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Showing results for tags 'Flat Spot'.
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Hey Y'All, My '91 Subaru Legacy seems to have a flat spot (I believe that's the correct term, but I'm still not fully versed on some of this stuff). Generally occurs when accelerating (usually somewhere between 2k and 3k RPMS) or climbing a hill: I'll depress the accelerator but nothing happens (RPMS don't climb, no speed increase). If I keep giving it gas it'll eventually surge and begin accelerating relatively rapidly (except when climbing hills, usually I just have to limp to the top); sometimes it'll surge then return to lagging, then surge again. Doesn't seem to demonstrate this problem above 3k RPMS, though every once in a while it does below 2k. What I've done since the problem appeared. I've changed or had changed: spark plugs and wires, intake manifold gasket, O2 Sensor, & Throttle Position Sensor. Originally it had the flat spot intermittently and would occasionally lurch or misfire on the freeway (and I'd get an occasional ECU Code, though at the time I hadn't pulled the codes), so I took it to a mechanic for diagnosis (this is about a month ago at this point). They told me the sparks and wires needed replacing and I had them replace them. The problem persisted, so I took it back to the mechanic; they diagnosed a bad O2 sensor, bad intake manifold gasket, and bad fuel injector seals. I replaced the O2 sensor and intake manifold gasket. Car was 10x worse (had no power at all, couldn't maintain speeds above 30 or 40, etc.), so I took it to another mechanic who pulled codes for a bad O2 sensor and replaced that (the O2 sensor I'd used was cheap and the mechanic said it likely was poor quality). Now it's back to the condition I originally described (flat spot under load). After doing some research, I replaced the TPS (twice, using TPS's pulled from junk yard subarus), and it's appeared to fix the problem very briefly, but within a few hours the problems return. It has been giving occasional ECU Codes, specifically for the O2 sensor (which I have trouble believing is bad since it's been replaced twice), and just yesterday it threw codes for the TPS and Idle Switch. I'm at a loss. Still need to replace the Fuel Injector Seals, but haven't been able to get them out and scared of breaking them. Wondering about the possibility of a wiring issue since the O2 Sensor and TPS have both been replaced multiple times and continue to throw codes. Saw one post suggesting a knock sensor might cause such a problem, but not stoked to pull out the intake manifold again unless there's more indication that is a problem. Anyone have any thoughts? Thanks. -
Hi everyone, I am new on this site to see if someone can help, hopefully this works. My 1998 legacy 250T EJ25 wagon has, what I would call a flat spot, or lag even though it's not turbo. It is happening at low revs when I accelerate from lights ect, or just when I want that extra little bit of speed, it does eventually get up and go but just seem to take a while to sort it self out. I took it for a good blow out on the open road and went very well. The CEL is not coming on. I have replaced the knock sensor, Co2 sensor, spark plugs and leads. Other than this frustrating flat spot, it is going well and idles fine. Does anyone know of this problem which can point me in the right direction, or should I carry on changing maintenance parts next would be fuel filter?? Or could it be something like TPS, ECU mapping ect...... Which I would have to take to a specialist. I appreciate any help. Thanks Pete.