Kind of a long post here...

Changed the plugs and wires today. Was running fine, but I'm thinking about getting a dyno later this month. Used to have stock wires with NGK TR55's. Swapped to new TR55's and the MSD wires.

Washed it (not the motor) and took it for a spin to test it out the new plugs and wires. Idle was smooth (it's an 2000 A4) and it felt nice and tight. Drove about 3 miles - start and stop city traffic - stopped at a store. Started up fine and drove to another store about 4 miles away - got up to highway speed for a couple of miles. Then sat and idled at a drive through - still very smooth and running great - then headed home. Checked the temps on the DIC right when I left the drive through and it showed nothing out of the ordinary, but it was definitely up to "operating" temps. Then things took a turn for the worse...

Sitting at a stop light a couple of miles from the house I was noticing how smooth the idle was - about 600 RPM. All of a sudden it "chokes and shudders" then smooths out again. Then started idling very rough. Light turned green and it was running very rough. Got up to 50 and mashed down a little on the gas and it seemed like it had about 150 HP - not good.

Made it home - checked the codes and there are none. Looked under the hood and it's too hot to do much but there are no plug wires hanging off anywhere. Pushed on a few that I could without burning my hands and they were tight.

1st questions...

So, I'm waiting until things cool off to recheck all of the plug wire connections. But I have to ask, do these symptoms sound like anything other than a wire loose? Running fine and then all of a sudden rough? Cracked plug? Loose plug? (I used a torque wrench set at 11 ft lbs) I'm surprised it's not throwing codes.

2nd questions...

I had 10k miles on my old plugs. The wear on them looked okay - gaps still good, etc. But, there was oil at the base of the threads (away from the electrode) on every one of them. Kind of "gummy" or thick oil. What might that be? Does that sound like bad rings? I do burn a little oil - usually a quart about 2500 miles.

Thanks for any input on this.

 

Same symtom as yours, cracked plug next to brake boost, showed up within one mile of starting car. The plug wires sometimes don't seat, did you use silicon in the boots? You' ll hear a slight snick as they seat. Good call on the 11 ftlbs. Good luck

 

sounds like a wire came loose and it is not firing correctly.

 

Here is a possible explanation for the sudden change. I had a similar experience after changing the intake recently. When you first start the car and are driving the computer is undergoing some self checks, per say. Monitoring MAF, MAP, etc. When these checks are done it adjusts the A/F accordingly. So the car will run good for a while then after about 10 min of driving things turn for the worse. If you do an idle re-learn I would bet the car would once again run good for a little while. I wish I good explain this a lttle better. I am surprised you did not get any codes. If the only thing you changed was plugs and wires I would start looking there. You might also checkl for any hoses or wires that might have accidently been pulled off.
Good Luck.

 

The oil on the threads is anti sieze. You should have put some on the new plugs as well. Why? Disimilar metals, Aluminum and steel react badly and will corrode together. It's not so bad if these plugs will stay in for the life of the car.
But sounds like a loose wire or cracked plug. If you want to ID the faulty plug/wire start the car and let idle until the roughness begins. Then disconnect one wire at a time from the spark plugs. If the cars idle get worse, replace the wire and move to the next one. When you pull the wire from the bad plug it will have no effect on the engines idle. If it's too hot to pull the wires then shut off the car between wire pulls. Replace that plug with a new one or one of the old ones if you need to. Don't pull the wire from the coil end for your own safety, the plug end has more insulation.

 

I saw a trick a mechanic used on my truck when it had a similar problem. He took a spray bottle filled with water and sprayed each spark plug/wire in turn with the engine warmed up and running. When the idle got worse, it isolated the cylinder with the problem Shutting off the engine, he pulled the plug and found a hairline fracture in the insulator.

 

Unable to isolate a problem with any single plug. Tried the "unplug one, start it, plug back in, unplug another, start it, etc." All equally rough. Put the old wires back in. Even rougher. (At least that confirms that they needed replaced. )

Finally, pulled the NGK TR55's and went with AC Delco Iridium's. Running like a champ now.

Go figure - my last set of TR55's worked just fine.

 

A couple more ideas. Make sure the plug wires double click into coil packs. Check to be sure the plug tips are screwed on tight.