I performed an upper intake cleaning a few weeks back to try to help with my pinging issues under WOT boost. I performed the cleaning through the pcv hose, got a lot of black smoke as usual. After the service I noticed the DSC light flashing?? Car went dead, I waited, started it back up and ever since I have noticed a severe misfire between 4000 and 6000rpms. Seems to be one big mis and thats it, just a big hesitation. The mis is most prevelant in 2nd through 4th gear, but it sometimes occurs in 6th after a long stretch of hwy driving and I nail it. Any thoughts on this 1 guys? I have new iridiums, I re-gapped them, 93octane fuel always........PLEASE HELP.......

 

Could have a piece of carbon one of the plug electrodes or stuck somewhere in the combustion chamber.

Did you inadvertently hit a plug wire, knocking it loose?

Were the plugs new before or after the "cleaning"?

Personally, ( please keep this as my opinion ) I like to run Marvel Mys Oil through the tank every 7k to 10k miles. Usually two full quarts in a tank. This keeps everything clean and running smoothly and is not as "harsh" as the "injection method".

 

If I have carbon it's not on the electrode, I have pulled the plugs 3 times to check the gap. I am baffled as to the problem................

 

What did you use to clean it? Also, remember the PCV goes to the SC. It may be residual. Some is left over in the SC and intake tract.

 

Just because the gap is good doesn't mean the plug is. I'm wondering the same thing as thatatvguy, did you change plugs before or after?
If you have known good plugs in there, make sure the plug wires are on all the way.

 

Plugs were changed afterwards, I even changed wires, guys it almost feels like the coil-pack is running out of fire? I'm stumped............... Remember the service was done over a month ago..........

 

Are you getting any fault codes?

 

Could be, but I'd go for a dud plug out of the box. It does happen - not often, but....
Or maybe a wire. You could always put the old plugs back in j/k

 

No codes, just a big ole stumble, 4-6000rpm, wonder why the DSC light illuminated briefly after the cleaning?

 

i would get ses and dsc on misfires . it was my coil .

 

Hmmm, DSC most always has to do with a wheel speed inconsistency. ( ie. slip ) I've seen this on an '07 when you get to going like mad. It's unexplained, but there nonetheless. Prob a sensor on the '07 b/c it's easy to reproduce.

I meant to include that if you accelerated at an increased rate after the cleaning and had the stumble it may have caused a surge in power enough to cause the DSC / slip. Just a thought.

 

Ok I may be a bit of a newb here, but to clean the upper intake did you remove any of the boost booties, etc.? If so you likely have a vacuum leak. That will then cause the problems you describe.

Good luck and keep us posted!