So, I bought this 01 2.4 4cyl. stratus with 60k miles on it a few months ago, it had been sitting for over a year, so I drove it a bit then changed the oil-oil filter, air filter, trans oil/filter, brand new spark plugs, and gave it a kiss.

drove it for about 1k miles and was kinda upset that i was only getting 19mpg average. that's with about 70% highway at 55-60mph (live in hawaii) and 30% city.

not happy, needles to say. then i heard that maybe it needed hotter plugs, (check engine light kept going on). no problem, got faster firing plugs, check engine light rarely comes on now, but mpg's only went up by about 1-2.

so, can anyone tell me what the problem might be? I should be getting over 20 mpg's no?

 

Well I have a 99, but it's also a 2.4L 4cyl. I average about 20-23mpg. The truth is, there are a lot of different things that could improve or hinder your gas mileage. Could be anything from worn tires to just having your A/C running. It doesn't necessarily have to be a mechanical problem. When a car is advertised as having '20mpg' that's a best case scenario. If you're only getting 19, I don't think it's THAT big of a problem. If you were getting 5mpg, THEN you might need to make a few phone calls

 

It sounds like you did a great job with maintenance, glad you didn't have problems after letting it sit. Don't forget to check your tire pressure, the correct pressure will be on the sticker on the drivers side door.

You should never ignore the check engine light. It can get expensive if you do (trust me). Most auto parts stores will read the codes for free, and tell you if you can afford to wait or if you need to get it fixed before it causes more problems. High fuel consumption can be caused by problems with the emissions system or the fuel injection system, and both could cause a check engine light.

Remember also that if you drive in areas with a lot of hills, it will be nearly impossible to get the factory mpg. They test that in optimum conditions, flat roads, no wind, windows up, AC off, etc.

Good luck!

 

Could be an Oxygen Sensor keeping you in a rich mode.

 

Yeah, update, I'm back to 19 mpg's with these plugs, I got Halo plugs that are supposed to fire faster, meh, its the same as the cheap auto-light plugs as far as I can tell. maybe it runs a little smoother but i could be hallucinating.

Guys, tire pressure, oil, gas, tires, it's all fine. Heck, i even waxed the car which should give it more of a gliding effect in the air causing time to travel backwards. joke. But that's all fine, something else is weird here. I used to have a '99 stratus with the same engine, under harsher driving conditions i was still averaging 25 mpgs with it.

Anyway, my code is P0601 which is an "internal control module memory check sum error". I guess that COULD be the culprit, but i like to ignore technology as long as i can before i acknowledge it. besides, it would mean replacing the ecm/pcm

If it's the O2 sensor, how can i test that?

 

Bad 02 sensor usually throws a fault code. I haven't seen this in quite some time, but they used to recommend the O2 sensors be changed every 60KM. A quick check is to look into the end of the tailpipe. If is black, it usually indicates you are running rich. The claim is that it should be a chalky brown/dark tan.

 

Bummer, its not black at all back there. More of a chalky brown, and not much of it at that.
Alright, well, I guess I'm forced to change the pcm/ecm, a couple of weeks and $200 later I will update.

 

That P0601 can possibly inhibit the PCM from generating a code. When you put the new one on, don't be surprised if you get one for something else.

Just use Champion copper plugs.