14 minutes ago, Eatonm112 said:

I think your fuel pressure regulator has a split diaphram which is why you can hear hissing so you car is running rich as a result. I would look at getting a new one 

I replaced the FPR. Ofcourse it is a used FPR (because at the service could not order a new one), but the results are the same, and a FPR to get bad it is rare.

3 hours ago, Joe82 said:

I replaced the FPR. Of course it is a used FPR (because at the service could not order a new one), but the results are the same,

With no pressure sensor on the fuel, there is no easy way to test the FPR that I can think of.

The combination of high measured HC and -ve fuel trim is an odd one. As I understand it, -ve fuel trim means that the ECU is narrowing down the injector pulses, to try to inject less fuel than is normal for the situation. So the ECU is trying to reduce fuel, but the HC measurement says there is still too much fuel.

In addition, I think the HC measurement is done at high idle, ie revving in neutral, and on Oct 6, you said that revving in neutral is exactly the time when the fuel trim goes to -25%.

Air leaks, in the inlet or exhaust, will not do this, they make the ECU add fuel, or they will reduce HC. A faulty O2 sensor would do the same, to get high HC would need added fuel, not reduced fuel.

Hence the FPR is the obvious thing that will increase fuel to all 4 injectors, to the point where even with the STFT at max negative, there is still a surplus of fuel, so causing the high measured HC.

If the MAF was reading too high, so the actual air flow was lower than the reading, then the ECU would have to use a negative trim to compensate, and if there was still not enough air for the amount of fuel, HC would be high. So that works, but the MAF reading you gave of about 80mg per cylinder does not sound high. I make a 0.4 litre (1 cylinder) amount of air at 57C and 23.5kPa to be about 100mg. Valve timing and losses have to be allowed for, so 80mg may be reasonable.

A copy of your data is here, for easy reference.

I am not sure about the cat. If that was knackered, then HC (& CO) could well be high. Whether it would cause -ve fuel trim I can't tell. Surely if the cat was working, it would use up O2 to oxidise the unburnt fuel, so a non working cat should produce a high O2 reading (lean), and thus cause +ve fuel trim. Your measurements give low O2 (rich) and -ve trim. But it is all a bit complex there!

So is it two faulty FPRs, MAF reading too high, or knackered cat. Or something else altogether?

On 10/26/2019 at 7:50 PM, Tdci-Peter said:

With no pressure sensor on the fuel, there is no easy way to test the FPR that I can think of.

The combination of high measured HC and -ve fuel trim is an odd one. As I understand it, -ve fuel trim means that the ECU is narrowing down the injector pulses, to try to inject less fuel than is normal for the situation. So the ECU is trying to reduce fuel, but the HC measurement says there is still too much fuel.

In addition, I think the HC measurement is done at high idle, ie revving in neutral, and on Oct 6, you said that revving in neutral is exactly the time when the fuel trim goes to -25%.

Air leaks, in the inlet or exhaust, will not do this, they make the ECU add fuel, or they will reduce HC. A faulty O2 sensor would do the same, to get high HC would need added fuel, not reduced fuel.

Hence the FPR is the obvious thing that will increase fuel to all 4 injectors, to the point where even with the STFT at max negative, there is still a surplus of fuel, so causing the high measured HC.

If the MAF was reading too high, so the actual air flow was lower than the reading, then the ECU would have to use a negative trim to compensate, and if there was still not enough air for the amount of fuel, HC would be high. So that works, but the MAF reading you gave of about 80mg per cylinder does not sound high. I make a 0.4 litre (1 cylinder) amount of air at 57C and 23.5kPa to be about 100mg. Valve timing and losses have to be allowed for, so 80mg may be reasonable.

A copy of your data is here, for easy reference.

I am not sure about the cat. If that was knackered, then HC (& CO) could well be high. Whether it would cause -ve fuel trim I can't tell. Surely if the cat was working, it would use up O2 to oxidise the unburnt fuel, so a non working cat should produce a high O2 reading (lean), and thus cause +ve fuel trim. Your measurements give low O2 (rich) and -ve trim. But it is all a bit complex there!

So is it two faulty FPRs, MAF reading too high, or knackered cat. Or something else altogether?

Good question.

The STFT with cold engine is positive and when the engine is warm goes down to negative. When the car is idle at 800 RPM the STFT is normal, when I press the gas pedal to 3000RPM  the STFT goes down to -25%(only with warm engine). The injectors were took out and cleaned and tested and they are OK, but after the injector clean and test in the morning when I start the engine it dies after 4-5 seconds and the RPM goes up to 2000RPM and down a few times, only with cold engine.

I found the problem. Replaced the PCV(positive crankcase ventilation) vacuum valve and the short term fuel trim now has a constant wave within -8 and -18 and the HC emission value is 120.

I have 2 holes on the exhaust, the mechanic said that if i replace it the emission will be good.

Here is attached 2 images, one with PCV valve and one with emission test.