Crawlerdan Posted February 20, 2015 Share Posted February 20, 2015 ok- so im not a noob, been working on subarus professionally for 16 years- but sometimes a problem needs other ears and eyes a friend has a 2002 outback with a sohc 2.5 and 5 speed it has about 20k on a complete rebuild, bearings the works, 200 on the car when i rebuilt it i installed a mild set of delta cams, a header, thats it thing runs like a scalded dog but- he has a 700 mile commute, sets the cruise at 70-75 and it will randomly try and accelerate, and slow down, without driver input. it does it with and without the cruise on when he reduces speed to 60-65 it will not do it as often, maybe once in 200 miles randomly it will stutter and hesitate, occasionally it throws a random misfire, nothing consistent, and randomly it will throw a po172 i have checked for vacuum leaks- none. i replaced the oem fuel pump last week and he noted an improvement everywhere, but problems occurred three times in 700 miles he noticed it happens more often at half tank and below, as opposed to full tank help please and thank you Link to comment Share on other sites More sharing options...
ccrinc Posted February 20, 2015 Share Posted February 20, 2015 Very possibly the cam grind. If it was done at Delta Camshaft, Scott can probably tell you which grind it has. Some are better for low end torque, some for constant high rpm...but all will usually produce a loping idle and as a side effect, a "hiccup" at constant speeds. Afterthought: have you checked the O2 sensors? Link to comment Share on other sites More sharing options...
Crawlerdan Posted February 20, 2015 Author Share Posted February 20, 2015 o2 sensors were replaced at 30k ago it ran flawlessly with the cams until just recently Link to comment Share on other sites More sharing options...
Fairtax4me Posted February 20, 2015 Share Posted February 20, 2015 Have you put a scanner on it and checked sensor outputs? Computer thinks its too rich so I would assume front O2 sensor is reading rich and fuel trims are probably going negative. Pull the plugs and see how they look. Link to comment Share on other sites More sharing options...
Crawlerdan Posted February 20, 2015 Author Share Posted February 20, 2015 Every time we pull plugs they look fine. So far I have only used an el cheapo scanner Link to comment Share on other sites More sharing options...
Crawlerdan Posted March 4, 2015 Author Share Posted March 4, 2015 bump Link to comment Share on other sites More sharing options...
Fairtax4me Posted March 5, 2015 Share Posted March 5, 2015 You almost have to put a scanner on it and see what the computer is seeing and doing. If plugs look OK and fuel pressure is good, the answer is probably going to be a sensor dealing with fuel that's out of range. MAF/MAP or O2 sensor. TPS maybe? Link to comment Share on other sites More sharing options...
Crawlerdan Posted March 5, 2015 Author Share Posted March 5, 2015 We have a scan gauge 2 on the car. It's not showing anything weird. We plan on trying a map sensor soon Link to comment Share on other sites More sharing options...
ccrinc Posted March 5, 2015 Share Posted March 5, 2015 I was leaning toward a speed sensor, but I also looked here http://www.cargurus.com/Cars/Discussion-t9991_ds508275 . Lots of possibilities. Worth looking over anyway. Link to comment Share on other sites More sharing options...
Crazyeights Posted March 5, 2015 Share Posted March 5, 2015 Knock sensor getting flaky perhaps? 1 Link to comment Share on other sites More sharing options...
nipper Posted March 7, 2015 Share Posted March 7, 2015 So what happens if you try to hold the gas pedal at 70-75 and not use cruise? Is it predictable enough that he can loosen the gas cap after it happens to see what the car does. This may throw a code (loose gas cap) but ignore it for now. Link to comment Share on other sites More sharing options...
Crawlerdan Posted March 7, 2015 Author Share Posted March 7, 2015 It occurs under cruise and foot control Link to comment Share on other sites More sharing options...
nipper Posted March 7, 2015 Share Posted March 7, 2015 hrmmm Is it just engine rpm or vehicle speed that changes Link to comment Share on other sites More sharing options...
Crawlerdan Posted March 7, 2015 Author Share Posted March 7, 2015 Both Link to comment Share on other sites More sharing options...
nipper Posted March 7, 2015 Share Posted March 7, 2015 Could it be the lockup torque converter kicking in and out? Maybe not an engine issue and more of a transmission issue? Link to comment Share on other sites More sharing options...
Crawlerdan Posted March 7, 2015 Author Share Posted March 7, 2015 5 speed Link to comment Share on other sites More sharing options...
nipper Posted March 7, 2015 Share Posted March 7, 2015 (edited) I don't like you. I'm going back to a flaky knock sensor. You can watch the engine timing with a scanner, or if you can get it cheap enough just swap it out. I rarely suggest just swapping out a part but its not a lot of money. Flaky TPS is also possible. Edited March 7, 2015 by nipper Link to comment Share on other sites More sharing options...
Crawlerdan Posted March 7, 2015 Author Share Posted March 7, 2015 I'll look into it Link to comment Share on other sites More sharing options...
idosubaru Posted March 7, 2015 Share Posted March 7, 2015 Wondering about the cruise and throttle cables/throttle body - something compromised might cause drift up or down via the throttle body/cabling? I had a non-starting 2001 EJ25 with no engine codes and no known issues. I swapped the entire intake manifold and it ran beautifully. How's that for terrible diagnosis and not at all helpful!?!?!? when it does it (with and without the cruise control on) is there a corresponding movement in the gas pedal? how significant of an increase/decrease are we talking. a tiny bit, noticeable, or a lot? Last resort guess work: $10 ebay knock sensor, swap crank and cam sensors, MAF, TPS to test. swap the entire intake manifold swap in an EA81 Link to comment Share on other sites More sharing options...
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