1376 posts
Autos, Fitness
San Luis Obispo, CA
7-23-2002
Q45 Spark Plug Gap
8:58 AM 10/4/2002
What is the gap setting for the Q45 spark plug? I cannot find it anywhere in the owners or service manuals. The last set I installed went in the way they came out of the box, but that didn't feel right even if it worked fine.
Black over Gray 1990 Q45, JWT ECU & TCU, Rear Sway Bar, Eibach and Tokico, Stillen Tension Rods and Strut Brace , Skyline Brakes, Steel Hoses, 17x8 Wheels, 255/45 Sumitomo HTR+. Really is Mom's old car with 90K miles!
I just looked in the manual on MA-17 and it says that it's not necessary to check or regap the plugs. They come pre-gapped from the factory, so I always just put them in... one of the few things that doesn't require tweaking!
Heath
1990 Infiniti Q45 **** AKA "Q2" 2005 Infiniti G35 **** Sedan A/T 2004 Nissan Frontier.. King Cab M/T
13902 posts
1990 Q45 325,000 miles 19.9 years ownership
Marietta , Georgia
4-30-2002
8:58 AM 10/4/2002
The serious amount of voltage available from individual coil on plug systems means that in theory any gap [in a wider direction]would be statisfactory. The reason for 60k recommended changes has to do with galling of the plug into the head and the necessity to examine the plug wells for oil leaks.
The NGK [PFR6B-11] plugs themselves seem to be fine for 100k or more assuming all sensors/ecu are opering correctly [mixture is under control] and the engine is not continuously driven in cool start [short multiple 10 minute trips per day]!
After the first 150,000 miles additional ring blowby [and or stem seal leaks] may add to combustion chamber deposits which could mean that 60k is the useful life without cleaning.
The above assumes that the injectors are clean and the rear of intake valves are not burbened with deposits.....altering the mixture.
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The serious amount of voltage available from individual coil on plug systems means that in theory any gap [in a wider direction]would be statisfactory. The reason for 60k recommended changes has to do with galling of the plug into the head and the necessity to examine the plug wells for oil leaks.
The NGK [PFR6B-11] plugs themselves seem to be fine for 100k or more assuming all sensors/ecu are opering correctly [mixture is under control] and the engine is not continuously driven in cool start [short multiple 10 minute trips per day]!
After the first 150,000 miles additional ring blowby [and or stem seal leaks] may add to combustion chamber deposits which could mean that 60k is the useful life without cleaning.
The above assumes that the injectors are clean and the rear of intake valves are not burbened with deposits.....altering the mixture.
The local NGK Distributor informed me that the - 11 part of the plug number indicates that the gap should be around 1.1mil. I guess that would have to be a starting point. When I checked mine out of the pack, 2 = 2.4mil, 3=1.8 mil & 3 were around the .6mil. I figured that to try to get an even burn in all 8 pots I should gap all the plugs the same. Any comments greatly appreciated
Yeh Thanks I don't like annoying you blokes too much if the info is already there SOMEWHERE. Wish I could get my hands on a FSM Great site, keep up the good work Regards Greg
I assume by "mil" you mean millimeter? We're still on English units over here. A mil here = .001 inches = .0254mm.
1.8 mm sounds pretty wide to me. 1.1mm = .043", which is close to common for most platinum plugs I think (.035-.045). There's no gap given in the FSM because they should never need to be gapped between 60,000 mile change intervals. I think I measured new plugs at .045".
Thanks Daedalus Will gap all of them at .045 then. What a hell of a job, it's taken me half a slab of stubbies so far and I only have 4 plugs out!!! Greg
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