170 tdi flat spot in 3rd at 4000rpm?

[richwill607]

Hi Guys, Just wondered if anyone else has experienced a bit of a flat spot in 3rd gear when accelerating hard after 4000rpm?

I was travelling back from London and pulled out to overtake having changed down in to 3rd, the car was accelerating great all the way up to 4000rpm when the power just seemed to suddenly drop and the car stopped pulling. I didn't actually think much of it at the time as I did have a car full off people however the same thing happened again this morning with just me in the car, having dropped down to 3rd to over take and hit 4000rpm and there's the flat spot again I changed quickly in to 4th and it keep on pulling again. Bear in mind this doesn't seem to happen in 2nd or 4th and the car seems to pull smoothly all the way to the redline, so just wondered if anyone has noticed it too?

[iAmbu]

I have noticed this also, however I have a stage 1 REVO remap (which is AWESOME by the way!), and I thought the re-map was the culprit..... I had the remap done back in November time-ish, and had no problems and no apparent flat spots up until about a month ago when I first noticed it. I have noticed I have a flat spot around 4,400rpm in 3rd, and multiple flat spots at the top end of the revs in 4th gear. It doesn't happen every time, but I can get it to occur fairly regularly especially when I accelerate hard (as you say). Interestingly when in 3rd gear, it 'rides through' the flat spot and then the power comes back in for the very last part of the rev range before the red line before I have to change up to 4th. It feels like a lack of boost.

I have taken my car back to the REVO dealer (who are excellent luckily). They came out with me in the car to data-log on their laptop as the fault happened. They have noticed when it happens the amount of air being drawn in / demanded by the engine suddenly drops significantly.
They are querying a faulty boost control valve or air mass sensor. But first they have spoken to REVO HQ, and have sent my remap code to REVO for analysis and to see if REVO can eliminate the problem their end.

I'll keep you posted.

p.s. Forgot to add, when I set the remap to 'Stock' mode via my REVO switch, I cannot get the fault to occur, as I presume the stock REVO map doesn't require or demand as much air/boost

[stevieboy]

Can't say I've noticed this on mine. I've done 10,000 miles since I had the car mid December'09 and it's been faultless, however....

...one thing I have started doing in the last couple of months is running it on Shell V-Power diesel. The difference is astonishing. The motor pulls much more cleanly and seems more willing to rev. Changing down through the DSG box, as the rev's rise in the lower gear, is so much smoother. I was putting Morrisons in before, because it's near and I'm lazy!

Just wondering if poor quality fuel may be a contributing factor?

[Ibanez33]

I'd say it wasn't the fuel. I've noticed too (particularly when overtaking), and I've only put vpower or BP (not ultimate as for the price it did feel any different).
It'll be great if revo can amend this as I'm sure I'll be getting mine revo'd next year

[richwill607]

Mine is just the stock 170 TDi with only 3000 miles on the clock and the story continues. Had a loss of power again last night but this time it was like hitting a brick wall, pulled out to over take and hit 4000rpm and all power just went.

Decided to take it to my local VW garage this morning and do a few test on the way, the fault is very intermittent sometimes it would happen in second gear and even 4th, but most noticeably in third. Got the car booked in for tomorrow but just before I left the girl asked if any of the warning lights on the dash had come on. At this point they hadn't, that is until I left the garage and tried to drive to work, this time the power went at 3500rpm and that’s where the revs stayed needless to say it stopped accelerating too. The glow plug light then started to flash and the warning on the MFD said Engine fault; Workshop. I turned straight back round and left the car with the dealer where hopefully now that a fault has registered they should be able to sort it.

[trix]

I hope you get it sorted, its dangerous especially as it happens intermittently. with the warning lights it should have left an error code for them to read

S

[richwill607]

Yeah fingers crossed they'll get it sorted out quickly, I don't like being with out it!

[richwill607]

Well so far Harrogate VW has not lived up to the great service I got at Leeds VW. Harrogate called me this morning and said someone has tested the car and couldn't find a fault, they also reckon they've plugged it in to the diagnostic computer but no fault has been registered. This seems very very odd seeing as there was a flashing warning light on the dash and the MFD said there was an engine fault!

I’ve told them that I don't want the car back until they can say it’s fixed as it is dangerous. They're going to have another look today. I have lost all faith in garages these days, if 'Computer says NO!' then they're stuck or they just can't be @rsed!

Rung VW customer service to try and speak to someone technical and they aren't able to help other than to suggest I take it to my next local VW dealer if Harrogate fail to find the fault!

[golfgtdude]

My brother had a problem just like this on his Audi TT sport 240 when we picked it up. Acceleration was great, then sometimes it would go flat but changing gear would bring it back. Eventually the problem became permanent.

I plugged up to VAGCOM and it said there was a problem with overboost.

Audi dealer had a look at it and said the the boost solenoid was defective. It was duly changed and cured the issue.

[iAmbu]

Got an update on my situation (described above)...

My REVO dealer (in liaison with REVO HQ) tried to eliminate the problem by installing a map on my Roc which is designed for cars in much hotter countries (South Africa etc.). Their theory behind trying this was they were querying whether the exhaust gas temperatures were getting too hot, which the car was sensing thus reducing power until the temp dropped sufficiently, then restoring the power, until the temp rose again etc. The map designed for hotter countries tones down the performance at the top end of the revs ever so slightly to counter this.

This however did not help or fix the problem.

My REVO dealer had my car for a day to test and diagnose what is causing the loss of power under load. They have now successfully diagnosed it as indeed being due to high exhaust gas temperatures. They proved this by driving the car at, say 3500 rpm in 3rd gear for half a mile (causing the exhaust temp to increase) - The problem then appeared much lower down the rev range than it ever used to. They were able to repeat this and re-create the situation time and time again, so they are confident that this is what is causing the issue. Luckily this means there is nothing major wrong with my car!

They are blaming this most likely on my DPF being partly blocked with soot. I do try to go on longish journeys frequently to allow the DPF to burn off the excess soot, but they say that the VW DPFs are still a design flaw! Unfortunately there is not much they can do about that issue until the car displays a DPF warning light (which they predict will happen at some point), in which case it'll be a VW warranty issue.

In the interim, the problem still remains They have liaised with REVO HQ who inform them that another REVO dealer has a Skoda with the same engine which is displaying the same issue. REVO HQ are going to take another look at the map coding to see if they can stop it happening. So it's just a waiting game now. Will keep you all updated.

[mr_patrick_bateman]

HI did you managed to get it sorted? had my tdi 170 mapped at revo HQ daventry (security encriped ecu), no probs yet, only done 2 months ago though! could they not do dpf regen at the dealer?

[iAmbu]

HI did you managed to get it sorted? had my tdi 170 mapped at revo HQ daventry (security encriped ecu), no probs yet, only done 2 months ago though! could they not do dpf regen at the dealer?

I'm waiting on REVO HQ to look at the coding to see if they can tweak it to overcome the issue. My REVO dealer told me to chase it up with them if I haven't heard anything after 3 weeks. Will update this thread when I know more.

Not sure if you can force a DPF regen

[mr_patrick_bateman]

I am sure you can do a re-gen on dealer software and vag-com. will look into it tomorrow we have vag-com in work.

[iAmbu]

I am sure you can do a re-gen on dealer software and vag-com. will look into it tomorrow we have vag-com in work.

Thanks I would appreciate that.

[iAmbu]

Update: I have been informed that REVO are releasing new (revised) re-map coding for the 170CR TDi engine tomorrow (Friday 19th Nov 2010)... This is in response to my car (and one other I believe) having the problem described above. I am going to have the new coding applied to my Rocco on Monday (22nd Nov) - Will let you know if it cures my problem. Fingers crossed!

[iAmbu]

I'm very pleased to say that the new coding from REVO has completely fixed the issue I was having, and the engine and re-map are now perfect again

[Ian_Mac]

Is it the case then that everyone with the 170 TDI Revo map should have it updated?

[iAmbu]

Is it the case then that everyone with the 170 TDI Revo map should have it updated?

I don't know to be honest - I guess you could say if it aint broke, don't try to fix it. Contact your REVO dealer for advice

[mr_patrick_bateman]

Glad you got it sorted in the end, will have to get mine updated with the revised software. I have not had any probs yet though but i have only done about 5k, did you notice a change in performance with the update?

[iAmbu]

Glad you got it sorted in the end, will have to get mine updated with the revised software. I have not had any probs yet though but i have only done about 5k, did you notice a change in performance with the update?

No, no performance update over-and-above the original remap, but it restored my remap to what it was (eliminating my problem without toning the power down)