2001 merc cougar engine sputtering

I have a 2001 Mercury Cougar 2.5l v6 with 142,000 miles. If I’m in idle, you can feel it discordantly kind of jumping. Guessing it’s coming from the engine. When I accelerate, normally from 35-45 mph the engine sputters and is very jerky but then accelerates as normal. I am going through gas more than before. I’ve replaced the spark plugs and wires and it hasn’t fixed. It runs worse when my AC is on, guessing because it’s more stress on the engine. don’t know if it’s relevant but I have a signal on my dashboard that shows how many miles I have left to drive with the amount of gas I currently have - and it’s become way off, is totally inaccurate now. I also know I need an oil change. Don’t know a whole lot about cars, but I can’t afford to have my car become out of commission. Anyone have any ideas as to what the problem would be? the last mechanic I saw said it needs a tune up, but it was expensive so I’ve been trying things myself first. Thanks.

Most auto parts stores will use a code reader to get any codes from the computer and they will do this free.
Write down the codes and return here and post them. They will be in the form (PO123, PO456, etc… Don’t let them sell you parts based on the codes until you list them and we can offer suggestions.

Did you replace the wires yourself ???

If so, you may not have pushed one of the wires down onto a spark plug or the distributor cap enough. You could also have mixed up two wires and have them on the wrong spot on the distributor cap. It’s easy to do.
The auto parts store may also be able to give you a print out of the wiring so you can recheck that.


Is the check engine light on? I ask b/c the symptoms sound like a misfire, and the CEL will often come on then. Sometimes intermittent misfires won’t turn on the CEL though, but often a diagnostic code (dtc) will still be posted in ECM memory, so the advice above about checking dtc’s is spot on. That’s the first place to start. Post any codes you find here.

There’s a dozen or more things that can cause this symptom. The best plan is to pay for a proper diagnosis, then if you like you can fix it yourself. If you want to go it alone, if I had this problem I’d replace the engine air filter if it hasn’t been recently replaced, inspect all the ignition components, spark plug wires, coils or coil packs etc, for anything amiss, do a thorough check of the vacuum system and vacuum operated devices, looking for any air leaks that allow unmetered air into the engine, probably measure the battery voltage in conditions when the engine is running poorly. If you feel lucky, use a hand held vacuum pump to check to see if the brake vacuum booster has sprung a vacuum leak.

You say you know little about cars, yet YOU replaced the plugs and wires. IIRC one has to remove the intake manifold to get to the back three plugs in the Cougar Duratech 2.5L V-6. My guess is you don’t have one of those rear wires all the way onto its plug, or one is installed wrong. Did you replace the intake manifold gasket? It could be leaking. I don’t think you can mix them up at the spark plug end due to length, but you could at the coil pack end. SOME coil packs are labeled as to which cylinder each wire goes to. Check that out.

Your fuel mileage to empty is probably correct. You’re running on less than six cylinders. The computer knows that. OF COURSE your MPG is way off.