Mixture problem, help!

[porkkis]

Ok. I finally plugged an A/F ratio meter to my car. The results were hmm, strange.

First of all the value is quite constant so in closed loop the lambda value does not rise and fall like it should. It stays constant in about lambda=1.

Secondly when running WOT and rpm over 3000 the mixture gets very rich. It actually goes off the scale so it must be lambda=0,7 or richer.

Thirdly the fuel supply does not seem to cut completely when "braking with engine". Dependin on rpm the mixture reading is about lambda=1,15. Higher revs causes richer mixture and it does not go extremely lean (fuel cut) if the revs are above 2000 rpm or so. The board computer shows 0 consumption.

The lambda probe is almost new. Changed around 2000km ago and it's a Bosch unit.

I tested 2 different ECUs with 2 different software and both do about the same. MTM 262hp 200kpa seems to be even richer than the Slovenian RSR 250kpa.

I don't know what cleaned fuel injectors affect or do they as they're still waiting to be installed. None were leaking but otherwise the cleaning was helpful. One had bad injection shape and all were a bit down in amount.

No fault codes what so ever.

I'm out of ideas. Must reinstall the injectors and test again. Then I will measure the thottle potentiometer and perhaps try another lambda probe and MAF?

Any ideas?

[Jamo]

Ok. I finally plugged an A/F ratio meter to my car. The results were hmm, strange.

First of all the value is quite constant so in closed loop the lambda value does not rise and fall like it should. It stays constant in about lambda=1.

Secondly when running WOT and rpm over 3000 the mixture gets very rich. It actually goes off the scale so it must be lambda=0,7 or richer.

Thirdly the fuel supply does not seem to cut completely when "braking with engine". Dependin on rpm the mixture reading is about lambda=1,15. Higher revs causes richer mixture and it does not go extremely lean (fuel cut) if the revs are above 2000 rpm or so. The board computer shows 0 consumption.

The lambda probe is almost new. Changed around 2000km ago and it's a Bosch unit.

I tested 2 different ECUs with 2 different software and both do about the same. MTM 262hp 200kpa seems to be even richer than the Slovenian RSR 250kpa.

I don't know what cleaned fuel injectors affect or do they as they're still waiting to be installed. None were leaking but otherwise the cleaning was helpful. One had bad injection shape and all were a bit down in amount.

No fault codes what so ever.

I'm out of ideas. Must reinstall the injectors and test again. Then I will measure the thottle potentiometer and perhaps try another lambda probe and MAF?

Any ideas?

I maybe wrong but S2Central can advise, but MTM and RSR may have done this deliberately as a safeguard. I know that superchips do the same and in general it is very bad pratice but is a safeguard they employ.

[KramRS2]

If you are using the stock lambda meter (the sensor) it should not be measuring correctly. The sensor output varies with temperature and it is far way to be the best thing to measure your mixture. Its only good to show you if you have a bad fuel filter or a blocked injector, but not to show accurate mixtures.

Use a wide band lambda meter.

[s2-1.5bar]

Hi,

I got Lumenition A/F meter installed on standard lamda probe, it works properly. The mixture jumps a bit up and down, gets constant when cruising at about 100mph. And shows nothing when lifting off throtle, or braking with lower gears. Very handy indicator I can say.

[porkkis]

That's just how it should be.

Mine does not "jump" as it should and it still gives a lean reading when lifting

Debugging continues tomorrow.

Can Mihnea or someone else who might know tell the conditions in moving to "open loop". Is there a boost limit or just WOT? Or is it even WOT or some other voltage the throttle position sensor gives?

[caterpillar]

you may have a bad fuel regulator too.......high pressure=rich fuel,low pressure=lean fuel..........on board computer,may have som prob too.....checked your alternator regulator,low volt????

[porkkis]

Good ideas but can't be as:

When engine braking the mixture will get leaner when rpm is lower and therefore less vacuum.
And vice versa when more rpm the mixture is richer and more vacuum present.

I've measured the fuel pressure some time ago and it was fine.

Voltage regulator is nearly new.

[audiman]

If you had fuel pump probs it wouldnt run rich!! It would be lean. I would suspect the Lamdba sensor. Check the voltage output with a DMM. When engine is warm and running, check to see what voltage you get, it should rise and fall between 0.05-0.95 volts. Also check it at 2000 rpm it should change frequently. Do you have access to a digital scopemeter?? That is the best way to test. It will give you a type of sine wave if working crrectly

HTH

[porkkis]

Thanks,

Some progress:

Now I took the signal directly from ECU connector. And guess what! It shows completely nice figures now. The fault has to be in the wiring then. Can't really be anything else.

Somehow the value isn't constant anymore. Now it jumps nicely as it should. I have no idea why?!

[porkkis]

Errm ehh. Problem solved. Actually there was absolutely no problem to be solved, but I solved it anyway

The A/R meter was just grounded to wrong place. As simple as that.

[audiman]

LOL

Thinking out loud on the forum can often make you find your own problems!!