And while I’ve heard some customers mix up the terms valve cover gasket and head gasket, I’ve never heard a professional repair shop do that. He was reading off a dealership receipt. They know the right names for things.
Geez. Thinking slowly today.
The oil leak onto the plugs was on the outside of the plugs. They are recessed into wells in the head, and the valve cover gasket has a hole for each well. When the part of the VC gasket that seals the well hole fails, oil leaks into the well and gets on the outside (hex, metal body, external insulator) of the plug. It makes a mess, and sometimes deteriorates the plug wire rubber insulator in that area, but it doesn’t affect how the engine runs.
If the plugs were oil fouled (burnt oil on the electrodes and internal insulator) that would be a different story, but that’s not what was described.
Interesting,
Under load, as in acceleration will produce same results regardless of hill. Most dealers operate under the replace until it is fixed strategy, hence, why so much was replaced to take care of a loose wire. (g)
I had the same problem, and if you had the four cylinder model, what happens on hills is lose wire leans the wrong way, allowing just enough seperation from plug to cause miss, and when one cylinder is missing on a four banger, this is a dramatic miss. (g)
Sorry I was late posting, but as a new member, just saw your problem. I hate to see people waste money at repair shops which rarely will simply fix problem, they will replace, replace, replace, as this is how they earn bonus money. I have been involved with engineering issues on vehicles of all types for years, and one wire loose will cause this symptom every time. If you look at your engine, you will notice short runs for wires, and when level, if plug wire was lose, it would be close enough to plug top to cross spark, and go unnoticed, then with angle increasing, the plug wire tilts back and that extra half an inch difference with dangling plug wire is all it takes.
Regards, Mike
Welcome to the Straight Dope, Mike.
Now I’m going to contradict some of what you said. 
In 30+ years of professional auto repair experience, I’ve never seen a plug wire so loose that it would tilt over on a hill but still stay on the plug. I wouldn’t say it’s impossible, but it sure is improbable.
On this engine, it’s a moot point as the plug connector part of the wire (included its rubber boot) is about 4" long, 1" diameter, and fitted vertically into the plug well through the valve cover and head. It cannot dangle. The whole assembly is too snug in its place to tilt at all.
Now, the most likely scenario in this case is that one or more plug wires was breaking down and shorting to ground under load. The sensible repair is to replace the whole set of plug wires, as when one goes the others are usually not too far behind.
A loose wire was almost certainly not the issue, and only could have been if it were not fully installed, which would be obvious in a quick visual inspection. Since the symptom apparently appeared spontaneously (i.e. not right after someone had the plug wires off), there’s no reason to think that was the case.
For the record, when the guy from the shop originally called me, he said that the plugs were fouled from the leak. From following your discussion this seems to make a difference.
I’m late to the party (as ususal) but let me throw in my 0.02.
Assuming that the valve cover leaked, I would expect that the oil would degrade the plug connector to the point where under load when extreme voltage is required to fire the plug, the voltage found an easier path to ground, hence the missfire.
Furthermore, I would expect that Saturn probably sells plug wires in a set, not per each. So even if only one is bad, you get a set the reason being that all of these wire are the same age, it only makes sense to change them in a set.
changing wires and not repairing the leak that caused the wires to deteroate would be IMHO silly. BTW, In all of my years in the auto business, I cannot recall if I have ever seen plug wires sold by the each.
Now on to the coolant temp sensor, and throttle cleaning. I am guessing that either there was a fault recorded in the ECM for the these items, or they are known issues with these cars. Either way not repairing the car fully is an inviation for the customer to come back and complain that they spent $X and the car still does not run perfect. Then the shop might then have to fix it for free. I mean would you be happy if I gave you your car back after spending $X, and while it did not miss on hills any longer, the check engine light was still on? You would have me in the pit in a New York minute.
Fouled from a leak. Can he elaborate? Are we saying the plugs fouled from oil leaking out of the valve cover gasket???
Now this is all from memory of the phone call, so I can’t be real specific (unlike the quote from the statement). He said that there was a pretty good leak from the valve cover gasket and that it was leaking onto the spark plugs. The oil from the leak fouled the spark plugs.
I’ve seen single wires sold, but they tend to be of the after-after-after market variety.
It’s an unfortunate choice of words. Oil from a valve cover gasket leak can certainly make a mess on the plugs, but only on the exterior portion. In common speech, one could say they were fouled, but in automotive jargon, “fouled” refers to the condition of the interior portion of the plug, which cannot be affected by the leak described. If that’s the word he used, he was being careless with his speech (or he’s a rookie who doesn’t know the jargon yet).
Thanks, Gary T. I’m reading the report and saying hunh?
The guy on the phone has been in the service dept at that dealer for at least 4 years. He was probably being careless or (correctly) assuming that I know nothing. Maybe both.
Which is why I couldn’t assume this guy was a experienced pro based on the original work description, and why I figured he might be talking about a head gasket leak. Valve cover leak leading to fouled plugs: yeah, it did need clarification.
If the plug misfired enough, it could very well be fouled, and the service advisor used the correct term. Or it could be that even though he has 4 years experience, he doesn’t know the lingo. Based my my experience with service advisors, I am not willing to bet any money one way or the other.
It could be fuel fouled. But we are told the service advisor said “The oil from the leak fouled the spark plugs.” That ain’t right.
I’ve seen dozens of cases where this type of valve cover leak let oil into the spark plug wells. Sometimes there were puddles of oil an inch deep around the plugs. In none of those cases was the oil affecting the performance of the plugs. Now, if you remove a plug in that situation while the oil is sitting there, the internal insulator and electrodes will get oil all over them. Still not the same as fouling. It cleans right off with a spritz of solvent, and doesn’t reflect the condition of the plug prior to removal. Based on my experience, I don’t find it believable that the oil affected the plugs in any way other than making them messy.
I don’t argue the wisdom of doing the described repairs. I do argue the service advisor’s contention that the oil in any way damaged the plugs.
As ususal you’re right. I had a hard day and didn’t read close enough.
I agree with you.
On a slight tangent I had a very good instructor many years ago say that if the engine is misfiring, change the thing that makes the fire (plugs) Simple, cheap, and often fixes the problem. 
My dad always used to say,“Do the cheap and easy things first.”