Backfiring, Loss of Power, and Check Engine Light - what's up?

[xboxizdope]

I think I posted a topic about this a while back, but I couldn't find the thread and the problems have worsened since. Before I got a couple backfires, but now it's becoming an issue every day.

The first problem I noticed was the loss of power when stepping on the gas from a stop, or after slowing down. The engine also sometimes would run rough when idling after a cold start, however it seems to idle okay right now, the main issues are the loss of power, and now many times I get a backfire while I'm losing power and have the gas down. My natural reaction is to slowly pump the gas when losing power, I don't know if that really helps, but I will definitely get a backfire if I floor it while the car is losing power.

Tonight after getting off work I was driving home, and I got on a freeway interchange behind a truck so I had to slow down to about 30mph, once I could merge onto the freeway I accelerated only, as usual, lost some power. However, I lost a lot more than ever before. I was going so slow that the slow truck in front of me was actually going faster than me, and I couldn't even change lanes because I was stuck at about 40-50mph with the car sputtering as if I was low on gas, or the engine was flooded. When this happened the check engine light came on, and ever after the car went back to normal the light stayed on for the rest of the trip. There have been a couple other times when the light came on, but it turned off as soon as the car started driving normally again.

I've searched around on these forums but I really have no clue what the problem could be, I was wondering if maybe it's the timing belt because I don't think it has ever been changed before and it has about 85000 miles on it. I did recently change the spark plugs, and it seemed to fix my problems for a week, but now it's back to where I was before only the problems seem to only be getting worse day by day.

I just hope I can hold out on fixing it for about 2 weeks, because I won't have the money until then. I know if it's the timing belt I really don't want to let that go, so I hope that's not the problem!

Any advice would be greatly appreciated, as well as what to look for when checking parts of my car. I'm not much of a mechanic so unless it's braindead easy I'll be having it fixed at a shop.

Car info:
2000 Dodge Neon (Highline)
Automatic
85000 miles
Recently replaced spark plugs, but not the wires
Air filter probably needs changed
Had transmission fluid changed last summer
I also drive about 75 miles every day to and from work, so in a week probably about 400 miles

[2000neon]

check your engine codes
i had to replace my wires and plugs now runs better than the day i got it

[xboxizdope]

how do you do that? I don't have any diagnostic tools or anything

[rice_eater]

Turn your key ON-OFF-ON-OFF-ON, within 5 seconds. Do not start the car, just turn the key to the on position. The CEL (check engine light) will flash out a series of two-digit codes. It will flash a number of times (thats the first digit), then there will be a 2-3 second pause, then it will flash another number of times (thats the second digit in the number). Then there will be roughly a 4-5 second pause and the CEL will begin to flash again, this is the first digit in the next two digit code. The process repeats itself until all current trouble codes have been relayed, after which you'll get code 55 (that is 5 flashes, short pause, 5 flashes), which is "end of transmission" code. Translations for the codes can be found in the Neon/SX General Talk section or just let us know which codes you got and then we can help you from there.

You're timing belt is not the cause of your problems, but I would get it fixed soon if I were you. If it breaks, your valves will drop, colliding with the pistons ruining your valvetrain and possibly your head and pistons, depending on how fast you are going when it happens. (this pretty much means your engine is shot) Timing belts should be changed ever 60k-80k miles, if i remember right, although some people chance it and wait until 90k or even 100k (NOT a smart thing to do). While you get the belt changed, go ahead and and have the water pump changed as well. If the water pump seizes up, it has the same results as a broken timing belt. (water pumps also recommended to be changed around 80k miles i believe) Expect a $600-$800 bill if you get it done at a garage.

[xboxizdope]

Thanks, I'll try that in the morning, however the check engine light didn't come on earlier today so I'm wondering if I'll even get an error code now or if I have to wait for that check engine light to come up. It usually only comes on while driving and loosing power, but usually turns off after the car picks back up again.

Either way I hope I'll get some code so I can figure out the problem, but I think the AIT sensor is dirty so I'll try cleaning that up tomorrow and see what happens. I'm thinking maybe because I let my air filter go so long being so dirty that it gunked up the sensor or something....I dunno I'll play with it tomorrow

Oh and I'm glad you don't think it's my timing belt, because I don't have the money for that right now but will in about 2 weeks so that's definitly one of the top things on my list....I'll also ask about the water pump, thanks because I wouldn't have even thought about that! I changed bids at my job to something that pays much better, so I really can't wait to get some work that's been badly needed on my car! Even though I hate automatics, this neon has been good to me and I want to get it back to tip top shape!

[RadarLove]

Autozone will also pull codes for free, and those are the 4-digit codes which give a little more detail. Even if the CEL clears, the code should still be stored in the PCM's memory.

There are so many things it could be. Having the CEL turn off while driving is kind of odd... Makes me wonder if it isn't just the cam sensor. Hmmm... codes will tell better though.

The recommended interval for the timing belt and water pump is 105k miles, but I personally wouldn't go much past 85-90k ever again... They should both be done at the same time, along with any of the timing belt parts (tensioner, etc.) that may seem wiggly in the least.

Best of luck!

[2000neon]

when i had the problem with wires and plugs the CEL went out also
cant remember what code was but it said something like cyl 2 misfire
and new plugs and wires and all fixed better than ever
oh yea no Platinum plugs found that out the hard way

[xboxizdope]

you know what, when I changed my plugs I think I did opt for Platinum, could that be my problem? The car ran great for about a week then the same problems I had before came back, only as I said it seems like they are getting worse now. Why are platinum plugs not a good idea? What would be the best plugs to get? Also what about wires since I should change those also.

Oh and I tried getting the error codes, but instead of the check engine light blinking I had 2 4 digit numbers come straight off the speedometer. These are the codes I got, I googled what they mean and here is what I got: (click here for the code page I used) (http://www.allpar.com/fix/computer-codes.html)
P-1684: Driver 5 Line 4
P-0302: Cylinder 2 Misfire Detected

Does anybody know what the first code means? And which Cylinder is 2?

[xboxizdope]

Oh I found a more detailed code page with even more codes in case anybody needs them. Maybe someone can add them to the sticky thread since the current one didn't have the codes I needed, and it also has many more codes.

Diagnostic Trouble Codes (http://www.hptuners.com/dtcs.htm)

[2000neon]

i was told by more than one machanic to get factory plugs (champion)
and never to go back to platinum
and i wont

this was the code i had

P0302 Cylinder 2 Misfire Detected

[xboxizdope]

thanks, I'll swap those out then, anyone know what the other code might mean; P-1684: Driver 5 Line 4?

[RadarLove]

P1684 is just the same thing as "12", which means the battery has been disconnected within the last 50 run cycles.

Single cylinder misfires are typically from a bad plug or a bad wire. New plugs may help. You can swap the #2 and #3 wires to see if the problem jumps to the #3 cylinder, and then get a set of new wires if it does... A clogged injector could do the same thing (theoretically), so if the wires seem to be good, try swapping the #2 injector with another, and make sure the seals on there are in good condition. If the problem still doesn't move, it's not the injector... A sticking or bent valve, or a seriously worn valve guide could also be an issue. You could also have a serious vaccuum or exhaust leak right at that cylinder's inlet/outlet port, but you'd probably see major idle issues, among other things, so we'll tackle that if it gets to that point...

Looking at the motor from the front of the car, the cylinders go 1 - 2 - 3 - 4, left to right. Should be marked on your coilpack as well, just follow the wires.

[xboxizdope]

You could also have a serious vaccuum or exhaust leak right at that cylinder's inlet/outlet port, but you'd probably see major idle issues,
Sometimes it does idle pretty rough, it stalled on me once after I put it in reverse to leave my work, but it's usually only on cold starts. Once it warms up it usually idles like normal. I'll change the plugs and maybe the wires too and see what happens, I just won't be able to do that till next weekend so hopefully nothing happens till then ::crosses fingers::

[2000neon]

i got plugs and wire for under 50 bucks
try that and see it wont hurt even if thats not the true problem but it was for mine