

However, I'm too lazy to make a 20-30 minute log and start playing with the tune. It's just not something I really want to mess with. So I deal with my unoptimized OFT tune for now. Once I go with a header and Delicious or Moto-East tune, I'll do some E-tuning sessions on the dyno to really get it dialed in.

On the turbo scoobs LTFT's are designed for up to 15% correction.
It is literally impossible to get it toactually stay at 0 for any significant length of time. You can get it that way for a few days, week, maybe even month if you were really nitpicky. But swings in fuel, weather, load, and other factors will make it add a tiny bit or subtract a tiny bit. It's what it's designed to do.

IMHO if you're over 5% then you can play with it. If you're under, it's likely a waste of time.

In either case, normal fuel trim swings will never affect the car the way he describes.

*edit: also we're talking about the maf scale, not the sensor itself being off.

**Edit: also your tgv's might be acting up too, which would lead to these symptoms.

Tried to check for boost leaks last night, and the hardware store didn't have the size PVC plug I needed so I'll swing by Lowes in the next couple days and get the right stuff.

How do I check the TGV to determine if that is an issue?

log it or just eyeball it with the logger to make sure both are opening exactly same time and exactly same amount. As soon as the car starts driving they should both open.

Had a guy on a 06 lgt a while ago that one was sticking or just not opening right, caused some funky stumbles.

When you say "as soon as the car starts driving" do you mean whenever it's off idle, or that they're only closed for startup and should be open during idle?

it's different on different years/models, but IIRC it's closed for warmup, but as soon as you touch the throttle and get the car moving, they open. You can just start looking at the 2 gauges in RR side by side, note the values, blip the throttle a couple times, and then get moving in 1st and watch em then too. Pretty sure all of those instances they should open

it was real obvious on the one I did, one was showing like half the value of the other

something something ask your tuner something something

tell your tuner to ask his tuner