yardie876

So twice over the past thirty days, I've had my GS go into limp mode while driving. The first time (back in January) I took it in, it was determined to be a bad spark plug in cylinder 6 as well as a fouled O2 sensor. I thought that was odd that one plug went bad but considering the car is over 100k miles I replaced all 6 plugs and the sensor. So fast forward to this past weekend and the car went into limp mode again. This time, there was a large amount of gas being dumped into the exhaust (evident by the smell and smoke). I had the car towed to the dealership where they found the cylinder 6 port injector malfunctioning and constantly dumping fuel into the cylinder. I ended up replacing all 6 injectors (peace of mind) and moved on. I can't lie, limp mode twice in 30 days has lowered my confidence in the car a bit but seeing how it's been bulletproof after 100k hard-driven miles I guess I shouldn't be too concerned...

Right?

SpicedRum

Well, I would say the chances of both an ignition system and fuel system failure on the same cylinder failing independently of one another would be pretty low.

But the chances of an injector starting to slowly go bad, undetected for a period of time dumping more fuel than optimal, eventually causing a plug failure due to deposits, uneven heat, carbon build up, etc, then soon after the injector fully failing would be more likely.

It's hard to know for sure but it sounds like you were proactive by replacing all of them.

Good reason to check those plugs at 60K like the manual states. Seeing one plug that is black would indicate improper fueling or ignition issues early.

I'm curious if you do a lot of Italian Tuneups. Might have put more deposits than were burned off? Did you smell any gas or rotten egg/sulfur for the last few months?

waygreen

I bet the injector has been on its way out which is what caused the plug to fail. I don't know if you had a shop do the work but if so, did they explain what they meant by plug failure? My car is just a few thousand miles away from the 100k mark. I bought it at 90k and immediately changed the plugs because I had no record of the 60k plug swap being done. The plug closest to the firewall on the passenger side had a tiny bit of gas on the threads. If that is cylinder 6, I wonder if there is something about that location that causes the injector to wear prematurely. As soon as I get through busy season at work, I'll check the plug again and swap the injector if necessary.

As for your question about overall concern, I haven't owned the car long enough to provide an real insight but if all you've done for 100k is plugs and an injector, I'd say it bodes well. Every German car I've owed has had more than twice the number of parts fail in half the mileage.

Mike552

yardie876

No, no Italian tuneups here lol. I do redline the engine quite often though. No sulfur smell, ever.

I've maintained the car exclusively at the dealer. The mechanic didn't explain what type of failure the plug had, but that it was just not functioning properly. Cylinder 6 is the one closest to the firewall on the drivers side, so opposite to yours.

The dealer price was around $200. It can be purchased for around $150 though.

waygreen

Hmm. Then I wonder if it has something to do with being near the firewall. I have an oil analysis outstanding and am interested in finding out what of oil dilution I may be looking at.

Mike552