intermittent rough performance with silverado

I have a 2001 silverado with 58000km. I have started having an intermittent problem, for no reason at all the engine will become very slugish, even stall, and also puffs out black smoke ( I beleive from too much fuel being dumped). The problem is that the problem goes away and runs fine for about a week and then starts to act up again. I have had it to GM twice now and the only code that comes up is misfire code. I originally thought it was bad gas, put in gas antifreeze, and it was fine but I think that was just a coincidance.
Any help would be greatly appreciated. A $100 both times just to tell me there is nothing wrong.

Thanks for any input.

[QUOTE=sfoster1541]I have a 2001 silverado with 58000km. I have started having an intermittent problem, for no reason at all the engine will become very slugish, even stall, and also puffs out black smoke ( I beleive from too much fuel being dumped). The problem is that the problem goes away and runs fine for about a week and then starts to act up again. I have had it to GM twice now and the only code that comes up is misfire code. I originally thought it was bad gas, put in gas antifreeze, and it was fine but I think that was just a coincidance.
Any help would be greatly appreciated. A $100 both times just to tell me there is nothing wrong.

If you havent tried it yet, do this. Change out your fuel filter, easy to do( relatively ) and add a fuel injector cleaner to your fuel. STP worked the best for me. If the dealer tells you that you need to flush your injectors, save you money. My error was "misfire" on such and such cylinder. I did it and havent had a problem since. DONT DO ONE OR THE OTHER. Change out the filter and add the fuel additive before using the vehicle again.

If you havent tried it yet, do this. Change out your fuel filter, easy to do( relatively ) and add a fuel injector cleaner to your fuel. STP worked the best for me. If the dealer tells you that you need to flush your injectors, save you money. My error was "misfire" on such and such cylinder. I did it and havent had a problem since. DONT DO ONE OR THE OTHER. Change out the filter and add the fuel additive before using the vehicle again.

I'd second that idea - although I 'd suggest using a fuel system cleaner that comes in an aluminum bottle - any of them in aluminum (Slick 50 is the one I use). If its in a metal bottle - it means it is more "petroleum detergent" oriented. If you put it in a plastic bottle - it would soften the plastic - which is why it comes in metal instead. Still should be $5 to $9 dollars - no more - but it should do a better job of cleaning. I'd run this thru first before changing fuel filters - then I'd change the filters after the tank is run thru with the cleaner in it.

Why you might ask? Just like with flushing the engine oil - the flush or cleaner may break some crud loose - and you don't want your new filter "catching it" - let the old filter do that - then the new filter is working with a clean system from time of install.

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