blitz

Cookie, I started driving during the 70's "emissions era" so the throttle feel of an overly-lean motor with retarded timing is etched in my brain. Lousy driveability as the end result of trying to get 60's engines to meet 70's emissions requirements. Who would've guessed that all these years later it would be essentially the same thing all over again?: Driveability issues related to getting 90's engines to meet 2000's emissions requirements? I get the feeling that certain '02 vehicles were beta test cases for trying to get the EJ-25 to conform to ULEV in advance of the Federal mandate. This way Subaru could monitor customer (guinnea pig) complaints in a more relaxed fashion as a measure of success or failure and make changes accordingly. :-\

Until about two years ago I knew avsolutely nothing about OBDII, but a buddy of mine who formerly was a service tech for Chrysler and did a lot of troubleshooting regarding "driveability issues" on individual customer vehicles explained a lot of things to me in a way that made sense. Myles is correct about the "cat-efficiency" function of the rear 02 sensor, but it functions on a different principle than the adaptive fuel trim. Instead of the ECU reading voltage, it counts and compares the number of "crossings" of the rear 02 sensor against the number of "crossings" of the front 02 sensor. The front sensor is supposed to switch like a mutha, and if the number of crossings slows down appreciably, then the sensor has become contaminated or "Lazy". If the cat is performing properly, the rear sensor shouldn't be switching much at all. However should the cat became completely non-functional (test-pipe?) then the rear sensor would be switching at the same rate as the front sensor thereby triggering a cat-efficiency (inefficiency) code.

It took about 8 months of driving and observing. First I extended a length of shielded cable from the rear 02 sensor into the cockpit so I could hook up a Fluke Multimeter and monitor the sensor's voltage output during real-time driving. The meter has a data-logging feature that records minimum, maximum and average. I noticed that the rear sensor doesnt "switch" in an active closed-loop control circuit like the front sensor does, but rather reads the oxygen content as it appears at that point in time. At the end of a drive I would read the recorded average, and after about 20 driving events I realized that the average of every drive would be close to .555 volts. Short, punchy, around-town type drives (more hydrocarbons) tended to move the average number higher initially, but ultimately it would learn itself back down to .555 Volts. Long, steady-state highway cruising (lesser hydrocarbons) would move the average number lower initially, but ultimately it would learn itself back up to .555 Volts. Thus the nature of adaptive fuel trim. The ECU averages the output of the rear 02 sensor just like the Fluke meter does, and when the drive is complete and the key is shut of, the ECU logs this average, and uses it to slightly shift the lambda target up or down in anticipation of the next driving event. Remember that the lambda target is the number which the front 02 sensor actively shoots for during all driving (except for full-throttle and cold startup). In other words the average voltage taken from the rear sensor ultimately becomes the arbiter of that point (lambda target) to which the front sensor is shackled to, as it attempts to control fuel mixture. I decided that using a resistor to shift the number by 3% would be a good, practical starting point. 100k gave me that 3% number shift. After a week of driving, I lowered the value to 82k for a week, then 68k, then 56k... and stopped at 27k to where the car feels strong now. I guess you'd know if you've gone too far by a drop in fuel economy and soot at the tailpipe. Just make slow, steady changes until it feels right.

I had the same off-idle hestitation and weak-in-the-knees throttle response problem with my '02 from the day I picked it up. Lean mixture city. Part-throttle mixture is controlled by the front 02 sensor "shooting for" (repeatedly crossing over) the lambda target. The default lambda target is stored as a part of the base (non-volitile) map. Resetting the ECU restores the lambda target back to this default value meaning that after a reset, the part-throttle fuel mixture will default back to a base starting value. Average readings taken from the REAR sensor are used to shift this base lambda target (trim the part-throttle fuel mixture) over the course of several "driving events". On my vehicle, part-throttle mixture would be fine after an ECU reset, but would learn itself to be leaner after several driving events, causing the off-idle-stumble, and the big hole in the throttle response. The fix: I tied a 27k resistor across the output of the rear 02 sensor. This loads down the sensor's output, dropping the voltage being fed back to the ECU by about 10%. ECU thinks that the cruising mixture is a little bit lean, so then predictably compensates by learning itself to be just a little richer. Voila, another 4 cent fix. You may have to run 89 octane anyway as your mileage accumulates, especially in hot weather.

I'll go you one better on the definition. I'll say that an engine that blows head gaskets with the frequency of the 2.5 is bored well OVER it's design limit (for safe or sane production methodology anyway). "Limit" being defined as the point at which reliable operation ceases.

Welcome Jay. I tried posting a technical question on rs25.com once asking if anyone had info about the effect of possibly destructive crank harmonics when using an aftermarket lightweight crank pulley. The first response I got was: do u have a stereo installed, stereo amp can draw more current causing battery to discharge I was outta there.

The coil packs are known to go bad which fits in with the weak spark you observed. You may be able to pick up a salvage unit for cheap.

About the only thing you can do is disassemble the calipers, remove the pads and apply a thin coat of anti-sqeal to the backside of the pads and a thin coat of silicon brake grease to the slides, then put it back together. The first thing on humid mornings the brakes are gonna sqeal no matter what, until you build a little heat into the pad material via one or two moderate stops which will will chase out the moisture.

Not looking for exact numbers obviously, but anyone have a rough approximation of a fair price for a WRX catback pull-off? I'm gonna start lookin' for one to swap-in onto my '02 OBS.

Almost everything there looks to be asscociated with the PCV system. If you've discarded the original intake tract for purposes of the swap, then you might have to re-plumb some of this, rather than re-connect it. Each valve cover has a fresh air entry point (breather) which must be derived from a source of filtered air (post air filter). The 1/2" metal nipple looks like the PCV valve, which connects to a source of manifold vaccum. The tank looks like an oil catch-can, but since I don't have anything like this on my '02, I can't comment, ditto on the plastic pitchfork thingy. Well... don't know if that helped much :-\

I gotta concur with hawksoob, if it's been a while since any of the scheduled maintenance has been done, start with that. Have a look at the plugs, and if in doubt... just change 'em, check that the plug wires or the coil pack aren't arcing, throw-in a new fuel filter. If that doesn't take care of it, move on to some finer points.

Question: Did it used to run fine, then just suddenly just begin to act up?

LOL No, it ain't quite that bad. :^) I slid underneath and gave everything a visual and nothing appears bent. I snugged the axle nut and it moved a bit, but didn't change the noise. I'm guessing the angular torsion created by the impact stretched/unseated some critical dimension in one or both of the bearings. I'll just have to drive it towards failure and see what happens. Thanks everyone for the response.

Yours truly put his summer tires back on three weeks ago during 60 degree weather and then proceeded to spin-out into a curb a week later in four inches of snow and ice. Uhh... well, I broke the lip off the passenger rear alloy in what was an almost perpendicular impact with the curb. The wheel's been replaced and the vehicle drives fine, but I'm left with a wee bit of ghostly howling coming from the rear area at about 35 mph, so I figure I tweaked something. Anyone have some general suggestions on what I should be on the lookout for? I'm thinking like the wheel bearing or something related to the thrust surface of the axle in the diff. I recon someone who's auto-Xed or rally-Xed might have some first-hand experience with the result of wheel-impact "events" and what typically suffers as a result. TIA

Closely examine the condition of the keyways on both the crank and pulley. If they've been expanded, mushroomed or mis-shapen in any way by the slightest amount (as a result of having previously come loose), you may find it impossible to keep the pulley secure.

Then... while your at it, throw in a 2.5 crank and wind up with 2.4 liters (almost a 2.457, minus the thin walking bores).

It might be my minor debacle that your referring to, except that I didn't actually bleed the system at that point, but rather I had air trapped there after having done the bypass mod incorrectly. Instead of correctly reconnecting the two hose sections after removing them from the TB, I simply capped them off, causing air to be trapped in the hose-ends (instead of letting it pass through and out). I still have a slow bubbling in the O' flow, but not as severe as when the TB hoses were capped off. Not sure what that's about but I've got my eye on it.

It's a tradeoff. MAF is a more accurate system than MAP on account of it measuring the actual amount of air ingested, but it restricts the airflow somewhat, and the sensor is relatively expensive, delicate and is easily damaged. MAP essentially extrapolates (makes a really good guess as to) the fuel requirements, so requires help from temp sensors, barometric pressure sensors, etc. It's a safe bet that MAP-based systems will become more prevalent as underhood computing power grows exponentially.

Within the last month, someone posted some info regarding the differences between 2.5 & 2.2 ECU's and IIRC, they were interchangable. I tried a search, but couldn't pull up the post. Maybe you'll have better luck than me, I know it's in the archives somewhere.

I went to an auto repair vocational school after I graduated high-school, and became ASE certified in all areas but didn't relish the thought of breathing hydrocarbon fumes 40 hours a week. I own a little shop where I service guitar amps & vintage studio gear, etc. My famous client list: Sheryl Crow Oasis Weezer Bush Fuel Kid Rock Sponge Dokken Joe Strummer Lenny Kravitz Cold Ron Asheton Thin Lizzy Eric Johnson Romantics Juice Newton White Stripes I love dropping names, it's such a cheap way to latch onto stardom. Also if there's any guitar players reading this and you're hip to the Naylor amp, I designed that in '93. I'm a hopeless tweeker, so there's no way I'd be able to tolerate a daily driver suffering from a poor fuel or timing map for more than half a year with out devising a solution. The amazing thing (to me anyway) is that electronic controls almost seem to make tinkering easier.

Yeah, I think that most all light dependant resistors and temperature dependant resistors that are based on the natural characteristics of organic materials have a curved transfer characteristic that starts out fairly straight at one end, and compresses at the limit. Thanks, good info ...that.

Sorry, I haven't been following closely. I'm not a Sube expert, so my knowledge is limited to my vehicle, but I'll explain what I can. This trick is universal to most modern EFI vehicles. Some Sube models have a stand-alone IAT sensor mounted on the front of the air filter housing. On my '02 2.5, the intake air temperature sensor is combined together with the MAP sensor (it's a two- in- one combo), and it's located on the top surface of the intake manifold plenum just to the right of the coil pack (looking into the engine bay). It says Bosch on it. A four-lead connector (labeled #1 - 4) mates to it of which leads #1 and #2 are associated with the IAT sensor circuit and the added resistance can be inserted into either lead. In order to get a feel for the range of resistance that the sensor normally shows the ECU, I heated it with a heat gun and put it in the freezer. Here's what I got: 100*F - 800 ohms 28*F - 9k ohms A general rule seems to be that a value higher than 100k is out of range and will throw an error (CEL). By messing with various values, I found no noticable change in the map beyond 47k. I reasoned that a log curve is probably used at the input to make a linear change at the output so I settled on five fixed values: Position 1. OFF Position 2. 2.2k Position 3. 4.7k Position 4. 10k Position 5. 22k Position 6. 56k The switch is available at Radio Shark.

Two words: General Motors.

I successfully used a couple of stainless-steel screws in this fashion to stop a heat shield rattle last week. I drilled pilot holes through the loose end of the shield, then ran the screws through right up to good 'n snug. I think it may have been one of your posts about six months back that gave me the idea. Thanks much.

Borrow an ohmeter and measure it (dissconnected from the ECU!). The exact number isn't super critical, you could probably be within 20% or so and easily fall within the ECU's allotted parameters (there is an allowable range). Also if it makes you feel more comfortable, you could include a SPDT mini-toggle in the cockpit that connects the ECU lead to either the grounded resistor or the sensor (normal/bypass). Always use solder, heat shrink, tie-wraps and ground-lugs. Don't wind, twist, tape, rig, or otherwise do a "hillbilly" wireup. You want the job to look professional be as secure as the factory would've done. :cool: