Hello, And Spontaneous Acceleration Issue

[AdrianHiggs]

Hi all

 

I'm new here, having just become the proud (if currently slightly concerned...) owner of an '03 1.9TDi 115. It's great to have discovered this forum.

 

Earlier today I noticed sitting in traffic that the car was idling a little faster than normal - a shade over 1000 rpm. I blipped the throttle and the problem went away.

 

This evening, it was rather worse. On starting (foot off the accelerator) the engine revved up to about 1500/2000 for a moment, then dropped back to a norma, idle. I got about 100 yards up the road before I had to turn back: bizzarre spontaneous acceleration at random intervals. This happened whether I had my foot on the accelerator or not.

Quite glad to be able to turn around and get back home without ramming anything...

 

I've scoured the forum and the only thing I can see that seems close is the ISV post here: http://www.fordgalaxy.org.uk/ford/index.php?/topic/13640-problems-with-isv/&do=findComment&comment=103773

Can anyone shed any light?

 

Many thanks,

 

Adrian

2003 1.9TDi 115

[gregers]

welcome to the forum,cant add anything for you,im sure someone will be along shortly to give you the correct advice.

[seatkid]

I would say two possibilities

 

1) Throttle Position sensor (TPS) - its mounted on the accelerator pedal. They are known to go intermittent, they are a dual device and fail when one side doesnt agree with the other (its a a dual track potentiometer). Usual symptom is loss of foot pedal control and engine speed defaulting to 1300-1500 rpm. On the MK1, you lose the pedal control and the glow plug light flashes to indicate a fault until the ignition is turned off - which is a bit silly and dangerous. Not sure but on your Mk2 its possible theyve improved the software by restoring pedal control immediately the sensor is working (both tracks agree).

IIRC They cost around £60 from a dealer.

 

2) Intermittent connection to the engine temperature sensor might lead to changes in idle speed? (not sure)

[SilverBeast]

I believe the throttle pedal is electronic and the throttle position sensor uses two potentiometers.  If they don't agree then the Engine Management assumes there is a fault and defaults to a fixed engine speed, so the vehicle can still be driven (sort of).  If this is just developing on yours it may be jumping around as they agree then disagree.  Sorry thats all I seem to recall reading (probably somewhere on this Forum).  I guess it could be worn potentiometers in the throttle position sensor or faulty wiring to it.

 

First port of call is to read the Fault Codes from the system.  VAG-COM/VCDS-LITE leads are less than £10 on ebay (search the Forum there are plenty of links) and the free limited version of the software  (good enough for most things) is  available to download from the manufacturers website (Ross-Tech).

[SilverBeast]

seatkid beat me to it - must type faster!

[AdrianHiggs]

Thanks chaps. Helpful stuff.

 

Interestingly, I had noted the engine temperature guage moving around pretty wildly (for example swinging from just above the coldest temp up to 90 degreees and back down again in the space of about 15 seconds half way through a motorway run) so maybe it's that. Here's hoping.

On the accelerator pedal pots, would I be able to check them with a simple ohm meter? I have one to hand, but would have to get hold of the VAG-COM/VCDS-LITE cables which would take  afew days.

 

Adrian

[AdrianHiggs]

Looking at http://www.fordgalaxy.org.uk/ford/index.php?/topic/11148-115-tdi-temp-sensor-replacement it seems the symptoms graemer was seeing (post number 4) are very similar to mine.

Hoping it's just a dodgy connection. If the sensor is shot, is there any hope that the sensor from a 1999 Alhambra 1.9TDi would fit and work? I know it's a different engine... just hoping since I happen to have a dead Alhambra sitting on the drive waiting for the scrap man.

 

Adrian

[jonbob]

Adrian

The symptoms you describe about wandering idle speed and temp gauge are exactly the same as on my 130 tdi when the water temp sensor went, also it may be worth checking the electric run on pump as well as you may find this kaput as well. As the others have said VAG COM will show the fault code (well it did on mine)

Jon

[seatkid]

Interestingly, I had noted the engine temperature guage moving around pretty wildly (for example swinging from just above the coldest temp up to 90 degreees and back down again in the space of about 15 seconds half way through a motorway run) so maybe it's that. Here's hoping.

 

That indicates that the problem is with the temperature sensor. As its jumping about, its probably a loose connector. The sensor is mounted at the back of the engine. see here http://www.fordgalaxy.org.uk/ford/index.php?/topic/11854-mk2-water-temp-sensor/&do=findComment&comment=98280

 

The ecu alters the fuelling with reported temperature and so the idle speed varies.