EA82 detonation

[paulpicard]

Well, after fixing the rattling heatshields, servicing the IAC, installing a new T-stat, cleaning various electrical connections, replacing all timing belts, tensioners, idler bearing, crank and cam seals, spark plugs, and inspecting about everything else, the remaining noise in my 92 Loyale has to be detonation, and scary at that. Timing checks out at 20 deg. with the green plugs connected, however the dist. won't rotate (corrosion?) but I didn't worry too much about that as I understand spark advance is controlled by the ECU. I have seen comments here that a bad EGR could be responsible. I have the Haynes manual but hopefully you guys can supply some additional info before I bust more knuckles. (Mileage is 275,000 Kilometres, doesn't burn or use oil, good power)

[GeneralDisorder]

When does the noise occur? Heavy load?

 

I would be checking fuel pressure and injector spray pattern if you suspect it's pre-det. That's usually a result of lean mixtures under load. Has the fuel filter ever been replaced?

 

GD

[paulpicard]

It appears under light to moderate load and part-throttle. It goes away under full throttle once past 2500 rpm or so. Good point on the fuel filter, as I have not replaced it, (I will) however the car has always made good power and the plugs were light tan so I think there's enough fuel. Can't work on it for a couple of days now but I think I'll check the EGR operation. Any opinions on retarding the initial timing?

[ahole]

You might want to check to see if your car has the factory recall pcv valve "fix" done to it. If not, like mine, that could be the problem. I made my own version of the fix, along with a catch can and filter. You should also make sure your pcv valve is of the OEM type (not FRAM) and working properly. Also do a decarbonization of the cylinders. I fought this same problem for months before it finally went away. It took me doing all these things, but it's worth it. Don't retard the timing; just a couple of degrees takes a quite noticable amount of power away which you probably can't afford.

[Gloyale]

Test the Coolant temp sensor, make sure the ECU is seeing the correct value when warmed up.

 

Try higher octane gas and see if it goes away. If it does, the problem may be carbon deposits on the piston tops raising you're compression slightly. Also, the carbon gets red hot like burning charcoal in there and contributes to the predetonation.

 

Try the higher octane, and if that works, run a few bottles of good fuel treatment/ cleaner through it.

[McDave]

Part throttle pinging is usually caused by a non-operating egr valve. Do a search of this forum for info on how to test it.

[ahole]

Check for codes. They might tell you exactly what you need to know.

[paulpicard]

Thanks, people. My Haynes has the EGR test procedure, and I did find a knowledgable thread here as well, the OP cured his detonation by restoring the EGR to correct operation. I think it has the test procedure for the coolant sensor and I will check that as well, although the pre-ignition is there right from start-up. Will work on it tomorrow and advise. Just took my modified Dodge on a 120 mile beer run, and it ate up about $60 worth of 89 Octane. Need the Soob badly!! (We're at a buck and a half a liter for 89, pushing 6 bucks a US gallon!!)

[Bill90Loyale]

Retard your timing to 18 degrees (instead of 20) and see if you find improvement.

[Loyale 2.7 Turbo]

...Or you can move Timing up to 22º or Around and see if by that way the Problem gets Fixed... but I Believe there`s an EGR Issue involved...

Good Luck!

[GeneralDisorder]

EGR shouldn't make any difference at all.

 

Are you SURE it's detonation? Could be a rod knock too. They sound very, very similar on the EA's. Can't hear them at idle, and it's a slightly metallic tap under load just as you describe. Those generally end with the rod comming out right under the manifold.

 

GD

[paulpicard]

GD that really makes me feel good!!! :mad: Anyway, here's what was done today: Pulled the EGR, checked and cleaned the valve seat and passages, confirmed the diaphragm is good, as well as the solenoid vacuum control. (I have a MityVac - one of my better investments!!) Checked the Coolant Temp. sensor - the Haynes called for 2000-3000 ohms cold engine,(15 deg. C) and 700 to 1000 at 50 deg.C I got 1600 ohms at ambient of 25 deg.C, and 350 ohms at fully warmed up temp. (assume 195 deg.F per new thermostat rating) So I believe the sensor is operating correctly. As prev. mentioned, I had cleaned and checked the I.A.C., and re-sealed the oil pump, which had a de-formed and hardened Mickey Mouse o-ring. I hose-clamped the loose exhaust heatshields. Now I have a quiet engine, and there are no trouble codes. You can hear the odd valve lash adjustor noise on cold start but they're gone in 5 seconds or so. My neighbor, who is a pretty good wrench, and I tried to get noise out of it and failed. We even used the trusty stethoscope, and he's convinced there are no lower-end noises. Drive it down the road, though, and the rattling is still there. We conclude it's still exhaust-related. Comments?

[McDave]

Any chance it's an automatic tranny so one of you can listen while the other power stalls it enough to make the noise? (short periods)

 

Is it an exhaust leak sound, or an exhaust rattle sound?

 

P.S. I hate doing sound diagnosis over the internet. :-p

[GeneralDisorder]

Subaru rod knocks are very strange beasts. The one I had was so slight that I didn't concern myself over it. It got extremely bad and blew in about a 1 mile stretch of freeway. That's all it took. Prior to that the sound wasn't enough to even concern me. Although I'm hyper sensitive now.

 

It very well could be exhaust related. Have you opened up the cat? I opened the one on my hatch to find no catalytic honeycomb - just the metal straps and the chain-mail stuff they wrap it in and some dust. All jammed into the discharge port of course. Gained 3 MPG that day. The 'comb burned away and left the metal bits. You should check it out.

 

Mufflers also like to rattle when the insides get loose.

 

Pull the whole exhaust and go through it.

 

GD

[McDave]

It very well could be exhaust related. Have you opened up the cat? I opened the one on my hatch to find no catalytic honeycomb - just the metal straps and the chain-mail stuff they wrap it in and some dust. All jammed into the discharge port of course. Gained 3 MPG that day. The 'comb burned away and left the metal bits. You should check it out.

 

Mufflers also like to rattle when the insides get loose.

 

GD

Mufflers really like to rattle when the cat's honeycomb breaks loose and ends up inside the muffler (or in this case inside the second cat). Possible??? I've seen it on other makes.

 

Edit: Let me refine that a bit. At that point the muffler probably doesn't rattle so much as just gets stopped up. A plugged up exhaust, wherever it may be, will cause a motor to ping under load. Heck, I'll even go so far as to say it's a contributing factor in beating the rod bearings out of a motor!

 

Paul, is the car down on top end power too?

[paulpicard]

Thank you all for the comments - since this is originally a rust-belt (Southern Ontario) car that I believe has been rebuilt, and has 275,000 kilometers, I tend to agree with you. GD, now I understand your fear of knocking noises:rolleyes: . Geez, I hate working underneath rusty cars!! I'll post results when I get them.:-\

[paulpicard]

The car doesn't seem to be down on power anywhere in the speed range - it'll pull cleanly to 150 KMH. But the rattling is back and loud as ever. (Imagine a coffee can full of marbles being shaken vigorously) It's also randomly independant of throttle or load, but somewhat RPM dependant. Here's another question - if (when:rolleyes:) I go through the exhaust, how sensitive would the EFI be to a missing O2 sensor?, or to a re-installed sensor in a gutted cat?

[ahole]

IIRC, the ECU goes into limp mode without the O2 sensor. That means it will run rich- not something you want. I can't imagine why you'd want to move it though. What's the reasoning behind that?

[Frank B]

Did you varify that the egr passages were open by pushing on the egr diaphram to see if the engine stalls?

 

Check the heat sheilds on the exhaust if you haven't yet.

[McDave]

I had a y-pipe and cat on my car up until a few minutes ago that had a rattle that sounded more like a real bad lifter tapping on the right bank. It would come and go mostly when the engine was cold, then go away once it heated up. This particular y-pipe came off a carbed engine and the only heat shields it had was around the cat, none on the pipes. I really thought I had a problem with the engine it was so bad.

 

After taking the pipe off it was obvious that the pipe's inner metal liner just below the flange is what was rattling/tapping, though I couldn't actually move it by hand. Weird. I put the original y-pipe/cat back on and it hasn't made a peep since.

[Frank B]

The egr will make a difference, on my hatch there was really bad pinging under load, uphills, accelleration, untill I removed the egr and dug out all the carbon blocking the ports, and the passages in the manifold. After that, no ping. I just drove to work yesterday with the egr disconnected on my loyale and it was pinging all the way. Hooked it back up and no ping.

[McDave]

The egr will make a difference, on my hatch there was really bad pinging under load, uphills, accelleration, untill I removed the egr and dug out all the carbon blocking the ports, and the passages in the manifold. After that, no ping. I just drove to work yesterday with the egr disconnected on my loyale and it was pinging all the way. Hooked it back up and no ping.

That's always been my experience too. If it doesn't ping at part throttle with an inop egr, then the timing is likely retarded.

 

What I find odd is that these cars seem to get egr when the engine is cold. You would think the ecu would take the cts into account and wait for it to warm up some before it allows egr. It helps to prevent a cold bog and allows the cat to warm up quicker. Weird.

[paulpicard]

FrankB, yep, I went through the EGR both on the bench and on the engine - no blockage of ports or poppet valve (cleaned them up anyway) and diaphragm is working properly. Engine stumbles at idle if I pull the diaphragm open with my Mityvac. As prev. mentioned, timing is 20 Deg BTDC as specified. Re: the O2 sensor question, I didn't think it would run right without it, and for sure I won't now. McDave, thanks for the info on the Y-pipe and heat shields. I already hose-clamped the loose outer shields on the driver-side pipe to no avail and your experience makes sense. I'll try checking that today. I'll report any progress. Thanks to all again.

[paulpicard]

I'm really pleased to tell you that, after discovering a complete and loose heatshield system from the 2nd cat back to the exh. pipe mount at the rear axle, removing it cured the "marbles in a coffee can" rattles completely. Now I know there's no sign of detonation, and even better, no sign of rod knock. Of course now I can hear a squeak here and a rattle there, but they are pretty few for a 17 yr old car. Thanks to all for pointing me in the right direction.