four-fleet-feet Posted August 5, 2008 Share Posted August 5, 2008 Here's the specs: 97 Impreza, 2.2, Auto, 169k. 5k on NGK plugs, fuel filter, PCV, timing belt service (all except oil pump and thermostat), and antifreeze, 3k on dealer trans flush, 28 miles on new air filter and knock sensor. Did not change plug wires, but resistance was ok at the time. Due for oil change. 5/30 Pennzoil in there now, on a Fram filter. (Yeah, I know, I have a Purolator for the next!) On Sunday I started having a surge/stumble at idle during long stop lights (3-street merge point). It rapidly became severe enough that I turned off the a/c; no change. It was happening about 3-4 times per light change. Immediately changed knock sensor (had a PO325), thought it was due to severely retarded timing. Under throttle smooth on Sunday before sensor replacement (although no power); smooth as silk after changing the knock sensor. I can accelerate again, and 75 is no problem. Even stomped acceleration/power to spare is easy. However, long idles at lights (or in a parking lot in Drive with the brake on) still brings up a stumble. It doesn't stall, just rumbles once and then runs fine. If it sits longer at idle it may or may not happen again. No pattern to the length between them. It can be two minutes, or ten. It's no longer a series of them, so perhaps it's not due to the sensor. Yes, I cleared the code; no CELs now. Been using Chevron Plus gas. Any ideas where to look? Aircraft-engineer and I have no clue. TIA, f-f-f. Quote Link to comment Share on other sites More sharing options...
EVOthis Posted August 6, 2008 Share Posted August 6, 2008 im sure youve already done it but....clean the IAC? Quote Link to comment Share on other sites More sharing options...
McDave Posted August 6, 2008 Share Posted August 6, 2008 Yesterday I left my car idling with the a/c on while I ran into the house for something. When I came back out I realized that the inconsistent lean misfire at an idle that could be heard at the tailpipe was no longer there. Last week I had treated the gas with a bottle of Techron to cure an off-idle lean condition and apparently it fixed it at idle too. I surmised the problem was with either a gummed up injector, or carbon build-up on the valves. Even though you use Chevron gas, an extra dose of Techron might be worth a try. Quote Link to comment Share on other sites More sharing options...
four-fleet-feet Posted August 6, 2008 Author Share Posted August 6, 2008 Thanks for both replies! Silly car idled 8 minutes with no rumble this AM (train crossing). Yesterday it did it twice in a minute at a short stop light. I guess I can clean the IAC again, Dragon's air filter only lasted 5k in Arizona (dusty + smog). I'd figured that couldn't be it, but maybe it's gunked up again. As far as the Techron goes, oh heck, why not? It's why I use Chevron gas in the first place. Never used the straight additive, but I guess it can't hurt. If it loosens sludge, I'll need a new fuel filter, but after Arizona's crappy gas (lots of mandated additives) it probably wouldn't hurt. I always needed to slap a new FF in my other vehicles after a trip to see the parents! Arizona gas = yuck! Quote Link to comment Share on other sites More sharing options...
BoostedBalls Posted August 7, 2008 Share Posted August 7, 2008 Fram and Penzoil???? !!!!!! Are you trying to kill the poor thing? Please get some quality oil in there (especially in AZ!) If you are on the cheap, at least get some Valvoline or Castol. Then run some lucas oil or seafoam in the fuel. Check for vacuum leaks with a can of starting fluid or carb cleaner. IF you don't find any, try lubing the IAC valve.. keep us posted... Quote Link to comment Share on other sites More sharing options...
four-fleet-feet Posted August 7, 2008 Author Share Posted August 7, 2008 Fram and Penzoil???? !!!!!! Are you trying to kill the poor thing?No, but I needed an oil change and I couldn't find a Purolator! D'you have any idea how hard it is to find Subaru ANYTHING in Arizona? Even the dealers say 'gotta order that' even just if it's a PCV valve. I was lucky I found a Fram! I found two Purolators only because the parts manager of that PepBoys was a Subaru fan and he ordered them for his car. Don't worry. Tomorrow AM Dragon's going to the dealer to get an oil change. The $28 is going to be well-spent, since they offered to do a full check and make sure she was safe for the trip home to Washington. If they find anything wrong, I'll fix it myself - but I'll know what TO fix. Since changing your own oil on hot concrete (not to mention the 110 degree heat by noon - or 'only' 100 at 7:30 in the morning) is akin to oiling yourself and pretending to be the steak on the grill, it's worth every penny to have them do it. Besides, I kind of like Pennzoil. After all, I've gotten over 500k miles out of my last 3 cars using it! Quote Link to comment Share on other sites More sharing options...
four-fleet-feet Posted August 15, 2008 Author Share Posted August 15, 2008 Thought I'd give McDave his due and mention his idea worked like a treat. One bottle of Techron in one full tank of Chevron Premium and voila! Problem solved within 80 miles. It's been over a week and it's definitely gone. As to the oil change... well, had a torn CV (fixed that) and a leaking rear strut (two coming up, in WA). Bad trans cooler lines, doing on Monday. At least the rumble's gone... Ah, used cars with two previous owners... you never know what they'll throw atcha. Even with the little parts here and there, though, Dragon's still $52k cheaper than that hybrid Lexus 400h I was drooling over... Quote Link to comment Share on other sites More sharing options...
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