3.2 motor issue

[WE349A]

Hey guys,

My 87' has a fully rebuilt motor by the PO 19,000 miles and ten years ago. It doesn't smoke at all on start up, uses zero oil in the 2,000 miles since I bought it and zero oil leaks. It does have a rough idle sort of like a miss. Its in for a valve adjustment and fluid change and I requested a leak down test as we had gone through all the usual suspects for the rough idle. All cylinders at 5% leak down except #5 which is showing 30% My mechanic is awesome and I trust him fully. He feels cylinder 5 may have a bad ring or cylinder damage. The car has a custom Steve Wong chip and is actually one of the cars mentioned on Steve Wong's website's test page. It was dialed in for a safe and conservative tune in regards to timing advance. Everything is stock other than the chip, euro pistons and exhaust. Compression ratio is around 9.7:1

So before we yank the motor and I wind up on that slippery slope of all kind of mods... any other ideas as to what could be causing the #5 cylinder leak down issue? My main confusion is the lack of oil usage or smoke at start up. Even when sitting for a few weeks, exhaust is clean at start up.

Thanks for any ideas.

[gomezoneill]

A tight intake or exhaust valve can cause those numbers.Did you listen to where the air was escaping IE through the intake or the muffler while putting the air pressure in the cylinder?

[WE349A]

I'm sure my mechanic did, I need to ask him for more details today, I'm going to pop in and ask. Valves are adjusted, checked and rechecked so all seems well there.

[T77911S]

valve adjustment. I would assume the test was done after the adjustment.
rings not seated
broken head stud
valve not closing due to carbon blockage. not likely with a low miles motor.

he should listen for where the air is coming out,. exhaust, engine block.
you could do a compression test, both dry and wet.

good news, you only need to pull on cylinder and head

[WE349A]

Yes, leak down was after the adjustment. I will report back on where the air was coming from and also request a compression test.

My worry is the motor comes out, the check book comes out. Next thing you know its a 3.4 twin plug!

[DRACO A5OG]

+3 We need to know where the leak is coming from. I am glad you trust your mechanic that does not mean he can make mistakes, he is human after all.

Prior to valve adjust, did you try to do an Italian Tune Up to help blow out some of the built up carbon? So he did the adjustment while engine was in the car? If he did, wow, that is rare for a Pro P-mechanic and more prone for errors as the back valves are basically done blind.

[GaryR]

Take her out and run her (very) hard, then readjust #5, then check again. As for the idle, I found on my 3.2 during rebuild that 2 of the six injectors were "trash" so if they have not been flow tested I would look at them also.. They can cause a lean condition that will not end well.

[Jesse16]

I agree that as little running time as it sounds like your car gets, an Italian tune up is a cheap place to start. A track weekend would not hurt at all or simply a track day or a few track hours. Those miles aren't even one oil change a year territory. You say clearly that valve adjust is good so go drive it hard some and not just a few pulls on the interstate. Some people find it frightening to get the revs up on a car but you may really need to get those kind of engine forces involved to make the rings work. Just my opinion.

[911 Rod]

Originally Posted by DRACO A5OG

So he did the adjustment while engine was in the car? If he did, wow, that is rare for a Pro P-mechanic and more prone for errors as the back valves are basically done blind.

You need to pull the engine to do a valve adjustment?

[WE349A]

Just back from his shop- air is leaking into the crankcase from #5. Italian tuneup- I actually did that prior to bringing it into the shop. I try to hit redline each and every time I go for a drive. PO had recommended that and always did that as well to keep carbon deposits to a minimum.

Valve adjust done with the motor in the car.

I will give it a better and more severe Italian tuneup once its back from the shop.

Injectors were flow tested and cleaned at the time fo the rebuild, I have the result paperwork. I also run techron through the engine a few times per year. I had planned on doing Sals injectors and computer upgrade. I'll have the current injectors sent out for testing again, it is a good point and a possible cause of detonation.

Thanks for the thoughts guys, very helpful!

[gomezoneill]

If the air is leaking into the crankcase is most likely rings or out of round cylinder wall. Possibly!

[WE349A]

Thanks, yes, this is what my mechanic thought as well. Now to decide if we will change the one cylinder/piston/rings or upgrade the whole set to 3.4 and complementary mods.

[SimonN]

Originally Posted by DRACO A5OG

So he did the adjustment while engine was in the car? If he did, wow, that is rare for a Pro P-mechanic and more prone for errors as the back valves are basically done blind.

In all the years I have been involved with Porsches, I have never heard of anybody dropping the engine to do a valve adjust. Maybe it's something that only happens in the USA, but if a mechanic told me he couldn't do a proper job with the engine in, I wouldn't let him touch my car. Anybody who says they can't do it is both incompetent and/or trying to fleece you for money.

As to the OP problem, my temptation would be to drive the car a bit and redo the test. Although less likely, there are a number of things that can cause this which self rectify. At worst, it's just one cylinder so resist the temptation to do the whole lot as the numbers seem pretty decent otherwise. Of course, once the engine is out and the cam's out on one side, it isn't that much more to change them, upgrade the header and muffler, get a custom chip................

[RedCoupe]

Originally Posted by WE349A

Yes, leak down was after the adjustment. I will report back on where the air was coming from and also request a compression test.

My worry is the motor comes out, the check book comes out. Next thing you know its a 3.4 twin plug!

Have your wrench do the compression test both dry and wet on the cylinder in question. If it's low compression dry and quite a bit higher after adding oil to the cylinder you have pinpointed the problem to rings/piston/cylinder wall.