wallaceg Posted June 30, 2008 Share Posted June 30, 2008 Car is a 1997 Impreza L Wagon, 2.2L 4EAT, 118k miles. Yesterday I noticed that the engine stumbled once on the highway at 65mph, but other than that it's been running fine. This morning it started but was running very rough and stalled a few times. CEL came on. Let it sit for a few minutes, then restarted and it seemed OK. Drove a few miles, then the engine started to hesitate a little, then stalled cruising at 30mph. I restarted in neutral while rolling, and was fine again. Stopped at the Autozone to have the codes read and it showed: P0301: Cylinder 1 Misfire P0302: Cylinder 2 Misfire P0103: MAF output higher than expected Seems like the first two codes could just be symptoms of a faulty MAF making the mixture too rich (increasing the fuel from the injectors to keep up with the abnormally high MAF reading). I have not had a chance to inspect inside the MAF yet, but the connector was on tight and is not wet or corroded. It is hot and humid today if that might be interfering with the MAF. Any insights onto whether the MAF actually is the problem, and if cleaning the sensor will help? A new MAF looks to be about $250. Thanks. Quote Link to comment Share on other sites More sharing options...
OB99W Posted June 30, 2008 Share Posted June 30, 2008 A hot-wire type MAF can usually be successfully cleaned (less likely with the later thin-film type), but it needs to be done carefully. Misfire is usually more typical with a lean mixture than a rich one. It's possible that there's a marginal ignition problem (plugs, coil, wires) with cylinders #1 and #2 (they're wasted-spark paired), making them more susceptible to mixture or other issues than #3 and #4. If nothing else, I'd suggest making sure the #1 and #2 ignition wires are tightly in place at the coil and plugs. Quote Link to comment Share on other sites More sharing options...
idosubaru Posted June 30, 2008 Share Posted June 30, 2008 What is the tune up history of this vehicle? I would start with new spark plugs and wires. Unless they're new already - then make sure they're in good shape and properly seated. Best to stick with NGK plugs and Subaru wires. That's true of the EJ series Subaru engines, they're not very forgiving. Quote Link to comment Share on other sites More sharing options...
wallaceg Posted June 30, 2008 Author Share Posted June 30, 2008 Plugs and wires were replaced two years ago at 90k. Could an out-of-tune engine cause a MAF sensor error code? Quote Link to comment Share on other sites More sharing options...
idosubaru Posted June 30, 2008 Share Posted June 30, 2008 have any oil-based air filters ever been used on this car - K&N, cone filters, etc? those oils can foul the MAF sensor. cleaning should help if that's the case. stores sell MAF sensor specific cleaner. and i have found faulty MAF sensors by removing them and looking at the hair thin wires that are threaded through the intake passage of the MAF sensor. a broken wire will mean the sensor is bad obviously and needs replacement. check the connector of the MAF sensor, makes sure it's seated properly and not dirty/corroded. when chasing multiple codes that show up around the same time there's a few tips: it's best to clear them and then check which come back or come back first. it's best to track down the most common codes first. cylinder misfires are common on EJ engines, MAF sensor failure is not. but that's not to say it isn't kaput of course. misfire causes have already been listed - plugs, coils, ignitor. were NGK plugs and Subaru wires used at 90k? i've seen brand new non-OEM wires, as well as not very old ones, cause issues many times on EJ engines...hence my earlier comments. Quote Link to comment Share on other sites More sharing options...
wallaceg Posted June 30, 2008 Author Share Posted June 30, 2008 The air intake is stock with a standard paper filter, and always has been. I used NGK plugs and Subaru wires at 90k. Sounds like I should check all the vacuum hoses, MAF sensor, and plug wires tonight. To clear the codes, disconnect the battery for 20 minutes, right? Quote Link to comment Share on other sites More sharing options...
idosubaru Posted June 30, 2008 Share Posted June 30, 2008 checking the MAF and ignition wire connections sounds like a good start. then clearing and reading the codes. Quote Link to comment Share on other sites More sharing options...
edrach Posted June 30, 2008 Share Posted June 30, 2008 How's your oil consumption? I had the mis-fire on #2 and MAF errors on my '97 Imp. Turns out I had bad oil rings on number 2 cylinder and the plug was badly fouled. MAF likely due to my K&N filter; replaced that with stock and installed another MAF, replaced the engine for the oil consumption issue (bad rings on #2) and haven't had any problems since. I have used good MAF if you want one ($50 shipped). Quote Link to comment Share on other sites More sharing options...
wallaceg Posted June 30, 2008 Author Share Posted June 30, 2008 Update: Looked at the MAF and it seems OK. No dirt or other buildup. Cable and connector look good too. Tried tapping the MAF and wiggling wires while the engine was idling and it didn't make any difference. Pulled out the #1 plug to have a look, and there was some white crusty deposit on the plug. I did not look at the #2 plug since it's a pain to get to. After putting the plug back in and reconnecting the wire it was running a bit worse than before. Quote Link to comment Share on other sites More sharing options...
OB99W Posted June 30, 2008 Share Posted June 30, 2008 Update: Looked at the MAF and it seems OK. No dirt or other buildup. Cable and connector look good too. Tried tapping the MAF and wiggling wires while the engine was idling and it didn't make any difference.It doesn't take much buildup on the MAF wires to cause a problem. As I mentioned previously, misfiring is typical when the mixture is lean, which is what a dirty MAF will cause. See the following MAF info:http://www.babcox.com/editorial/ic/ic110034.htm http://endwrench.com/images/pdfs/EWMAFAug05.pdf Pulled out the #1 plug to have a look, and there was some white crusty deposit on the plug. I did not look at the #2 plug since it's a pain to get to. After putting the plug back in and reconnecting the wire it was running a bit worse than before.Deposits can cause fouling misfire. Ignition wires can go up in resistance (as can the resistor inside a plug). The spark can take a path other than across the plug gap, due to damaged insulation, etc. Here's how to read spark plugs: http://www.ngksparkplugs.com/techinfo/spark_plugs/faq/faqread2.asp Here's info on ignition/misfire: http://endwrench.com/images/pdfs/IgnitionCoil.pdf http://endwrench.com/images/pdfs/DirectIgnition.pdf There are errors in the "DirectIgnition.pdf" info. In the "Ignition Coil Testing" section, the terminal numbers listed are reversed between the primary and secondary; however, the diagram is labeled correctly. The correct numbering relative to expected resistance is in "IgnitionCoil.pdf"; you can use the diagram from "DirectIgnition.pdf" to identify the terminal numbers. http://endwrench.com/images/pdfs/IgnitionCoilSum04.pdf http://www.babcox.com/editorial/ic/ic30332.htm http://www.babcox.com/editorial/ic/ic90140.htm Quote Link to comment Share on other sites More sharing options...
wallaceg Posted July 1, 2008 Author Share Posted July 1, 2008 I replaced all 4 plugs and wires with NGK/Subaru parts, and there is no improvement, maybe even got a little worse. The engine is still idling rough and stalls occasionally. Looked at the vacuum lines but didn't see any obvious cracks. Looks like it might be the MAF, but I don't want to try swapping out a $200 part on a hunch. Quote Link to comment Share on other sites More sharing options...
OB99W Posted July 1, 2008 Share Posted July 1, 2008 [...]Looks like it might be the MAF, but I don't want to try swapping out a $200 part on a hunch.Did you read the two articles about MAFs that I provided links to? They include some pretty good info. Is there a particular reason that you aren't trying to clean the MAF before considering replacing it? Quote Link to comment Share on other sites More sharing options...
wallaceg Posted July 2, 2008 Author Share Posted July 2, 2008 For the sake of posterity (and anyone in a similar situation). After changing the plugs and wires, inspecting all the vacuum hoses, and cleaning the MAF, I caved and took the car to my mechanic. He happened to have a used MAF on hand (seriously, what are the odds?), swapped out the faulty one, and the car was running like a top again. Makes me wish I had just asked if he had one available and then installed it myself. Costs: $60-Plugs, wires, and MAF cleaner (Would have replaced them soon anyway.) $180-Used MAF and labor ($60 less than the new MAF I was going to buy!) $60-Rental car for a day :-\ Quote Link to comment Share on other sites More sharing options...
edrach Posted July 2, 2008 Share Posted July 2, 2008 I hate to rub salt in the wounds, but didn't I offer you a used, working MAF for $50 shipped? If nothing else, now I may ask more for the next one. Glad to hear your car is fixed. Quote Link to comment Share on other sites More sharing options...
wallaceg Posted July 2, 2008 Author Share Posted July 2, 2008 I hate to rub salt in the wounds, but didn't I offer you a used, working MAF for $50 shipped? If nothing else, now I may ask more for the next one. Glad to hear your car is fixed. Yes, although it would have cost me $60 for each day I waited for it to arrive since I have no other vehicle.... Still, thanks for the offer! Quote Link to comment Share on other sites More sharing options...
monk50 Posted August 31, 2008 Share Posted August 31, 2008 How's your oil consumption? I had the mis-fire on #2 and MAF errors on my '97 Imp. Turns out I had bad oil rings on number 2 cylinder and the plug was badly fouled. MAF likely due to my K&N filter; replaced that with stock and installed another MAF, replaced the engine for the oil consumption issue (bad rings on #2) and haven't had any problems since. I have used good MAF if you want one ($50 shipped). Do you still have the MAF? Quote Link to comment Share on other sites More sharing options...
98obster Posted August 31, 2008 Share Posted August 31, 2008 I replaced all 4 plugs and wires with NGK/Subaru parts, and there is no improvement, maybe even got a little worse. The engine is still idling rough and stalls occasionally. Looked at the vacuum lines but didn't see any obvious cracks. Looks like it might be the MAF, but I don't want to try swapping out a $200 part on a hunch. wow, that didn't do it? when did you last replace the fuel filter? Quote Link to comment Share on other sites More sharing options...
wallaceg Posted September 2, 2008 Author Share Posted September 2, 2008 wow, that didn't do it? when did you last replace the fuel filter? Just to answer your question, the fuel filter was replaced about a year/12k ago. The MAF was in fact the problem and the car has been running great since replacing the faulty sensor. Quote Link to comment Share on other sites More sharing options...
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