FSRBIKER Posted February 11, 2005 Share Posted February 11, 2005 I have replaced the plugs, wires(OEM), air flow meter and coil pack and my car still hesitates when accelerating. The check engine light is on and if I reset the com puter it used to run fine for a few hundred miles and then the light come on and slowly the hesitation would get worse...now it only takes 25 miles or so. I even had a local Subaru dealer look at it and they scratched their head saying lets start with plugs and wires first again. I found out that Subaru has a TSB(Technical service bulletin) out on thsi very problem and what they will do is replace the computer with a new one with updated fuel/air and emmissions info that cures the problem. Since this was never made a recall i can't get them to replace it for free, has anyone had their computer replaced because of this? If so can you look and get me the part number(and any other numbers) on the computer so I can search the local boneyards for a replacement. Thanks in advance Quote Link to comment Share on other sites More sharing options...
Commuter Posted February 11, 2005 Share Posted February 11, 2005 What is the CEL code? I presume you have a 2.5L auto? These engines are known for running rich. I'd be interested too if there is an alternate ECU out there. I've never heard that before. Is your hesitation at low rpm, or mid range rpm? If the former, you might have a carbon issue. (Been there, done that twice.) Also, this will be aggrevated by a sluggish O2 sensor. If the latter, it might be a knock sensor problem. Good luck. Commuter (97 OB also, 430k km) Quote Link to comment Share on other sites More sharing options...
FSRBIKER Posted February 11, 2005 Author Share Posted February 11, 2005 It shows a misfire. I had my buddy check it out with his OBDII code reader from Lexus after we reset the computer and he would swear the car had 20,000 miles on it not 160,000. It is a 2.5 5 speed and the hesitation is off the line to 3,000 rpm...after that you can't really feel it. What is the CEL code? I presume you have a 2.5L auto? These engines are known for running rich. I'd be interested too if there is an alternate ECU out there. I've never heard that before. Is your hesitation at low rpm, or mid range rpm? If the former, you might have a carbon issue. (Been there, done that twice.) Also, this will be aggrevated by a sluggish O2 sensor. If the latter, it might be a knock sensor problem. Good luck. Commuter (97 OB also, 430k km) Quote Link to comment Share on other sites More sharing options...
FSRBIKER Posted February 14, 2005 Author Share Posted February 14, 2005 Here is a copy of the TSB: HESITATION ON ACCELERATION - 11-53-98 (2/99) Applicability: 97-98 Legacy, Impreza, and Forester Manual Transmission Vehicles with 2.5l and 2.2l engines. In the event you encounter a customer complaint of a slight engine hesitation between 1500-2500 rpm's when the engine is cold or hot, perform the following Eliminate all external influences, such as an incorrect or dirty air filter, loose or tracked intake duct, dirty fuel filter, low fuel pressure, PVC system, or low engine vacuum that would indicate an external leak or an internal engine component. If all external components are confirmed to be operating within vehicle specifications, the hesitation may be caused by the ignition control logic in the ECM. Under certain low rpm driving patterns, the ignition control system can pick up engine vibrations through the knock sensor and may retard the ignition timing. This ignition timing is learned by the ECM and placed in memory. NOTE: This area of memory can not be viewed by using the Select Monitor. When the vehicle is driven uinder these conditions, the timing may be retarded and could cause the engine to hesitate on acceleration. To confirm this condition, road test the vehicle while viewing the Knock Sensor Signal on the Select Monitor. If you duplicate the hesitation, and the reading on the monitor is around -10 degrees, you will need to change the ECM to correct the concern. [my note: this is an enhanced ECM, not a replacement with the same component Quote Link to comment Share on other sites More sharing options...
FSRBIKER Posted March 9, 2005 Author Share Posted March 9, 2005 Well replaced the PCV, air filter(again) and the ECM with one from a boneyard and then reset the computer. I then went for a hard drive taking the car close to redline a few times and parked it at work, coming home from work I could swear the car felt more powerful but had a slight stumble off the line but the conisitent hesitation was gone. It was good for about 100 miles and then in stop and go traffic this morning the light came on after about 30 minutes. Any more ideas? Knock sensor?... and if so how easy is it to replace?? Quote Link to comment Share on other sites More sharing options...
FSRBIKER Posted March 10, 2005 Author Share Posted March 10, 2005 Ttt Quote Link to comment Share on other sites More sharing options...
SubeeTed Posted March 11, 2005 Share Posted March 11, 2005 Hi! My 1997 2.5 DOHC Legacy had similiar problem. Turned out to be a valve adjustment that was TOO TIGHT! I had my CEL on, #3 cylinder misfire. It had hesitation problems and gas milage went to about 20 MPG, I get around 24 now. Good Luck, SubeeTed Quote Link to comment Share on other sites More sharing options...
FSRBIKER Posted March 12, 2005 Author Share Posted March 12, 2005 Interesting, did you have work done before this happened? I had my Outback about 20,000 miles before the CEL came on so I don't think it would be a valve adjustment but I am willing to try just about anything right now since I have to go for inspection this month and NJ FAILS any vehicle with a CEL on. Hi!My 1997 2.5 DOHC Legacy had similiar problem. Turned out to be a valve adjustment that was TOO TIGHT! I had my CEL on, #3 cylinder misfire. It had hesitation problems and gas milage went to about 20 MPG, I get around 24 now. Good Luck, SubeeTed Quote Link to comment Share on other sites More sharing options...
SubeeTed Posted March 12, 2005 Share Posted March 12, 2005 I did the same stuff you did. Wires. plugs, coil pack. I did one thing you didn't mention. It's run this stuff you can get from the dealer that burns off the carbon build up. It's cheap, sort of works like that "Sea Foam" stuff I hear about. You basicaly run it through the engine via a vacuum hose, I used the large hose from the master cylinder. I think I have a different head on my 2.5 DOHC engine. it's a "Shim PAck" engine. Basicaly they use "Shims" to adjust valve clearence. Did you do a compression check or leak test? This will tell you if you have a valve problem. GOOD LUCK!! SubeeTEd Interesting, did you have work done before this happened? I had my Outback about 20,000 miles before the CEL came on so I don't think it would be a valve adjustment but I am willing to try just about anything right now since I have to go for inspection this month and NJ FAILS any vehicle with a CEL on. Quote Link to comment Share on other sites More sharing options...
tarabull Posted March 12, 2005 Share Posted March 12, 2005 Before reading my post, please be aware that I am NOT very knowledgable about cars so I may be saying or asking things that have already been said or asked.... Just bought a '97 Legacy Outback. During the first two test drives, the car seemed to run fine. Then, after handing over the check and signing the title... it began to act up. It was doing just what was described in a post above; it seemed to be hesitating on acceleration. I took it in and they checked the plugs, wires, coil pack, air flow sensor, fuel pressure and were unable to diagnois a problem. One thing he suggested was the it could have been bad fuel? So, when the tank was down below 1/4, I filled it up and it appeared to run better for a day or so. Then, I began experiencing the same problem. It's very sporadic, not consistent at all. So, the neighbor took it for a test drive today. He said it felt like the car wasn't shifting down upon acceleration. He wanted me to find out if the transmission is electronic or vacuum controlled. And, then, suggested I have either the Throttle Position Sensor checked (if electronic) or look for a vaccum leak (if vacuum controlled). So, I'll prolly take it in on Monday. What do you guys think of this? The bulletin that was posted was for a manual? Does the same apply to automatic? Thanks! Quote Link to comment Share on other sites More sharing options...
FSRBIKER Posted March 14, 2005 Author Share Posted March 14, 2005 SubeeTed I had used Seafoam over the summer on it, didn't make much difference. Replaced the Plugs with NGK Laser Paltinums this weekend, reset the computer and within 50 miles the CEL is back on but so far the car is running great....that is except when cold the cars throttle appears to be sticking(2500 rpm's) which has happened occasionally in the past. So now I am going to check the EGR valve and throw some fuel injector cleaner in. Anyone clean their MAF? Quote Link to comment Share on other sites More sharing options...
FSRBIKER Posted May 28, 2005 Author Share Posted May 28, 2005 Replaced the oxygen sensors and now the CEL doesn't flash but I get the hesitation on occasion still and the CEL light is lit. I also bought a new Suabru coil pack but no change. Anyone seen or tried this: http://www.geocities.com/hobiegary/hesfix.htm Quote Link to comment Share on other sites More sharing options...
Cougar Posted May 28, 2005 Share Posted May 28, 2005 I would hold off on the circuit modification. I remember at least one poster stating that replacing the knock sensor fixed his hesitation problem. Replacing the sensor is pretty easy but I have heard you need to be carefull about how much you tighten it. I think the spec is 16 ft.lbs. but I'm not sure on that. The sensor is around the same cost as the circuit I think. I have also heard that bad ground connections can cause a problem like this. Quote Link to comment Share on other sites More sharing options...
Olnick Posted May 28, 2005 Share Posted May 28, 2005 You also might want to remove and clean your idle air control valve--they get pretty gunked up and sticky. Recently did the Seafoam thing, cleaned the MAF sensor, throttle body and IACV and replaced the engine coolant temperature sensor (it was giving me a CEL) and my hesitation went away. That was on my '95 2.2L. Quote Link to comment Share on other sites More sharing options...
FSRBIKER Posted May 28, 2005 Author Share Posted May 28, 2005 I actually bought a new knock sensor but before replacing it I tested the one in the car with my Ohm meter and it is good, so i returned it for the coil pack. I guess I can check the engine ground to make sure it's clean. I would hold off on the circuit modification. I remember at least one poster stating that replacing the knock sensor fixed his hesitation problem. Replacing the sensor is pretty easy but I have heard you need to be carefull about how much you tighten it. I think the spec is 16 ft.lbs. but I'm not sure on that. The sensor is around the same cost as the circuit I think. I have also heard that bad ground connections can cause a problem like this. Quote Link to comment Share on other sites More sharing options...
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