This car has been nothing but trouble since I bought it 3 years ago (bought it new....and now its at 42,600 miles). Anyways, the mileage was slipping (use to get 30 miles to the gallon). Then slowly it started getting less and less.....till finally it only got 20 to the gallon (but didn't give me a trouble code during this time). Well it finally spit out a trouble code P0300 (mis-fire on all cylinders). I checked the various forums and pretty much the standard issue was the coil pack, wires and plugs. Alright....changed those out (screaming demon coil pack, crane wires and their recommended plugs). Still no luck shutting off that light.....but the gas mileage went up a little. Well, started feeding the little bugger some fuel injection cleaner at every fill-up and the mileage is up to 27 to 28 a gallon.....but it still runs bad (and its shouldn't need cleaner at every fill-up). While I'm at idle it will run rough (it vibrates pretty bad) and will cause the already lit check engine light to blink until I'm going again. I don't have any problems while at speed.....just at idle. It appears that its running pretty rich....due to being able to smell gas at start ups and black soot on the exhaust tips. Also, I don't know if this may help.....but it appears to have a weird sound at start-ups (sounds like a tapping sound similar to an exhaust leak). It already has the standard neon "rod knock" but this is a different sound then that. Also, on occasion it has thrown a P0302 trouble code (kind of scratching my head on that one). I'm starting to think that I have either a dying MAP sensor, a glitching cam/crank position sensor or maybe the TPS.....or maybe a clogged cat ((but nothing is making sense here)). I can't seem to figure this out.....and I've used the search function (thats what got me to replace the coil, wires and plugs originally). To top it all off the sensors are parts that are not available at local parts places (special order only). So, it appears that I'm stuck heading off to the stealership on this one (I may have them do a diagnostic.....but that last time they did that with my truck they couldn't pin-point the problem.....turned out to be a $6 gasket and about 20 minutes of snooping around with a mirror to find the problem). Anyways, any help on this would be great......the car is a 2004 SXT and it has a manual trans.

 

You have a powertrain warranty let them fix it. Sounds as if you may have a stuck IAC or EGR and also maybe an exhaust leak. They need to fix it. If you have your original coil I'd put that back on and maybe some good 'Ol Champion plugs and let them figure it out. If it is under warranty then they can figure it out for you and if they just shrug their shoulders recommend they send it to a dealer with a good technician that can fix it for them. You have at lest one valid code.

If you still want to look further before going in just remove your belts for a minute and see how it runs that would eliminate your accesories from being the issue. After that also make you have clean oil and air filter as well. Take your intake off and clean your throttlebody and as much of your IAC passages as possible.

Would not think clogged cats as you would have no power going down the road. But sensors should show up on a scan tool (Not just a code reader) or from background knowledge of the products.

Let them know you have Codes P0300 and P0302 and what you have tried and it still idles like CRAPOLA! they should fix it.

 

Well spent a good hour cleaning the throttle body (every part I could....even removed the sensors so I could really get it spotless), and as much of the intake and the tube between the 2 as possible. Put it all back together and no more light!!!!! I couldn't believe it.....so I took it for a....shall we say...spirited drive and nothing! Better still the idle was perfect....but it does look like I have a bad engine mount after all (engine rocks pretty bad). Funny thing is that there wasn't that much crud in the TB at all. Just a very thin line of sludge around the plate as well as on it.....not what I was expecting. Also, found a very sizeable puddle of oil in the intake (so its time for an oil catch can)....needless to say I was surprised. Thank you ewetho for the assist.