Replaced head gasket and engine idles rough and has poor gas economy.
Check the firing order, The push rod has 2 differnent sizes for intake and exhaust, If they get switch you get the rough idle
SOURCE: I have a 1991 Buick Park Avenue. Runs rough in
Here are the common cause of surges, cold stalls, stalls at stops, slow idle speed, erratic idle speed, rough idle and engine hesitation (and other problems), it is in most cases the idle speed control air-bypass valve and or throttle valve and upper intake, these area's get full of gunk and combustion residue over the miles and cause idle issues (stalls, low idle) like yours.
To correct this problem I want you to get a can of intake cleaner (ABOUT $5.00) from any local auto parts store like NAPA or Carquest, do not use carburetor spray, intake cleaner only or u will damage the Teflon coating inside the throttle valve and air bypass valve, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake.
Testimonial: "Thank you, I'm sure if your advice it was I'm looking for. But at least if this works, it will save me a lot money from having to replace expensive sensors."
SOURCE: rough idle
fuel filters rarley cause idle problems. i would look at the egr valve or possible vaccume leaks.
SOURCE: Rough idle at start up
My 1997 lesabre has developed the same problem. I replaced plugs,wires,pcv valve and O2 sensor to no avail. Also tried several tanks of high octane. Yesterday I left the store and it wouldn't start at all. Had the car towed to a good local shop. Today they said it starts fine and has been all day! They checked everything they could think of and can find nothing wrong. The head mechanic suspects the crank sensor but said it should give a check engine lite if it was having a problem. Of course the third time I started it after picking it up the damn thing barely ran for a minute or so before finally smoothing out. No check eng lite. This is becoming very frustrating!
SOURCE: Rough idle,stalling,trouble code 41
might wanna have a fuel injetors checked
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