Weird hot IAT issue with VEMS on AUDI 5cyl engine

[AVP]

Hi,

as we all know, audi engines have to have the idle mat/tps table adjusted in a way to be able to get the lamda sorted when the IATs become high.

On my engine today i had this issue:

On 35 or more C of IAT, the lamda (with EGO off) was showing 0.90 and going richer. The engine was running fine like that.

Once i tweaked the tables, to get it to 1.00, the car started to act as if it was lean!!!

i couldnt understand why!
Is that an issue with my wideband lamda? could it be that it needs recalibrating?

ALso at the same time, my bosch 044 fuel pump started to become really loud and whiney, and it is less than 1 year old in use.

can someone shed some light as to how to proceed?

Should i replace the pump?
Should i recalibrate the wideband?
Should i replace the wideband?

thanks

V

[AVP]

after a few more checks today i can say that the plot thickens...

It appears that if i leave the car after it has warmed up and go and fire it up again, esp. with MAT being above 40 or 50C. as soon as it fires up it is very lean. IE lamda = 1.15.

SO i can fix this by getting my MAT/TPS table adjusted.

Fine, so i drive off, go around for a short drive, MATs drop down to 35C, the MAT/TPS table is also nicely set there as well..

Then gradually, i start noticing when finding traffic lights that now my idle fueling is overly rich!!! EGO correction having to take away fuel, down to 90 or 86 EGO correction to keep my lamda=1.02.

I cannot understand WHY when i start if from stationary, it is lean, and when i drive for 5-10mins it gets rich??

Only thing i can think of replacing is my N80 EVAP solenoid just in case it has been stuck open....

[GintsK]

Because of hot fuel and fuel system parts what loose density a much.  Probably also hot injectors change its characteristics a bit.
I suggest to use just afterstart enrichment to settle the hot restart problem.

Gints

[AVP]

i see
how much would you use?

i noticed that it may take even 5min or more to get it back down to being rich, so as the mat/tps table to work there. WOuld you only do it so as to allow EGO to take over?

[GintsK]

like 11...15% 300...500cycles. And then - ego correction.

[AVP]

i have the EVAP valve connected and functioning with VEMS on overrun and i will try to see if that is malfunctioning and keeps bringing fuel vapors all the time in the car. If that doesnt do anything then it means that something of the above is causing the problem

At which case i would have to keep the MAT/TPS table for idle as lean as required, and try and use more EGO correction.

[AVP]

If there are no faulty parts, what should I be expecting to see around 50-70C MAT on lambda? How much richer does it get?

[AVP]

Yesterday i did the following:

1) replaced the battery which was dead(i had already recharched it 3 times)

2) Replaced the EVAP valve, but mine seemed to be working ok.

3) Adjusted the Misc Outputs for the EVAP to work below 38kpa only

I went for a drive and my mixtures on hot engine do not flick from lean to rich anymore. They stay lean, due to heatsoak i presume and the hotter the car gets, the leaner they get. SO i adjusted the MAT/TPS table accordingly and i will keep an eye on things!

thanks