6 minutes ago, KeithCheetham said:

34 - 35, cooling towers up to Chapeltown isn't steep so should have no issues. The next part is theoretical working in my head. Boost is not really related to revs - drive at 70mph on flat with light throttle and look at boost value, floor throttle and boost should go up - but more to pedal position and fuel being burned producing gasses to spin turbo and vehicle loading (resistance to speed change). Obviously map fuelling curve will also have some effect on limiting fuel allowed in to be burned. Cannot comment on exhaust temp but appears strange - can it be run with back box off, think single pipe to box with 2 tailpipes on 1.9TDI so possibly only 1 joint to break - could it be blocked as restriction would stop boost building.

 No exhaust pressure gauge I don't think, generally for before/after DPF but someone may clarify.

 I am running Torque 1.8.205 which has an option for "Turbo Boost & Vacuum Gauge".

 Areas to clarify as I don't think I have seen timeline history.

 1/ Was the car un-mapped when bought - were these issues present

 2/ Did you have it mapped and were issues immediately apparent

 3/ If issues after having mapped, did you get a copy of the original map. If you have a copy I may be able to run under VAGEDC15P and see what power/power curve it shows. 

 

 Just a shame you don't have boost values before the turbo was swapped out as strange it feels worse - could new turbo be restricted on boost by blocked backbox? As you may note, above not based on actual facts but general gut feelings and RCA (Root Cause Analysis) methods. 

Thanks for the detailed reply, I think the throttle-boost relationship was correct upto 3rd and then it started falling off once on the motorway, foot flat and the speed is just dropping off to the point I join the lorry ranks.

 

I was watching the turbo and vac gauge, it defaults to vac when idle it seems in the image above. I'll log my commute tomorrow (centre of sheff to Barnsley) so can hopefully give a clearer picture of numbers rather than quick glances.

 

1- unmapped when bought and honestly just thought this is what a 20yo car was so wanted to try and make it fun whilst it lasted. The map was a very cheap one (from an alright place) so they only checked for errors and then flashed it, barely started engine. (Car was only £800 to me so didn't want to throw a £300 proper map at it)

 

2- map actually made it a bit better! Was sluggish before but think the map made the throttle a bit better

 

3- not 100% how the mapping works but in my head they took a copy of the original and sent it off via some online service and got the tuned one back.

 

I've been reading alot of forums with TDI issues and some have been similar symptoms with blocked up cats etc so could be! Would be nice if it was (nice to have a simple solution, not nice to spend money). I can look at how hard it would be to take the backbox off and see what it does.

12 minutes ago, xman said:

Classic MAF sensor drift symptom.

 

Try a new MAF sensor

 

Make sure you get the correct part no for your engine

Definitely a new line of enquiry for me, think I'll take a look at mine and give it a clean. Was reading that the atd engines don't like running without one, but if it's knackered could it believe it already is? Does anyone know what these values should look like so I can compare?

Cleaning the MAF sensor rarely helps on this engine. The type fitted basically slowly burns its sensor element away over time and its output drifts, fooling the ecu into thinking the airflow is low, so backs off the fuelling to prevent it smoking and limiting top end power. Doesn't cause limp mode which turbo related problems would.

They are pretty cheap, just replace it.

 

Btw a blocked air filter would give similar symptoms.

Edited 6 December, 20214 yr by xman

I think you could just unplug the MAF and see if performance improves.

2 hours ago, maw_mk1_fabia said:

 

Few points from this:

-1st and second gears boost is going to around 15ish psi (will record my commute tomorrow), 3rd was a similar story but on motorway in 4th and 5th it was dropping down to 11-12ish (slight hill between 34 and 35 if you know the M1)

 

 

This can happen when the vacuum pipes to the turbo actuator become degraded and can collapse under the vacuum when there is a lot of heat generated, it also needs a miniscule leak downstream of the collapsed pipe for the vacuum to be lost and the actuator returning to its base position.

 

Yours sounds quite advanced but its following exactly the same characteristics, in the lower gears boost is not held very long and the temperatures are lower, the longer and steeper the hill, the hotter the day, the more load you are carrying the quicker it will occur but it is always a total loss of boost which can usually be regained by cycling the ignition but if you dont back off and the load & heat are unchanged it will collapse again double quick.

 

Something else to check which costs very little to replace if they are suspect.

2 hours ago, maw_mk1_fabia said:

 

Few points from this:

-1st and second gears boost is going to around 15ish psi (will record my commute tomorrow), 3rd was a similar story but on motorway in 4th and 5th it was dropping down to 11-12ish (slight hill between 34 and 35 if you know the M1)

 

 

This can happen when the vacuum pipes to the turbo actuator become degraded and can collapse under the vacuum when there is a lot of heat generated, it also needs a miniscule leak downstream of the collapsed pipe for the vacuum to be lost and the actuator returning to its base position.

 

Yours sounds quite advanced but its following exactly the same characteristics, in the lower gears boost is not held very long and the temperatures are lower, the longer and steeper the hill, the hotter the day, the more load you are carrying the quicker it will occur but it is always a total loss of boost which can usually be regained by cycling the ignition but if you dont back off and the load & heat are unchanged it will collapse again double quick.

 

Something else to check which costs very little to replace if they are suspect.

1 hour ago, sepulchrave said:

I think you could just unplug the MAF and see if performance improves.

Again rarely works, more myth than fact.

1 hour ago, J.R. said:

This can happen when the vacuum pipes to the turbo actuator become degraded and can collapse under the vacuum when there is a lot of heat generated, it also needs a miniscule leak downstream of the collapsed pipe for the vacuum to be lost and the actuator returning to its base position.

 

Problems with the turbo control system and vacuum pipes will usually cause an underboost or overboost and triggers limp mode and then you get no boost at all until the ignition is cycled.

 

Also remember the vacuum pump is shared between the turbo control and the brake servo, so check for splits in the brake servo vacuum pipes

Edited 7 December, 20214 yr by xman

Vac pipes are good I believe, garage checked them over and I have recently swapped the brake booster hose as that had a split a while ago (was fun stopping a ship with no help!)

 

I'll get the maf out and test it over lunch to see if there's anything obvious, sadly the m1 was standstill today so not a great recording but one thing of note is a very peaky maf recording (driving around 30ish but peaking to 600+). Used the torque datalogger to make the quick and dirty graph below. Small snippet of a 30mph road and then the m1 slip (not perfect due to other cars but the spikes are evident). I'll try again on the way home (sadly mostly downhill so not as bad)

 

I can give data if anyone is really bored but just to show the general behaviour 

Grey = revs

Blue = MAF (g/s)

Yellow = Speed 

Orange = boost (psi)

 

MAF is generally around the 30 mark but the peaks are 500+

 

9 hours ago, xman said:

 

Problems with the turbo control system and vacuum pipes will usually cause an underboost or overboost and triggers limp mode and then you get no boost at all until the ignition is cycled.

 

Agreed, from the description it sounded like there was no boost.

 

I had a blocked catalytic convertor on my Galaxy, albeit a petrol engine, it was driving fine before I went to Australia for a month, when I got back & drove it I was jet lagged so driving slowly anyway but it didn't feel right, on the M25 the next day it was gutless just as the OP described & then on an incline a hose (some emissions device) blew off the exhaust manifold & made a farting noise.

3 hours ago, J.R. said:

Agreed, from the description it sounded like there was no boost.

 

No, from his earlier description and the graph there is some boost.

 

What his graph does show is the MAF output is not scaling linearly, mostly nil output and spiking every now and again. i.e. Its probably duff

 

Iirc limp mode with 1.9tdi engines usually is accompanied with a flashing coil light on the dash

 

Edited 7 December, 20214 yr by xman

I never had any dash lights for limp mode after sticking turbo vanes on my MK1 non PD TDi and my MK2 PD TDi but it was a real rarety on the MK2 and may not even have been sticking vanes, both vehicles always responded to my automatic default cycling of the ignition switch.

 

Thanks for the explanation, I had not gone through the graphs & things, difficult for me to read.

Edited 7 December, 20214 yr by J.R.

Just checked, ATD is a PD 1.9 engine so my comment re flashing coil light probably wrong was thinking of the older TDI with rotary pump injection. I also think that this PD engine has a conventional wastegate turbo so no vanes to stick but check to make sure.

 

Limp mode will trigger an OBD error code which can be read with a reader. Obviously best read before the engine is turned off.

Edited 7 December, 20214 yr by xman

PD100 has a VNT, this is why they'll remap to 135 BHP.

 

MAF is not the dominant input on a PD, it's more for fine tuning and emissions, I'd be looking for a vacuum leak preventing the actuator from giving full boost.

I don't have any experience with PD but earlier Tdi with VNT (AFN) a common problem was leaking at the vacuum reservoir, a tennis ball size/shape plastic thing ,Item 5 below (on ATD)

Edited 7 December, 20214 yr by xman

26 minutes ago, sepulchrave said:

PD100 has a VNT, this is why they'll remap to 135 BHP.

 

MAF is not the dominant input on a PD, it's more for fine tuning and emissions, I'd be looking for a vacuum leak preventing the actuator from giving full boost.

 

If it were me and my car I would have jerryrigged my Mityvac to the actuator on a test drive.

 

Splicing it in with a T piece you could also see the vacuum on the guage and started pumping if it fell away.

 

After testing the actuator with the Mytyvac first to see the full operating range.

IT'S ALIVE!

 

Firstly thanks to everyone for the suggestions and knowledge, has been a steep learning curve!

 

This morning I thought I'd test the MAF sensor using a multimeter as per hatboyharvey's video on the tubes (really useful playlist) and the cable was fine but the sensor was reading alot lower than the one in the video (idle at 1.2V compared to ~2V and then revving it hardish it didn't go above 3V). I needed to pop around the corner anyway so thought I'd unplug the sensor 'just to see' half expecting a cel and limp mode on the way. I WAS WRONG, the car had life! It could spin the wheels and drive like a normal car, got there and plugged it back in for a comparison on the way back and it was pathetic af like before.

 

This was the night and day difference I expected from the turbo swap tbh.

 

Collected a new MAF from ecp (https://www.eurocarparts.com/p/bosch-air-mass-sensor-air-flow-meter-434440617) Bosch 434440617 (40% with winter deal and gave old one back for another £35 back, bargain!) and fitted in 10mins (brew wasn't even drinkable by the time I'd finished). Started her up and I had values on the obd tool (result) so took it for a drive... She now can spin the wheels going into 3rd! Drove it like an asbo for a good hour just smiling! Fast pulling from lights and the M1 slip (that I crawl up every day) I can now power up and actually have to lift off and then driving on the motorway was great, it didn't even register the hills that killed it before and was still puling above 70!

 

/dldr

Car now drives like a car should! Changed maf sensor and suddenly powerful! Happy days

Congratulations!

 

Shame about you being taken for a new turbo though.

Few points because I couldn't find them on here before:

 

MAF readings do rise when engine idling, not sure why but they are reading ~550 g/s when stopped/slowing down as shown below (maf is blue, revs are grey)

town driving

Sliproad and motorway driving (same route as earlier graph (maf follows revs pretty much)

 

Normal driving values are ~20-40 g/s

Motorway values are 40-90 (90 being hard overtake accel +70mph)

My old one was spiking (but not constant as above) and not reading above 35ish on the motorway.

 

My max boost (for that journey) is 16psi

 

 

The sudden jerky motion when taking foot off/putting on of the accel has stopped completely (following the maf change) and the drive seems much smoother now.

1 minute ago, J.R. said:

Congratulations!

 

Shame about you being taken for a new turbo though.

Thanks, massive relief as it was looking like a money pit or scrap yard!

 

I can only assume the new turbo was needed (oven cleaner might've achieved the same goal though), but for them to miss the MAF and then blame the egr (glad I didn't bite) raises a few questions as a electronics engineer with an obd tool and google should not be able to solve things a £75 p/h diagnostics can't.. but that's for a different email and not on here.

 

Thanks again for the help, I'm sure now I've found the big issue others will show their heads!

Glad to hear you've got this fixed.

I'm glad you  got this sorted, 👍 Xman and others

 

maw_mk1_fabia, I want to give you some advice (or old man's moaning) to help you but think it may not be welcome or appreciated let alone wanted, possibly others have had thoughts similar to mine, or not and may express them.

 

Had a 1.9tdi caddy with the exact same symptoms.

But it has a sticking egr valve. First second and third gear were fine. But as soon as it hit 4th / 5th gear. I could floor it and it would have trouble overtaking people on the highway. Like it had a limiter on it. At first i rammed a can of egr cleaner down its throat. Which caused it to spew a pitch black cloud out of its tail pipe that obsecures the general view for anyone in the area. The problem then became intermittent. I eventually replaced it and got it sorted. It has held up so far.

Edited 4 January, 20224 yr by Xsr