1.9 Tdi Auto Slow To Pull Away

[tricky72003]

HI,

I have a 2003 Galaxy 1.9 TDI auto which i feel is very slow to pull away from a standing start. I have followed instuctions on this site about fault finding and would like to thank everyone however i have found a problem:-

 

while on my cheap dianostic reader I have found that the MAP sensor is always reading 75.3

I understand that this could be fault relating to the problem so I changed it for a new one, however the new one is also reading 75.3.

 

When i remove the sensor from its location it still dont change. I ve checked the wire from the ECU to the sensor for a damaged wire and could not find one.

 

I have been reading on the net that I may need a new ECU, if i do change this would it need re-programming (a 2nd hand unit not a new one). or could some help me!!!!

[chromedome]

Do the gears change at all? It could be in Limp Mode (Third Gear). You can always try disconnecting the battery for half an hour to see if the fault clears, make sure you have the radio code.

[tricky72003]

yes the gears are changing , i had someone come out with a snap-on reader the other day and told me no codes are present on the engine or gearbox. I just have the problems with the reading on the map sensor

[alan_131]

I have Mk1's so this could be different, but on mine the output from the MAP sensor is in millibars and in the range 900-2500 ish - or loads more than yours. I'm wondering if either your MAP is sending a duff - and right at the end of the range - signal - which I would have expected to be detected by the ecu as a problem code - or if this is the temperature reading which IIRC is sent by the same physical sensor assembly (TMAP) on a MK2 as opposed to the MK1's separate sensors.

 

Could I suggest uplugging cable from the sensor and seeing if the value changes - or it flags any faults. Also, you could try reading other temperature values before the car is run in the morning - they should all be pretty much the same.....

Might also be worth comparing boost and atmospheric pressures reported with the engine stopped.

 

I think most sensors are read by the ecu directly, (ie it senses voltage/resistance/some waveform etc presented to it across the loom and translates it to a value like temp or pressure ) and that's why there's a possiblity the ecu needs replacing if a value is wrong. But, I'd think that the ecu is fairly robust provided that it's not presented with some voltage much outside what it expects, so very much a last resort if it was my car.

 

I've often thought about buying a standalone reader, though nowadays more to keep in the car "just in case". Be interested to know what you think of yours. I started using vcds-lite recently and have become an instant huge fan. If it were me, I'd probably be tempted to buy a cable (<£10 on ebay) to see if vcds agrees with your reader and use some of the logging features.

Good luck.

[tricky72003]

if i unplug the sensor i still get the same reading.

its mad i understand that this then should read 0 with it unplaugged but I dont get it.

[alan_131]

Sorry that didn't help. I'm wondering if your reader is really pointing in the right direction. I know it's a bit of a pain, but I'd really trust the output that vcds gives over a standalone reader, just because the software is specific to vw and used enormous numbers of people. And being software easily updated if a problem is spotted. . .