Engine bogs down after startup / low power

Crgwal

Crgwal

A2OC Donor
Scotland
Hi,

I have a couple things going on with my FSI. My engine feels like it struggles at high speed. Engine feels like it is straining a lot and not really very smooth. Feels like it is lacking power. Anything above 3k RPM makes me want to hold back on the throttle.

Second thing is when I start the car, which starts fine it always bogs down before recovering. When it's hot sometimes it will bog down enough to stall.

Car history.

135k
New injectors.
New timing belt.
High pressure fuel pump. Serviced.
Fully serviced and all filters/sparks replaced.
Compression test. OK.
Only ever used VPower high octane.
Oil breather replaced.
Most recently I replaced the oil filler pipe. So I am completely confident on air leaks in the system now.
Pro Boost installed (this has only made the issue more obvious)
Manifold Flaps fixed.
No errors with original ECU.
Scanned again today. Zero errors.

I have a new mesh filter ready to replace under the crank case just to see if this will do anything. I feel my issues are around the valves, as the car is a little ticky to listen to but who knows.

I also have full VCDS if anyone has any recommendations on what I could monitor on the software for more clues.

Any feedback welcome

Thanks for reading.
 
Last edited:
Crgwal said:
Hi,

I have a couple things going on with my FSI. My engine feels like it struggles at high speed. Engine feels like it is straining a lot and not really very smooth. Feels like it is lacking power. Anything above 3k RPM makes me want to hold back on the throttle.

Second thing is when I start the car, which starts fine it always bogs down before recovering. When it's hot sometimes it will bog down enough to stall.

Car history.

135k
New injectors.
New timing belt.
High pressure fuel pump. Serviced.
Fully serviced and all filters/sparks replaced.
Compression test. OK.
Only ever used VPower high octane.
Oil breather replaced.
Most recently I replaced the oil filler pipe. So I am completely confident on air leaks in the system now.
Pro Boost installed (this has only made the issue more obvious)
Scanned again today. Zero errors.

I am taking off the rocker case in a few days to just have a look at things and redo all the wiring around the coil packs.

I have a new mesh filter ready to replace under the crank case just to see if this will do anything. I feel my issues are around the valves, as the car is a little ticky to listen to but who knows.

I also have full VCDS if anyone has any recommendations on what I could monitor on the software for more clues.

Any feedback welcome

Thanks for reading.
Click to expand...
If possible, beg borrow or steal, (not really), a non ProBoost ECU, and fit it. Scan, save results, (press Copy button on screen, and and paste into Note Pad or similar), clear any DTCs, and go for a drive. Use as much of the rev range as possible.
Scan again, copy and paste, then post here.
As far as I know, there is no scan tool, or DTC listing for ProBoost, hence the ECU swap. Good luck.
Mac.
 
Okay, I just read this post. Which has got me thinking.

Forgetting the bogging down for a minute.

I have a perfectly running car at idle. I have a rough engine at high rpm as well as low power. In my opinion.

Could my timing belt be off a little, even with no errors? (This was done about 8k miles ago)
 
PlasticMac said:
If possible, beg borrow or steal, (not really), a non ProBoost ECU, and fit it. Scan, save results, (press Copy button on screen, and and paste into Note Pad or similar), clear any DTCs, and go for a drive. Use as much of the rev range as possible.
Scan again, copy and paste, then post here.
As far as I know, there is no scan tool, or DTC listing for ProBoost, hence the ECU swap. Good luck.
Mac.
Click to expand...
Thanks for that. I still have my original ECU

I would add that I had zero errors before I swapped the ECU only a few months ago though
 
Last edited:
Crgwal said:
Okay, I just read this post. Which has got me thinking.

Forgetting the bogging down for a minute.

I have a perfectly running car at idle. I have a rough engine at high rpm as well as low power. In my opinion.

Could my timing belt be off a little, even with no errors? (This was done about 8k miles ago)
Click to expand...
My guess, can't resist, is that the flaps are stuck up, and ProBoost assumes the flaps are down. Worse with ProBoost, because the FSI ECU knows the flaps are not where they should be. Just a guess, so probably rubbish.
Mac.
 
PlasticMac said:
My guess, can't resist, is that the flaps are stuck up, and ProBoost assumes the flaps are down. Worse with ProBoost, because the FSI ECU knows the flaps are not where they should be. Just a guess, so probably rubbish.
Mac.
Click to expand...
I should have added that the flaps were repaired before I put the ProBoost in. All was sound. I used to get that engine boost around 3k rpm.
 
Andrew said:
Wild guess N80 - Andy
Click to expand...
Funny that, I have that sensor in my workshop for replacement over the next few days. Had it a while now. Was a wild guess for me too.

I am really set on this being a timing issue. Until I change my mind
 
I’ve had 2 FSI’s with the same symptoms. Both made worse with the fitment of a ProBoost and it has been down to the high pressure fuel pump. If you are confident that the hpfp has been refurbed properly then look at other fuel supply components. No perished fuel lines, dirty fuel filter?
 
What’s the misfire count like?

I got mine to a stage where it wasn’t reporting any errors but I could see in VCDS that I had a misfire on 1 and 3.

Occasionally I would get an air intake leak fault due to it leaning out

Sticky injectors were the culprit
 
Thanks for the replies.

Fuel filter was changed

I have wondered if it was a fuel starvation problem too. Everything does look good though. VCDS is giving me readings that are in tune with other FSI's when it comes to the hpfp.

I just spoke to Glasgow Audi £170 per hour for labour. What a life.

Is there somewhere I can look and count how the engine fires in real time? No signs of miss fire on the car though. Idle is steady at least.
 
Try these blocks

14Misfire recognition
RPM/min-1 Load/%Misfire counter Misfire recognition/Text:activated/locked
15Misfire recognition
Counter Cyl.1 Counter Cyl. 2 Counter Cyl. 3 Misfire recognition/Text:activated/locked
16Misfire recognition
Counter Cyl.4 Counter Cyl. 5 Counter Cyl. 6 Misfire recognition
 
A2Steve said:
I’ve had 2 FSI’s with the same symptoms. Both made worse with the fitment of a ProBoost and it has been down to the high pressure fuel pump. If you are confident that the hpfp has been refurbed properly then look at other fuel supply components. No perished fuel lines, dirty fuel filter?
Click to expand...
@Crgwal is seeing 90 Bar at the fuel rail, so although a possibility, looks OK. To be sure, log Groups 001 and 140, with VCDS on a drive.
I'm assuming that although ProBoost inhibits some of the errors that would be generated by the standard ECU, the Groups themselves are still being monitored. Take a look at Group 142, flap position.
Mac.
Crgwal said:
Thanks for the replies.

Fuel filter was changed

I have wondered if it was a fuel starvation problem too. Everything does look good though. VCDS is giving me readings that are in tune with other FSI's when it comes to the hpfp.

I just spoke to Glasgow Audi £170 per hour for labour. What a life.

Is there somewhere I can look and count how the engine fires in real time? No signs of miss fire on the car though. Idle is steady at least.
Click to expand...
If the belt was out a notch, the engine electronics wouldn't know, so I don't think that monitoring the ignition timing would help.
Knock and misfire counts might give a clue though.
I really think a scan>drive>scan with the original ECU is the best way to go.
Would be good if you can copy and paste the results as text, then share here.
Mac.
 
Last edited:
Hi,

So I have put the old original ECU back in the car and have driven 60 miles. City and Motorway. Again on the motorway I almost feel unsafe with low torque at high speeds and the engine just sounding rough.

Just scanned the car, I still have no errors.

I change out the N80 just because I had one around but no change.

So.

Car bogs down most of the time when hot on startup. Usually recovers back to idle, sometimes fails and switches off.

What feels like low power particularly at higher speeds.

Looking at misfires, I counted about 2 per minute through vcds on idle.

The scary thing which I don't even know if I want to talk about in this thread. I get valve clicks when I am moving at higher speeds with some throttle. It's like 3 or 4 super quick clicks, that go away as quick as the came on.

I've struggled with this engine for so long, maybe it's time to rebuild it 🤔

Thanks for any feedback as always.
 

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Sounds like intermittent earth leakage/breakage, have you checked the earth strap to the head, I have seen many of these that look good but corroded away under the rubber sleeve, well worth a try.
 
Its so odd that there are no stored engine fault codes, when the engine is clearly struggling. The FSI has so many sensors and fault conditions, which makes the lack of logged faults incredibly hard to reconcile with the reality you are experiencing.
Take a look at some engine groups data, to look for anything not right, despite not being recorded as such. I'd suggest Groups 102,105,140, and 141.
Just at idle, to be on the side of caution.
Mac.
 
Thanks folks, I had cleaned out the earth cable behind the headlight maybe just under 2 years ago. I will have a second look.

I also have ordered a low millage fuel pump for £35. The fuel pump i have actually isn't showing the fuel level correctly sometimes. I think the contacts are dirty. So maybe try fixing two things at the same time with that.

@PlasticMac i will have a look and thanks for that information.

Not sure how worried i should be about the valve clicking. i do wonder if there is engine damage. The timing on the engine was way out before i got it changed. I had one day of crazy valve clicking the day before i had the car in for its timing. This 99% stopped after the timing was done.

Anyway if i learn anything new i will report back.
 
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