Changing spark plugs-When should you?

[hink12341234]

01 S-10 with the 4.3 and autotrans- My truck is closing in on 50,000 miles. Because of a disability I don't drive it that much. Case in point I have only put on 2,000 miles on it since July. I firmly believe it's best to drive a vehicle more than this but not much I can do about it. For some reason my gas mileage is way down. Around 6-8 mpg. Truck starts and run's perfect. Have scanned it and nothing shows up. The vehicles that I have owned in the past would start running rough and that's when I would change the plugs. So with my driving habit would the plugs be kaput or will they go 100,000 miles? If it's not the plugs I don't understand why a CEL has not come on. Like I said it run's perfect. I'll probably change the plugs for good measure. How about a faulty 02 sensor?That should trip the CEL or maybe not. What plugs would you reccomend? Thanks!

[j cAT]

Originally Posted by hink12341234

01 S-10 with the 4.3 and autotrans- My truck is closing in on 50,000 miles. Because of a disability I don't drive it that much. Case in point I have only put on 2,000 miles on it since July. I firmly believe it's best to drive a vehicle more than this but not much I can do about it. For some reason my gas mileage is way down. Around 6-8 mpg. Truck starts and run's perfect. Have scanned it and nothing shows up. The vehicles that I have owned in the past would start running rough and that's when I would change the plugs. So with my driving habit would the plugs be kaput or will they go 100,000 miles? If it's not the plugs I don't understand why a CEL has not come on. Like I said it run's perfect. I'll probably change the plugs for good measure. How about a faulty 02 sensor?That should trip the CEL or maybe not. What plugs would you reccomend? Thanks!

if this vehicle runs fine and no codes the most logical reason for poor gas mileage is the gas is evaporating ....from tank......check air cleaner and air ducting with no frequent use rodents may have nest in the air box .........or somewhere else............

[old_master]

AC Delco platinum plugs and all oxygen sensors should be replaced at 100,000 miles unless a problem arises earlier. If there are any problems with any of the sensors, the Service Engine Soon, (SES) light should come on and set a Diagnostic Trouble Code, (DTC). There are a few exceptions to this rule though so it would be best to have a qualified technician scan the system for DTC's in memory and check each sensors output. There's also the possibility that there is a problem in the fuel delivery system or secondary ignition system, neither of those systems are directly monitored by the On Board Diagnostic, (OBD) system and cannot set a code or illuminate the SES light.

[Larry Derouin]

With Mileage in the 6 to 8 mpg range I'd look at a bad fuel pressure regulator 1st. It's inside the Intake Manifold. Quick way to check if it's bad is to take an inspection mirror on a stick (sound like Jeff Dunham now......) open the throttle WIDE OPEN, and look in the intake. If the passenger side is "washed clean" and the drivers side is dirty, you need to replace it. Takes about an hour or two, depending if you've opened one of these intakes before.

One more thing with the later 4.3L's is the "spider" distributor. They tend to corrode quickly, and will contribute greatly to poor gas mileage and other problems. The actual problem is the "vent screens" in the bottom which will allow condensation to build and then corrosion of the contacts sets in.

1.) CHANGE the CAP AND ROTOR.
2.) Clean all internal parts and remove the screens.

(Note: Use EXTREME CAUTION when removing/replacing the Cap screws. The BOTTOM housing IS PLASTIC and the mounting ears WILL crack causing the cap NOT to tighten down. Remove the thread sealer from the holes with a dental pick and from the screws on the cap. ) Your other option is an aftermarket billet distributor. Accel makes one specifically for the 4.3. But that's a last resort option in your case I would imagine....$$$$$.


Check the FPR 1st. Then check and repair/replace the cap/rotor/ plug wires(GM Packard wires are cheesy after the 1st year or so.) and plugs.

Taylor Wires (8.5mm or larger) are good stock replacements.

The AC DELCO Plugs you have in there from the factory are probably the best all around plugs for the engine. I think you'rs are 31-942's. Double check tho. I'd stick with those or NGK's. Stay AWAY FROM BOSCH PLUS 2 or PLUS 4's, SPLITFIRES, or any of the gimmicky plugs. They have a tendency to misfire after a few thousand miles.

If you need to replace the coil, get either the ACCEL Supercoil, or the MSD BLASTER. They are a direct replacement for the stock coil, have better power stats, and cost 1/2 as much. Even the Summit house brand coil is better.

Pull off and clean the EGR. They sometimes have a tendency to clog causing a drop in mileage.

MAKE SURE THE GAP IS DEAD ON. Don't trust the gap set from the factory.

Get two cans of SEAFOAM. Pour 1 directly into the gastank, fill the tank. Take the other and pour it into the engine (thru a vacuum line) to clean the upper end. Follow the directions. Between the two cans will clean the whole fuel system, the upper end of the engine.


Hope this helps. Let us know what happens.

Larry

[hink12341234]

Thanks for all the info! It's given me a number a things to check out. Will let you know what I find. Again,thanks.

[old_master]

Originally Posted by Larry Derouin

With Mileage in the 6 to 8 mpg range I'd look at a bad fuel pressure regulator 1st. It's inside the Intake Manifold. Quick way to check if it's bad is to take an inspection mirror on a stick (sound like Jeff Dunham now......) open the throttle WIDE OPEN, and look in the intake. If the passenger side is "washed clean" and the drivers side is dirty, you need to replace it. Takes about an hour or two, depending if you've opened one of these intakes before.

A leaky fuel pressure regulator will cause a drop in fuel mileage however, opening the throttle will not allow you to see if anything is leaking on this engine. The older Vortec engines have a tuning port on the upper intake plenum. You can remove the cover and look into the port and check for leaks. The only way to "see" a leak on the newer engines is to remove the upper intake. A much easier way to check for a leak on any 4.3L W or X engine, is to run a fuel pressure leakdown test. 100% conclussive results and takes about 5 minutes to do.