getting cel codes after UDP install

blackflame · Post by **blackflame** » Sat Sep 13, 2008 7:04 pm

So...I got the check engine light to stay on...pulled the codes. It was just blinking on and off at WOT. Now its staying on.

P0300 (M) Multiple Cylinder Mis-fire Misfire detected in mulitple cylinders
P1684 Battery Loss in the Last 50 Starts The battery has been disconnected within the last 50
starts

Is that P1684 code right? It doesn't seem right. I couldn't find anything higher than like 0800 in the haynes manual. I haven't Last time I disconnected my battery was a while ago and I never got a code from it.

Anyways, only came on at WOT. Now its stuck on all the time and you can definitely hear the engine missing. This is only after the UDP install. Does anyone know why its misfiring?

NickKo · Post by **NickKo** » Sat Sep 13, 2008 7:21 pm

Is this a 2002 Neon ?? That is the only model year to have a problem with triggering the CEL after installing a UDP.

However, it sounds like you have a real misfire, in this case ......
When was the last time you cleaned or replaced your spark plugs ?
How are the spark plug wires..... are they old, and need replacing ?

I had a misfire problem once, that was caused by one of the coil towers shorting / arcing voltage right through the insulator to one of the hold down screws ! (when it was damp and wet outside).

I capped off the hold-down screws with some vinyl caps, I have not had that problem since.

- Nick

blackflame · Post by **blackflame** » Sat Sep 13, 2008 11:28 pm

well the wires and plugs both have only
20k miles. This is a definite misfire. I can hear the clunking

. But yeah, its 2002. Maybe
thats why the light blinked when I was at WOT and only then. I wonder if this is somehow
related to me not having the PS/AC belt on.
I wouldn't think that would do anything. But
now that this is happening...idk. I mean
without that belt my car seems waaay quicker.
I wonder if I pushed it too hard and the engine
couldn't take it. I know neons can usually take
250wtq but...idk.

The worst thing is that I still got drive it. I'm pretty sure its knocking. I have never actually heard a car knock before. I'm go to go get a video and see if you guys can tell me.

Post by **Canada** » Sun Sep 14, 2008 12:08 am

'02 is a notorious year for triggering a CEL with an UDP.

It seems as if the knock sensor was a little more sensitive that year. Since your new UDP doesn't have the same dampening force your stock one has, the computer is reading this as a misfire.

As far as plugs go, go and buy some cheap Champion coppers and change them out every other oil change, they are so cheap and our Neons love them.

blackflame · Post by **blackflame** » Sun Sep 14, 2008 12:09 am

alright, here is a video. There was also this weird noise that sounded like it was coming right from where the belt is. There were just a few random clunks.

http://www.youtube.com/watch?v=uCwVJOXWSEU

Post by **racer12306** » Sun Sep 14, 2008 12:14 am

2002 Neons have problems with UDP's.

It happens above 5000rpm. The computer senses something, knock maybe, and kicks a code. It is what it is.

blackflame · Post by **blackflame** » Sun Sep 14, 2008 8:40 am

yes but this is below 5000 rpm now lol.

gilly02le · Post by **gilly02le** » Sun Sep 14, 2008 11:02 am

My 02 pops a code when i go over 5000rpm. No big deal, if you don't rip it for the next three drives you take, it will clear on its own.

Mine also does not misfire because of the UDP. It says its does, but it makes no odd noises, nor does it stop accelerating.

Who installed Your UDP?

excon · Post by **excon** » Sun Sep 14, 2008 4:02 pm

i know this sounds strange, but check your timing belt. My plymouth acclaim (see pic) jumped a tooth or so after WOT one day and then ran kinda funny... it felt like it wanted to cut off and felt like i was missing.

blackflame · Post by **blackflame** » Sun Sep 14, 2008 10:14 pm

I thought maybe timing. But here is the thing that is weird. I don't FEEL any misses. Don't you usually feel the car hesitate like you are letting up on the gas really fast? Every car that I have road in that had a miss did that. Not mine.

I have a new theory. I was doing some reading and I found that a guy thought his engine was knocking but it was just the tensioner for one of his belts. My PS/AC belt isn't on and that is leaving the tensioner loose and free. That may be it? When I turn right and the weight transfers to the left of the car the noise comes back. Unlike knocking would usualy be, the noise isn't always there. So, that tensioner, would that cause a cel?

I'm going to put a belt I have on tomorrow and see. The belt I need is 50" but the one I have is 49.5". Do you think it will be ok?