View Full Version : AC Delco platinum plug gap settings for N*

08-26-09, 10:07 AM
Just replaced the plugs in my 2001 DTS with AC Delco platinums. Hooked every connector and vacuum hose back. Car misfires with P0300 DTC. Spent hours double checking everything. I ended up resorting to take the car to stealership and they just called and said I must have just "dropped" the plugs in the holes because "every" plug is not gapped correctly! Really!? Every plug!? Everything I read on this forum said platinum AC Delco's shouldn't have to be gapped. My question is how could they know that every plug is not gapped properly without removing all plugs from the engine and physically measuring them? Can they do this with diagnostic equipment while the plugs are in place? Also, I use a piece of tubing to set the plugs in place and begin threading them before I put a socket on them. They have never been "dropped in".:wtf: Oh and they will be happy to re-gap them for me for $225.00 on top of the $120.00 to diagnose. Happy Times!

08-26-09, 10:23 AM
The ACDelco #41-987 plugs for your engine come gapped to .050". If an elephant didn't squash them during shipping they should have been OK. Impossible to read a plug gap without the actual plug in your hand.

Did the plug boots look clean with no dirt or carbon tracks visible ? Same for the 2 ICM multi-pin connectors on the coil cassettes.......

If the dealership is in the $80 - $100 per hour labor range, they're hitting you at book rate for a plug change: diagnosis + 1.6 hours.

08-26-09, 10:34 AM
Plug boots were replaced when plugs were replaced 2 days ago. Connectors looked good and clean.

08-26-09, 11:57 AM
Just picked the car up from the dealer. I'm going to verify that the gap is correct on each plug.
The car was still misfiring on the way back. One thing I noticed on the way home was the temp gauge bouncing when I would stop at a light or stop sign. It would only bounce from the 10 o'clock position to 12 o'clock position. Not sure if this is a fluke or related to the engine misfiring. Time to go check gaps.

08-28-09, 09:37 PM
if the plugs are changed when the engine is not fully COLD what are the issues?

That seems normal according to the info I got from sub and N* http://www.cadillacforums.com/forums/northstar-performance-technical-discussion/175762-normal-operating-temperature.html

In the Bay Area right now its around 80-100 degrees, which is very unusual (and sucks IMO), and I was parked and turned on the A/C for about 30 seconds; my temp rose to about the 2 oclock position and once I turned on the car and turned the A/C off and drove it went back to the 12o'clock position.

08-28-09, 10:33 PM
if the plugs are changed when the engine is not fully COLD what are the issues?
None. You can change the plugs when it is hot if you can hold on to them.

08-29-09, 01:42 PM
The Factory Service Manual (and personal experience) cautions that pulling spark plugs out of a hot aluminum head runs the risk of galling or stripping the threads in the head. Better safe than sorry.

08-29-09, 09:17 PM
LOL, ok

I dropped my car off around 930 to have them changed then picked it up around 1pm and the car was slightly warm still so I know it wasn't fully cold...

08-30-09, 12:17 PM
Guess I am still thinking old school iron engines. Maybe I should read the FSM a little more.

08-30-09, 03:02 PM
Yeah, that ^^^

I too have pulled a lot of hot plugs out of aluminum heads (and screwed up a couple), BUT, when it comes to open Forum advice, when there's a potential for problems, better to play by the book.