A4 3.0 tdi power loss/hits a wall ideas?

[fulham4eva]

So my A4 is hitting a brick wall at the following revs
In neutral 4,000 (might be normal)
In 3rd 3,500
In 4th 3,000
It just stops pulling and up to that point it pulls hard. I tried tricking it by hitting the 3k limit in fourth then dropping into 3rd this threw the car into limp mode and the glow plug symbol appeared, once switching the car off and on again the symbol disappeared and I'm able to drive the car in the new norm.

SO FAR
Both heads have been cleared of crap(off the car)
EGR system all cleaned up as well as inlet manifolds and swirl flaps, the actuators perform as expected.
Turbo has been cleaned and checked over with new bearings and a new actuator plus I forget the name of it but the part internally that connects to the lower arm from the actuator needed replaced so that's been done.
Injectors are all refurbed and there's no smoke at all from the car
I have tried another MAF no joy.
And did a quick scan but with the battery being disconnected for another job it throws up a bunch of low to intermittent signals etc, so cleared everything and no faults so tomorrow I can try again.

IDEAS???
I know the DFP could be clogged up
N75 valve
Cam sensor
Boost solenoid
And I'll check all the boost pipes to make sure there all tightened up but like I said the car is perfect up to 3,000 revs
I'll also try running with the MAF disconnected
Is there anything else that could be the culprit?

 

[northpole]

Nope.you got all bases covered...

 

[Charlie Farley]

So my A4 is hitting a brick wall at the following revs
In neutral 4,000 (might be normal)
In 3rd 3,500
In 4th 3,000
It just stops pulling and up to that point it pulls hard. I tried tricking it by hitting the 3k limit in fourth then dropping into 3rd this threw the car into limp mode and the glow plug symbol appeared, once switching the car off and on again the symbol disappeared and I'm able to drive the car in the new norm.

SO FAR
Both heads have been cleared of crap(off the car)
EGR system all cleaned up as well as inlet manifolds and swirl flaps, the actuators perform as expected.
Turbo has been cleaned and checked over with new bearings and a new actuator plus I forget the name of it but the part internally that connects to the lower arm from the actuator needed replaced so that's been done.
Injectors are all refurbed and there's no smoke at all from the car
I have tried another MAF no joy.
And did a quick scan but with the battery being disconnected for another job it throws up a bunch of low to intermittent signals etc, so cleared everything and no faults so tomorrow I can try again.

IDEAS???
I know the DFP could be clogged up
N75 valve
Cam sensor
Boost solenoid
And I'll check all the boost pipes to make sure there all tightened up but like I said the car is perfect up to 3,000 revs
I'll also try running with the MAF disconnected
Is there anything else that could be the culprit?

You need to do a proper full scan and see what faults are logged along with some real time diagnostics, then progress to the next stage, until you have a clearer overview of how all systems and the engine is working you could be just clutching at straws.

 

[NHN]

I'd be checking the boost logs to see if it's always limp at the same boost pressure so to speak, the gear & revs maybe a red herring.

Was the turbo actuator setup correctly.

Need logs tbh.

 

[fulham4eva]

You need to do a proper full scan and see what faults are logged along with some real time diagnostics, then progress to the next stage, until you have a clearer overview of how all systems and the engine is working you could be just clutching at straws.

Yeah I think I'll start with the vag first

 

[fulham4eva]

I'd be checking the boost logs to see if it's always limp at the same boost pressure so to speak, the gear & revs maybe a red herring.

Was the turbo actuator setup correctly.

Need logs tbh.

The turbo was professionally done, came with a warranty

 

[NHN]

Doesn't mean much in some cases, you need to do boost logs.

I was once supplied a brand new hybrid turbo by a so-called reputable company, spent months trying to figure out why it had boost issues & limping, turned out the stupid sales guy, who was fired, sent me the wrong one, hence me & my tuner were at a loss as to why it was an issue, problem resolved eventually, but just goes to show you can't trust everything you're told.

 

[fulham4eva]

I did another scan after a quick run, only getting an open circuit on glowplug 6 P161F and the aircon G65 pressure too low - intermittent 00819
After it hit its limit in 4th 3k I dropped into 3rd and got it above 4k, so I'm starting to think it's a DFP issue

 

[NHN]

As advised, it could be a red herring, do your boost logs.

 

[fulham4eva]

G001

F0

G010

F2

G011

F1

G011

F2

G034

F3

G000

Marker

TIME

Group 1 - Field 0

TIME

Group 10 - Field 2

TIME

Group 11 - Field 1

TIME

Group 11 - Field 2

TIME

Group 34 - Field 3

STAMP

Engine Speed - (G28)

STAMP

Boost Pressure - (actual)

STAMP

Boost Pressure - (specified)

STAMP

Boost Pressure - (actual)

STAMP

Boost Pressure - (actual)

/min

mbar

mbar

mbar

mbar

0.48​

2352​

0.65​

1744.2​

0.13​

2295​

0.13​

1366.8​

0.3​

1428​

1.17​

2583​

1.34​

2142​

0.82​

2305.2​

0.82​

1938​

1​

2101.2​

1.84​

2835​

2.01​

2325.6​

1.5​

2305.2​

1.5​

2152.2​

1.67​

2213.4​

2.51​

3108​

2.69​

2335.8​

2.19​

2305.2​

2.19​

2346​

2.35​

2356.2​

3.19​

3255​

3.35​

2162.4​

2.85​

2295​

2.85​

2335.8​

3.02​

2325.6​

3.85​

3276​

4.03​

1815.6​

3.52​

2295​

3.52​

2040​

3.7​

1978.8​

4.54​

2688​

4.72​

1468.8​

4.2​

1683​

4.2​

1693.2​

4.37​

1581​

5.23​

2184​

5.41​

1407.6​

4.87​

1091.4​

4.87​

1428​

5.05​

1407.6​

 

[fulham4eva]

I've also noticed a little judder with minimal throttle or no throttle, more so when the car is cold

 

[NHN]

Do you notice the boost timings match times of power loss.

 

[fulham4eva]

Do you notice the boost timings match times of power loss.

I did that run in 3rd gear, so on the rev counter it cuts out at 3,500. Honestly I'm not too sure what I should be assessing, if I look at 3,255 revs it appears to be over boosting a little. Will it make more sense in a graph?

 

[Sloppy_1]

is the inlet working properly, sound like the inlet valves are not swapping as they should, like old s16's/mi16s with the vac inlets!

 

[fulham4eva]

is the inlet working properly, sound like the inlet valves are not swapping as they should, like old s16's/mi16s with the vac inlets!

as far as i'm aware they are, I used to get lower stop not reached dtcs but since adding some brackets I haven't had any issues with the inlets. Only thing I can think of doing would be to remove the flaps

 

[pelhamsdetailing]

is the inlet working properly, sound like the inlet valves are not swapping as they should, like old s16's/mi16s with the vac inlets!

If you mean the swirl flaps, opened or closed they won't stop the engine revving past the RPM walls he is hitting. I had this on my old A5 B8 CAPA 3.0TDI and it was because my DPF was blocked. I'd hit about the same rev limit in the same gears as OP. Your intake manifold may be coked up, which could be contributing. Check your soot mass measured / calculatated data on a supporting OBD app (or VCDS). Also check when it last did a regen.

 

[desertstorm]

If you suspect the DPF log the DPF pressure sensor. This measures pressure on the engine side of the DPF. You will soon see if it's blocked. If the DPF is blocked and you try and rev it hard you could end up damaging the engine. Try logging EGT's as well. These will be high if the DPF is blocked anything over 950 degrees and engine goes into protection.

 

[fulham4eva]

If you mean the swirl flaps, opened or closed they won't stop the engine revving past the RPM walls he is hitting. I had this on my old A5 B8 CAPA 3.0TDI and it was because my DPF was blocked. I'd hit about the same rev limit in the same gears as OP. Your intake manifold may be coked up, which could be contributing. Check your soot mass measured / calculatated data on a supporting OBD app (or VCDS). Also check when it last did a regen.

It's actually starting to look like my car doesn't have a DPF, in vagcom I get 0 for all readings except temperature(pressure, oil ash and carbon mass all zero). I asked around on rosstech. Which means the question becomes what is in there? and could it be blocked? . Also on last regen it says 0.001 of fuel since

 

[fulham4eva]

If you suspect the DPF log the DPF pressure sensor. This measures pressure on the engine side of the DPF. You will soon see if it's blocked. If the DPF is blocked and you try and rev it hard you could end up damaging the engine. Try logging EGT's as well. These will be high if the DPF is blocked anything over 950 degrees and engine goes into protection.

All I have going into the exhaust near the turbo are two lambda sensors

 

[Sloppy_1]

All I have going into the exhaust near the turbo are two lambda sensors

ive yet to see a b7 3.0 with dpf, mines a late 2006 not dpf, just take a pic of exhaust underneath i can soo tell you if it has one!

the 'internet' tell you they all have them in reality that not accurate.

think im breaking mine soon, so if you need any parts let me know, it works perfectly in that area (performance is not an issue!) just need lots of annoying jobs and ive had enough.

 

[fulham4eva]

ive yet to see a b7 3.0 with dpf, mines a late 2006 not dpf, just take a pic of exhaust underneath i can soo tell you if it has one!

the 'internet' tell you they all have them in reality that not accurate.

think im breaking mine soon, so if you need any parts let me know, it works perfectly in that area (performance is not an issue!) just need lots of annoying jobs and ive had enough.

Yeah I know the feeling the only reason I'm persevering is because the car only has 66k on it and its been in the family since it was a year old, I have no need for a big car any more and this is the second Audi that's gone badly wrong on me but I want to sell it when it's completely right. The DFP issue I was under the impression it had one but it doesn't seem to, so I wonder what it has and if it could be an issue. I've now replaced the boost sensor in the passenger side intercooler, put a new fuel filter on, and today a new MAF. I've got it to go to 3,900 revs in 3rd and 3,500 in 4th and sometimes it seems to change back to 3,600 in 3rd. And i've logged some more data runs, the bank 1 intake had a very random drop, and the specified versus actual boost is really off. So i'll be looking at both inlets and to make something up so that I can pressure test the intercooler system.

 

[northpole]

Is it a manual or a multitronic?

 

[fulham4eva]

Is it a manual or a multitronic?

It's a manual

 

[northpole]

Worst case your cat is blocked... people tend to forget that that also can get blocked.

 

[B7Tourer]

I know it might sound silly but are you sure your glow plugs are working correctly, since that was the initial warning?

 

[fulham4eva]

Worst case your cat is blocked... people tend to forget that that also can get blocked.

I can only assume that if the CAT was blocked it wouldn't have passed the emissions test

 

[fulham4eva]

I know it might sound silly but are you sure your glow plugs are working correctly, since that was the initial warning?

At this point nothing is a stupid idea, all the glow plugs are new but the previous set were overtightened and the glow plug in the 6th cylinder snapped so we had to drill and put a new insert into it. I do get a fault on it in vagcom after it's been driven but as far as I'm aware the glow plugs are mostly needed for starting the car but I'll do some more research into it

EDIT - had a quick look at symptoms and nothing lines up, the car starts almost immediately, no smoke and misfires.

The regular symptoms I have are occasional judder under minimal throttle(goes away with the MAF disconnected)Brand new MAF btw I've tried three different ones, the hitting the wall in every gear and I noticed another symptom where If I accelerate in 4th gear on a slight incline starting from 1,500 revs there's no reaction to putting my foot down, it used to pick right up.
When I've forced it into full limp mode(hit the limit in 4th then drop into 3rd) I get a bad misfire and two boost codes P0235 and P0238 this is after replacing the MAP sensor in the intercooler. I did manage to get 3rd up to 3,900 revs and 4th 3,500 but this was after both a new MAP sensor and a cleaning of the MAF(since bought a new one)

 

[B7Tourer]

I do get a fault on it in vagcom after it's been driven but as far as I'm aware the glow plugs are mostly needed for starting the car but I'll do some more research into it

This is often a common misconception, I think. Glowplugs also do come into play whenever the internal cylinder temperature may fall below less than ideal, mainly because obviously compression ignition is not as guaranteed always as spark ignition. It might be worth revisiting them, just a thought.

 

[fulham4eva]

This is often a common misconception, I think. Glowplugs also do come into play whenever the internal cylinder temperature may fall below less than ideal, mainly because obviously compression ignition is not as guaranteed always as spark ignition. It might be worth revisiting them, just a thought.

Ok I'll look into it