Dielectric grease applied to both ends of ingition wires -- now rough idle and stalls

dukbludvl · November 25, 2020

So, I'm a moron. It's been years since I've changed plugs and wires. This week, I installed new Delco platinum plugs and new Delco wires on my 2003 GMC Yukon 5.3L 2wd with Delphi coils, about 150k on the motor. Everything went well with getting the old plugs out and new plugs in. Then, I went ahead and installed the new ignition wires and mindlessly glopped a bunch of dielectric grease on BOTH ends of the ignition wires before putting them on, thinking it would help with conduction and not act as an insulator, as it obviously does.

I should have known right away that I effed that up because I figured I'd fire up the engine and she'd be smooth and happy. But, it was actually a little hard to start then it wanted to stall. I drove it around some -- ran in to work and back to the house, so maybe 30 miles round trip, with a couple stops in the middle. It idled rough, but otherwise ran fine most of the time -- no ticks, knocks, bangs, and seemingly no misfires, but maybe I missed some misfires? It did stall on me a few times when I started it and tried to put it in reverse to get out of a parking space.

Anyway -- need your advice. How do I undo this mix-up? My plan is this:

A. Remove these wires with all the grease in them and put on a totally new set of wires with only a thin coating of grease applied with a Q-tip to the boot only -- and not to the conductive metal/wire ends inside the boot.

B. Wipe the grease off the plug terminals that the boots were installed over as best I can with a paper towel.

C. Take a Q-tip and try to wipe the grease off the inside of the coil boots/connectors, and wipe the outsides of the coils with paper towels to try to get all the grease off as best I can.

My questions are these:

1. Any other suggestions about how to get the grease off the plugs so it won't interfere with the conductivity of the plugs? Is wiping it off sufficient, or should I replace my new plugs with another set of new plugs?

2. Have I permanently damaged the Delphi coils by essentially cramming grease up them from pushing the wires on? Do I need to replace my coils?

3. Anything else you all recommend?

Thanks in advance for your help on this. I just want to get my Yukon back running right again. The stalls and rough idle had me freaked out for a bit.

Jon

CamGTP · November 26, 2020

Just wipe all the grease off/out and slap it back together, it should be just fine.

The electrical grease won't damage anything like the wires or coils.

Mike GMC · November 27, 2020

I always put some dielectric grease on both ends. Double check that they are fully "clicked" on and fully seated. If that doesn't work, ohm the wires. New doesn't always mean good. Did you gap the plugs or just trust that they were correct out of the box?

CamGTP · November 27, 2020

The only real way the gap would be a concern is if they were like .080 or something.

They run fine on .025 and .060. People who run boost run lower gaps for spark blow out but you may notice spark blow out at high rpm's with .060.

SierrraLC9 · November 27, 2020

The grease shouldnt cause an issue and will help seal and lubricate the boot. Make sure you didn't leave a vacuum line or breather tube loose.

Mike GMC · November 27, 2020

13 hours ago, CamGTP said:

The only real way the gap would be a concern is if they were like .080 or something.

They run fine on .025 and .060. People who run boost run lower gaps for spark blow out but you may notice spark blow out at high rpm's with .060.

Very true. But I have seen rough idle when the gaps are different from plug to plug. They all work, but they all work a little differently. As long as the are all basically the same, I agree, anything in the range you mention works.

dukbludvl · November 28, 2020

I didn't check the gaps with a tool, but I eyeballed them and they all looked the same coming out of the box. I'm starting to think I don't really have any issues with the plugs/wires, and that maybe this is more of an air/fuel mixture or air delivery issue. I drove it about 30 miles tonight with a few stops/starts and had no issues with idle or stalling. In fact, I think maybe the idle is better now than it was before the plug/wire change. It's steady at 650, whereas before it was usually around 500 but a little bouncy and sometimes dipped below 500. I just got this Yukon a month ago from the only other owner who got it new in 2003 and had it for 17 years. He installed a K&N cold air intake years ago, and the K&N filter is quite dirty. So, there's that, plus I think maybe my rough idle and stalling could have been due to a sticking throttle body. My old 2000 Yukon did that for the first time in 2002 and it freaked me out. That 2000 Yukon had drive by cable, so I just moved the butterfly plate in the TB and cleaned all around it good and it was good fro the next 100k miles or more. This 2003 is drive by wire, so I think I need to find a buddy to get on the accelerator pedal to open up the butterfly plate while I clean around it -- is that right? My plan is also to reinstall the stock air filter box and get rid of the cold air intake. I'll clean up the TB when I do that hopefully this weekend.

Now, for a perhaps related issue -- or maybe it's a totally separate issue. I had a CEL code on last week before I did the plugs/wires, and I had it read and it came back as P0420, Catalyst System Efficiency Below Threshold (Bank 1). The CEL stayed on for a day, then went off for a day -- did that most of last week. Now, after the plugs/wires change, the CEL has been on steady, so I just had it read again at AutoZone tonight. It's showing the following:

P0420 Catalyst System Efficiency Below Threshold (Bank 1)

P0101 Mass or Volume Air Flow Circuit Range/Performance

P0102 Mass or Volume Air Flow Circuit Low Input

P0101 Mass or Volume Air Flow Circuit Range/Performance

Not sure why the same P0101 code is on there twice. Anyway, the AutoZone print out say "ASE certified Master Technicians have seen this issue on your type of vehicle and the most like solution is: Repair Engine Control Module (ECM) Wiring.

Anybody have any insights into what might be going on with this?

stevejones · November 28, 2020

You really want to be viewing the data stream to accurately diagnose your DTCs. In lieu of that; we'll load up the internet parts cannon & fire: your cats are shot (P0420) and you need a new MAF (P0101/2).

Good luck!