Rough/boost on idle

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Mr_Gav
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Rough/boost on idle

Post by Mr_Gav »

Hello, did any of you guys / girls have a similar problem with your Polo? :cry: :?

https://www.dropbox.com/s/fupro7qp7mlqg ... 6.mp4?dl=0

I just want to let you know that the car is doing it by itself, I'm not doing anything on the above video.

A few months now I randomly have increased boost/rough on idle (it is not happening all the time). I don't have any error codes at all, I don't have any power loss when pushing it to the limits, I did my service a month ago (sparks,oil,oil filter replaced), we did engine compression test and everything seems fine, we replaced PCV valve, we checked the tubes that goes to turbo, bov etc. end everything seems to be fine, but I think I have a leak somewhere. When this happens AFR becomes rich 11:1,10:7 and I hear backfires from the exhaust, plus oil smells gasoline.

Thanks in advance
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alexperkins
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Re: Rough/boost on idle

Post by alexperkins »

You have a vacuum leak somewhere. Check all your vacuum hoses and do a smoke test if that doesn’t show anything.

Unplugging the MAF temporarily should stabilise the engine confirming you have an air leak somewhere
Mr_Gav
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Re: Rough/boost on idle

Post by Mr_Gav »

Hello there, no it wasn't the sensor after all. The HPFP was leaking gasoline to the oil. The fumes from the gasoline were absorbed by the PCV and made that rough engine idle. I started to smell gasoline inside the cabin and after a research I removed the oil cap and tears came to my eyes. So we had 2 options either the injectors or the pump. Since I didn't have any misfire or EPC error we went with the pump and that was it. Pump seals was leaking gasoline.
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alexperkins
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Re: Rough/boost on idle

Post by alexperkins »

Glad you fixed it. That’s an unusual issue!
Mr_Gav
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Re: Rough/boost on idle

Post by Mr_Gav »

It really was, thanks again for the comment ✌️
Dawit Tesfaye
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Re: Rough/boost on idle

Post by Dawit Tesfaye »

alexperkins wrote: Sat Jun 20, 2020 10:13 am Glad you fixed it. That’s an unusual issue!
Dear Alex, I have polo iv 1.2 9n, 2004 and is stalling at low acceleration at traffic ... could you please give me any idea where to check.
Thanks
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alexperkins
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Re: Rough/boost on idle

Post by alexperkins »

I would check for vacuum leaks, check your air filter is clean, clean the throttle body to start with
Dawit Tesfaye
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Re: Rough/boost on idle

Post by Dawit Tesfaye »

Thanks Alex, it took me a while dealing with diff. Things.
Problem: It starts and run for one...two minutes and engine shuts on idling no matter what temperature it has unless I press the pedal.
Fault codes: there were 18041, 18047, 18088 and 18556 a while ago. After cleaning the throttle body, changed spark plugs, cleaning of injectors and changing fuel filter it has gone.
Now it has no dash light, no fault code as diagnosed.

I really have no idea what to check next. Wiring looks neat and clean, compression test become >140 per cylinder

Please give me any idea where I should focus

Thanks again
Dawit Tesfaye
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Re: Rough/boost on idle

Post by Dawit Tesfaye »

Oh one thing I forgot; once it stalls by itself it doesn't start unless battry reset, waiting for it fore for more than 20 min. Or disconnect the spark plug fuse (#37).
The stalling makes the fuel pump shutoff and ignition system out of power. When I disconnect the fuse (#37) and connect it back, I hear the fuel pump working then it starts again to stall soon.
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