hello, My 2000 5.7 express van i just got has a miss fire at idle and when running at no load speeds. it will blow black smoke during these times as well, however when i step in to it ,motor smooths out no miss and black smoke stops. i have put in correct plugs and wires checked cap. only codes are for o2 censor. also even though im sure it cant cause a miss but someone removed one of the cats other is still there.
thanks

 

Fuel injectors could be the problem for misfire. Before replacing the injectors you can test by swapping the injectors from right bank to the left bank. If you still have misfire you need to change the injectors. Oil problem can cause for blue smoke. Make sure that you change the oil every three months for best results.

 

If it's sucking in a lot of oil under vacuum (no load), it would cause the smoke. It could also cause the misfire, if the oil leak is severe.

How many miles are on the engine?

 

X2 it could also cause all the codes O2, ect.

 

I was reading some of yours guys help and im thinking "what oil problem" theni read my thread...lol aww should have proof read first. yea its black smoke that comes with the mis fire not blue.

 

it has 270xxx thats not bad is it? lol well short of no loadmis fire runs out very well. and as i say when you step into it it runs very good no miss

 

Your thread states blue smoke. If it it black, it probably is an injector issue.

 

What are the code numbers? It has to have a code in it due to the missing cat? Either P0420 or Po430 depending on which one is missing. You can not move the injectors around due to the fact the are in the intake and are and assembly. The injector assembly has been updated due to a known problem with them. Unless you "O2 codes" are for the heater circuit they are most likely seeing the problem (rich or lean) and are not the problem. Bad O2 sensor could cause a misfire if they read rich but the system truly not rich then the computer could pull back the fuel creating said misfire. Post the code numbers then we can go from there. 95% of the time on the 5.7 if the ignition system is working correctly then they have bad injectors.

 

Yea, if it's black smoke instead of blue...
I would be taking a close look at fuel management.

 

I changed it in the body of my thread but it wont let me edit the headewr. I was thinkin of one thing and typing another. next time I will pay more attention and proof read first.