My 2005 Yukon XL

[DieselSlug]

Spent some time last weekend with my annual Fluid Film undercoating. Yukon is coated and ready for its 6-month salt bath:




I also spent some time checking spark plugs to see if a visual identified could be seen. Even my newer scanner doesn't have cylinder balance or misfire checks. I would assume if it is misfiring the computer isn't catching it, so a scanner wouldn't. Also I am not even sure if this vintage GM has the "smarts" to provide a scanner this data. Most plugs looked good and similar to all the others:



I did start pulling plug wires right off the coil while the truck was running and noticed some deviations in spark jumping from the coil across about 3/4-inches to the plug wire boot I was holding. Most of the OEM coils would arc nearly 1-inch of gap! There are some gray coils (maybe 3-4 total) that look aftermarket on there and they barely arc with any gap. I swapped what I could with my last 2 junkyard grabbed units. Visually checked arc jump again on all and I still have 2 other weak ones that I want to replace. One being the newer Napa one I got a few months back on cylinder 6. The idle felt much better, smoother.

After about 100-miles on the odometer I got a flashing CEL, and to be honest expected one of my junkyard acquired coils to be bad. However it was a totally separate coil from any I replaced prior. I need to get more coils as there are a few of the gray aftermarket, and several OEM that look very rusty (old). To date I have replaced 3 coils. I'm thinking several are slowly failing.

 

[dbrannon79]

Sounds like fine made chineesium parts. I know there expensive, but I would try looking for made in USA Delco units. if there is room, try relocating them to a inner fender away from all the heat too.

 

[DieselSlug]

Sounds like fine made chineesium parts. I know there expensive, but I would try looking for made in USA Delco units. if there is room, try relocating them to a inner fender away from all the heat too.

I'm sure, I would like to know what manufacturer the gray ones are from. It would be very tough to relocate, would need coil harness extensions, plus longer plug wires as they mount directly on the valve covers themselves.

So you can still get AC Delco units, issue is when in a bind, nobody has them within 1 week. Same with Denso version. Which I would almost bet none are made in USA anymore. Thus the reason I got the crapa one when I did. Only decent option is RockAuto for them at $80 each plus S&H which isn't horrid, but still a week plus out.

Been my last resort to pick through the junkyard for OEM only units that visually look in decent condition. I plan to go back today and grab more, need to make a trip with the Yukon tonight to a soccer game over an hour away.

 

[DieselSlug]

Picked up 3 of the best looking junkyard OEM coils yesterday. Put another on last night, so far a total of 3 I have replaced with the junkyard units. All have great arc now when pulling the boot except for 1 remaining gray one. Will swap that one out too but the Yukon made the 2 hour trip with no issue last night.

 

[DieselSlug]

Normally I don't like doing stuff like this, but with my only other option being to "re-tune" the computer, its just not worth it. I have been having issues towing and plowing with temps mainly due to the electric fan setup and its "triggering" parameters in the computer. By the time fans are commanded at full speed coolant temps are over 225-degreees F.

I will be installing a manual override switch as clean as possible while retaining factory functionality. Reviewing the wiring harness I found a good point to access the trigger wires for low and high fan operations. There is a 2-pin connection near the fuse box. I grabbed a few extra pigtails from the junkyard and created a plug and play jumper setup by inverting a set of connectors to plug in-between my current connectors:



If I ever decide to remove this setup I easily can without the worry of a hacked harness. I purchased a switch plate to go into the center console cubby for installation of rocker switches. I purchased a 3 position switch, up will be high override, center will be no-override, down will be low override. I am going to have an issue with the switch as the circuits I need to connect are grounds, so the switch lighting function wont work. For low the green wire only needs to be grounded. For high, the green and the blue need to both be grounded.

 

[dbrannon79]

If you want that to be automatic, you could use a Hayden fan controller on those two trigger leads. adjust it to the temp you want and leave it.

 

[DieselSlug]

You are correct. I did think about this, and ultimately may do it as well.

Only reason I was going to do the switch for now is I plan to add some A-Pillar lights to aid with plowing at night. I had hoped to get those done before this winter, but it got cold fast as it always does....