acorad

Hi guys,

1987 Porsche 944 Turbo w/LS1, about 65k miles on the engine.

I have had ongoing miss-fire and oil consumption issues.

So I replaced all my valve guide seals (from the dealership) and put in new plugs (NGK TR5s) in Sept 2014, so 8 months and about 8,000 miles ago.

Although the new seals did not slow down my oil consumption at all, the miss-fire did go away until a month or so ago, when I again developed a miss-fire under load.

I pulled the plugs last week and was really surprised how oil fouled some of the plugs were (esp #7), but how clean the rest were. I guess I expected that all the plugs would be fouled.

As you can see below all the passenger side plugs were clean, and all but cylinder 5 on the driver's side were oil fouled.

Any ideas why?

Zmg00camaross

iTrader: (11)

How many miles on the engine? You have issues and no matter what I think you going to be pulling the engine.

acorad

Hi Zmg, about 65k on the engine.

Sure hope I don't have to pull the engine.

Andy

Zmg00camaross

iTrader: (11)

Well I would do cylinder leak down and compression test. Helps try and diagnois basic engine problems. Rings/valves etc.

acorad

Ya, thanks Zmg.

I have a 5.9 liter Durango that's also having some miss-fire issues, and it turns out that that engine is notorious for blowing out the intake manifold gasket which allows oil to get sucked in and foul plugs.

Was wondering if the LS1 engine had any similar sort of notorious issue.

Andy

Zmg00camaross

iTrader: (11)

Make sure you PCV is working correctly.

acorad

Zmg, I replaced the original PCV valve with the later model smaller/fixed orifice valve.

Absent installing a catch can, how would I make sure the PCV is working correctly?

Would a faulty PCV only foul certain plugs?

Andy

RockinWs6

You have a ring-piston issue, carbon pasted rings or cracked rings or cracked- broken ring lands.

HISS

iTrader: (52)

Does the car have ported heads? Sometimes when cathedrals are ported and the rocker bolt extrudes into the intake port it can cause oil consumption smoking etc. always use thread sealer on the rocker bolts if this is the case. Barring trying a catch can if you have excessive oil in the intake manifold I'm inclined to agree that those plugs indicate a major ring seal issue.

acorad

Thanks guys, I'll check compression etc, hopefully tomorrow.

HISS I bought the car already built, but the builder said the motor was stock.

Andy

dlegolpolp

Well I would do cylinder leak down and compression test.

RockinWs6

Before I would check or do anything decarbon the engine. These engine carbon up so badly its kookoo from all the oil entering the intake. Amsoil makes a good top engine cleaner and the Mopar top engine cleaner is good too. I'd put some ATF in the oil to help free the oil rings. What ever product you choose let it sit with the product in for a few hrs so it gets the rings freed up.

thunderstruck507

iTrader: (18)

Have you inspected the valve seals again? A lot of people damage them during install.

acorad

Rockin, I sprayed about a quart of water into the pcv inlet into the intake body a couple days/100 or so miles before I pulled the plugs.

Afterward the car had noticeably more get up and go via the butt dyno so I guess it did clean something.

acorad

thunderstruck, I haven't checked seals yet, but I will. Seemed pretty straight forward to install them, but I'm no expert!

acorad

thunderstruck, what would I be looking for for damaged or incorrectly installed valve seals?

RockinWs6

Good way to ruin alot of parts quickly. PLUS it doesn't clean the rings, I've seen perfectly good engines ruined using water to clean them. It shocks the parts from hot to cold instantly breaking the carbon off but at the same time changing the parts structures.

acorad

Thanks guys, I did a quickie Harbor Freight leak-down test on the #1 cylinder as that was one of the oil-fouled plugs, and it's only, say, a 5 out of 10 on the pita scale to get to in the 944.

The engine was cold as I didn't want to brand myself on smoking hot headers. I've read conflicting advice regarding doing these tests cold, but my guess is that they really should be done hot.

To find tdc on the compression stroke I hooked up the leakage gauge and compressor to the cylinder and turned the crankshaft until the hissing air sound went away. Hopefully it wasn't bdc.

It was a bit of work to get the HF cheap a$$ leak gauge needle to sit on "0" but eventually it did, and the leakage on that cylinder read 18%. Which is not bad though probably not too conclusive either as the engine was cold and the HF leakage tester is pretty lame.

Inconclusive at best but I could hear air leaking through the oil filler tube, but not though intake or exhaust, so if anything I would guess it's rings. Maybe the engine had more miles on it than the seller claimed when the PO bought it and installed it.

Sorta doesn't matter at this point, really, as I'm not pulling the engine any time soon.

I'll probably pull the valve covers off in a couple days and eyeball the intake valve seals to see if I can see any obvious problems with 1, 3, & 7 as they were the oil-fouled plugs.

When I pulled the NGK TR5s I replaced them with one step hotter TR4s. I've put about 500 miles on the new plugs and I pulled 1 & 3 today (those are two of the three previously oil-fouled locations).

They had some light oil on the top edge of the threads, but both electrodes and the ceramic surrounding the center electrodes were all clean.

So I think I'll just monitor the plugs for now and see how things work out.

Andy