2G Sometimes rough idle and sometimes not - Need help!

[Rydsei]

Sorry if this topic has been done to death, but I did search but mostly came up with 1G and not 2G for my problem

My car is 97 Eclipse GS 4G63 and I was wondering what you can can make out of this behaviour.

Rough Idle Problem:

Right, So I started the car this morning it had an horrible idle it would barely stay alive, i shut down the car immediately, waited a few good seconds and fired it up again, and that time the idle was all normal.

Drove around for couple of minutes to the supermarket, at this point the car temp had gone up quite a bit as expected due to the hot summer weather.

Got back to the car, I started the car once again, and noticed a slightly less rough idle, much less than before, did not bother much and drove away and it did not take long before the CEL came on. The car was pretty much driveable and normal except the stop and go part where the idle was rough. But at high speed, all normal.

I got back home and let the engine cool down, I unplugged the negative terminal of the battery to see if the CEL or ECU would "reset" and sure enough it did.

Cold started it again and the idle was all normal, no CEL. Makes me really wonder why it had such a rough idle that one time, is it random then?

Now the question is what can cause this? Is it a bad EGR valve or alternator? And am I expected for the same issue to occur again if I drive around and get it up in hot temperature? I have not driven it since this happened.

P.S all fuses are checked

Thanks in advance

 

[pieceofcloth]

Is there a specific reason why you wanted to see if the cell would reset?

The cell is your friend and is trying to help you, please dont dismiss your help/friend.

Could be fuel related because fuel having tough time reach engine. Once you accelerate, you are holding throttle to give it/for a fuel to engine. Fuel will stay in lines for a bit so at a store stop, fuel would still be near engine to startup again. Rough start in morning because it has to travel from fuel tank, thru fuel filter and it may have a rough time doing so w a dirty filter. When stopped at a sign, you're off throttle which decreases the flow so the travel will be rough again w foot off the accelerator.

Your alternator recharges your battery. Your battery is fine because it continues to start up. You should recieve a battery light if it is weak or alternator not charging.

I may be wrong because I dont know what our cell/friend is missing

 

[Rydsei]

Is there a specific reason why you wanted to see if the cell would reset?

The cell is your friend and is trying to help you, please dont dismiss your help/friend.

Could be fuel related because fuel having tough time reach engine. Once you accelerate, you are holding throttle to give it/for a fuel to engine. Fuel will stay in lines for a bit so at a store stop, fuel would still be near engine to startup again. Rough start in morning because it has to travel from fuel tank, thru fuel filter and it may have a rough time doing so w a dirty filter. When stopped at a sign, you're off throttle which decreases the flow so the travel will be rough again w foot off the accelerator.

Your alternator recharges your battery. Your battery is fine because it continues to start up. You should recieve a battery light if it is weak or alternator not charging.

I may be wrong because I dont know what our cell/friend is missing

Thank you for the reply, any help is appreciated. Yes you are right about the CEL, I guess I just wanted to see if it would return on the next drive.

You might be right about the fuel, no idea when the previous owner changed the fuel filter last time on the car, if ever. I've only owned this car since March so I still got a lot to get familiar with. But I will definitely check the fuel filter, sounds like a good cause to the problem.

But it could be the alternator still too no? Suffering from undervoltage for fuel pumps and sparks etc? Causing rough idle? Correct me if Im wrong.

I tried to scan the car with an OBD2 reader but I am only getting "Communication Failure with ECU" so I have no way knowing what that CEL is :/

 

[pieceofcloth]

Thank you for the reply, any help is appreciated. Yes you are right about the CEL, I guess I just wanted to see if it would return on the next drive.

You might be right about the fuel, no idea when the previous owner changed the fuel filter last time on the car, if ever. I've only owned this car since March so I still got a lot to get familiar with. But I will definitely check the fuel filter, sounds like a good cause to the problem.

But it could be the alternator still too no? Suffering from undervoltage for fuel pumps and sparks etc? Causing rough idle? Correct me if Im wrong.

I tried to scan the car with an OBD2 reader but I am only getting "Communication Failure with ECU" so I have no way knowing what that CEL is :/

Check the terminals are clean. check the cigarette lighter fuse. It is connected to the obd port and can cause obd port to not recieve info/work. Autozone can check alternator for free if you can get it there. There is a designated light for the battery voltage being low. Turn your key forward once & view your lights on your dash, you should see all them light up. If the battery/volatage light doesnt appear, the bulb may be out but you will know what to look for.

 

[Jk's97DSM]

You needed to read the code before resetting. It sounds like it’s related to heat. Did it get beyond operating temperature?

 

[Rydsei]

Check the terminals are clean. check the cigarette lighter fuse. It is connected to the obd port and can cause obd port to not recieve info/work. Autozone can check alternator for free if you can get it there. There is a designated light for the battery voltage being low. Turn your key forward once & view your lights on your dash, you should see all them light up. If the battery/volatage light doesnt appear, the bulb may be out but you will know what to look for.

Checked the cigarette fuse and its not blown

 

[Rydsei]

You needed to read the code before resetting. It sounds like it’s related to heat. Did it get beyond operating temperature?

Yeah I tried to read before I did the reset, would not let me communicate with ECU unfortunately.

And no, never went beyond operating temperature