Changed plugs....issues...

hikerboy · August 9, 2015

Strange day. Changed my factory plugs on my 95,000 mile '05 Z-71 Sierra, replaced with the new double platinum 41-962 AC Delco as recommended. Reused my stock wires. Started right up, seemed to idle nicely. Drove fine for about 10 minutes, but noticed some engine "stumble" on occasion, and then it died at a stoplight. Restarted, headed home - - noticed that the electric fans were running on high speed, without the A/C on. Bought new AC Delco plug wires, replaced, drove again....same issues. Now the check engine light is on. The dash temperature gauge started behaving strangely - - it shows a very high temp, then it falls to 160 and stays there, even as the engine continues to run at seemingly normal temp. Fans run all the time until the engine is turned off. What the heck? No issues removing or reinstalling the plugs.

Coincidence with changing the plugs, or ??? I've got an appointment at the GMC dealer next week to see what the heck is going on. Ideas?

2017SierraSLT · August 9, 2015

Need to know the code(s) that caused the CEL to illuminate..

DaveH71 · August 9, 2015

Check your coolant temp sensor, make sure it's plugged in or that you didnt damage it during the plug install.

Its behind the power steering reservoir, just above the #1 spark plug on the driver side head. It's a round sensor screwed into the head with a 2 wire connector attached to it.

hikerboy · August 9, 2015

I checked the wiring on the coolant temp sensor, it appears to be OK (it's still attached to the sensor). I guess I'll just wait and see what the CEL codes come up at the dealership and hope that it's a simple fix - - maybe a bad plug, relay, or something like that. Strange that the problem happened after I did a seemingly simple thing - - especially when the project went so smoothly...

wilsonz71 · August 9, 2015

Same thing happened to my bosses Yukon after a plug and wire change. Coolant temp sensor was broken when changing plug #1.

hikerboy · August 9, 2015

This is beyond embarrassing. I took one last look under the hood as I started it up this morning....I smelled a rich exhaust odor on the passenger side....I noticed one of the plug wire boots was wobbling as the engine idled.....I had neglected to tighten/torque one of the plugs. Good grief. Tightened the plug, check engine light went off later today after a couple of ignition cycles, and it runs like a top.

Dealership appointment cancelled.