July1

Hi guys,

My car has started to overfuel.
Sometimes I even got some black smoke on the exhaust..
I got the codes P1127 & 29
I also had a bad lambda P0134
I changed both precat sensors then i got also sensors behind cats aging so I changed these too..

But still my LTFT keep going down and down until CEL..
Since the behavior is symmetrical I doubt it's a leaking injector on both banks..
I cleaned the MAF with no result so I changed it but no improvement either.
The values seems high with 35-40 Kg/h at idle and about 90-100 @ 3000rpm

As I found out it was a pb with the early engine loom melting. I checked the part number and it was the good .12
I was worried after 20 years it could happen again anyway so I changed it too with no improvement

Next step will be to change the DME loom too but if you have other points I could check..

I really doubt the fuel press could have rised but honestly I didn't checked it.
Mainly because the car has been upgraded with GT28RS and a full dyno and road remap and has an adjustable fuel press regulator and don't know the setting.. the adjustment screw is tightened that's all I could properly checked :/

Also I got peaks in the reading in Durametric I wonder if you have also when you log datas..?

Thanks for reading !
Julien

July1

Also still on the MAF I checked the power supply and I got the battery voltage (13.8) at idle.
Somewhere I read it should be 10.8 does someone has information on that..
The DME is a 96 unit (swapped for the engine upgrade since the genuine 95 wasn't fit for that..)

July1

This is the peaks I'm talking
For those using Durametric do you also have this kind of readings?

MarinS4

A boost leak will create a rich mixture. This is because a the air gets metered by the MAF then leaks out. Check the boost hoses from the turbos to IC. They tend to rip right at the turbo outlet.

July1

Thanks for your input

Unfortunately I already checked the boost hoses and since I can smell rich mixture at idle I doubt that the cause.
I'll check the fuel pressure this weekend if I get my hands on the proper fittings..
Maybe the adjustable fuel regulator is stuck.. I don't think that's possible but since I checked all the rest this must be done.

July1

I found something.. one of the dump valve is leaking between the intercooler side and the vacuum line.
No air is escaping the system so I doubt it's my initial problem..
I ordered a couple of brand new Forge ones since this issue had to be solved anyway.
This should only increase the idle speed as it bypasses the TB and rise the pressure on the turbo during gear change but I don't see why it would make the mixture richer :/

I checked the fuel pressure and it was normal as expected.. but I discovered that I had no residual pressure as should be... I removed both rails and pressured but no leak on the injectors.. I cleaned them anyway and I'm currently waiting for a rebuilt kit to put all back on the car.. probably have to investigate the regulator and the pump for that too but once again, I don't see this being a source of richer mixture :/

DiegoR

Not sure but how is the IAT sensor? For watercooled engines if it's bad the coolant sensor it can create really rich mixtures.

July1

Readings are correct from both IAT and CHT sensors