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 Post subject: Idle Surging (only when engine is warm)
PostPosted: Sat Mar 23, 2019 12:00 pm 
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Joined: Sat Aug 11, 2018 8:51 am
Posts: 11
Location: Portugal
Hey,I have a Swift GTI mk2 (1992) 1.3 G13B (stock engine)

When I cold start the car the idle is at 2000rpm (too high). Minutes later, when the engine is starting to warm up (and the termometer gauge is going up too) the idle surges beetween 1500 and 2000rpm. Does someone have an idea on this?

My biggest question is why it only happens when the temperature goes higher... Is my temperature sensor deffective? Because I guess I have a real reading on my instrument cluster.

The temperature sensor that sends the signal to the ECU is the same that shows us the temp on the instrument cluster?

I recorded this video, might help
[https://photos.app.goo.gl/imsbaHhZpq5yKrr88]

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 Post subject: Re: Idle Surging (only when engine is warm)
PostPosted: Sun Mar 24, 2019 7:13 am 
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Joined: Mon Dec 19, 2016 10:40 am
Posts: 910
Location: NZ
Perhaps see if your cold start valve is faulty? The thing on the back of the intake manifold.
Warm the car up. Isolate the valve. It bypasses air to increase the idle when cold....then stops doing it when the car is warm....


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 Post subject: Re: Idle Surging (only when engine is warm)
PostPosted: Sun Mar 24, 2019 12:05 pm 
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Joined: Tue Sep 17, 2013 7:12 pm
Posts: 234
Location: Brisbane
I found my cold start valve was a problem when cold but it still could be, block it off and find out. My guess would be the tps needs calibrating and maybe clean the maf as well. It could also be a fuel pump problem. Lots of potenial things but they are the main ones.


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 Post subject: Re: Idle Surging (only when engine is warm)
PostPosted: Mon Mar 25, 2019 8:41 am 
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Joined: Mon Jun 16, 2008 7:02 pm
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Location: Northern Beaches
Had a similar issue years ago (Mk1) and it was to do with the Coolant Temp Sensor where the copper-strand wires into the actual sensor end had all but snapped (due to vibration/movement) and the 2 or 3 strands that remained were not carrying enough signal to the ECU causing funny idling issues once the car warmed up.


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 Post subject: Re: Idle Surging (only when engine is warm)
PostPosted: Mon Mar 25, 2019 4:50 pm 
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Joined: Mon Dec 19, 2016 10:40 am
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Location: NZ
yes if the WTS is faulty (or the wires broken) then the ECU is not getting the information it needs to run the mixture correctly....the water temperature sensor is very important info for the ecu.....


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 Post subject: Re: Idle Surging (only when engine is warm)
PostPosted: Tue Mar 26, 2019 5:31 am 
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Joined: Sat Aug 11, 2018 8:51 am
Posts: 11
Location: Portugal
I replaced MAF sensor and cleaned the throttle valve and the idle valve. Some people told me that it can be the intake manifold gasket broken. I found out today that my radiador fan does not turn on when the temperature is high. So, I should check the coolant temperature sensor and its wires, right? Any tips?

That sensor is near the Thermostat right?

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 Post subject: Re: Idle Surging (only when engine is warm)
PostPosted: Tue Mar 26, 2019 5:47 am 
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Joined: Sat Aug 11, 2018 8:51 am
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Location: Portugal
Also, I run my car normaly. I can ride at 8000rpm every gear and the car doenst fail at any RPM range. Only when on idle

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 Post subject: Re: Idle Surging (only when engine is warm)
PostPosted: Tue Mar 26, 2019 7:09 am 
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Joined: Mon Dec 19, 2016 10:40 am
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Location: NZ
Yes check your water temperature sensor and your radiator thermostat switch. Check your wires! Mine was broken at the water temp sensor plug on the sensor. So you can boil these in your jug and check the resistance....one will change resistance as the heat goes up....wts and the thermo switch will go closed circuit at the fan switch on temperature.


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 Post subject: Re: Idle Surging (only when engine is warm)
PostPosted: Tue Mar 26, 2019 9:23 am 
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Joined: Sat Aug 11, 2018 8:51 am
Posts: 11
Location: Portugal
swift12 wrote:
Yes check your water temperature sensor and your radiator thermostat switch. Check your wires! Mine was broken at the water temp sensor plug on the sensor. So you can boil these in your jug and check the resistance....one will change resistance as the heat goes up....wts and the thermo switch will go closed circuit at the fan switch on temperature.


I changed the thermostat for a new one recently. I guess I did it in the correct way...

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 Post subject: Re: Idle Surging (only when engine is warm)
PostPosted: Tue Mar 26, 2019 9:26 am 
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Joined: Sat Aug 11, 2018 8:51 am
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Location: Portugal
Is this red plug here?


Attachments:
File comment: (Below the distributor)
IMG_20190325_225749 (1).jpg
IMG_20190325_225749 (1).jpg [ 735.87 KiB | Viewed 15 times ]

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 Post subject: Re: Idle Surging (only when engine is warm)
PostPosted: Tue Mar 26, 2019 9:27 am 
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Joined: Sat Aug 11, 2018 8:51 am
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Location: Portugal
I still have the same question. The sensor that sends the temperature to the gauge at the cluster is the same that sends the signal to the ECU? (and the one that turns on the fan?)

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 Post subject: Re: Idle Surging (only when engine is warm)
PostPosted: Wed Mar 27, 2019 7:10 am 
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Joined: Mon Dec 19, 2016 10:40 am
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Location: NZ
Ok...yup....temperature is sensed by the wts and sent to the ecu...I’m pretty sure it sends the info to the gauge but I’ll need to check in my book when I get home. It does not turn the fan on.

Ok...on the pic....that reddy brown plug (large one) is definitely your thermo switch. This does not go to the ecu....it turns the fan relay on when the water gets hot past a certain level. Then turns it off again....it simply controls the water temp between two temps by operating the fan.

The thermostat is put in with the little bleed hole at the top....the thermostat will be the right way around because it would have killed your motor by now if not!

Go to the left of the reddy brown switch....there is another smaller sender with two wires to it...it’s under the thermostat housing...that’s the WTS.


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 Post subject: Re: Idle Surging (only when engine is warm)
PostPosted: Thu Mar 28, 2019 8:45 am 
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Joined: Sat Aug 11, 2018 8:51 am
Posts: 11
Location: Portugal
Hey!

The problem is solved now!
I shaked the wires and reconnected the plugs.

Another thing, I looked at the reservoir at the coolant was at the FULL line, but I opened the radiator cap and there was no visible coolant. So, I filled with coolant and started the engine and I did the "bleed".`

Is this normal? Coolant by the full line and not enough coolant on the radiator/circuit?

Thank you for all your replies!

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 Post subject: Re: Idle Surging (only when engine is warm)
PostPosted: Thu Mar 28, 2019 10:39 am 
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Joined: Mon Dec 19, 2016 10:40 am
Posts: 910
Location: NZ
shaking wires means you have broken wires inside...typical...I rewired my whole car...you might have to renew the wires where they sit against the hot engine...they get brittle and you might find they are stiff all the way back to the main loom.....just cut out the end 8 inches or so and solder on new wire...then insulate.....will save a lot of heartache in the future....

NO...coolant not in radiator is not normal....check for leaks.....check your radiator cap....normally if the radiator cap is faulty it will push coolant out of the radiator into the overflow bottle.
does your engine run rough when you first start it? is your oil milky? if the answer is no to the above its likely your head gasket is not blown. check for a wet floor on the inside of the car....heater leaking is a poss. If no leaks....and the above two questions asked are no....then maybe replace your thermostat and rad cap....the radiator when you take the cap off should be full....the overflow bottle goes up when hot....and down when cool....and keeps rad full. hence the hot and cold lines on the bottle.
good luck.


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 Post subject: Re: Idle Surging (only when engine is warm)
PostPosted: Fri Mar 29, 2019 6:00 am 
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Joined: Sat Aug 11, 2018 8:51 am
Posts: 11
Location: Portugal
Hey, I'm back again... :(

The engine Idle is okay, but...

Now the engine revs it self between 1500~2500rpm when I slighlty press the throttle. So I guess I have to adjust my TPS, right?

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 Post subject: Re: Idle Surging (only when engine is warm)
PostPosted: Thu Apr 04, 2019 5:37 am 
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Joined: Mon Dec 19, 2016 10:40 am
Posts: 910
Location: NZ
I’d try cleaning the throttle body. Then check the TPS for function. Carbon can build up around the throttle butterfly and so it’s worth using throttle body spray on it. Did you fix the wts wires or just wiggle them.


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