Fairtax4me Posted July 9, 2009 Share Posted July 9, 2009 Ok, 96 legacy 2.2. Runs awesome, good power, no missing stuttering or chugging. Out of nowhere, and seemingly at random, it will just die. Sometimes it will cough one or twice, the idle will fluctuate a bit, lasts maybe three seconds then all is well again. Most of the time it will just die. Driving down the road it does the same thing. Any gear, and seemingly at any random time the engine will just quit. Seconds later its back running (all on its own usually because it's still in gear) and away I go. I've driven for a half hour with no trouble out of it. Then it might do it a dozen times in five minutes. CEL is on and shows a code P0100 MAF sensor circuit malfunction. It just doesn't act like a bad MAF sensor. Never hunts for idle, it doesn't stumble or anything when it's running. Air temp and/or motor temp have no noticeable effect. It might die right away on a cold start, it might warm up first and then die. Then sometimes it won't idle for more than 30 seconds on its own without dieing. Always starts right back up right away and runs just fine. I've searched and searched, and read page after page and can't find anything else that is described like this. All the other MAF threads that I can find are rough idle, loss of power, or stumbling under throttle. And that's what I've normally encountered with MAF related issues. So has anyone else run across this? Any suggestions on what to check? Haven't tried a new MAF yet, but it does die if the MAF is unplugged. Help? Link to comment Share on other sites More sharing options...
Log1call Posted July 9, 2009 Share Posted July 9, 2009 Wriggle the wires and plugs with the motor idling. Link to comment Share on other sites More sharing options...
Fairtax4me Posted July 9, 2009 Author Share Posted July 9, 2009 Wires on what? The MAF? Tried that, no change. It did quit once, but I don't think that's evidence enough to indicate a wiring issue. When it's idling the wire harness doesn't move at all, and it will still die on it's own. I forgot to add in the first post that when the MAF is unplugged, then engine will still start and run the same. Idle is a bit higher (800 rpm) and throttle response is a little slow, but other than that it runs the same. Link to comment Share on other sites More sharing options...
Log1call Posted July 10, 2009 Share Posted July 10, 2009 You could try wriggling the main engine connector and, if you are really keen, the wires going into the ecu. Ok, only one code, Hmmm, it could be either the main relay or the fuel pump relay or power supply. It could even be a dirty fuel filter. Recommended procedure is to do a standard tune up and service, including inspection all the vacuum hoses. Then I'd check the fuel pump's connector under the back seat(because it's easy), then I'd probably pull the main and fuel pump relays(which isn't easy) and check them both and/or substitute a known good one. Link to comment Share on other sites More sharing options...
EVOthis Posted July 10, 2009 Share Posted July 10, 2009 well, obviously its throwing that code for a reason....have your tried tapping on the MAF with the butt end of a screwdriver with the engine running? does anything happen to the idle than? have you cleared the code? if so has it come back? how many miles are on this vehicle? Any recent maintenance performed? Have you tried cleaning the MAF with some CFC MAF cleaner? have you visually inspected the sensor/hot wire itself?...If its throwing this code I would def. rule out all possibilities of the MAF system/sensor/wiring before searching for anything else....I was also kind of inclined to say crank/cam sensor ( they have been known to cause odd "hic-ups" like this, however you dont have any codes related to those... Link to comment Share on other sites More sharing options...
Fairtax4me Posted July 10, 2009 Author Share Posted July 10, 2009 I've tried wiggling every wire harness I can get my hands on under the hood. I did smack the main relay a few times, the yellow one under the dash next to the steering column I think is the right one? It had the biggest wires, so I just assumed. Where is the fuel pump relay located? I'll try it, but I kinda doubt that's the problem. It's not like it sputters and coughs a second before it quits, it just straight up quits like I turned the key off. Fuel filter looks new. It's not coated in gravel dust like everything else. I believe the MAF has been recently replaced as well. The intake tube wasn't clamped tightly to the sensor, and it was also a lot cleaner than the rest of the engine compartment. And theres a mark on it like it came from a junkyard. I'm guessing they replaced it and it didn't fix the problem. Is there somewhere I can find a wiring diagram for the MAF harness so I can poke around with my VOM and see if it's losing power when this happens? Link to comment Share on other sites More sharing options...
Fairtax4me Posted July 10, 2009 Author Share Posted July 10, 2009 Well I have managed to duplicate the problem three times by pulling on the wire harness for the MAF in just such a way. So it's either a loose connection or internal break in the wire. Gonna call the Soob dealer tomorrow and see what a new pigtail will cost. I work for a sister store of the same company, getting parts at cost rules! Thanks for the help guys! Link to comment Share on other sites More sharing options...
EVOthis Posted July 11, 2009 Share Posted July 11, 2009 If you have a haynes manual it would def. come in handy now...there are some diagrams in there that would be helpful...also a little slew of tests for the MAF to make sure its getting the 5v ref. voltage and whatnot.... Link to comment Share on other sites More sharing options...
Fairtax4me Posted July 13, 2009 Author Share Posted July 13, 2009 I haven't bought a manual yet but its on the list for sure. Haynes manuals aren't usually good for much besides torque specs and sometimes wiring diagrams. Half the time they don't even have a diagram for what I need. I prefer to get a factory service manual if I can. I popped the wires out of the plug and crimped the tabs together so they would make a nice tight connection and got no change out of it. Then I stripped off part of the insulation off the wires and found nothing but clean wire. No breaks or corrosion like I had expected. I'm thinking it must be an internal break in the MAF now, since it still seems to act up if I tug on the wires just right. :-\ Link to comment Share on other sites More sharing options...
Log1call Posted July 13, 2009 Share Posted July 13, 2009 Ha, don't tell anyone I said this but... Perhaps you can push the wires just right and it will stay good. A little wooden wedge jammed in somewhere? Just kidding. Managing to reproduce the fault is the most important step in a diagnosis really. With out that, you can never be sure you have cured the problem. It sounds like you have found your problem(almost). Now to find the cure. Link to comment Share on other sites More sharing options...
davebugs Posted July 13, 2009 Share Posted July 13, 2009 I have several complete intake assy's if you decide to go that route. Don't know what a good one goes for. Most of mine are known good and they are all marked. Link to comment Share on other sites More sharing options...
Fairtax4me Posted July 14, 2009 Author Share Posted July 14, 2009 Well I don't think I need the whole intake. I'm just gonna make a trip to a junkyard about an hour for me and try to grab a few things, including a MAF sensor or two. There's still the possibility that there's nothing wrong with the MAF and that it just happens to die while I'm screwing around with that part of the car. It'll probably be two weeks at least before I know anything solid though. Plus since I haven't even paid for the car yet, its kinda dumb for me to be spending a bunch of money on parts already. Never stopped me before though... Link to comment Share on other sites More sharing options...
Fairtax4me Posted July 16, 2009 Author Share Posted July 16, 2009 A thought just struck me. I've spent all this time on trying to figure out what's been causing this problem. It never crossed my mind to just unplug the MAF and take it for a drive. I know it runs with the MAF unplugged, but I never thought to just let it sit and see just how long it would run. It makes too much sense, so I'm gonna do it tomorrow and see what happens. If it dies the same way again, then I can start looking elsewhere. If not, then I'll know damn well that its the MAF and I can rest assured that replacing it will solve the problem. Link to comment Share on other sites More sharing options...
Olnick Posted July 16, 2009 Share Posted July 16, 2009 It makes too much sense, so I'm gonna do it tomorrow and see what happens. Yes! Let's hope it tells you definitively what you need to know. Link to comment Share on other sites More sharing options...
Fairtax4me Posted July 17, 2009 Author Share Posted July 17, 2009 Well it ran for about 35 or 40 minutes. Didn't cut off once. Drove it all around the lot at work a few times, it wasn't happy to be driven, but it didn't ever cut off. Killed it and hooked the MAF back up, ran for less than a minute and died. That's the proof positive that I've been looking for. Link to comment Share on other sites More sharing options...
2.5GL Posted July 17, 2009 Share Posted July 17, 2009 My experience says MAF. Its not very often the wiring is bad. If it is it usually looks bad as well. See if you can find somebody near you whom you can barrow a MAF for a day, go though your normal routine (drive to work out to lunch, home again) and see what happens. If nothing happens, get yourself a new one.... Link to comment Share on other sites More sharing options...
Fairtax4me Posted August 4, 2009 Author Share Posted August 4, 2009 Been a while but I figured I would update this. Finally made it to the yard over the weekend and grabbed a MAF as well as a few other odds and ends. Found one that looked pretty new, although it was from a previous generation Legacy, it had the same part number. Popped it in and drove about 20 miles with no trouble. I'm gonna drive it a few days to make sure, but I think I'm gonna call it fixed. Link to comment Share on other sites More sharing options...
subynut Posted August 4, 2009 Share Posted August 4, 2009 That is intristing, my parents 97 outback with the 2.5 will not run at all without the maf connected. I wonder what the difference is. Link to comment Share on other sites More sharing options...
Fairtax4me Posted August 5, 2009 Author Share Posted August 5, 2009 Dunno. The first time I started it without the MAF it shut right back off. The second time it set the CEL and then seemed to start just fine. Idle speed was a little jumpy, but it never stalled. I pulled the vacuum line to the MAP sensor (it was close) and the idle evened out a bit. It should run in failsafe mode without the MAF connected. Just like if you unplug the TPS or the O2 sensors, it will run on a preset fuel/spark profile that should at least get it down the road, though likely not very well. Link to comment Share on other sites More sharing options...
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