OB99W

The manner in which silicones can damage an O2 sensor is that high temperatures (even those less than in a combustion chamber) convert them to silicon dioxide. Silicon dioxide is a glass-like insulator, and a very thin film of it on the sensor will prevent it from working correctly. While I've seen evidence that liquids like motor oil can carry away some uncured silicone, I've yet to find a reliable source that indicates fumes during the curing process contain any significant amount of silicone compounds that could be intake-air-borne. (For Silicone II, there's some methanol released, and the moisture cure generates ammonia.) If you believe that your O2 sensor has been contaminated by silicon dioxide, then you might also have reason to be concerned about the catalytic converter; SiO2 can contaminate the catalyst as well. However, since you haven't experienced any trouble codes, that would seem to indicate the problem is still subtle. Are you sure that nothing else was disturbed while you were applying the sealant? The best info I've found so far is from a MSDS (Material Safety Data Sheet) for GE-5000 Silicone II, http://www.e-barnett.com/MSDS/000842.pdf . I'm not a chemist or chemical engineer; if a forum member is, please enlighten us.

Doing engine "mix and match" with different models/years/transmissions/ECUs can make finding a no-start problem difficult. If you're not sure wiring is correct, checking sensors should be done at the ECU end, in order to verify that output is getting to the proper input. See page 5 of the "Direct Ignition" PDF to identify the difference in the signals.

By the above, can we assume that you mean there is no cranking? If that's the case, do you hear a click when you turn the key?

Silicone can damage an oxygen sensor, but it has to actually reach the sensor. As far as I know, the fumes that are given off during the curing of RTV shouldn't do that (GE Silicone I emits acetic acid fumes, while Silicone II gives off mainly ammonia). The danger is in using RTV that isn't "sensor safe" when sealing parts of the engine that come into contact with crankcase oil or something else containing silicone that can get into the combustion chambers (like if there's a bad HG). I'm assuming that chunks of RTV aren't coming off your intake. But what, exactly, did you seal?

From your description, it seems that there's no switched pulse getting to the coil primaries. Do you have a voltmeter? If so, you should probably trace the problem back, as described in the EndWrench link above. (Nipper mentioned the igniter.) Yes, the problem might be in the ECU, but there are possibilities other than that and the coil. By the way, was the engine transplant a direct, exact replacement? Did electrical components just plug in, or was wire splicing or anything of that nature necessary?

Each coil in the pack fires two plugs at a time (they're "paired" in series), using the "wasted spark" method. The three wires you're referring to connect to the two coil primaries; the center one is common to both. When a cylinder is on a power stroke, its paired one is on an exhaust stroke. Only a few kilovolts is "wasted" jumping the gap in exhaust, leaving most of the rest for ignition of compressed mixture in the other cylinder. This may help with diagnosis http://endwrench.com/images/pdfs/DirectIgnition.pdf , but the info on coil primary and seconday numbering and resistance is incorrect. See http://endwrench.com/images/pdfs/IgnitionCoil.pdf for the correct coil terminal identification.

Any luck? You're welcome. If you need the full procedure, just ask.

Having a new gasket on hand might be a good idea. Since the problem is intermittent, I'd suggest checking electrical connections as well.

Congratulations on getting the problem resolved, and thanks for getting back to us. O2 sensors often become "suspect" by around 100,000 miles (converting from kilometers, that's about where your car was at).

I assume that was meant to say "SHOULD NOT CONNECT". The "green plugs" are for diagnostic purposes, and normally are left apart.

Try looking for info on "idle air control valve" or IACV (or IAC). Have a peek at http://endwrench.com/images/pdfs/Fuel.pdf , page 6. Also, http://endwrench.com/current/spring04pdfs/InsiderInfo.pdf , page 30, last section. By the way, a single short drive after clearing codes may not be enough to get accurate info; some codes aren't set until a problem occurs on two or more consecutive drive cycles.

I don't know what your manual says, but I do know that the one for my own car (a '99, also using the Alpine system) has info not at the "cars101" site. See if this previous post of mine helps: http://www.ultimatesubaru.org/forum/showpost.php?p=390602 If that doesn't do it, later I'll post the entire procedure verbatim from my manual.

To clarify things -- I think poorly-sealing rings are only a part of the problem, as others have said. In fact, if enough unburned gas is washing down the cylinder walls, especially if the oil is becoming gas-diluted and isn't changed frequently, that in itself can reduce ring sealing and lead to excessive ring/bore wear. Suggestions that have been made in this thread are worth pursuing. Sooty plugs and high CO/HC obviously point to a too-rich mixture (or one that isn't being properly burned, anyway), and the rhythmic shudder and drop in vacuum could indicate valve issues, possibly timing-related; checking that the crank pulley is tight, the crank keyway isn't worn, and the timing belt hasn't jumped (among other things) is worthwhile. Just because there aren't DTCs doesn't mean that a particular part or system is healthy -- pre-OBDII left something to be desired (as does OBDII ). I'd suggest that if you're going to tear the engine down, inspect things carefully before or as they come off; you may find one or more obvious problems in the process.

Take a look at Scenario 4; what's described in your sentence I quoted above fits it (ignore the 15-17 inches part -- a Subaru engine that's healthy typically has a vacuum reading at idle that's above 18 inches, usually closer to 20). Between the low compression, the increase when "wet", and the vacuum readings you've reported, it does seem that the rings aren't sealing well.

Okay for this time, but just don't let it happen again. By the way, parasitic load doesn't usually draw over 30 mA (milliamperes). For a fully-charged battery to become discharged in three days to the point that it won't start the engine would typically require a draw closer to 1/3 amp (333 mA) or more. Since that's better than 10 times the usual max current, an ammeter should easily reveal if there's an excessive load.

What Nipper said, but use an ammeter (not a voltmeter) to determine if there's excessive current draw. If the draw is reasonable, then it's possible the battery may not be able to hold a sufficient charge. Perhaps the alternator isn't delivering enough; a loose drive belt could be a simple cause.

It seems I didn't make my point clearly enough. Checking auto trans fluid level isn't like checking engine oil. You have to run the engine and put the trans through the gears, even when checking cold fluid; if the torque converter has drained down, that will usually refill it and provide a more-accurate level. Yes, as I previously suggested, checking hot is better than doing so cold.

You didn't say whether you had the engine running, put the shift lever through the gears, etc., when doing the "cold" check. If not, you need to do that; "cold" means just that the fluid is cold, but otherwise the same procedure is followed as when checking "hot". It's best to use the procedure in the manual and check the hot fluid level. Be sure to allow the dipstick to remain in the tube for a minute after wiping it, before withdrawing it again; removing the stick tends to pull fluid up the tube, giving a falsely high reading. Also, look at both sides of the dipstick, and assume that if one reads lower, it's the correct one. In some cases, if the fluid is exceptionally low, it will get aerated (air bubbles will be formed), giving an apparently higher reading than the actual level.

Here are a couple of articles to read that may help:http://endwrench.com/images/pdfs/ACTheory.pdf http://endwrench.com/images/pdfs/ACMechanism.pdf It's possible that your A/C is low on refrigerant. There's a switch mounted to the receiver/drier that senses refrigerant pressure; it won't allow the compressor clutch to engage if the pressure is too low. The switch can be checked for continuity to determine if that's the problem. If so, the A/C system will likely need to be recharged, but should be checked for leaks before a complete recharging is done.

A direct link to the PDF version of the article is http://www.motor.com/MAGAZINE/Pdf/102006_09.pdf Motor Magazine articles can be found at http://www.motor.com/ ; click on "MOTOR MAGAZINE". As to P0420, sometimes it's due to an O2 sensor problem, sometimes the cat itself is bad, sometimes a bad enough O2 sensor that has been ignored for a long time will cause damage to the cat and you'll need both, sometimes other engine problems kill the cat, etc. In general, if the O2 sensors have been in use for a lot of miles, it's prudent to consider changing them (especially the front one) as a first step -- if the problem goes away, great; if not, at least the new cat has a better chance of having a long life.

You're very welcome, glad we could help. Yes, we do. We also appreciate people who get back to us with the outcome in general, even if just to say that the problem didn't get resolved or that it did but wasn't anything we suggested; it gives us a chance to rethink the problem or add to the "database". Some systems run better on a bit of negative feedback, but of course the positive kind is always nice.

Too true; only one of the four alloy wheeels on my car doesn't leak. That's after dismounting, removing corrosion, sealing/remounting/rebalancing the other three a couple of times. (I'd really like to know what "magic" keeps the remaining one from being like the others. :-\ ) I'm in the "rust belt", but steel wheels hold air here. I've learned to keep the tire chuck handy, just wish I didn't have to. Of course, salt corrosion probably isn't a big issue in California, unless you're driving on a beach.

Whining (as opposed to "whooshing" or "whistling") is often due to an over-tensioned belt, or failing bearings and other things that increase the load in whatever the belt drives. It can be related to the "accessory" belts (alternator, A/C, PS), or the timing belt. Temporarily removing an accessory belt can help with the diagnosis. If you eliminate the external engine accessories and belts, consider the possibility of it being internal to the engine. Since Subaru uses an automatic timing belt tensioner, you might wonder how the t-belt tension could be too high. Unfortunately, it can happen if a camshaft is starved of oil and is beginning to seize; the belt will slacken in the portion "before" the cam with the failing bearings, and "tighten" afterwards (as the crank sprocket "pulls" against the extra resistance). Sometimes a failing idler can cause the same problem, and would usually be an easier and less expensive repair as long as it's caught soon enough.

Could be; jowens said the fuel filter was replaced, but if there's debris, it could be partially obstructed again.

There could be more than one problem. Since the symptom is more prevalent with a low tank and going uphill, there may be contamination of the gas by water, or even possibly by some debris; however, many cars have at least some tendency to misfire when the tank is very low. Furthermore, since cylinder #4 is misfiring while the others apparently aren't, there may well be issues with the #4 ignition and/or fuel injection that make it more sensitive to fuel quality or delivery. It's also possible that the problem has no relationship to the newly managed gas station, and coincidentally cylinder #4 began misfiring for another reason. If you believe there's water in the gas tank, adding some anhydrous ("dry") alcohol might help. E85 contains a very high percentage of alcohol (ethanol up to 85%), and you have to be careful not to add too much of it to your tank. While some have said they have no problem using up to 50% E85 mixed with 50% "pure" gasoline, Subaru suggests not exceeding 15% alcohol. You could just add a "drygas" product instead. Don't use "rubbing alcohol" from the drugstore; it's almost always 70% isopropanol, but the remaining 30% is water. If the alcohol doesn't do the trick, it's probably time to investigate the #4 spark plug, etc. You also should verify that P0304 is the only code.