BesideTheBox

No. I had come across your thread with all the investigation that you did before your rebuild. That's part of the reason why I ran the compression test last weekend. To give me some sense of engine health. The top end was done at 44K by Park Place in Bellevue, WA.

Maybe I can do that tomorrow. It will be -snowing- here, so that might mess up the audio if the wind is blowing.

I agree, it would be great to eliminate it. But even if I get a used muffler, no way of knowing if it was in good shape before I get it. I posted in the member to member wanted section.

IainM

It'd be easy to blow some air through the mufflers, give them a shake and see if you can hear anything.

geolab

There are two types of bolts that hold the exchangers. The regular bolts and the round bolts that go through the exchangers' holes to the cylinder heads.

The module is the one in red in picture.
.
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pp000830

At least you don't have a general misfire code indicating an air leak.
An easy test to see if the wire is leaking current is to either look at the wire in the dark while the car is running and see if you see grounding sparks. Or you could just replace that one wire and plug. Or you could do the old school thing and spray a little wd40 on the wire and see if the misfire settles down a little for a short period - a dead giveaway of a bad wire. These cars run with extremely high ignition voltages so even a marginal plug will work. Would avoid whole scale replacement of the wires or plugs as if you had a broader issue you would have some other codes showing up.
Remember the twelve step program for Porsche owners. You know the line “accept the things I should not fix, have courage to fix the things I must and have the wisdom to know the difference”

BesideTheBox

Ah, through the exchanger holes to the cylinder head, I have regular 13 mm bolts. They were tight.

Regarding the intended location for the ignition module, it is clear from your pictures where it should be located.

It is simply not in that location in my car. Should I pop out the 'security' fasteners and go on a fishing expedition? What would I use to replace those fasteners?

Here's what I have.

Picture from the back.


Picture from the side.

TMc993

I would focus on the exhaust and eliminate that as a cause before getting into electrics. Given that the puffing is coming from the right side, and given as much damage as the right side muffler seems to have, it is possible that the muffler internals have been damaged enough to have a section of the muffling material flapping/rattling around inside the can, intermittantly interrupting the exhaust flow which would cause the "puffing" and possibly noise. Have you considered pulling the mufflers and running the engine with just the cat in place? If it is a misfire, it would be louder and more pronounced with the mufflers off. If it's the muffler, you should be able to tell because the "puffing" will be gone.

Just an idea...

BesideTheBox

The 993 PET shows the following for the ignition module (ignition switch unit). Looks like it is only on -95 cars.

geolab

I do not have the electric diagrams handy, but it looks like you are right, it could be integrated to the DME on the OBDII.
the irratic behaviour of the coils bug me.
I forgot whilst following the problem on several threads, did you try to swap the DME relay with a new one ? if not, you lose nothing trying if you have a spare.

BesideTheBox

I did have a spare DME relay and I installed it last week. I was running with the original DME relay, now it is serving as backup. No change in engine behavior.

BesideTheBox

I'm guessing that pulling the mufflers and shaking them had an effect on the mufflers. Either that or... ???

Warmed up the car for 15 minutes (to avoid getting the P0306 CEL), then drove the car maybe 20 miles. Spirited. I didn't wail on it. Maybe 5K rpm tops.

Listen and let me know what you think. After the drive today, it is extremely regular and consistent. Less metallic, more 'flapping', I think on every round through the firing order (half the rpm of 760). I don't hear the flapping noise in the car.

Mike J

That sure does not sound like a loose baffle or muffler to me anymore - definitely a consistent mechanical sound. Funny on the first video it was quite random, now is steady state. Good in that its consistent and in your face, so its easier to find. Sounds like one piston is missing, almost like if you disconnected that piston.

Have you disconnected each of the sparkplug wire pairs at the cap (starting with #6) to see if it alters the sound. It almost sounds like one piston is not even firing ...

Cheers,

Mike

BesideTheBox

The consistent flapping is now inconsistent and more mechanical like it was before. I just started up the car. Still warm from the previous drive. No noise initially, takes about 20 seconds for the noise to start.

I pulled each injector, one at a time, and THAT gives the flap, flap, flap, sound of the most recent video. *edit* And pulling the injector makes the engine shake. It was not shaking like that in the most recent video.

So I wonder if you can get the same flap, flap, flap when it is simply due to no combustion. So maybe that noise can be the result of no fuel -OR- no spark.

Can you give me some guidance on pulling plugs from the caps? Can I do this with the engine running safely, or should I stop the engine for each cylinder that I'm checking?

IXLR8

Other than frequency, does it change as you bring up the RPMs and oil pressure?

RFMASSA

I have 97' with 45,000 miles and it makes pretty much the same noise on the left side of the exhaust for about 3 years or more. Never had a problem driving and it runs very well. I did a couple of simple tests just now after seeing this thread. I found that it does not puff and make a nose intermittently until the engine is warm. By puffing, I mean you can put your hand in front on the exhaust and you can feel the extra puff of pressure when the noise id heard. The right side does not do this, and is more constant of a pressure feel. When the left side does not puff, the pressure feels just like the right side. This is all at idling.

When I move the RPM's to about about 1200, the pressure feels perfectly smooth again, no extra noise or puffing. Maybe this helps, maybe not. But more data can't hurt!

When my mechanic heard it, he said it sounded like something was loose in the exhaust, but I never pursued it and he did not seem concerned about it at the time. And I have no CEL codes thrown from this.

-Ray

Mike J

You can pull the wires off the caps when the car is off, then start it. If you disconnect both the upper and lower #6 plug wires from the cap (i.e. pull them off the cap and leave them hanging) and start the car, you will get a fair amount of engine shake since it's running on 5 cyliners, and the sound should be very similar. This should be the same as if you pulled the injector wire on the same piston.

IF you are pulling the injector wires one by one, there must be one that make less difference, given you have misfires on #6, it should be that one. Does disabling that injector make less of a difference than say disabling #4?

All we are doing is isolating a cylinder as the likely culprit - it sure sounds like one piston is not firing right in the video.

Cheers,

Mike