1993 Legacy LS Knock and Ping

[Sawbonez]

Experiencing Knock and ping while going uphill. Have changed spark plugs,fuel filter,air filter,oil/filter and fuel
grade. Used top end/injector cleaner. No change. Bought a Haynes manual but it doesn't cover '93
EFI/Emissions. Car doesn't seem to have a visible EGR. Does anyone know if this model has an EGR or have
any suggestions? Any help would be geatly appreciated. Thanx.

[SLODRIVE]

Welcome to the BBS! You might want to check out your knock sensor to make sure it isn't damaged or loose.

[Sawbonez]

I'll check it. Thanx very much!

[Jessekrs123]

Haha, no the first generation legacys do not have an EGR. Trust me, I was looking for an EGR on mine and couldn't find it. All the first gens have are charcoal canisters which just extract leftover gas from the engine when it is not running, then puts the gas back through the fuel pump when it is running if I remember correctly. Also when you say you changed fuel grade, what did you change it from? That could be the problem, incorrect fuel grade could cause pinging.

[brweber352]

From what I know, Turbo cars use valve overlap instead of EGR, NA should have an EGR(correction no EGR valve on these either). The charcoal canister holds fuel VAPOR from gas tank and gets sucked out via purge control solenoid and plumbed to intake manifold.

CHECK THE KNOCK SENSOR, look for cracks on the round portion of sensor or a broken wire at the plug.

Brian

[vrg3]

Jessekrs123 is right about EGR -- no North American 1st-generation Legacy has EGR.

Brian is right about how the canister works. It's unlikely to have anything to do with your pinging problem.

Definitely check your knock sensor as SLODRIVE and Brian suggest. The original knock sensor these cars were equipped with had a design flaw that made them fail prematurely, sometimes in a way that the ECU didn't detect. This caused the engine to hesitate at times. For a while, before Subaru issued a fix in the form of a redesigned sensor, people were trying some really ghetto fixes including putting padding between the sensor and block and electrically dampening the signal. The biggest danger with these "fixes" is that they can result in knock going undetected by the ECU. Maybe a previous owner did that do your car.

If your knock sensor has a gray connector on it, replace it with a new-design one regardless. The new one will have a white connector.

How did you do the top end cleaner? And what kind did you use? Several other board member have had success with slowly feeding Sea Foam into the intake manifold as the engine is kept at a high idle. What I like to do is remove the PCV valve and thread in a nylon fitting from the hardware store that's attached to a narrow hose through which I feed the Sea Foam.

It may also be worth checking your oxygen sensor. If somehow it's readign too rich it could be resulting in negative fuel trims that make the engine run too lean at high load. You can try unplugging it the sensor and resetting the ECU; it should run okay without the sensor.

[Sawbonez]

Thank you all very much for your advise. I'll be checking the sensor over the weekend. I'll let you know how it goes.