Need help diagnosing engine running rough

[SalvadorP]

Originally Posted by 360beast

Mine is the exact same in that it seems to forget the 850rpm idle after the 1st stop, but I've found if I stop for about 5 seconds it will go back down to 850 and stay there from then on.

The issue is that mine doesn't. It takes like 30 mins to 1h of riding it for it to "normalize". The other day it was doing it. I then parked at the shopping mall, when to eat and when I came back to the car not long after, it was idling normal. Well, it has a misfire, but that's another issue. What I mean by normal is that it was back at 900.

[SalvadorP]

https://www.youtube.com/watch?v=2yKp-ATW23k
I decided to try to unplug the IAC valve while idling. I read conflicting info on what is supposed to happen/not happen when you do so. So I'm not sure whether or not this means that something can be wrong with it. I guess if there is something wrong in regards to the IAC it could also be a fuse right?
Today I ran the car to shoot this video, it was already afternoon and it hasn't been raining. The car idled at 900, granted, with the misfire, but not anything weird like 1500rpm or sudden surges.

I had an Opel Corsa, my first car, it would act up everytime it rained or the air was humid. I spent a lot of time an money trying to solve that issue. Ended up selling the car cheap to a friend who needed a ride and he put on a new distributor (or maybe just cap and rotor) and the car gave him a few good years, until his untimely death, unfortunately.
Anyway, my point is that I can't avoid drawing similarities between the symptoms of the 2 cars. But since I cleaned the cap and rotor and it made absolutely no difference, I'm kinda trying other options first. Then again, if it is the distributor itself, cleaning the parts wouldn't have made a difference.

[YOUTUBE]https://youtu.be/2yKp-ATW23k[/YOUTUBE]

[Laird Scooby]

Originally Posted by SalvadorP

https://www.youtube.com/watch?v=2yKp-ATW23k
I decided to try to unplug the IAC valve while idling. I read conflicting info on what is supposed to happen/not happen when you do so. So I'm not sure whether or not this means that something can be wrong with it. I guess if there is something wrong in regards to the IAC it could also be a fuse right?
Today I ran the car to shoot this video, it was already afternoon and it hasn't been raining. The car idled at 900, granted, with the misfire, but not anything weird like 1500rpm or sudden surges.

I had an Opel Corsa, my first car, it would act up everytime it rained or the air was humid. I spent a lot of time an money trying to solve that issue. Ended up selling the car cheap to a friend who needed a ride and he put on a new distributor (or maybe just cap and rotor) and the car gave him a few good years, until his untimely death, unfortunately.
Anyway, my point is that I can't avoid drawing similarities between the symptoms of the 2 cars. But since I cleaned the cap and rotor and it made absolutely no difference, I'm kinda trying other options first. Then again, if it is the distributor itself, cleaning the parts wouldn't have made a difference.

[YOUTUBE]https://youtu.be/2yKp-ATW23k[/YOUTUBE]

That sounds horribly like the throttle butterfly is flowing too much air, it should have dropped the engine speed to 6-700rpm when you unplugged the IACV. That is assuming the IACV is working as it should be, however the raised idle (1500rpm) suggests it is working.

Out of curiosity, what year was the Corsa you mention? Some later cars had the LH-Jetronic, many earlier cars did not.

[SalvadorP]

Originally Posted by Laird Scooby

That sounds horribly like the throttle butterfly is flowing too much air, it should have dropped the engine speed to 6-700rpm when you unplugged the IACV. That is assuming the IACV is working as it should be, however the raised idle (1500rpm) suggests it is working.

Out of curiosity, what year was the Corsa you mention? Some later cars had the LH-Jetronic, many earlier cars did not.

When you say "flowing too much air" do you mean it probably needs adjustment or would it be another issue?
I recorded a video of the car idling. But the camera was set inside the car and I was outside with the microphone at the engine bay. Turns out sound levels were too high, so the sound is actually ruined. I'll record again tomorrow with proper levels so you guys can hear what the car sounds like.

It was a 94 Corsa.

[Laird Scooby]

Originally Posted by SalvadorP

When you say "flowing too much air" do you mean it probably needs adjustment or would it be another issue?
I recorded a video of the car idling. But the camera was set inside the car and I was outside with the microphone at the engine bay. Turns out sound levels were too high, so the sound is actually ruined. I'll record again tomorrow with proper levels so you guys can hear what the car sounds like.

It was a 94 Corsa.

Probably needs adjusting but you'll also have to adjust the idle switch afterwards - in fact if the idle switch isn't adjusted correctly that can also cause this problem.

[SalvadorP]

Originally Posted by Laird Scooby

Probably needs adjusting but you'll also have to adjust the idle switch afterwards - in fact if the idle switch isn't adjusted correctly that can also cause this problem.

What's the proper way to go about it? Does it have a marked position or is there a way to know the best/proper adjustment?

[griston64]

Think I've already asked this question but have you cleaned the throttle body ?

I don't mean by spraying a bit of carb cleaner up there but removing it and cleaning it properly





That's 130k's worth of gunk

[SalvadorP]

Originally Posted by griston64

Think I've already asked this question but have you cleaned the throttle body ?

I don't mean by spraying a bit of carb cleaner up there but removing it and cleaning it properly





That's 130k's worth of gunk

I sprayed in there but honestly it is pretty clean. It looked spotless really, that's why I did not clean it properly. Didn't think it was worth it

My butterfly looks like yours after you cleaned it, to be honest.

[c1800]

Any update?

[SalvadorP]

So after giving up on this issue, because I was tired of chasing after it, I got back to trying to solve it.

Next on my list of things to do is checking injectors. I did the screwdriver sound tst while back and they are firing, but they may be clogged.
So I have 2 routes, either I clean them myself or a have them professionaly cleaned.
I wasn't in the mood for another diy project so I called a shop nearby and asked how much it was to test and clean 4 injectors. No instalations/uninstalation. To my surprise, they quoted me on 89€ (i'm pretty sure plus taxes). wtf i didn't know how much it would cost but 90 bucks is wildly of.

What do you say? How much would you pay/charge for that service?