My Neon needs a bit of work, struts, evaporative line...but it's paid off!

Well, it threw me for a loop yesterday. I took a light rather fast and, when I'd finally straightened out and began to accelerate, the car began to drop to idle. It didn't die, didn't run rough, it just dropped to idle. I finally turned into a parking lot.

Each time I'd press on the accelerator, the car would run up to about 2400 RPM and then drop to idle, then run back up to 2400 RPM, over again. It was quite strange, like some rev limiter gone awry. If I'd thought of it, I'd have taken a video with my phone and posted it on YouTube.

So, I work with servers - you know how to fix a Windows machine, right? REBOOT! I turned the car off and started it again, and it ran just fine! I didn't look for a code (my check engine light is already on for the evap line).

Anyone have similar experiences?

 

Just because the CEL is one for one code, doesn't mean there can't be anymore stored.

 

I didn't make that clear, sorry. I meant since the check engine light was already on, it didn't hit me to check for any new code. My mind was focused on trying to get the car to run correctly, diagnostic codes was waaaaay off my mind. Had the CEL been off all this time and then turned on when it started acting up, I probably would have checked for a code.

 

Have you since looked for a code then?

 

Managed to get a video after this happened again yesterday:
http://www.youtube.com/watch?v=qiqH4zawarU
While the engine drops from ~2400 down to idle and back up, I had the pedal in the same spot.

I did look for codes and got between 5 and 7 of them, but on the side of the road I didn't capture them all. The ones I remember:
P0442 - EVAP
P0440 - also EVAP - I've already changed my gas cap, no joy.
P0137 - O2 sensor - I have them, just need to change them.
I believe P0356 - ignition coil - if memory is correct, it makes a bit of sense. The last set of plugs were ashy white and weren't more than a few months old.

Next event, I'll capture the codes in full.

 

That's not a rev limiter problem, that's an idle quality problem. Vacuum leaks will cause that to happen, and can also cause EVAP codes. Check the PCV line and such in the engine bay. The hoses coming off of the carbon canister (black box looking thing under the car, in front of the RR wheel) will crack and cause EVAP codes too. Somewhere to start looking anyways...

 

Well, it clears up when I restart the car. If what you say is true, then it's causing the computer to randomly go crazy. It could be a culmination of all that junk, too. OK, time to start picking over the hoses.

 

Had another event yesterday so I now have the codes.
P0442
P0456 - pretty good writeup on this, http://forum.2gn.org/viewtopic.php?t=28793&highlight=
P0440
P0137
P0340

I have a sneaky suspicion whatever is throwing the last code is causing the car to freak out.

 

The hose(s) in that write up are the ones I mentioned: the ones coming off of the carbon canister. The user "darthroush" in that thread is me. Silicone fixed mine up just fine and I've not had that code since.

That last code will cause all sorts of problems...
Usually, it is the sensor, but it can be other things.

 

Good stuff! Good to know. About the last code, there was at least one person saying it can be the wiring and not to replace *just* the sensor. I'll take that to heart. Thanks! I'll update this thread once I get some fixes in place.