2000 Neon 5 spd:

Engine light came on and I took it to Autozone and read the code which said a air/fuel fault. Meant it could be either: o2 sensor, spark plugs, MAF sensor...or? So i changed plugs and air filter. Light goes off, then comes back on a day later.

Take it to dealer. Says it's an air/fuel fault caused by 02 sensor. Great. $150 later they say it's fixed. Then a day later the light comes on again! What the heck? Any ideas?

I'm tired of taking it back to dealers and mechanics and getting charged an arm and a leg for them replacing part after after. I have a good mind to do my own trouble shooting parts replacement and save the labor.

One interesting thing I found when I changed plugs was that one of the 2 inner spark plugs was so corroded that you could not see any of the ceramic insulator! I've never seen anything that bad. The entire gap was nearly gone from built up black, carbon deposits. I'm talking the open space between the insulator and the edge of the sparkplug threaded wall (inner area) was filled up with corrosion or deposits. It was nasty. I thought that might have been the problem but apparently it wasn't. Something in me says it's a faulty coil that's causing the air/fuel fault and corroded the spark plug.

What do you think about that? And can I replace the coil that I believe was responsible? What's a good online parts source for that part? An online microfiche would be helpful if anyone has one.


I should note the plug wires are only a year old.

 

First thing... Neons have a MAP and not a MAF. Probably just a typo, but they are very different.

Are you sure they/you replaced the correct o2 sensor? What is the "P" code your car is throwing?

 

Deposits like this?

 

YES, that's exactly what my plug looked like!!! What causes this?

And how is a Map diff than a MAF? Do you mean like a computer map? Or does MAP stand for something?

The dealer replaced the down end 02 sensor, the one closer to the cat.

Here's the update: I'm currently in Colorado Springs after having driven from Fort Leonard Wood, MO to here in Colorado (end destination is SLC, UT) over the last day with my engine light on. My average mpg is about 25-26mpg. This down from the low 30's that I normally get.

I don't remember the exact code but I did just manage tonight to get a new o2 sensor for the one right out of the exhaust manifold so all the 02 sensors have been replaced. If the engine light comes on again and my mileage sucks I guess I'll keep searching.

 

Usually it is bad rings, causing super-excess blowby. You are getting the CEL for A/F because those cylinders are not burning the A/F mixture at all. I'd say re-ring, but if you are taking it all apart anyways, might as well freshen everything up. Did the dealer really not figure this out, or were the plugs changed beforehand?

I wouldn't worry about anymore sensors of any kind at the moment. Your actual engine most likely has a major problem. I would get a leakdown test done, and a compression test, especially if your plugs are looking like that to confirm the condition of the engine before you spend hundreds more on sensors.

 

Crap, POS Neon.
Yeah I changed the plugs before I took it to the dealer. I did however tell him what I found on the plugs as I figured it was related. My car doesn't burn excessive oil though, so wonder what's going on?

Apparently the service guy didn't pass it on to the mechanic or something? That's why I hate working with a shop where you don't actual talk to or know the mechanic. It's like chatting with the office receptionist at a doctors office about your problem and then you get to see the doctor but don't actually talk to him about what's wrong when he's examining you. Like a crap shoot.

 

That would **** up my week.... how long would it take for that to form on the Plugs?

 

I honestly don't know. These are the plugs that were pulled from the engine...gosh, about 1.5 years or so after we bought the vehicle? They were supposedly changed very recently before we bought it. If I had to guess, I'd say probably a couple of months to get that bad with an engine in as bad of shape as what they were pulled out of. What makes it harder to determine is that the plugs had rust on them. I change the plugs in my truck (that big brown thing in the pictures) probably once a year or so and I have never seen rust on them, or any plug I've ever changed on any vehicle for that matter, so who knows? The people we bought it from weren't that honest about some other things anyways which adds to the uncertainty.

 

One more engine question my mom had a upper version of this car a few years back I rememberer it making alot of engine noise. Now the one i have makes a similar noise. Is this Normal?

It just sounds like s slight knocking and IMHO seems to completely go away above 4k rpm's

Now,what would be easiest way to determine if had a bad bearing or if it's reallly knocking. I have No CEL. but it just seems louder than i rememberer.

I also changed plugs and wire plugs looked normally worn but otherwise fine.

 

The Neon engines make noise. Some do, some don't, some do at certain times. Dodge calls it spark knock. Others say it's the oil pump. I've never noticed mine make a knocking noise.