SteveG

These Beru plugs are out of my '93, they have 10K miles on them. It does burn some oil, about .5 litre/500 miles. I just completed a trip from Long Isl. to central Ohio and back, about 1,100 miles total. About 2 hours into the trip I noticed a miss on acceleration. It also did it at idle, intermittent, roughly once every 15-20 seconds. By the time I returned to home, 5-8 times in 20 seconds at idle. Much more noticeable on accel., no bucking or backfire. They don't appear fouled; the first 3 pics are cyl. 1-4; there is a pale yellow/lemon cast to several of the exterior electrodes, most visible on last pic, the last are plugs 5-8. I think the wires are original.

I am going to put them back in and mist the wires to see if I get any arching.

If no arching, I will hook up Theo's diagnostic tool, I don't know what the EZK page can detect, but it does record Knock, which I don't think is at issue. I will report back. I tried searching for Youtube videos, on plugs, but none focused on anything other than lean and oiling issues. I don't think these look that bad. I'm curious about the lemon cast to the electrodes, Any comments?

ROG100

Number one they are not the correct plugs for a GTS 5.4L.
Should be three ground - WR7 DTC or NGK BP6ET

dr bob

The slight yellow is probably fuel additives, especially since it's common to all. Or might be oil additives considering how much she's swallowing through the intake.

You are a prime candidate for one of the cylinder head oil scavenging systems, like one that Greg Brown puts together for the strokers. Or at least a ProVent and some associated plumbing to separate the oil mist before it's drawn through the intake. A liter every thousand miles may be 'normal' per Porsche at least as a warranty threshold, bit that's a lot of oil (and pinking/knocking) for any engine to endure.

davek9

^^^^ yes ^^^ also wondering if this is an early GTS the ones with only two vented Cam covers on the left side?
If so even more reason to upgrade as suggested by dr bob

rnixon

Were the previous plug any better?

SteveG

These are the previous plugs, i.e., for as long as I've had the car, these have been in it. I should add the car has 76K miles, the plugs were installed by Beverly Hills Porsche at 66K, at least the work order says 8 plugs, but the code (999-170-156-90) doesn't match anything I can find in PEK. I'll give them the benefit of the doubt due to industry changes, but I will upgrade to a better plug. I have some other upgrades in the works for this engine.

I have Greg's system, just haven't gotten it installed. I just put plugs back in and it isn't missing now, no knocks detected on the laptop, no faults in the EZK tab at all. I misted the engine bay, no light show.

Thanks for the comments.

rnixon

Sounds like whatever it was has been resolved by reinstalling them. I don't know how old these plugs are, but they're cheap enough to replace reasonably frequently.

ROG100

see post #2 for the correct plugs - special for GTS use only.
This is the incorrect part number and is for Bosch WR7DC+ - not correct for the GTS
You need 999 170 189 90

Porsche $10.60 each
NGK $4.00 each

And yes I stock both

SteveG

Roger, thanks. When putting the plugs back in I noticed one of the leads off the distributor was raised about 1/4 inch. A push and it went down snugly over the collar of the cap. I don't know if this was the problem, it would seem to affect that one plug; I don't know if it would show anyway, it wasn't an oil or ring problem. I ran Theo's diagnostic in the garage and nothing came up. It sounded smooth. Highway, it ran smoothly no missing that I could feel. So for now, I'm going to say it was the wire. Motor mounts must be OK and engine movement must have caused this connector to disengage up off the cap??????

GregBBRD

Tough to tell, from your picture (especially on my cell phone) but the far left plug in the first picture appears like the brass contact that attaches to the plug wire connector could be discolored....a sign of poor contact, increased resistance, or corrosion.

Visually check the inside of the spark plug connectors and make sure there is not any corrosion inside. Very common.

I always spray the inside of these with a contact cleaner and oil.