???? about EGR valve & spark knock.....

[Budman]

I have a friend with a 97 SL-2 that has pretty noticeable spark knock under moderate to hard acceleration. The noise stops if we disconnect the EGR valve. We put a new one on with no change. We've also been running it with 93 octane with octane booster and it doesn't help. we have also tried colder plugs, MSD coils and wires with no success.......HELP!!!!

The engine has been modded some.....bored .20" with stock compression, CAI, ported head, port matched intake and header, high flow valves from SDA and 2 1/4" exhaust.

Any help would be much appreciated as the techs at Saturn are at a loss.

[TimT]

Got some sort of spark/fuel control? Sounds to me like to much timing. You can always get one of those EGR simulators.

Tim

[TheMU47]

I had a car come in with unusual knock and it turned out to be the belt tensioner.
I've seen knock from clutch chatter also.
maybe check on those.


how long has it been doing that?
made any changes at that point that could possibly rattle or knock?

[Budman]

I had a car come in with unusual knock and it turned out to be the belt tensioner.
I've seen knock from clutch chatter also.
maybe check on those.


how long has it been doing that?
made any changes at that point that could possibly rattle or knock?

The car is running with stock computer and fuel system. Only mods are those listed above.

It has done this since we rebuilt it about 6 months ago. Can't see that it could be from the clutch or belt tensioner since the noise stops if we disconnect the EGR valve. It acts like the PCM is trying to lean out the the air/fuel ratio via the EGR valve which is causing spark knock. Does that sound feasible? We have checked timing and it is right on.

It is also showing a code P0300 (random misfire) and a little bit of a random misfire on the #2 cylinder on the misfire graph. We've got new NGK plugs and MSD coils and wires on it and also have done an injector flush.

It also idles around 1300 rpms when cold started and this gradually drops down to about 900 as the car warms up. We ran performance test on the PCM coolant temp sensor and IAC sensor and both seems to be functioning normally.

Any other ideas?

[SupraCharged007]

the noise you hear is most likely just the egr valve i bet

[Budman]

the noise you hear is most likely just the egr valve i bet

I've owned 4 DOHC saturns (94, 94, 96 & 02) and none of them have made this noise. This isn't normal and really sounds like spark knock.

[SupraCharged007]

eh maybe not. I just know that I got the same thing when I put an intake on my old car. It was just the egr valve I found out. Not saying that's definately what your's is, just saying it could be. If it sounds that bad though. And doesnt do it with the egr unplugged, unplug it haha

[S.Bretz]

The egr does have something to do with spark timing...as the pindle opens and closes, the PCM will adjust timing. If the EGR valve is bad interanlly so that the PCM thinks in some place its not (likeit not opening) then it will start to knock as the PCM puts in more spark advance.

Also, do your selves a favor and take the MSD coils off the car. Put stock coils, stock wires and leave the NGK's in.

If it still does it, try moveing the spark plugs are...put 2and 3 into the 1 and 4 possitions, and put the plugs in 1 and 4 into 2 and 3. If you missfire moves to another cylinder, then you know you have a bad plug.

[therealm0rh0us]

if you have a p0300 and a assumed lean condition causing a school bus like pinging noise
then you might want to check for low fuel pressure
random multiple misfire is usually from low fuel pressure or clogged injectors
cpi chevys

[S.Bretz]

When was the lst time the fuel filter was changed?

[Budman]

No idea if/when the fuel was changed. I'll do that tomorrow after work.

The car had the original coils & wires on it after we built it and it was having these same issues. Tried another set of factory coils and same thing. Thought that maybe car was running too rich and that MSD coils & wires might help with that...but did the same.

BTW the car runs well under full throttle. Only makes that annoying noise at anytime you accelerating except for WOT.

Guys in my shop have given up....they have no clue why it is doing this.

[S.Bretz]

What year car did the crank come from?

Also, its possible that you are hearing a bad lifter, or loose clearances. Or even a noisy injector. Its hard to tell threw a computer screen though, so I'm only guessing.

Can you pull the plugs and take a couple good pics for me? One of the ground strap, one down into the plug, and a good shot at the center electrode

[therealm0rh0us]

bad lifters sound like a bad engine
whats the fuel pressure?

[Budman]

OK.....still having this same problem so let me go over it again.

I am getting a fairly loud rattling/spark knock sound from the engine when under partial throttle with a bit of a misfire. The noise is not present under hard acceleration. I am getting no codes from the pcm. The noise goes away if I unplug the EGR valve. I have tried a brand new EGR valve, spark plugs & wires and cleaned the injectors twice and it still makes the noise and still has a miss. I am a Service Advisor at a Saturn dealership and even my techs are scratching their heads on this one....granted they only work on stock cars, but mine only has the typical bolt ons. The noise is not a lifter or rod type of noise or it would still be present with EGR disconnected....ideas???

Sorry S. Bretz, but I don't have a digital camera to take pics. Engine is original. Crank was bought reconditioned unit from Advance auto parts. Engine was built by one of our "A" techs.

[liamrh]

Get an EGR simulator. Unplug the POS. Problem solved.