Have serious trouble with lean mixture under engine load. I'm using Innovate wideband AFR to monitor the mixture.
Here is the symptoms - when on 2nd,3th,4th gear and engine becomes under load(2500 - 5000rpm), and boost is between -0,2(vacuum) - 1.0bar, mixture vary between 15 - 18AFR.....when boost comes in full again runs slightly leaner, but i assume that now engine sucks more air because i ported head and intake after remap was done....or i just hope so.
Checked so far - plugs in good shape......countless checks for leaks before and after the turbo(have SIP and FMIC).......Walbro did 7-8bars when started, completed fuel pressure test from the manual........no signs of misfire or banging under acceleration.......inlet rubber donuts changed with DIY's - no difference......servo keeps vacuum for ages, did one run with servo hose disconnected and it's exit tapped - no difference.......perfect coils.....DV26 tested numerous times - no leaks........fuel vapor and crankcase breathings vented and it's exits tapped.....MAF cleaned and works fine.....all 5 injectors checked for leaks and with 16 - 17 ohms.......
I'm running 4bar FPR, GT28RS with Flea map for 1.4b......
Really have no idea what can cause this, still can't find spare 4b FPR to see if any difference.......have new lambda sensor for comparison and if no solution, i don't know what can be investigated anymore......
For me it's fuel mixture related problem, idle mixture is perfect.......
Any ideas.....
Will try to capture some clip with real time readings, afr gauge,boost controller and rev counter are close to each other on the dashboard....
Any ideas?????

silly question have yo changed the fuel filter

to test the fuel pressure get a regulator with a pressure gauge
http://www.ebay.co.uk/itm/sytec-adj...SM&hash=item2571084bdf#ht_500wt_1416

Did all "wise" things and checks with no results, so all silly questions welcomed.....
Fuel filter changed twice for 2 years, less than 9k km's since i bought the car from UK.....last change was this january from my memory.

I tested the fuel pressure according to the manual here, and it's as it should.....as i said, another 4bar FPR will be nice to try, but must find one.....will try to find regulator as on this ebay link.....

i work on a celica gt4 and a must is a adjustable FPR with a pressure gauge to me a gauge you can see if there is any problems and have you done the direct wiring for the fuel pump

Yes....

get a fpr with a gauge .... it will prove if there is a problem with the fuel presure

If you're running up to 18 on boost, I'm sure you would have melted something by now.

Where are you measuring the afr from?

When my wideband bosch give way few months ago, i put my spare from the trackday Alfa - because of the heat i remount it with new bung away as possible from the turbo - where originally cat converter sits.....
My imagination said that the car don't had it's full power, but maybe cause i now there is a problem.
Had a look to the pistons when inspected sparks, and no visible worry, plugs also in good brown condition......
Today i'll try to measure fuel pressure when driving and eventually change the lambda sensor with new spare i have.....
And will capture onboard video.....
P.S - FiatEcuScan reports no fault codes, did few ecu resets......

If you connect the ecu scanner while driving you can read the original lambda voltage while on boost. If fuelling is ok then it will read around high (around 0.8v) while boosting.

I think the original lambda sensor's only at work on idle..?

They pump out a voltage all the time once warm, just that the ecu doesn't use it on boost. Used a widget showing lambda voltage in the past to convince myself a performance problem wasnt fuel starvation.

If the engine was really running so lean on boost, you would have engine damage by now for sure.

If I were you I'd put the new lambda sensor in, to eliminate the sensor as being the source of the problem.

If the sensor isn't faulty: "an air leak in the intake or exhaust manifold or even a fouled spark plug, for example, will cause the lambda sensor to give a false lean indication. The sensor reacts only to the presence or absence of oxygen in the exhaust. It has no way of knowing where the extra oxygen came from. So keep that in mind when diagnosing oxygen sensor problems."

Yeah that's what I mean, sorry. You need a full-width lambdasensor under load.

Picture of the plugs from yesterday.....as i said pistons looks ok....


That's my DIY intake manifold "donuts", when was on i sprayed almost 1 tube of carb cleaner around with engine idle and no change of the revs.....removed and old ones back just as precaution......


Hour ago did fuel pressure test driving around, it's rock solid, this evening will try my spare lambda with last hope of success.....

If you want a measure of how rich it is then yes but if you just want to know if its above/below stoich then standard will tell you. In this case if it reads rich when the wideband doesnt we know that one of the lambdas is faulty or there is an air leak between them. If both lambdas agree then the problem must be upwind of there.

Not related to your problem but your gap looks too big on your plugs. Have you gapped them at all?

Well i'm equally happy and mad.....
Lambda sensor was faulty......it was changed few months ago because it shows wrong afr through entire revs range and idle.....and this one only between 2 - 5k rpm......idle was fine......that's confuse in the beginning of "investigation"...
Changed with my spare and it's OK......
But that's second wideband Bosch sensor in half year.....and this one was placed as far away as possible from the turbo.....i'm really mad about that......had a thought that i must start with it, but i did not expect failure so early......

Anyway happy that there is no problem anymore....


Yes they are OK - picture lies......

The link did not work for a while, now fixed.....
Fiat Coupe AFR Test
Here is an video clip i made tonight - note that it was raining, boost lowered to 1.2, had camera in my left hand, and the road only allows second and 3th gear, without full throttle cause i don't want any extra wheelspin.....
BTW can some identify the sound present on 1:53 min of the video, it can be heard only for a second when engine on 4800 - 5k rpm????

After Looking at the Youtube movie I can only say: you do not have any problems with AFR during boost.

Yes - video was taken when lambda was changed, and AFR now OK, but with the old sensor readings looks horrible.

Just saw a document that had lots of causes of premature failure and remembered this thread. Might be worth a read see here

Bosch recommends oil consumption of less than 0.7L/1000km
Interesting!

Yes, i know most of precautionary things to do, don't have only heat shield,but the sensor is about meter and half after turbo......
No oil loss.....
Anyway i'm glad that it's sorted now.....