So I built this fuel economy gauge which tapped the VSS and one of the injectors off the ECU. Was working fine for a month. Today, I had disconnected the battery for a bit, and when I put it back together, the car is idling REALLY rough. Looking at the injector pulses, they seem really off. Seems to be across all of the injectors, so I'm wondering if something happened to the ECU (pulling the gauge didn't help). So now the car will feel like its running almost normal with my foot on the gas, but foot off the gas it either idles rough an at like 250rpm, or stalls out. So, to confirm or rule out an ECU issue I was curious if someone had one I could plug in for a few minutes to see if it helps. Otherwise it's a fuel problem *somewhere* :unamused:
Cool, I'll send him a PM. I think, however, anything '02-'05 would work... Please correct me if I'm wrong though.
Ok, I may have access to an ECU, can someone confirm that the '02 N/A ecu will work or not in my car?
Negative. You need the 2005 N/A ECU. 2002~2004 was standard controls. Yours is drive by wire. In 2006 they added VVL, so it will not work either. So its a 2005 N/A impreza ECU or nothing.
Oh wow, I didn't realize the '05 was drive-by-wire... Could have sworn that started up in '06. But now that you mention it, I don't remember ever seeing cables going to the throttlebody. Damn, this makes it difficult. Maybe someone can chime in whether the ECU sounds like a plausible/likely culprit: Symptoms: No CEL Low idle (around 250-500) Rough idle - motor rocking harmonics are uneven Abnormally high exhaust temp on startup, very moist, and smelling slightly of fuel Hesitation before revving (but it will rev) Stalls or nearly stalls after taking foot of the gas Slight tapping sound coming from driver's side of motor (valve tap?) The circumstances surrounding this issue: Recently (40 miles) filled up - possible bad gas? Recently built that economy gauge - this taps the VSS line and an injector line to count pulses and display MPG... more about that here: http://ecomodder.com/forum/showthread.php/mpguino-release-one-workspace-2115.html Once when I first installed that device the injector line (injector 1) shorted to gnd for a minute and it acted the same, but clearing that short resolved the issue (this was maybe 2 weeks ago) Yesterday I pulled the neg. terminal of the battery while checking starter wiring (working on SVXgirl's starter and was comparing) When I plugged the neg terminal back in, the issue started on next crank The day before the battery drained and I charged it back up w/ a 10A charger - didn't have the issue on first crank then Plugging that gauge back in on injector 1 showed no injector pulses being received (or out of threshold to be recognized) until I stepped on the gas Same thing happened when I switched it to injector 4
sounds like a battery issue. Reset ECU: if gone, then good. If not gone, swap battery for a good one. If gone, then good. If not after one or both of those: electrical issue elsewhere. How many miles on it?
I did try resetting the ECU by pulling the neg terminal again, stepping on the brake a few times, and letting it sit disconnected for ~20 min. Didn't help... the battery is strong enough to crank, but it's definitely on its last leg... I can try a new batt. The car has 75k on it. Oh yea, I just did an oil change too yesterday. Checked my dipstick and its still full. How can I check for a vacuum leak? And would a vacuum leak issue come on so suddenly? Or could it have been there and the ECU was compensating until it got reset?
Several things: 1. Battery 2. You need to do a software ECU reset. There have been cases that an ECU does not truly reset with a loss of power. 3. PCV valve needs to be changed every 30k miles. When was that last done? A bad one will make the car run like complete monkey ass. 4. Same for spark plugs: every 30k. 5. Air filter and MAF. Dirty? Replace with SUBARU air filter and clean MAF off with high power brake cleaner and compressed air.
You sir, are the man. I owe you a beer when you next are up this way. My buddy Zach (toguetuned) whose house the car was sitting at tossed in his battery (not the best shape but better) and she's running much better. I will still do the above maintenance as it is, admittedly, overdue. Thank you so much. :bowdown: That could have been the most expensive battery ever - $100's in diagnostic fees plus an overpriced OEM battery. :eek3: Oh yea, how to do that software ECU reset, b/c it is still dipping down briefly to ~500 on throttle lift... Something I can do or a shop needs to do? Zach's father-in-law is opening a shop next Monday so I can have it done then... or maybe sooner if they get the equipment in early.
When you do the PCV/Plugs/Filter/MAF cleaning, rest the ECU after you do all that. Get a TACTRIX cable and get some software from t3h intArwebz to do a software reset.