Boost Surging

[RamJam258]

Hi Guys

My 1.8 BJX is currently having boost surge issues (I Think). When the cars all warmed up and i plant my right foot on the throttle, the boost rises and then drops off, and builds up again and drops off.
The whole time the car will still accelerate however the car does feel like this its surging forward and then back as the boost builds and drops off.

Is this the Recirculating Diverter Valve? Which I believe is the original, Or the N75 Valve. (52000 miles on the car)

Cheers
RamJam

[h100vw]

Hi Guys

My 1.8 BJX is currently having boost surge issues (I Think). When the cars all warmed up and i plant my right foot on the throttle, the boost rises and then drops off, and builds up again and drops off.
The whole time the car will still accelerate however the car does feel like this its surging forward and then back as the boost builds and drops off.

Is this the Recirculating Diverter Valve? Which I believe is the original, Or the N75 Valve. (52000 miles on the car)

Cheers
RamJam

How long have you had the Polo?

Did it just start doing this?

You need to get it logged with VCDS. Find someone that has the lead and I'll explain what you need to do. You can flick the logs to me and I'll check them out.

DO NOT buy any parts before you do this.

You can check the Diverter valve Physically, there's lots of how to's in google.

Gavin

[RamJam258]

I've had it sine May 2015, never really noticed it until the last couple of months, not to say it hasn't been like it longer, i live in a small town so a lot of the time its only driven gently which doesn't cause any issues. Im going to see if the DV holds a vacuum tomorrow to see if this is the case.

Can it be logged using VCDS Lite or does it require the full version.

RamJam

[h100vw]

I've had it sine May 2015, never really noticed it until the last couple of months, not to say it hasn't been like it longer, i live in a small town so a lot of the time its only driven gently which doesn't cause any issues. Im going to see if the DV holds a vacuum tomorrow to see if this is the case.

Can it be logged using VCDS Lite or does it require the full version.

RamJam

I lived in Somerton for 2 years.

You'll need to buy a license if you're running VCDS lite. It's worth the cost.

The boost control is pretty crap on the on VW software. Can you actually feel it surging or are you just looking at the boost gauge and watching the needle swing all over the place?

[RamJam258]

Somerton UK? Literally 15 Minutes from me.

You can feel the car surging, its feels like the car gains power as its under boost, then as the boost goes you get a drop in power, then it picks up again surging the car forward. This happens really quickly to, under full throttle it surges between 5 psi and 10 psi, on the gauge.

[h100vw]

Yeah, I know it's up the road. I worked as a contractor at Yeovilton and Westlands factory in 97 and 99.

Check the DV and then get back to me about logging it

[RamJam258]

I'm a permy at westlands or leonardo, whatever we are calling the place now, such a small world. I'm going to see if I still have a vacuum pump to test it, if not I read you can hold you finger over the top port and push the spring underneath to see if it holds the vacuum created using your finger. Am I correct in this?

RamJam

[h100vw]

You don't need any test equipment, just suck on the nipple at the top. If you can keep sucking, it's ****ed. If it gets harder, then it's ok.

I worked in the flight shed, doing mods and stuff on Lynx. I was there while they finished the EH101 for the RAF.

Tony Pearce is still there, he joined after leaving St Mawgan. There'll be plenty of SAR boys that remember me from the Sea King School and HMF.

[RamJam258]

I've worked on everything there, on the lynx now myself, I'll give the DV a sick tomorrow and see what happens. Fingers cross this is the issue. I'll report back tomorrow.

[RamJam258]

You don't need any test equipment, just suck on the nipple at the top. If you can keep sucking, it's ****ed. If it gets harder, then it's ok.

I worked in the flight shed, doing mods and stuff on Lynx. I was there while they finished the EH101 for the RAF.

Tony Pearce is still there, he joined after leaving St Mawgan. There'll be plenty of SAR boys that remember me from the Sea King School and HMF.

Okay so when i got home from work i unplugged the N75 Valve and measured the resistance which was 29.5 Ohms, which is just within the tolerances ive read about on the internet, however this won't prove that is working completely. As the problem only occurs during full throttle could this valve still be the issue as I know that the N75 runs of throttle position. I also removed the vac pipe from the DV and attached some tubing of my own and did the suck test, and it didn't loose vacuum.

So i got my tablet and using the torque pro app (I know its not as good as Vag-Com). Before going for a drive i had zero fault codes. After going off and giving it some beans, i got home and re scanned and had P0141 (02 Sensor Heater Circuit (Bank 1 Sensor 2)
Could this be the issue causing it to surge?

I also noticed that it spikes and holds boost on half throttle and only surges when you have your foot flat to the floor.

Ramjam

[h100vw]

Okay so when i got home from work i unplugged the N75 Valve and measured the resistance which was 29.5 Ohms, which is just within the tolerances ive read about on the internet, however this won't prove that is working completely. As the problem only occurs during full throttle could this valve still be the issue as I know that the N75 runs of throttle position. I also removed the vac pipe from the DV and attached some tubing of my own and did the suck test, and it didn't loose vacuum.

So i got my tablet and using the torque pro app (I know its not as good as Vag-Com). Before going for a drive i had zero fault codes. After going off and giving it some beans, i got home and re scanned and had P0141 (02 Sensor Heater Circuit (Bank 1 Sensor 2)
Could this be the issue causing it to surge?

I also noticed that it spikes and holds boost on half throttle and only surges when you have your foot flat to the floor.

Ramjam

The heater fault isn't the problem.

You need VCDS or a way of logging multiple blocks at once. ME7logger will do this with an ebay VCDS cable.

I don't think there's anything wrong with the N75 either

Google that, I can send you one of the files you'll need to enable the logging to work for the Polo ECU.

Gavin

[RamJam258]

The heater fault isn't the problem.

You need VCDS or a way of logging multiple blocks at once. ME7logger will do this with an ebay VCDS cable.

I don't think there's anything wrong with the N75 either

Google that, I can send you one of the files you'll need to enable the logging to work for the Polo ECU.

Gavin

Okay that would be great, ill download ME7logger now.