Vacuum line leak especially if it runs rough at idle. Bad spark plugs or plug wires.
Did you replace the fuel filter?
I get the gist of the question. Could be a plugged fuel filter or a plugged catalytic converter. Try the fuel filter first as it relatively cheap.
A method of making a rough measurement is: Estimation Answered by :PopTy13
The cabin air filter can not cause a rough idle. It only filters the air for the ac/heater.
The 1998 Blazer could have several problems causing rough idle. Check the air filter, fuel pressure, and EGR valve for a clog to look for the problem.
Depending on the make of the vehicle, it could be any number of things. It could be a plugged fuel filter, air filter, vacuum leak, ignition problems, etc.
there are several reasons it may run rough. since i don't know exactly what you mean by rough.... the transmission may be slipping under a load, you can check the fluid, if it is a dark reddish brown instead of just red, or has a burnt smell, it will need changing along with the associated filter. if it is making a noise but running fine the motor mount may be lose causing the fan to hit the shroud. you may also have a sensor problem but the engine light should come on for that. and finally it could be a fuel delivery problem, like the filter or pump. other problems could be internal engine problems but are unlikely with a vortec engine! hope this helps, maybe not tho!
Did they change the fuel filter and the air filter as well. Odds are they didn't replace the fuel filter as they're kind of a pain in the rear to get to.
A Ford Explorer that runs rough may be experiencing a clogged fuel filter, dirty air filter, or worn spark plugs. A proper tune-up can solve most problems associated with an engine running rough.
Low fuel pressure, clogged air filter or off timing can all cause rough running. There could be sensor issues or more serious engine internal problems.
I just changed fuel filter,pump,sparks plugs and wires on mine and it runs great!
There are several things that can cause your 2004 Chevrolet Trailblazer to idle rough. The most common causes are a dirty fuel filter or a dirty air filter.