Revs dropping below idle

[scooobi]

Hi Type R owners

I am new to this so I do apologise if this has been covered. I have read through some of the post which have a similar issue to what I am experiencing regarding revs dropping below idle but i dont think its what i am experiencing. I shall try to articulate my issue with as much details as possible with the hope someone on this fine forum could shed some light or point me in the right direction that been said here we go.

I have an 05 face lift EP3 which I have proudly owned for around 3 years for the record this is my third one. I had brought it completely stock on around 80k miles on the clock and its been used as a summer weekend toy mainly and the occasional track use.

Since my ownership I have carried out the following

4 -2-1 japspeed manifold
3 inch solid fab exhaust system
Tegiwa carbon induction kit
Rbc inlet manifold
70mil tegiwa throttle body
Kpro v5 ecu

All work was carried out by TDI north including the map around 2 years ago mapped to 253 bhp I was one of the lucky ones that got in just before they closed for business.

Right on with this dreaded issue I am having with regards to the revs dropping below idle.

When I start the car up from a cold start the revs idle as they should around 1.6k ish when I rev the car the revs drop below the idle to around 500k and some times lower to the point where it sounds like it's going to stall and than the revs return to its idle at 1k. It does this for around 30 mins and than the revs are completely fine and return to the 1k idle. However that been said, if I turn the car off once the revs are settled and restart it for example a stop at the petrol station the revs dropping below idle returns all be it I don't have to wait 30 mins for it to settle again but I'll have to wait for around 10 mins.

At first I thought it's a cold start issue but it does it wheater it's a cold start or a warm start.

The waiting time for the revs to settle from a cold start is longer than a warm start. I have had it looked over by my mechanic who has assured me that everything mechanical is in working order and advised me it's an electrical issue VSS sensor and circuit board as that's the only thing that comes up on the reader and could also be a possible issue with the map?

Would like to mention when I had the work carried out by TDI North I had a 2.5 inch M2 motorsport exhaust system which I have replaced with a 3inch solid fab system. It ran fine with the m2 exhaust system and it ran fine when I had fitted the solid fab exhaust system this issue has started when i pulled it out this summer that's gone by.

I have tried to attach a little video of the issue which hopefully can create a better picture for you guys however keep getting an error stating the uploaded file does not have an allowed extension?

Thanks to all those who have taken their time to read this post and any help / advise would be greatly appreciated and apologies for the long read.

 

[Shoonk]

Have you looked at the throttle position sensor? Have you upgraded your engine mounts?
If the mounts are stiffer it can cause more vibration which can effect the TPS which in turn can cause fluctuations with your idle, maybe worth checking.

 

[scooobi]

Hi Shoonk

I haven't personally looked at the throttle position sensor and I'm not sure if my mechanic had checked this when he had the car in, he did say mechanically it is sound other then the VSS sensor fault code therfore put it down to it being an electrical issue. Could a bad VSS cause the revs to drop as I described. That been said I shall get the TPS looked at is there any tell tail signs of a faulty TPS. As far as engine mounts they are stock which I am planning on replacing but want to clear this revving issue before I commence with any further work.

Thanks for your reply

 

[Shoonk]

If there is a code saying a vss fault then that is most probably it then, they both give very similar symptoms to be honest that's why I thought it was worth mentioning. If I remember correctly I think the OEM throttle position sensor is a wiper style sensor that can wear or stick over time giving false readings.

A friend of a friend had very similar issues with revs dropping and almost stalling on his old EP3 and his issue was the TPS, you can put a multimeter on it to see if it's giving a correct reading, however, I am not too sure on what the readings should be sorry.

Having said all this, personally I would go down the vss route first seems you have a fault code for it.

 

[scooobi]

If there is a code saying a vss fault then that is most probably it then, they both give very similar symptoms to be honest that's why I thought it was worth mentioning. If I remember correctly I think the OEM throttle position sensor is a wiper style sensor that can wear or stick over time giving false readings.

A friend of a friend had very similar issues with revs dropping and almost stalling on his old EP3 and his issue was the TPS, you can put a multimeter on it to see if it's giving a correct reading, however, I am not too sure on what the readings should be sorry.

Having said all this, personally I would go down the vss route first seems you have a fault code for it.

Thanks for the information/ advise. Need to find a decent auto electrician and get it booked in for a vss replacement. I shall update this post once done.

Thanks

Kind regards