jwox Posted October 1, 2010 Share Posted October 1, 2010 My daughters '99 Legacy sedan AT recently developed a strange problem. The car starts fine but when you give it gas it hesitates pretty bad. It doesn't miss and, if you're light on the accelerator, the car drives okay. If you keep steady pressure on the gas it slowly accelerates and then the car leaps quickly with good power when the car reaches around 20 mph. Then, when it shifts, the car hesitates again. When I bought it for her graduation gift (about six months and 3k ago) I had to replace the anti-knock sensor so it shouldn't be that. I'm hoping that the experts here can point me in the right direction!!! Have a good weekend everyone! Quote Link to comment Share on other sites More sharing options...
86subaru Posted October 2, 2010 Share Posted October 2, 2010 maf needs cleaning, or fuel filter, Quote Link to comment Share on other sites More sharing options...
OB99W Posted October 2, 2010 Share Posted October 2, 2010 Welcome to the forum. How many miles are on the odometer? Other than the knock sensor, has any other maintenance (preventive or otherwise) been done by you? Do you have any information as to what work was done on the car by the previous owner? Does the problem present itself any differently if the engine is cold versus warm? Can we assume that the CEL/MIL light isn't on? What happens if, while the hesitation is occuring, you give it substantially more throttle? I suppose that's enough for now. Quote Link to comment Share on other sites More sharing options...
Suba9792 Posted October 2, 2010 Share Posted October 2, 2010 to me it sounds like the well known 99 AT problem, try flushing the tranny and the give it a bottle of Trans-X, then top off with your regular ATF. But it could also be the MAF but they rarely fail. If it continues after doing the tranny flush then I'd seriously take it in. Those specific trannys have a seal in them that fails and causes it to not engage correctly, it sounds as if yours may be beyond the trans-X fix, if that is the problem. Quote Link to comment Share on other sites More sharing options...
OB99W Posted October 2, 2010 Share Posted October 2, 2010 to me it sounds like the well known 99 AT problem, [...] It could be trans slippage, if the engine revs are going up but the car isn't correspondingly accelerating. Quote Link to comment Share on other sites More sharing options...
jwox Posted October 2, 2010 Author Share Posted October 2, 2010 The check engine light isn't on, I changed the fuel filter right away when I bought it too. I'm going to clean the MAF sensor and see if that helps. I didn't see any vacuum leaks but I'll look better today. The car runs the same when it's cold, or warmed up. I don't think the tranny is slipping at all. The car just doesn't have much for acceleration until it revs up a bit. It was fine when she drove it to work, but when she was heading home after her shift the car started acting up. I didn't know there was an issue with the AT transmissions on these cars. I haven't had it flushed yet so I should get that done. Thanks for the ideas! I'll do a little more checking and see what I can figure out. Quote Link to comment Share on other sites More sharing options...
Suba9792 Posted October 2, 2010 Share Posted October 2, 2010 Look on here, there are tons of threads about the known tranny issue, I believe its 99-00 that they had the issue, and from my understanding you can temporarily fix it with a flush and the trans-X stuff. But odds are you will probably have to replace it, I'd go with one from a 97-98 should fit just fine. But yes it does have an issue and it is called Delayed engagement, there is a seal that doesn't hold up and fluid goes by it causing a lack of pressure when changing gears, which could be your problem. Sit in the car with the engine running(idle) put it in drive and count the sec before it engages into 1st gear, should be no more than 3-4 sec, if it takes more than 5 sec to engage then you do have the problem, did you get the car from a dealer? and how much did you pay and mileage? see if you can find anything out about what work has been done, to the tranny. Quote Link to comment Share on other sites More sharing options...
jwox Posted October 2, 2010 Author Share Posted October 2, 2010 I went out to the car to take it for a drive. The transmission engages into drive right away so I'm guessing the delayed engagement isn't the problem. (thank goodness!) I had to do some cement work today so I didn't get any checking done with the car. It seems to run better today though when I did take it out. I'll go over it tomorrow and see if I can find something. I sure like how the legacy's drive! When my daughter buys another car I'm thinking that I might want to buy it from her and keep it for us. The all wheel drive sure is nice during the snowy season! The temp is really dropping so it won't be long. Quote Link to comment Share on other sites More sharing options...
Suba9792 Posted October 2, 2010 Share Posted October 2, 2010 thats good that its engaging correctly, BTW how many miles are on it, because from what I understand the problem tends to be between 70k-120k. Check all emission related parts, if I'm correct yours should have an EGR valve since its an AT, but I could be wrong, check that too. Quote Link to comment Share on other sites More sharing options...
jwox Posted October 3, 2010 Author Share Posted October 3, 2010 I forgot to say that it has 192k on it. The car still looks surprisingly good for being in Minnesota. I thought I'd do a search for checking the EGR and oxy sensor as either might be getting old. I bought the car from a small dealer so I have no idea who owned it previously. Quote Link to comment Share on other sites More sharing options...
Manarius Posted October 4, 2010 Share Posted October 4, 2010 I forgot to say that it has 192k on it. The car still looks surprisingly good for being in Minnesota. I thought I'd do a search for checking the EGR and oxy sensor as either might be getting old. I bought the car from a small dealer so I have no idea who owned it previously.192k? MAF's dead. Cleaning it may help. It may not. I'd be on the hunt for a cheap replacement/one to borrow to confirm diagnosis. I think the kind of acceleration hesitation you feel is due to the engine constantly misfiring at low RPM's, not because the transmission is holding it back. Does it buck under load? Rough idle? Shuts off randomly? Quote Link to comment Share on other sites More sharing options...
Suba9792 Posted October 4, 2010 Share Posted October 4, 2010 how would you clean the MAF anyway? isnt it very delicate Quote Link to comment Share on other sites More sharing options...
Manarius Posted October 4, 2010 Share Posted October 4, 2010 how would you clean the MAF anyway? isnt it very delicateWell, they sell dedicated MAF cleaner at your favorite auto store. I just usually use like 97 or 99 % rubbing alcohol, a q-tip, and a gentle hand. Quote Link to comment Share on other sites More sharing options...
OB99W Posted October 4, 2010 Share Posted October 4, 2010 There are two basic types of MAFs, "hot wire" and "hot film". The wire type runs hotter than the film, and tends to not contaminate as readily. Many hot wire ones have the ability to self-clean by elevating the wire temperature way above that of usual operation. Not so with the film type. The '99 used a film type MAF. They've been somewhat troublesome, and there was a bulletin issued (WWG-90). If you have a defective one, it should be replaced. Check with Subaru of America at 1-800-782-2783. Please let us know the outcome. Quote Link to comment Share on other sites More sharing options...
Suba9792 Posted October 4, 2010 Share Posted October 4, 2010 So my 97 would have a film type MAF then? would you clean it the same way? (sorry to hijack) Quote Link to comment Share on other sites More sharing options...
OB99W Posted October 4, 2010 Share Posted October 4, 2010 So my 97 would have a film type MAF then? would you clean it the same way? (sorry to hijack) No, '99 was the "lucky" model year for the problematic MAFs. Previously, they were hot wire, and in 2000 the SOHC engines got a MAP-based system. Quote Link to comment Share on other sites More sharing options...
Suba9792 Posted October 6, 2010 Share Posted October 6, 2010 sweet, because I just cleaned mine for good measure, was a pain to separate from the intake though. My idle and acceleration improved as well. Quote Link to comment Share on other sites More sharing options...
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