Idle problems on a 1998 1.3GLXi Kia Pride

[mtristan]

Hi,

My girlfriend's Kia Pride is starting to get on our nerves.

The problems started a few months ago, after stopping the car for a few minutes, it wouldn't start again and my girlfriend says smoke came out of the engine bay, on the passenger side. She isn't interested at all in mechanics, so she didn't look at it and just prayed it wasn't catching fire
A few hours later it started "correctly".

Since then, the idle has been really problematic : Once warmed up (cold idle is OK), it will randomly misfire, but only when idling. Sometimes this misfire is so strong the engine stalls, typically at a red light or a stop sign.
So the only way to prevent it from misfiring (and thus from stopping) is to press the gas pedal a little, which is quite annoying. Sometimes the misfiring are so bad it will stall after idling only for a few seconds.
There is no problem for restarting the engine, but the misfires come back right away...
It also sometimes misfires around 2000RPM, but it's not frequent at all.

We've replaced the distributor, spark plugs, and the air filter.
I have no idea where the smoke could have come from, and what is causing the problem...

I've tested unplugging each spark plug separately, to check if it was only one cylinder causing the problem, but it didn't change anything.
The battery seems fine, I didn't try to test with another one, because this one is fairly recent, I've tried doubling the ground wires in case one was faulty... Nothing new.

I could maybe try to set the idle higher, but that doesn't fix the problem...

Now, the fuel filter seems to be as old as the car (1998, around 180000km), and I know that's a bad thing. But she doesn't want to spend money (yup, we're students, 25€ is not nothing...) on this if the problem comes from something more critical.

I was thinking maybe a relay could cause this? like a faulty soldering... But I don't know how to reach them on that car in order to look inside...

If you have any idea, it would be really appreciated. I've been searching the Internet for days, and nothing comes up...

Also, if someone knows how to retrieve codes, I'd like to know. Because the car has a diagnosis plug but no CEL (so I don't know if there is a code...), and I don't own a diagnosis tool...

Thank you very much (and sorry for the length of this message...),
Tristan

[thes]

it will one of your tps sensors,check the hoses for any splits...fuel filters cheap here uk £4.00 mikayo..re first tps sensor number t3-90323839 just 2 screws hold connecter.the other bolted bulkehead,1 10mm,than 8mm to remover sensor,

[mtristan]

Thanks for the reply
I tried to unplug the TPS, it didn't change anything, only caused the RPMs to drop when I accelerated, then the engine would rev normally.

[mtristan]

Hi,
Tried to reset the ECU by unplugging the battery for half an hour, nothing changed.
I will try to get a little video

[mtristan]

Here is the video : https://www.youtube.com/watch?v=T2GHqftpxK0
I tried to stabilize the engine around 2000RPM to show that it was OK when not in IDLE, but doing so I realized I could feel some little bumps in the pedal, not sure if it's linked though...

[thes]

still say you should check air manifold pressure /map sensor,,,,also temp which goes into air filter box,...

[mtristan]

I tried to unplug the temp sensor on the air filter box, didn't change anything either :/
However, I don't know how to check the MAP sensor, can anyone tell me how to test it?
Thanks

[mtristan]

Hi, I'm just bringing some news :
I used a stethoscope to listen to the injectors, and I found out that when the engine misfires, the injector which is the furthest from the belts doesn't click. It's the only one that doesn't work correctly, so I will try to replace it and check if the engine runs better.
I couldn't find any for sale on the internet, does anyone here know the reference, or on which other cars/engines they've been used?
Thanks

[Movin]

Check the connector for corrosion?

[mtristan]

Yep, I'm going to try that during the week. Could it come from something upstream? If so I'll try to use a test light and check if it lights up regularly.

[Movin]

If you want to try something you can wiggle the connectors while the car is running. You would want to associate a change in running with your wiggling to prove a fault. Otherwise just look at or inspect the connectors.

Could the running problem come from something upstream? Yes but would likely be the crisp digital on and off becoming less crisp, visually a lab scope would show more of a round shape instead of the box shape that a good system has. This can occur on one or more injectors.

Farther upstream input data from sensors could have an error coming from one. This can be complicated as one sensor can cause enough change in the way an engine runs to make other sensors read outside of the normal values. This kind of problem causes the length of time the injector is turned on to be incorrect to properly run the engine. This type of problem also tends to affect all injectors equally.

When using a test light on the injector the incandescent type is hard to read, it really just tells you power and ground are working. A LED test light is fast enough to show the on and off and may even indicate differences between cylinders.

[mtristan]

Great, thank you very much for your answer. I'll check that when I get a moment