Confused on a simple Subject

MAC88 · May 26, 2003

Hi I am new to the forum and I am a mechanically inclined guy but this is a question that requires a little more knowledge or experience

I just picked up a used 92 K2500 (7200GVW) witha 5.7/Auto and when I went to do the spark plugs, my haynes manual gave me a gap of .045 and the VECI label under the hood gave me a gap for the plugs of .035.

I have never really come across this type of difference before and since this is my first gas GM truck I figured better to ask than guess which would be correct!!!

mcali17 · May 26, 2003

Maybe these TSBs will shed some light on your problem. Hope this helps. But check and see what size type of plug you are using.

#1

SPARK PLUG TYPE UPDATED BY TSB # 88-T-64

Spark Plug Gap 0.90 mm (0.035 inches)

Spark Plug Torque 20 Nm (15 lb. ft.)

Spark Plug Type AC R43TS

NOTE: Check the gap specifications given on the Emissions Control Label. If the gap is different from what is listed here, use the information on the label.

#2

BULLETIN NUMBER: 93-6D-2

SECTION: 6D

NUMBER: 1

CORPORATE REFERENCE NUMBER: 166001R

DATE: September 1992

SUBJECT:

NEW DESIGN SPARK PLUGS (SERVICE INFORMATION)

MODELS:

1991-93 TRUCKS WITH GASOLINE ENGINES

THIS BULLETIN CANCELS AND REPLACES GMC TRUCK SERVICE BULLETIN 91-6D-76, DATED MARCH 1991 TO PROVIDE UPDATED TOOL INFORMATION. ALL COPIES OF 91-6D-76 SHOULD BE DESTROYED.

In 1991 GM introduced a new design spark plug for use in all trucks equipped with gas engines. These new design spark plugs have a ceramic insulator which is approximately 1/8 inch longer than the insulator used in previous model years.

The longer length spark plugs, which conform to S.A.E. and I.S.O. Engineering guidelines, magnify the problem of cracked insulators because currently, most spark plug sockets are not of sufficient length to properly engage the shell hex. If the spark plug shell hex is not fully engaged in the spark plug socket wrench, the socket may cock at an angle and cause insulator cracking and/or breakage during plug installation or removal.

When servicing these new design spark plugs, make sure that the spark plug socket being used is deep enough to accommodate the longer length insulator. The spark plug socket wrench should conform to the proposed S.A.E. and I.S.O. world standards for spark plug socket wrenches. Spark plug socket wrenches that conform to these standards are designed to accept the lengthened spark plugs and allow full engagement of the hex nut on the shell of the spark plug.

Use of a spark plug socket which is NOT deep enough may result in the cemmic insulator becoming cracked above the spark plug shell.

NOTE:

SOME CRACKS IN THE INSULATOR MAY NOT BE VISIBLE SUCH CRACKS MAY LATER CAUSE A SPARK PLUG TO MISFIRE. SPARK PLUG MISFIRES ARE OFTEN MISDIAGNOSED AS A SLIPPING TRANSMISSION DEFECTIVE TORQUE CONVERTER CLUTCH, ENGINE IMBALANCE, OR MALFUNCTIONING FUEL SYSTEM. To prevent insulator damage, it is recommended that the proper spark plug socket wrench be used when removing or replacing spark plugs. One such spark plug socket is the Kent-Moore J-39358 spark plug socket. The tool is available from Kent-Moore. For ordering information call 1-800-345-2233 or write: