: new spark plugs and radio static

04-07-11, 07:10 PM
Apologies if this is a double post I did a search and could not find an answer.

I recently had an engine misfire code, and decided to change the plugs.

I found that the post on the ignition coil for cylinder 8 was discolored (all others were clean), so I decided to replace the coil bank.

All was good except for a rough idle.

I found that the rubber tubing to the PCV valve was broke, so I replaced the valve and the tubing.

That cured the rough idle, and there is no engine misfire.

However, I am now noticing static on the radio. I am wondering if I have not installed the coils correctly.

When I removed the coils the springs were set somewhat deep. Is there supposed to be a gap between the ignition coil posts and the springs, or is there supposed to be contact?

When I installed the coil springs they were not set very deep and the posts were in contact. Just a thought, maybe there is another problem, I don't know and am seeking suggestions, solutions, thanks,

04-07-11, 07:28 PM
The proper AC Delco Platinum plugs, #41-987, were designed for your engine. They should not cause radio static.

Your engine should be coil-on-plug - each coil connects to its respective plug by a boot with integral spring conductor, and that spring should make good, solid contact with both the coil tower and the plug itself. Also, make very sure that the coil cassette ground spring is clean and makes good contact, as well as the ICM in the L leg of each cassette.

04-07-11, 07:58 PM
I installed AC plugs #41-987.

My engine is coil on plug.

I installed new boots and springs.

When I installed the springs I just pushed them in with a needle nose pliers. Not sure if there is good contact with the plug itself. I just pushed them in until they caught.

I am also not sure that I made good contacts with the rear bank ignition coil, because of the sight limitations.

I am going to remove and re install tomorrow to make sure.

The front ignition cassette is clean because it is new. I put di electric grease on each post. The rear ignition coil was replaced in 2007, and is still clean. Thanks,

00 Deville
04-07-11, 09:35 PM
You didn't happen to have the rear defogger on when you experienced the radio static did you? If so... I remember seeing a TSB on the 2000 Deville... not sure if it also covered the Seville on radio static being caused by the rear defogger being on in some cars.

04-07-11, 09:44 PM
^^^ That can happen if one or more of the defroster lines is broken.

04-08-11, 08:24 AM
Curious observation - the boots in the picture came with the springs already installed and they already had dielectric grease in the lower tips.

04-08-11, 11:23 AM
I just removed both ignition coils to inspect.

The front one (the new one I just installed) the center ground spring was bent over and not centered in the cavity. I adjusted the spring and re installed the coil. I started the engine and still had minor static on the radio. Yes, it is on FM talk radio far left on the dial (clear channel).

Sooo, I took off the rear ignition coil, and everything looked fine. I just added more lithium grease to the posts because it was light on grease. I re installed, started the engine, and still had a little static. I switched channels back and forth to check reception, etc. After running a little while the static seemed to stop. Maybe it will come back, don't know. Minor issue I guess. I did check the rear defroster, it is not on. However, if I keep getting static I will check the wiring.

My coil springs came separate and I had to install them. I just pushed them in with a pair of needle nose until they stuck. The engine is running perfectly now.

The next issue I want to check out is the carbon deposits. I had a lot of gunk on the plug in cylinder 5, and a little oiliness on the adjacent cylinders (rear bank). I also get a loot of carbon soot on my garage floor at the tail pipes.

Thanks for the comments,

04-08-11, 11:41 AM
I had a lot of gunk on the plug in cylinder 5, and a little oiliness on the adjacent cylinders (rear bank). I also get a lot of carbon soot on my garage floor at the tail pipes.

The "oiliness" - if the oil was on the spark plug upper insulator and outer shell, then that's due to the O-rings in the plug wells - cam cover to head seals - they tend to weep over time; not a problem.

Now, if the plug tips themselves were oily, then you have big problems - excessively worn oil control rings for starters.

Soot on the garage floor - I didn't go back through this thread - have you checked the Fuel Pressure Regulator for raw gas in the vacuum nipple ? Some Northstars will leave black deposits on the floor - from the weep holes at the low point of each muffler. Normal. There's a LOT of water vapor created by petroleum combustion, and that's why tail pipes drip and steam in cool weather - until the exhaust piping heats up it acts just like an inefficient still.

04-08-11, 12:00 PM
You said you put dielectric grease all over the plug tips and coil contacts? Dielectric grease is an insulator, it's designed to go on the ceramic portion of the plug to prevent corona discharge. I would probably take the excess off and see if your radio static goes away.

04-08-11, 12:12 PM
Post #7 - I'm not so sure that I'd use lithium grease as a dielectric - isn't lithium some sort of metallic compound/precipitate ?? So it's a conductor, not an insulator ??? Dielectric grease is a silicone compound - insulator and moisture barrier.

04-09-11, 10:50 AM
Not sure, but a quick Google seems to point to Lithium Grease as non-conductive. I'd be wary of smearing any kind of grease all over the plugs on this ignition setup. The springs inside the boots don't made as solid a contact as the metal in a plain old spark plug wire. It probably can't displace the grease and make a good metal-to-metal contact. Then the spark has to jump the insulating gap of dielectric grease and causes the static.

If I was going to use dielectric grease, it would be a thin layer on the ceramic of the plug only. Don't even really need that, as the plugs are very well protected in the plug tubes.

04-11-11, 06:13 PM
Back after a slight delay. Internet issues.

Regarding the grease, I coated the coil contacts. I did this because when I pulled both the front and rear bank coils they had some kind of coating in place, looked fresh and clean except for cylinder 8 which had "burned off". It may have been silicone originally, I don't know, my bad. There was a coating on there does anybody know what it should be?

When I installed the boot for the coil spring I put a dab of dielectric grease on the bottom of the boot which slips over the plug.

04-11-11, 09:05 PM
You're good - those cassettes exert more pressure on the boot conductor springs than you would think. The dielectric grease is to prevent moisture from collecting in the boot itself and assisting a ground path for the high tension spark voltage down the outside of the insulator ceramic. Many modern plugs use a resistor molded into the plug - for EMI control - so anything you can do to make the voltage stay inside the plug is to your (and the engine) benefit.

04-12-11, 10:38 AM
I need to ask again about the oil I discovered on the spark plug mentioned earlier. It was cylinder 5 plug, on the threads. Not heavy but noticeable and by touch. The adjacent cylinders 3 and maybe 7 showed trace oil but light (on the threads). I am afraid to ask, but guess I need to suck it up, is it the rings, and what would be the next step? I probably should start a new thread on this topic. Or please suggest any known threads, thanks

04-12-11, 01:18 PM
That's from the O ring oil seal in the cam cover. It's just seepage. Ignore it and clean it out again next time you do the plugs.

04-12-11, 05:06 PM
Cool Beans. Thanks to all for the comments. It really is driving good (knock on wood).