Revs dipping when idleing

[kriso]

My ebay Vag-Com lead doesn't seem to want to work with my car with the engine running so I'm unable to test this, but I'm suspecting this could be a sensor problem. I was convinced it would be the coolant temp sensor, but the temp needle on the dash doesnt seem to move from 90 when the engine is warm.

Is there an engine temp sensor too? And does the needle on the dash look at this or the coolant temp sensor? I can't find the engine temp sensor on ETKA too so can't see where it is or get a part number.

 

[CupraStoo]

engine temp is the temp of the coolant as far as i know

ive never seen a car with a sensor for both

 

[Nath.]

the needle on the dash will be the coolant temp,
there are various sensors within the car that measure temp, charge/inlet manifold and fuel temp spring to mind along with the one in the front grill for the exturnal reading and then the climate internal cabin sensor

I'm sure the engine ECU gets temp readings from various sensors

 

[kriso]

ok, im going to buy a new coolant sensor and replace that to see if it makes a difference...i suppose if it is giving a reading that the engine is too hot or cold, then it will adjust fueling which is why the revs spike up or down for a second then back to normal. And this only happens when the engine is up to temperature.

 

[Nath.]

there is deffo another temp sensor for the ECU, it's green IIRC and well easy to replace

do a search mate I'm sure people have reported problems with poor starting caused by it and also pics of it under the engine bay

 

[Hudson]

Having read through this I'd say this is definatly the throttle body needing a good clean out. I've had this on 2 previous vag engines where i would break for a junction my revs would drop, idle then drop below idle and sometimes even cut out.

Did you manage to get the throttle body off? Give it a good blasting clean and see what happens. Also just out interest (daft i know) when was the last time you changed ur fuel filter? You revs dropping mite be starved for fuel - i doubt it but its a cheap thing to check.

I had a quick google and found a few guides, obviously the engines arent the same but the principle is and at least you know what ur looking for. (think its a guide for a jetta turbo)

http://forums.vwvortex.com/zerothread?id=1116399

Oh and read this:

http://forums.vwvortex.com/zerothread?id=3626234


Happy hunting.

 

[kriso]

cheers...I havent attempted getting the throttle body off. I was going to try removing the intake hose and squirting some carb cleaner in there. It it worth removing the whole throttle body and having to replaqce the gasket etc.?

I haven't checked the fuel filter. Not sure if it was done at service or not but car is only on 19000 miles. I'll look into it.

Ordered a temp sensor today anyway - £25!

 

[Small]

Mine does this also and seems to be more noticeable after my remap. It does not drop below 600rpm and it only does it every so often so i put it down to a characteristic of the map/car. If it gets more noticeable or worse then i'll investigate further and try the above suggestions.

 

[kriso]

Mine has always done it since I got it I think I'll try the throttle body clean idea. Just thought it might be related to the coolant/temp as it only does it when up to temperature.

 

[kriso]

Ok I was going to clean the TB but couldn't get the hose of the throttle body. It seems pretty well stuck on even after removing the clip. Any tips on how to remove this thing? I didn't want to try levering it off with a screwdriver incase it splits.

 

[OFX]

hi people i have a 57 plate cupra and i have had the same problem but i think it was the fuel that i was using when i put 95 unleaded in it i got that problem when i swich it to 98 the problem stoped so it mite be the fuel you are using because in the manuel it says you should use 98. so i will say give it a try

 

[kriso]

I only ever use Shell V-Power or BP Ultimate so don't think the fuel type/octane level is the problem unfortunately.

 

[OFX]

and when i asked my seat dealer he said that some times it can be the ecu program so he just reset the ecu for me i know that because he done it infront of me and my be that is the problem there can be may thing that is causing it but it is all just a triel and error thing so may be give that a try.

 

[kriso]

I fitted a new coolant temp sensor today and after taking it for drive and then leaving it idleing for a couple of mins, the revs seemed pretty stable. Time will tell, but hopefully this has cured it

 

[m_zafar]

whats the latest mate, as i have done what you did and the revs sometimes drop (not allthe time)?

 

[kriso]

It's better than it was but still does this sometimes, although revs dont seem to drop quite as much as they did (before it almost sounded like it was going to stall).

It's had a new MAF sensor and new coolant sensor now, so the next thing I will try is cleaning the throttle body but the intake pipe is really difficult to get off which is why I haven't done it yet.

 

[m_zafar]

Exact same problem as i'm experiencing with the same fixes. The car got to a stage that it wanted it seemed like it was gonna stall. The temp sensor made the biggest difference. Vag Com shows there the following:

17705 - Pressure Drop between Turbo and Throttle Valve (check D.V.!)
P1297 - 35-10 - - - Intermittent

Makes sense as well however for the life of me cant find a leak. Used carb cleaning spray and couldnt detect a leak. Have a forge DV. Might change it with a standard second hand one and see what happens.

 

[kriso]

I dont have any faults logged on mine. My vag-com only works with the engine not running which makes it hard to diagnose. If I could monitor more values while running, maybe I could get to the bottom of my problem.

 

[m_zafar]

i get the fault with the ignition on and the engine not running.

Gonna use the following link to disconnect the DV and reconnect it next wekend:

http://uk-mkivs.net/blogs/uk-mkivs_diy_guides/archive/2005/01/01/243574.aspx

 

[m_zafar]

ok, changed the fuel pump relay and idling is miles better