Technical Lean mixture O2 Lambda 1.2 8v 60 SPI

[Ultimatum Demon]

176B4.000 (single point injection)

My engine is running extremely lean and I'm running out of ideas on what to change.

Periodic Symptoms:
Weak low end torque. Choking at launch, gear shift and with slightes press on gas while driving. Weak response on full throttle.

(It sometimes do drive normal, which is really confusing)

Changed parts:
Fuel pump, filter.
Lambda/O2 sensor.
Spark plug, wire, coils.
Map sensor, vacuum line.
Air temperature sensor.
Idle control valve.

Things that's left:
Injector.
Charcoal filter.
Crankshaft sensor (got it cleaned).

Just wanna hear if any of you have an idea, before i waste more money on this.

 

[bugsymike]

Only thought, if it sometimes runs normal could this suggest an electrical poor connection?
On a car my daughter had, an 06 Grande Punto a fuel pump relay wasn't getting trigger instruction which I eventually traced to a rotted wire inside it's plastic coating a few mm from the ECU.
I am not suggesting this is your answer, but have you tried with engine running moving/repositioning wires/looms to see if it affects running.
Have you checked voltages at the Lambda sensor against known good.
Some years ago I stupidly sold a Lambda tester that could alter the signal to make the vehicle run richer or weaker whilst engine in use. It basically was a potentiometer and some resistors etc. I see Sealey and others make a modern version.

 

[Ultimatum Demon]

I have only tried to change the parts.
A thing i want to do is "the big 3" which is more power and ground cables.

But do you know where the relay is located?

 

[bugsymike]

I have only tried to change the parts.
A thing i want to do is "the big 3" which is more power and ground cables.

But do you know where the relay is located?

On my daughters car it was one of the relays in the engine compartment fuse box, sorry it was a long time ago. Your model will be different but I am sure a Forum member will know where.

 

[SemSu]

Hi, from your list I think only injection is relevant.
Is that result from an Independent O2 sensor or the cars own?

 

[SemSu]

Do You hear a hissing sound when U open the fuel tank cap after a prolonged drive?

 

[Ultimatum Demon]

Do You hear a hissing sound when U open the fuel tank cap after a prolonged drive?

Yes i do.

 

[SemSu]

Ok I guess You should first check your fuel tank ventilation. Basically the fuel pump creates a vacuum if no air can get in to replace the used petrol.

 

[bugsymike]

Ok I guess You should first check your fuel tank ventilation. Basically the fuel pump creates a vacuum if no air can get in to replace the used petrol.

This is certainly true on older vehicles but some newer ones have a form of positive pressure at the tank via a carbon filter return system.
You could soon prove or disprove this suggestion by driving a safe distance with fuel cap off.

 

[SemSu]

This is certainly true on older vehicles but some newer ones have a form of positive pressure at the tank via a carbon filter return system.
You could soon prove or disprove this suggestion by driving a safe distance with fuel cap off.

Yes and exactly that carbon element can be clogged. I saw that happen on a Peugeot 307. It ate 3 fuel pumps in 6 months.

 

[Ultimatum Demon]

T

I always drive with the cap slighty loose so it won't make pressure in the tank.

Where is this vintilator that i have to look for in the tank?