Well I told my dad not to but he bought 4 new o2 sensors and the truck still has a missfire.I cleared the codes and parked the truck. I haven't tightened the exhaust leak yet. What do you guys think I should do next. I put new plugs in while the engine was out and dont recall breaking any porcelin?

 

Where is the exhaust leak? If its around the o2 sensor then the readings will be wrong causing it to misfire.

 

Update one plug wire was loose and one was off completley truc runs great now.

 

Joe, since you did this back in July, has the light come back on? Before everybody says "retune", the vehicle I'm gonna try this on isn't supported by HPT. It's a 95 Sonoma with a W-code 4.3 liter. It was brought to me after another shop couldn't make it run well. They replaced both o2 sensors and installed a 'test pipe'. I found it to have a leaking fuel injector assy inside the intake manifold as the root cause. After replacing that, a tune up(plugs were fouled), and new o2 sensors again(the new ones were clogged with soot), the truck runs great! Today it threw the cat efficiency code.

So I'm gonna try this and I'm wondering how long til the light comes back on. I read one thread where the light comes on after 900 or so miles.

Thanks Joe,
Roger

 

Roger, I have a 97 C1500 with a 4.3L Vortec just like you. The light has not come on since I've done this. I easily have 8K miles on this setup and not even once has the light tripped. Make sure you don't go too big with the drill bit though, you'll take out the threads. I forgot what size I used. Just keep stepping up with your drill press until the sensor fits in.

 

Off topic, but W-code huh? I replaced a bunch of W-engines back in the late 80's early 90's...I believe that they were 3.? liters though...front wheel drive Grand Prix and/or Grand Am maybe? It's been a long time, but I remember that the block would crack in the rear corner by the head, making many techs think that it was a head gasket problem...

 

In this particular model truck they had 3 possible 4.3L's you could order. There was a TPI 4.3L that was put only in the high end 4.3L trucks (like the super sport) then a "x" variant and a "w" variant. The "x" was rated at 180HP and I believe the "w" engine was rated at either 185HP or 190HP. The only difference I was ever able to figure out years ago was the camshaft. The work trucks (C/K) and certain S10's got the W engine for stronger midrange.

 

For the 4.3 liter V6 used in S & T series pickups and Blazers, there were 2 different engines. Z or W. The Z-code 4.3 was throttle body fuel injected. The W-code 4.3 was CPI injected and was labeled 'Vortec'. I don't remember the hp/tq numbers, but the W engine was more powerful.

X-code came later, and was SFI injection.

I think most 4.3 liters that made it into C/K trucks were Z-code, but I'm not positive.

Joe, thanks for your response.

 

Too damn many to keep straight - sorry for the 4.3L mis-info

 

Not very many of us study the 4.3 liter. No worries. The only reason I know about them is that I worked for GM for so long.