GTI help!

I wasn't too bothered about the poor MPG at first because I was just ironing out problems with my GTI conversion but I'm getting a bit fed up of it now, especially seeing as my 2.9 VR6 is doing about 37-40mpg. I'm getting 50 miles to £10 which I think is ridiculous, thats about 30mpg. So what I think is its not going in to closed loop mode, the only error code I am getting is speed sensor which from what I have read is only a problem if the speedo isn't working, which it is.

Is there any way of finding out for sure if its going into closed loop? I'm thinking either the temp sensor isn't working properly or the lambda sensor isn't but I've already replaced a load of parts and would rather go down the fault finding route than the trial and error route.

The only other problem I have other than the poor mpg is a bit of a poor idle, it sometimes sits happily at 1100rpm but other times anywhere between 400-1500rpm and fluctuates.

Any help would be most appreciated!

Im sure the lambada controls the loop
Have you changed your fuel filter recently?
What mods are on the engine?
Is there a chip in the ecu, I change mine back to std when im not using my lumpy cams, if I leave it in theres a significant change in the mpg coz the std chip isnt dumping loads of fuel in at lower revs

Gary

OK, guess I'll change the lambda. I did do a test as per the workshop manual and it seemed fine, I can never remember if its higher or lower voltage makes it rich but it was fluctuating slightly above 0.45v but mostly below.

As far as I'm aware no mods, I'm even running standard air filter. Can't remember the last time I changed my fuel filter to be honest, are you thinking that could be the cause of the lumpy idle? may have a point.

Before replacing it try cleaning the carbon off it and see if its any better. The voltage seems fine so it doesn't seem knackered

she was running very rough at low revs and terible idle few years back, i changed the filter and it was fine
obviously if the lambada is shagged then you will notice a difference
how about the rotor arm and dizzy?
get the timing checked and get the tps properly calerbrated, only little things but they all help

dont get me started on fuel filters, all i can say now is iv fitted a nissan micra 1.3i filter. way better and cheaper

Ahh ok I'll give the fuel filter a go, the lambda sensor is looking a bit worse for wear and they are only cheap anyway so I'll get one of those as well. I've changed the dizzy but not the rotor arm.

Timing I have checked, double checked, triple checked and quadruple checked! Also calibrated the TPS several times. I have replaced the MAF as well.

I was thinking that even though I had the lambda unplugged I wasn't getting an error light, presumably the temp sender will inform the ecu at the right temperature to switch over to closed loop, I am getting a temperature reading on my dials but could it be possible for it to give me a correct temperature reading but not tell the ecu the right temperature?

What ecu are you using?
Has it got an I or F on the casing
Coz the ph1s didnt even use a lambada, I think some used to come with a small dial near thefusepannel that adjusts the richness at idle

Its a 1992 so whatever that makes it, a mk3? I'll have to check whats on the ECU later though just in case the previous owner has been swapping ECU's or if I've accidentally mixed my mk1 stuff up with my conversion parts.