Urs4 running lean . Lambda, MAF, pressurer regulator?

[Isaksa]

Hello!

My URS4 is running lean when boosting.
I am using rs2 maf in 4" pipe, "bosch green 0280155968" 440cc injectors with 4,85bar fuelpressure (turbosmart fpr800) with vacuum of.

I have an average between 14.6-14.9 in air fuel ratio at idle/slow traffic.
Earlier when boosting (1.8bar) i had afr readings down to 11.8, witch is right i supose.
Now i don't get less than 14.0 afr when boosting. This can't be good, so i am not using my car until i have fixed the problem..

What can cause it running lean ?
Lambda, Maf? Fuelpressure regulaor?

[slow2]

Hello!

My URS4 is running lean when boosting.
I am using rs2 maf in 4" pipe, "bosch green 0280155968" 440cc injectors with 4,85bar fuelpressure (turbosmart fpr800) with vacuum of.

I have an average between 14.6-14.9 in air fuel ratio at idle/slow traffic.
Earlier when boosting (1.8bar) i had afr readings down to 11.8, witch is right i supose.
Now i don't get less than 14.0 afr when boosting. This can't be good, so i am not using my car until i have fixed the problem..

What can cause it running lean ?
Lambda, Maf? Fuelpressure regulaor?

What was your boost presure when your afr was at 14.0 ?

[UrS4boy]

Is your fuel pump big/strong enough to actually supply that crazy high fuel pressure? IF not = lean under boost.

[slow2]

Is your fuel pump big/strong enough to actually supply that crazy high fuel pressure? IF not = lean under boost.

Originally Posted by Isaksa, Earlier when boosting (1.8bar) i had afr readings down to 11.8,

IF you read the post in full, he say's before problems arose he had afr's of 11.8 at 1.8 bar boost, so I think the pump must be big enough in the first place to achive afr's of 11.8 at 1.8 bar boost.

[UrS4boy]

IF you read the post in full, he say's before problems arose he had afr's of 11.8 at 1.8 bar boost, so I think the pump must be big enough in the first place to achive afr's of 11.8 at 1.8 bar boost.

I believe him when *HE* answers, i.e. no speculation.

[slow2]

Hello!

My URS4 is running lean when boosting.
I am using rs2 maf in 4" pipe, "bosch green 0280155968" 440cc injectors with 4,85bar fuelpressure (turbosmart fpr800) with vacuum of.

I have an average between 14.6-14.9 in air fuel ratio at idle/slow traffic.
Earlier when boosting (1.8bar) i had afr readings down to 11.8, witch is right i supose.
Now i don't get less than 14.0 afr when boosting. This can't be good, so i am not using my car until i have fixed the problem..

What can cause it running lean ?
Lambda, Maf? Fuelpressure regulaor?

You could check the small hose between Fuel pressure regulaor and inlet manifold is not split or come off.
How long since the fuel filter was change ?

[Laaf]

Do a boost leak test by pressurizing the intake system.

[Ugemi]

Well if you use the maf in 4" hose and the ecu has not been changed to compensate that, your ecu will only measure as it was in the standard(3" I think?), so it gives you fuel for that. So either test the standard tubing, of change the software. 4" hose flows 79% of more air than the 3" hose, so no wonder...

[Ugemi]

Also, boost leaks usually make it go rich, as it measures more air, than actually enteres the engine.

Or did this accure suddenly, nothing was made to the car as it started? If so, just check the suction hose to the turbo.

[Isaksa]

What was your boost presure when your afr was at 14.0 ?

Thanks for the many great tips,
I am Using a Bosch 044 fuel pump. This should have been changed the day before I bought the car (according to previous owner). To be honest, I do not know why they running with this high fuel pressure. I have not dared and touched the fuel pressure regulator since the afr is nice at idle / slow driving.

I am Using custom Motronic that supports 4 "maf.

When i found out my AFR value is abit high, i regulated down the bosst pressure, to about 0.5-0.7 bar. This is while i am testing so i don't make so much damage if it is running lean.
What AFR could i expect with 1bar?

[Isaksa]

Iv'e been trying to check for leaks, but how do you guys perform a leaktest? Do you disassembly the airfilter and insert air that way, or do you block innlet on turbo and insert air in any vacuum hose?

Regards

[Ugemi]

You could also check the gas filter, it may not flow correctly?
If the pressure is set that high and they changed the pump, there may have been some problems with this before?
Does it run ok, no misfires etc?

[Ugemi]

Pressure test is easiest to do with a car air ventil(sorry my bad english, I mean the kind of, that you have in you tires http://www.tarvikkeet.fi/img/kuvat_pienet/444.jpg ) and a suitable sice can of some sort, that you can connect to you turbo inlet http://razur.pp.fi/S4/vuototesteri.jpg . Then just add pressure with a air compressor for 2 bar, or so http://urly.fi/b3E.

[Isaksa]

You could also check the gas filter, it may not flow correctly?
If the pressure is set that high and they changed the pump, there may have been some problems with this before?
Does it run ok, no misfires etc?

Yes i would og to the shop and buy a new fuel filter now, and change it. Just in case.

The engine sure runs ok, no misfiring. When accelerating there is nothing wrong except the afr value. It runs like hell

There is no faultcodes stored in ecu.
Earlier I was unlucky and ran into a puddle on the road, big one. And the engine check light came on. Then the Ecu have stored mixture failure... But i cleared fault codes and the engine check light never came back.

[Ugemi]

I dont think it´s on the pressure side. I think it needs to be on the fuel side. You can always disconnect the fuel rail with the injectors and get hoses from the injectors to bottles just to see if there running the same amount of fuel in a minute or so.
This seems that it works fine on idle, but with boost it gets lean, so it is not getting enough fuel. There are not too many reasons for that, either the pump is getting dead, the filter is dirty, or the injectors are.. Are you sure that the pump is really changed? It is not too nice job to do, check the cover from the gas tank. You can see it in the trunk and if it has been opened, it should show in this old car.