Tune Ups

Tune Ups

If you are doing a tune up on your truck I have found the following guidelines help eliminate some common problems.

  1. Setup your Sy or Ty in an area, preferably shady and cool area with good lighting available. Have your tools within reach.

  2. Jack up the front of your SyTy to unload the front suspension and always use jack stands.

  3. Remove the ECM A and ECM B fuses from the fuse panel, (this will erase any BLM adjustments that the computer may have stored.)

  4. Until recently AC CR42TS plugs were exclusively used, but some are now having good luck with NGK UR5. A swivel spark plug socket is available from AutoZone or Sears and allows you easy access the # 3 plug fairly easily (behind the steering shaft). Use a long extension through the fender well with this socket.
    Gap all plugs @ .035″. Tighten the gap .032″for higher boost and more Fuel Pressure, or when running alky/water injection.

  5. Spark plug boots can be troublesome at times. Get a boot puller to safely remove your wires without damaging them.
    When reinstalling, apply a small amount of dielectric grease to the inside of the boot to seal out moisture, and prevent the boot from sticking to the plug.

  6. A quality Distributor Cap and Rotor like the Conrad unit (@ AutoZone) usually lasts a year before degradation starts to appear. It is a BRASS terminal design and very robust, the rotor has a lip to keep “arc over” from happening within the Cap itself. Bottom line, don’t buy Accel especially or any other cheap brand.

  7. Once plugs, cap and rotor have been changed. Take a few moments with a flash light and check your vacuum lines etc. The hard lines start to show wear and tear fairly quickly as these trucks age. I changed all of mine out with new 7/64 line and zip tied all the end connections, this also eliminated some interesting problems that I actually didn’t know I had.

  8. Put the truck down, and reinstall the ECM fuses. Fire it up and let it idle to warm up, after about 2 minutes or so, turn on the headlights with driving lights (loaded alt. forces the idle adjustment etc.) Place foot on brake, with lights on, put it in reverse, then neutral, then Drive, each operation a few seconds at a time, let the idle under these circumstances have time to adjust and settle.

  9. Misses? Stumbling? Check wires and plugs, if care is not taken, it can be fairly easy to crack a plug insulator or not seat a wrie fully during install. Check under Tips Engine if you need help on the firing order or timing adjustments.
  1. Starting in new plugs can be a pain, I have found that if you put a 3-5″ piece of vacuum line on the end of the plug and use this to spin the plug and pilot it into the hole, you get (2) advantages.
    a. You will not “cross thread” the plug, if it doesn’t spin in fairly easy, then you are not lined up correctly.
    b. Lining up to the hole is easier and the vacuum line extension allows your fingers to thread the plug without hitting the shield or manifolds.

  2. AC Delco CR42TS & NGK UR5 availability, sometimes hard to come by, C=Commercial I.E. Heavy Duty. However planning ahead, CarParts.com &www.sparkplugs.com have them.

  3. Timing, remember to disconnect the TAN wire (inside truck, passenger side footwell, behind cover), there have been several posts on this. Though this has been covered, disconnection, setting to zero, then shut down, reconnection (tan wire) and go ahead and pull the ECM fuses for a few moments, you should be ready to go.

  4. Timing, our harmonic dampeners have a tendency to walk on the ring. Replacement on trucks that are approaching 50,000 or above may need to be considered. Check true TDC by using a piston stop. And always pull the tan wire on the pass floor board to set timing.

  5. If you continue to have issues with throttle stumble, and a tune up was performed in the above manner. Then consider replacing the TPS (Throttle Position Sensor) as well as Oxygen sensor especially if you are approaching 100K or so.
  6. Don’t forget to replace both PCV valves, GM Part No. 8995910 (CV 799C), and the fuel filter. Clogged PCV valves can also cause rough idle, and most people never bother replacing the fuel filter.

    ECM/MEMCAL location and replacement