Vcds help

[Andy9]

Hi all, can someone point me in the right direction on how I can test my map sensor using vcds and I how I can test for vac and any boost leaks, my car is randomly going into limp mode and have to cycle the ignition (usual story)!!, Had this prob last year so stripped and cleaned turbo/inlet man completely and replaced Maf /checked all boost pipes for splits/ egr blanked off and all seemed good but prob has returned. I scanned engine and getting 17965 charge pressure control/positive deviation/intermittent/ just wondering if map sensor could play a part in all this but don't want to go replacing parts willy nilly, this has turned into abit of a brain drainer!!, Any help will be gratefully received. (2004 Audi A4 b6 1.9tdi quattro 174,000mls)

 

[pauldazzle]

Sounds like you have sticking turbo vanes or a dodgy N75 valve to me.
http://wiki.ross-tech.com/wiki/index.php/17965/P1557/005463

 

[Andy9]

Yes, I forgot to mention I replaced N75 last year with a brand new one, the chra and actuator in the turbo was also replaced last year and and turbo recalibrated on flowbench and was deemed a good unit, could the vnt ring itself have a slight bit of wear in it causing it to stick slightly, I'm possibly thinking now about changing this but looking at the vnt I can't see any real wear, I also thought about replacing the map sensor for another and trying it but would like to test my old one first before throwing more money at it, IL try and upload some pics of my turbo vnt which I took last year while stripping/cleaning turbo, any thoughts ?

 

[pauldazzle]

Turbo vanes sticking then. Try the Mr Muscle fix it usually works if you do it correctly.

 

[pauldazzle]

Vanes don't look too bad in the photo, but the Mr Muscle fix is cheap to do so worth a shot.
Pull the vacuum pipe off the turbo actuator, & manually work the actuator to see if it's moving smoothly, & has full travel. If it doesn't then the Vanes are sticking.
Also worth replacing all the vacuum pipes as they fail eventually. There's a T piece to the brake servo that commonly fails too, but if that happens you get a hard brake pedal & poor stopping power.
If the MAP sensor has died I would expect a fault code. BTW, You can clean the MAP sensor with Carb cleaner or Isopropal.

 

[Andy9]

Hi mate thanks for your help, last year i stripped the turbo completely and let the vnt part soak overnight in petrol and was spotlessly clean when i reinstalled it all, i replaced all the vac lines with silicone ones, brand new N75, cleaned map sensor in carb cleaner, removed intercooler and washed out in petrol, checked all boost pipes, replaced Maf sensor (non -genuine)although there was a small amount of oil leaking from bottom fins of intercooler , i did make a small repair to this but i think its still weeping, would this cause a limp mode prob ?, ive also blanked the egr off with a plate and fitted a small bolt in vac pipe, i did notice in vcds the maf readings are higher than the specified range since blanking the egr, could this cause a prob ?, thanks again for all you help, cheers, andy

 

[Andy9]

Upon cleaning up and inspecting the vnt side of the turbo i did not think the vnt looked particulary worn and dont really want all the hassle of stripping the turbo again and buying a new vnt unnecessarily, i did replace the Coolant temp sensor (non genuine-EBAY) and im gonna replace this with a genuine one although its not throwing any codes?, I also replaced the thermostat with a Gates item, funny thing is over the winter the car was going into limp mode all the while with the temp gauge sometimes only reaching 70c and now the weather has got warmer the temp gauge is going up just under 90c on warmer days with only intermittent limp mode ?

 

[LayerzA3]

Are you logging things things in VCDS? Fuelling, MAF values, Fueling, Boost requested vs actual? something should give a hint.

 

[Andy9]

Yes, I have been looking at various parameters in vcds and all things look withing spec although Maf reading is outside specified target and giving an higher reading, not sure if this is because egr is blanked off ?, I'm still abit of a novice where vcds is concerned and still learning how to use it properly!!

 

[LayerzA3]

Back when I had my A3 I had a MAF issue that threw me right off in hunting the issue - I used VCDS to look at the MAF readings and how they'd affect fuel and I think I found that the torque limiter was being way restricted due to the MAF seeing 550 mg/r or nothing working.
However I was making boost fine - I don't think I'd of sussed this one easily to 100% confirm it was the MAF.

Funny thing too on my A4 2.5 TDI I've been way down on performance which was due to a boost leak but in VCDS I was seeing the requested boost! Allbeit a bit later then you'd expect so I suspect a bit of overwork - this reminds me of the A3's boost leak where a pipe was aged and started to occasionally split and go into limp.

 

[Andy9]

Yeah I've scowered (if that's a word) over the boost pipes and took each one off and examined them minutely looking for any sort of split or deteriation but nothing, the only things I did found was the boost pipe (metal) that runs under the radiator that seems a bit corroded as the undertray was missing when I bought the car and the intercooler looks abit grubby and there is a slight oil leak from it in the bottom corner ( would this leak boost pressure ?) I'm gonna try and rig up a diy boost leak test (plastic pipe/ shearer valve) and try and pressurise system using a 12v compressor, I'm gonna reinstate the egr and look at Maf readings although I think the car runs better with the EGR blanked , thanks for you help and comments, much appreciated

 

[LayerzA3]

I don't think the EGR is part of this equation tbh.

If you can get some logs sorted of normal running and when you see limp mode and post them I think we will be closer to the issue- I know it's a ballache though my laptop sucks and overheats so I need to use an invertor and keep it cool when I log.

 

[Andy9]

Hi, I'm sorry for lack of an update but I've been struggling with a prolapsed disc in my back so not been able to do much however I'm now up an running again and managed to service the car today and have a good look, while inspecting the boost pipe that runs under the radiator I noticed the bottom of the intercooler is covered in oily grime and is very wet and looks like the bottom of the intercooler is leaking, will this create a boost leak ?,can anyone tell me is this sort of normal or is my intercooler kaput( sorry but still learning about diesel engines), I've looked at various engine parameters with vcds on idle and all looks normal apart from Maf reading which is 485-500, but put this down to egr being closed and blanked off, am I right ?, Cheers,andy

 

[LayerzA3]

Is the MAF reading 500ish across the range? On my A3 1.9 TDI the MAF baseline when not working was 550 mg/r but higher pretty much all the time otherwise.
If you could post a log or graphs it would be great.

 

[DieselJake]

Hi, I'm sorry for lack of an update but I've been struggling with a prolapsed disc in my back so not been able to do much however I'm now up an running again and managed to service the car today and have a good look, while inspecting the boost pipe that runs under the radiator I noticed the bottom of the intercooler is covered in oily grime and is very wet and looks like the bottom of the intercooler is leaking, will this create a boost leak ?,can anyone tell me is this sort of normal or is my intercooler kaput( sorry but still learning about diesel engines), I've looked at various engine parameters with vcds on idle and all looks normal apart from Maf reading which is 485-500, but put this down to egr being closed and blanked off, am I right ?, Cheers,andy

Normal for it to have oil in but not normal for it to be leaking! I'd say remove it, clean everything (so it isn't wet else the connectors will just slip straight off), spray a load of hairspray on the intercooler and connecting joint (or glue if your feeling extreme, basically something to hold them together), then reattach. I'd also use a few clamps if you can at different angles just to be sure.

From what I recall the later 1.9tdi's like yours have plastic ends which are prone to leaking, etc; if you wanted to get rid of this and upgrade to something more stable I've got a bigger full metal version (metal ends), probably got some clamps and similar (Darkside ) pipework/connectors I can chuck in too if interested.

 

[Andy9]

I cleaned it out thoroughly last year and i repaired a small leak in the bottom right corner where the fins meet the body with some radiator leak repair stuff i had knocking about, but i think looking at this it would be just best to replace it (174,000) as surely if its leaking oil it there must be an air leak ? regarding my high maf readings i did recorded some logs but im having trouble finding them on my laptop!!, typical, il get some more done, thanks for all you help as always its much appreciated

 

[desertstorm]

Without an EGR delete the 1.9 TDI at idle is around 250, with EGR delete you are looking at around 450-500 .
Usually when a MAP sensor fails they show full boost all the time. The two that I have seen did anyway. They were showing maximum boost at idle, which is obviously incorrect. If you are seeing a 17965 charge control code then that means it's over boosting. It won't be due to a boost leak anywhere as these cause negative deviation events.
As you know these are usually due to N75 issues, MAP or VNT mechanism sticking.
What make of N75 did you replace the OE part with. There are a lot of cheap Chinese parts around that are no where near the quality of an OE part.

 

[Andy9]

Without an EGR delete the 1.9 TDI at idle is around 250, with EGR delete you are looking at around 450-500 .
Usually when a MAP sensor fails they show full boost all the time. The two that I have seen did anyway. They were showing maximum boost at idle, which is obviously incorrect. If you are seeing a 17965 charge control code then that means it's over boosting. It won't be due to a boost leak anywhere as these cause negative deviation events.
As you know these are usually due to N75 issues, MAP or VNT mechanism sticking.
What make of N75 did you replace the OE part with. There are a lot of cheap Chinese parts around that are no where near the quality of an OE part.

 

[Andy9]

The replacement N75 was Pierburg and was a direct replacement for what came off, i went through everything to be honest inc replacing all vac lines, examined all boost pipes, i removed the egr and cleaned last week even though it was blanked off and did the mr muscle on the turbo as part of a general service and all seems ok at present, when i took the undertray off and had a look underneath i noticed the bottom of the intercooler was covered in oil and has oil drips hanging from it, should i replace intercooler ?, what i would like to do is do a boost test and check fuel trim with vcds and log it but im abit unsure how to do it, could someone give me a walkthrough how to do it ?