if you unplug the knock sensor, you will get horrible performance. ECU will go into safe mode.

 

I suppose if you put a resistor inline that is the same value as the knock sensor, it would not freak the ecu out. But not sure I'd do that.

93leg. If knock sensor is suspect, how about running a few tankfuls of a high octane blend and see if that effects the problem.

 

Just a thought, relatively inexpensive and certainly easy.

The post "Stalling 92 Liberty" has a post reply by Logan "Knock sensor" that has remained in my mind because of the similarities between his 94 Legacy and mine and the fact that their one year a part. I would like to be able to identify exactly what it is, but the problem is, that it is intermittent and ceases if the engine stops, or is turned off, and then restarted. I have a hard time convincing myself it is an injector, or ignition problem. I have replaced the wires and plugs and checked the resistance of the coils.

 

Still looking for an answer and open for suggestions.

A disconnected knock sensor or failing knock sensor will not cause the engine to spudder or die. It will just make it run with very low timing advance and engine will feel gutless.

 

Your symptoms are close enough to possibly be a MAF sensor issue. I'd probably start putting my efforts there.

Over the weekend I rechecked the error codes. I found a knock sensor code, so I replaced the sensor. I do believe the engine has more power now, but I don't know if it has fixed the original problem. Only time will tell. Stay tuned.

Well, I'm still waiting to see if any of the sensor replacements take care of the so-called misfiring. This is my wife's car, which I seldom drive. I did remove and inspect the MAF sensor. Not much to look for though. Mainly, I wanted to make sure there were no obstructions, or debris on the delicate sensor.

Do you notice if the cooling fans come on when it starts to misfire? I have a '92 Turbo Legacy and I also have a temp sensor that is going bad. It causes the fans to come on prematurely and this makes the engine idle slow and sometimes dies. I am replacing the radiator this weekend and am replacing the sensors that have come up on a code check. Cam sensor, temp sensor and knock sensor are the codes I have which is different from your codes but may be related.

 

Qman

I have never noticed the cooling fans coming on, but then again I drive it very little. I'll make note of this incase it does happen when I'm driving.

I thought I had it fixed, but I was wrong. I drove the car over the weekend and pushed it a little bit. Just as before, less than two miles down the road, it began missing. I wish I wasn't taking my son to work, because I would have jumped out of the car and tried to diagnose it along side the road. I'm not giving up. I'll continue looking.

 

Does anyone know if you can purchase an ignition tester pen that detects spark through the plug wires? When I lived at home we had a pen like instrument that was designed to lay on top of the plug wire. It would glow with each shot of voltage passing through the wire. This would be useful, because I don't want to pull off plug wires and kill the motor when it is acting up.

 

Do Subaru shops have component tests for coils, amplifiers and the like? I would gladly pull these off, if they could be thoroughly checked.

Just a thought here, but would a regular timing light work for you? By using inductance, the light will flash during the presence of a spark. Theoretically, you can mount the timing light (after you wire up the pos, neg, spark plug pickup) near the cab or on top of the hood. Then using a zip tie, depress the trigger in the engaged position and drive your car around. By looking at teh light light, you could possibly detect which cylinder is misfiring. You would need to move the pickup from wire to wire in order to isolate the missing cylinder.

 

Wild idea, but it's a shot if you're desperate. I do this when I troubleshoot the ignition system on my other vehicles.

I've seen the same symptoms on a 1992 Legacy 2.2 4WD Auto, turned out to be faulty intake manifold gaskets (false air).

 

Let the car idle when the problem occurs and have someone spray brake cleaner or similar on the mating area between intake manifold and cylinder heads. If the engine starts to runs smooth again, you've found your leak, if there's no improvement, it's not false air.

 

Good luck.

Thanks for the above ideas. There's no cost to them and they should help to diagnose the ignition and gasket areas. Now I'll wait for the next oportunity to use them.

 

Thanks to all.

Well, still trying to diagnose the problem. I haven't had a chance to use the timing light idea yet, but the problem is still there. However, during a long trip another interesting thing happened. While traveling up a grade for a long distance using the cruise control, the demand for more throttle caused a loss of power. The car slowed as if it was starving for fuel. By backing off it recovered. But during a 75 MPH straight away, there was no loss of power. I have checked the fuel line pressure.....all seems fine. I unplugged the vacuum line to the regulator, and reinstalling it I watched the pressure readings. All followed the manual specifications. How about a volume check? Any ideas?

You may want to clean the connectors for the engine harness. Pull the battery and disconnect the three connectors on the bracket just behind the battery. Use some good contact cleaner and you may fix your problem. I had many codes on a 90 legacy and it took care of most of them. Good Luck.

Well, I've tried to use the great timing light idea, and I also connected a pressure gauge to help diagnose the problem on my 93 Legacy, but all I find are more problems and questions. Now I have experienced not a missing, but more of a dying condition while pushing the car. Within a mile stretch on an incline, and close to wide open throttle the car pulls fine, but then it feels like it runs out of fuel. It slows down to the point of shutting off, although there is no drop in fuel pressure, and the plugs are still firing. When I try to restart it, turns over for a few seconds, and I'm not sure, but I think there is a lack of spark for the first few revolutions before it kicks off, and then it runs rough for a few seconds. I have repeated this condition a couple of times. I am going to recheck for codes tonight. Any thoughts?

Some of your symptoms sound like a bad/clogged catalytic converter.

 

Often shows up only under load, after warmup.

 

 

 

Carl

1 Lucky Texan

Sounds like it could be a clogged cat.

Does anyone know of a method to check the catalytic converter?

Sometimes the backpressure can cause leaks where the block y-pipe come together. Look for exhaust leaks at the block. You could disconnect the exhaust before the cat, and see how it does. Otherwise emission test? Does the engine sound very muffled before it dies? Do you hear any rattling from the cat, like marbles , try tapping on the cat and see if anything sounds loose.

I don't recall any suspicious noise when this happened. Is the exhaust a single welded unit? Can the Catalytic Converter be removed, or replaced?

Sorry, I'm not sure ir your car is a single welded unit, or bolted - crawl under and take a look-see. The cat can be removed (illegal), or replaced. Some pull the cat out and beat the innards out to improve performance, however I would never consider it (my state does emission testing and it is illegal). The cat is an expensive part and not something you wanna just throw a guess at. See if it unbolts.....if it does, run it (loud as all get out) to see if it is the problem, then replace it if it fixes the problem, otherwise bolt it back up and move to other possible problems.

Pulled error codes last night and found a 32, O2 sensor. I know that is not the problem since it was replaced. May be a sign of a restricted catalytic converter. Back pressure may be causing the faulty O2 readings. I'll keep looking.

I have at home a procedure - using a vacuum gauge - to test for a clogged converter. I'll try to post it as soon as I can.

From Frag:

 

Vacuum test for restricted exhaust

A few days ago I promised someone (searched for the post but did'nt find it) I would post the procedure to test for a clogged converter with a vacuum gauge.

 

I'm finally back home so here it is:

Connect the gauge to the intake manifold (dowstream from the throttle).

«Run the engine at about 2500 rpm for about 15 seconds. If vacuum drops during the period and does not incrase when you close the throttle, you're almost certainly looking at a restricted exhaust.»

Hope that's not to late to help.

 

 

__________________

Gilles (Montreal)

1992 Loyal wagon, 5sp, 192,000 kms, june 99 - stolen 0ct 00.

1996 Legacy Brighton wagon, 5sp, 200,000 kms, dec 2000 - for ever ?

 

 

 

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09-28-2003 01:01 PM

 

 

 

93leg

Newbie

 

Registered: Aug 2003

Location: Hanover, PA

Posts: 8

I Think You Were Looking For Me..THANKS

Well, I'm going to give it a try once I find a good vacuum gauge. I hope I can soon find something, because winter is approaching and I don't have a heated garage. Thanks Again.

93leg......

 

After reading all your driving and Diagnosis,

 

I feel very strongly that your Coil Pack is going out......

 

Reason you get O2 code is that under load if one or 2 holes are missfiring, you get raw fuel into exhaust, a knock due to the stumble associated with missfire, and computer trying to compinsate for all the above......

 

I have had 4 cars Locally all have these same symtoms, all came to me from the Dealer Locally, cause they couldn't figure it out.....????? All of these were Auto's.....????? Is your car stick....?

 

With your car parked, can you get it to missfire or hesitate bad once warmed up....? or in gear ( if Auto ) with brake set and someone stepping on brakes,

 

Do the timing light trick on each plug wire at the plug end.....put the car in drive and put a load to it lightly, see if you get a stumbling light.....???

I will wager that either 1-2 or 3-4 is misfiring/stumbling.......meaning that that part of the coil is breaking down under load......

 

Several folks on the Board right now seem to be experiencing the same issue.......

 

Check it out that way, and let us know......

 

Later, John in Oregon......