A couple of codes and questions

Batass · Post by **Batass** » Sun Jan 25, 2009 5:17 pm

Had a code a few weeks ago something to do with the evap system. Hasn't come back since then though.

P0300 random misfire. Changed all the plugs and wires today and noticed the two rear passenger plugs maybe were detonating a little. Had some crusty stuff and the tips were buggered up. Haven't had the code a week before changed the plugs and wires though. Why the detonation or pre-ignition? Vacuum leak? I only run 87 octane in it.....

It lags downshifting out of overdrive. It'll bog until it really slows down, or I put my foot in it. These transmissions don't have any vacuum lines right? Don't they use the tps sensor?

04crewvt · Post by **04crewvt** » Sun Jan 25, 2009 5:46 pm

First check and replace the caps and rotor, remove the vent screens if they are still in there. Then have the intake manifolds checked for coolant leaks. Your evap code was most likely a loose gas cap that's what sets it most times. We just went through all this in another thread today two below this one P0302 All the P codes 0300, 0301,0302,0303,0304,0305,0306 are misfire codes P0300 is random multiple misfires and the rest tell you which cylinder is affected.
The lag suggests the cap rotor should be first on your check list. then fuel filter/injector cleaner.

F9K9 · Post by **F9K9** » Sun Jan 25, 2009 5:56 pm

04crewvt wrote:First check and replace the caps and rotor,......

After researching the bejesus out of the topic. If, you don't you are going to end up costing yourself a few hundred dollars. It is all here for you to find through a proper search. Yeah, it will eat up some time but, you make the choice. Pay a dealership hundreds or spend some time perfecting search techniques. Do not limit a search here, explore a little.
A little known fact is that our distributors are plastic. Screw up that cap replacement and get ready to pay some bucks. Take you time and reseach.

Good luck!

Reed

Batass · Post by **Batass** » Tue Jan 27, 2009 9:49 pm

I hooked up a gauge to it today and noticed when it lags in OD, the timing went all the way down to 2 degrees! The timing is fine otherwise.

I didn't know the cap and rotor even needed checked. What the heck is a distributor doing on this thing?

04crewvt · Post by **04crewvt** » Wed Jan 28, 2009 4:41 am

Same thing it does on every other GM Motor of that era. Remember the 4.3L was introduced in 1985, well before the modern distributor less ignition systems and stretches it's roots back to 1978 when GM basically lopped the last 2 cylinders off a 350 to create the 90 degree V6.
Timing needs to be read with a SnapOn or TechII gauge using a very set procedure to be worth anything.
Buy yourself a cap and rotor carefully read the different posts on which one to get and how to install and see what happens. My guess is you will see burnt and/or corroded contacts inside the cap. Like the t-stat fix JUST DO IT. It can't hurt if it's not the problem and it will give you a better idea if there's a bigger problem if it does not fix the code.

F9K9 · Post by **F9K9** » Wed Jan 28, 2009 6:47 am

I am guessing that he will find something similar to this.

This had less than 20K on it, BTW.

Batass · Post by **Batass** » Wed Jan 28, 2009 10:44 am

I can't see the picture. Thanks for the help though, I'll check it out.