Suby Skier Posted March 11, 2007 Share Posted March 11, 2007 I am having a persistent hesitation from idle on a 99 Outback wagon, Auto, CA emission vehicle, 148,000 miles. I had to repalce the engine a year ago for the dreaded head gasket problem. The new rebulit engine still has the same hesitation from idle. I have done the following: Replaced PCV valve Cleaned EGR valve and passages Replaced both O2 sensors Replaced Air filter Replaced fuel filter Replaced spark plugs with NGK dual platnum Used BG-44K to clean fuel system Cleaned MAF Cleaned Idle Control Valve Replaced all fluids in the vehicle I pulled codes which I have none. I did a search on hesitation but have not found a similar problem or fix for a hesitation from idle when you hit the throttle either in neutral or in gear. Thanks in advance for any advice as to what could be causing this problem. :confused: Ken Quote Link to comment Share on other sites More sharing options...
porcupine73 Posted March 12, 2007 Share Posted March 12, 2007 How did you clean the MAF? Did you clean the throttle butterfly and stuff? They like to get caked up real nice. How's the knock sensor? Quote Link to comment Share on other sites More sharing options...
Suby Skier Posted March 12, 2007 Author Share Posted March 12, 2007 I cleaned the MAF with a Q-tip and rubbing alcohol. It looked fine before hand. I have not checked/replaced the Knock sensor but will try that next. The butterfly valve seemed to be OK. Quote Link to comment Share on other sites More sharing options...
porcupine73 Posted March 12, 2007 Share Posted March 12, 2007 I forgot to welcome you to the board! Welcome! The MAF could still be flaky even with cleaning. Do you have any aftermarket cold air intake or anything installed? How about your TPS adjustment? Quote Link to comment Share on other sites More sharing options...
Suby Skier Posted March 12, 2007 Author Share Posted March 12, 2007 I forgot to mention this before, but I swapped out the MAF from my 97 Outback Sport, which appeared to be the same. I still had the hesitation from idle. I thought about adjust the TPS before but was scared off from adjusting it because I read in the Chiltons manual I believe, that it should be adjusted at the factory only or you needed special test equipment. Thanks, Ken Quote Link to comment Share on other sites More sharing options...
porcupine73 Posted March 12, 2007 Share Posted March 12, 2007 Wow it sounds like you covered all the usual suspects already. Are there any exhaust restrictions/excessive backpressure maybe? Quote Link to comment Share on other sites More sharing options...
OB99W Posted March 12, 2007 Share Posted March 12, 2007 [...]Are there any exhaust restrictions/excessive backpressure maybe? That sort of thing shouldn't affect operation directly off idle; it's usually more apparent at higher speeds and loads. Ken/Suby Skier: I've had a very minor stumble right off idle in my '99 OB pretty much since new, but never enough to be worth the trouble to me to diagnose. Just how bad is the hesitation on yours? Is it noticable if you very slowly depress the accelerator? Not that I'm suggesting you do it if you're concerned, but you could scribe the TPS in a few places before trying to adjust it, so that it could be set back to very near the original position. However, putting a meter on the TPS output and verifying that the voltage changes smoothly when the throttle is moved off idle should probably be done before touching the adjustment. If the voltage is at all "jumpy", cleaning or replacement may be the key. More basic than the above, have you checked the ignition wires? Corrosion or loose fit at the plug or coil ends can sometimes cause problems similar to what you're describing. Clean, tighten (carefully, as to not damage the boots), and check that resistance is within spec. Quote Link to comment Share on other sites More sharing options...
OB99W Posted March 12, 2007 Share Posted March 12, 2007 I forgot to ask -- does the hesitation seem at all related to temperature and/or humidity? Quote Link to comment Share on other sites More sharing options...
Commuter Posted March 12, 2007 Share Posted March 12, 2007 I am having a persistent hesitation from idle on a 99 Outback wagon, Auto, CA emission vehicle, 148,000 miles. ... I did a search on hesitation but have not found a similar problem or fix for a hesitation from idle when you hit the throttle either in neutral or in gear. Thanks in advance for any advice as to what could be causing this problem. :confused: Ken I guess you didn't turn up any of my posts. I'd lay 10 to 1 odds that you have a carbon issue with the engine. I've faced this 3 times in total now with my 97 OBW (540,000 km now). It's not common, but I have heard of a few others having the same problem. A Motorvac treatment fixed me up the first time. The second time, the problem was being aggrevated by a weak O2 sensor. The last time (this past winter) it was fairly mild (I know the symptons well now) and a can of Seafoam in the gas cured it about 90%. (I had also tried Marvel Mystery Oil, but it did next to nothing.) Note that most over the counter cleaners will not fix things up as the problem is usually too severe. You need something more industrial in nature. What I have heard is that the fuel maps are on the rich side in these engines, leading to the issue with a few of us. Commuter Quote Link to comment Share on other sites More sharing options...
Suby Skier Posted March 13, 2007 Author Share Posted March 13, 2007 Thanks for the replys, The hesitation is fairly slight and just of idle. It seems to do it when the engine is warmed up and idle lowers. It is more of an annoyance. It is my wifes car so I do not drive it much, but am wondering if this problem is related to fairly poor MPG. I am getting around 23 in mostly highway driving. I am going to try SEA Foam to see if it helps before I try a new knock sensor. I also need to check into the ignition wires as was mentioned. Thanks, Ken Quote Link to comment Share on other sites More sharing options...
Suby Skier Posted April 1, 2007 Author Share Posted April 1, 2007 Hesitation fixed (I hope) I think that I finally fixed my hesitation from idle problem. The last things I did was changed the spark plug wires, the knock sensor and put most of a can of Seafoam through the PCV valve. I think that the Seafoam most likely was the most effective. Thanks for all the advice. Ken Thanks for the replys, The hesitation is fairly slight and just of idle. It seems to do it when the engine is warmed up and idle lowers. It is more of an annoyance. It is my wifes car so I do not drive it much, but am wondering if this problem is related to fairly poor MPG. I am getting around 23 in mostly highway driving. I am going to try SEA Foam to see if it helps before I try a new knock sensor. I also need to check into the ignition wires as was mentioned. Thanks, Ken Quote Link to comment Share on other sites More sharing options...
unverviking Posted April 2, 2007 Share Posted April 2, 2007 From the sounds of it you may have licked it... We had similar issues with our 01 OBW when we bought it new. Took it to the dealers several times for them to look at it, all with no avail. They did tell us that there were several complaints and that SOA was working on it. Even the service manager's 01 Forester was doing it. Eventually they issued a recall to reflash the ECM, after that the stumble was gone. Not sure if the 99 model year was included on the recall. Since I don't have the car anymore, I can't provide you with the recall info... Sorry.. but I thought I'd chime in with my 2 pennies worth in case it were to return... Quote Link to comment Share on other sites More sharing options...
unibrook Posted June 4, 2007 Share Posted June 4, 2007 My fix turned out to be the front 02 sensor. Here is my review from a diff thread: I have a 2001 Forester L with 85k miles on it. I have been chasing an intermittent hesitation under load problem for the past year since 80k miles. Only occurred when engine was warm. The front 02 sensor had been replaced once at 40k miles. I suspected it again this time, but since the only codes thrown had been cyl's 2&4 misfire ( p0302 & p0304) I assumed it must be ignition related. So I replaced plugs and wires 8 months ago...no effect. Did the dollar bill test over exhaust pipe, it was fine. Misted the coil, no sparks. I mentally sort of ruled out the fuel filter since it only happened when the engine was warm. Finally, a week ago while cruising on hwy at 65 mph, I felt the hesitation again (I wasn't even accelerating this time) and a new code was thrown....p0172. AutoZone read it for me, I described the symptoms to the guy and asked if he thought it might be the front 02 sensor. He said, "absolutely." So I decided to replace it next. Cost me $100.75 incl tax for the oem part# 22791aa00a from Cityside Subaru. I asked the Parts guy there if his experience was that this model engine needed a new front 02 sensor every 40k miles. He said, "no, these sensors are good for 100k miles." Well, bullsnot on that. I replaced the new front 02 sensor in 1 hour reaching from the top over the passenger side of the engine using an adjustable wrench. Be sure to use the thread lube so you can get it out easily next time.....after another 40k miles. I took out the air channel assembly first for better access. That seems to be the fix. No further hesitation since. Car runs like new. Quote Link to comment Share on other sites More sharing options...
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