Ever since I got this car it's had problems idling properly. I've gone through everything from stalling, stuttering to the engine down right shaking.

Cleaning the throttle body (it was disgusting) and the EGR valve (gunked and not 100% closed) fixed most of the problems. I no longer have any issues with stalling and it doesn't idle rough anymore.

However it still has 2 problems. The first one being that it idles at 1000-1200 instead of 750-800. A lot of times its stable at 1000 but occasionally it likes to twitch.
Second "problem" may help diagnose it. Basically when your stopped or in park if you hit the gas, say to 4k. As soon as you take your foot of the gas it drops quickly (like normal) until about 1.6k at which point it practically stops and slowly crawls back down to 1k (takes about 20-30 seconds).

I took the IAC off today thinking that may fix it. Both the motor and the valve we're pretty dirty so I gave them a good cleaning. Before reinstalling it I tested the resistance and got a steady 52.8 on pins 1-4 and 53.2 on the other pins (pins 2-3 I believe). The engine was not warmed up and it was about 48 degrees out. That being said I believe thats still within specs.

But even after cleaning it the problem still persists.
I do have a CEL, I had a mechanic scan it a while back (when I knew about 2% of what I know about cars now) and he said "it's probably an O2 sensor". It's also worth noting that I believe I have a bad head gasket, although I'm uncertain if that would contribute to this.

Originally posted by Darkrocker
I do have a CEL, I had a mechanic scan it a while back (when I knew about 2% of what I know about cars now) and he said "it's probably an O2 sensor". It's also worth noting that I believe I have a bad head gasket, although I'm uncertain if that would contribute to this.

Hit up Autozone or Advance for free cel pull (or you could do the keydance depending on what year Eclipse you have) and give us that info. I suspect that will be helpful.

Cant make it there tonight but I have a 97 so the "keydance" should work. I've heard it mentioned before but never knew what it meant until now. I'll go give it a shot.

Ok did it a couple times and here's what I got.

12 pause 21 pause 55 (55=done, correct?)

I'm going to look it up and edit it into this post when i find it.

Edit 1: ok 55 is end of codes and 12 is basically because I just reset my ECU when I had my battery out earlier today. Still trying to find the "21" code, sadly the list on this site that everyone links to is down.

Edit 2: Alright correct me if I'm wrong since this is taken from a neon forum but I believe code 21 can mean any of 10 codes. All O2 sensor related, although 5 are for the upstream and 5 are for the downstream. Regardless at least one of my O2 sensors has to be shot, figured.

According to this list a 21 error code is a #1 injector control circuit fault.

Originally posted by Darkrocker
Ok did it a couple times and here's what I got. 12 pause 21 pause 55 (55=done, correct?)

Nice work. Makes it so much easier.

Originally posted by Darkrocker
Regardless at least one of my O2 sensors has to be shot, figured.

Yup, change out your front O2. That should get you in there. If that doesn't do it, then check out your TPS. That can sometimes cause suspicious activity.

And what makes you say you have a bad headgasket?

Originally posted by bullettdsm

Originally posted by Darkrocker Ok did it a couple times and here's what I got. 12 pause 21 pause 55 (55=done, correct?)

Nice work. Makes it so much easier.

Originally posted by Darkrocker Regardless at least one of my O2 sensors has to be shot, figured.

Yup, change out your front O2. That should get you in there. If that doesn't do it, then check out your TPS. That can sometimes cause suspicious activity. And what makes you say you have a bad headgasket?

Do you know the resistance/pin out on the front O2 sensor so I can test it? (or know where I can find the info).

As for the headgasket. For a while the car was burning oil, exhaust was smoking quiet a bit. Some Stop Smoke put a band aid on it for now. But recently I started to burn coolant as well, I don't have any leaks, and I'm getting that lovely white exhaust/moisture every once and awhile. I figured the car burning oil for an extended period of time is what contributed to the death of the O2 sensor.

Originally posted by bullettdsm

Originally posted by Darkrocker I do have a CEL, I had a mechanic scan it a while back (when I knew about 2% of what I know about cars now) and he said "it's probably an O2 sensor". It's also worth noting that I believe I have a bad head gasket, although I'm uncertain if that would contribute to this.

Hit up Autozone or Advance for free cel pull (or you could do the keydance depending on what year Eclipse you have) and give us that info. I suspect that will be helpful.

What year did they disable the keydance, anyway? I know it worked on my 95 (when it was still running on that garbage stock ECU ;) ) but I tried it on my 99 Avenger and it didnt work.

Not sure what year they disabled it, but it worked fine in my 97.

Also I could be wrong but I believe that list is for the Scan tool codes. I've seen to very different lists and the one I got that info from specifies it's for the keydance. I'm hoping someone will chime in that's familiar with these codes.

I am having same problem with my eclipse. My problem is basically what your having with your eclipse. I did the key dance and got back my egr was bad. But i have the same issue with my eclipse with the idling and stalling. I have no idea on how to fix it. I will be cleaning the egr and throttle body this weekend to hopefully fix this idling and stalling issue. If you fix it please list what you did.

If you read my first post you'll see that the stalling and shaking we're problems I had previously. I fixed them by doing what your thinking about doing, cleaning the EGR and the TB. But if your EGR is giving you a CEL cleaning it might not be enough. It will probably still help but your EGR solenoid might be bad and that could be giving you the CEL.

Originally posted by Darkrocker
Also I could be wrong but I believe that list is for the Scan tool codes.

Yeah, I was looking at the 1st column. The 3rd column lists the keydance codes. Front O2 it is.

I was having an idle issue for the longest time. I changed out everything from intake gaskets to complete fuel rail to no avail. Took the car to get it painted and the guy doing the paint just happened to be a really good mechanic and mentioned that it was a vacuum leak. Told me to spray carb cleaner or throttle body cleaner on the lines to find it. I did and it was the vacuum line that goes to the fuel rail ( It's a 95'). Problem no longer exists.

Sounds like it's at least worth a shot. I'll give it a quick try today and if I don't find anything I'll really look at all the hoses tomorrow when I have more time.

I got the time to give it all a good look over today. Checked plenty of my hoses and fittings, gave everything a good spraying of TB cleaner, no sign of any vacuum leak.

Does it only have those symptoms at idle? Does it smooth out while driving and revving to a higher rpm or do it throughout all rpm range or only do it at certain rpms?

It's only at idle. After it's been warmed up for a bit the idle drops down to close to normal range (about 900). But no matter how warmed up it is I still have the problem with it bogging down around 1600-1000 rpm. It seems like something that would be caused by the IAC but the resistance was within spec. A new IAC is only $20 anyway so I might try that out soon for the hell of it.