350i running rich?

[nks350i]

Hello All,
Trying to get my 350i flapper back on the road, had an MOT and failed on CO just (3.58%) HC 169ppm 2 to 4ºBTDC now set at 8ºBTDC & back in 2013 (last MOT) had similar problem but passed in the end with CO 2.91% HC 135ppm. These CO numbers look high compared to others that I have read on here and the CO screw is 9.5 turns out!! idle 5 turns out. Been out for a run down the dual carriage way and the exhaust is black on return and getting 4.2% CO on a gurston digital, stop and test again I get 2.2% (idle 950rpm ish) seams to be inconsistent (or it could be the tester). I am thinking that this means that it is running rich, been through some of the wedge epistles (http://www.theseacpages.co.uk/media/wedge_epistles_mk2.pdf) checks for EFI page 10+ with these results (test not done = - ):

0) no fuel coming through pressure reg vacuum connection OK,
1)-, 2) 12.5v OK, 3)-, 4)-, 5A)-, 5B)-, 6) Air flow resistor 1.55V OK,
7) Airflow pot all at AFM 6/9 = 4.36V OK, 6/7 CLOSED = 0.61V 6/7 OPEN = 2.75V says it should be 3.7 closed & 1.6v open - is this correct thinking it this is wrong more fuel will be demanded??
8) Aiflow pot resistance at AFM and ECU 6/8 = 363 OK, 6/9 = 561 OK, 8/9 (NOT 6/9) = 202 I ASSUME OK.
9) Throttle pot at pot Yellow/green = 4.36V OK, Yellow/red closed = 4.02 open = 0.77v, green/red closed = 0.33v open = 4.35v - yellow/red and green/red seem to be swapped??
10) res of air temp sensor = 1980 Ohm (around 20ºC) OK to Steve Heath book
11) Coolant temp sensor at sensor and ECU (I am assuming this is the sensor with the white plug behind the other temp switch) Warm = 850 Ohm, hot 384 Ohm OK
12) Extra air valve was not connected looking though it is slightly open about 4mm square orifice - should this be fully closed when hot - but wouldn't being open make it lean?
13)-, 14)-, 15)-

Fuel line pressure = 2.5bar (36psi) running, off stays at 2.0 for some time, next day zero pressure.

Some of the pipes on the plenum do not have clips on but I would have thought they would lean the mixture if they leak.

I hope someone can offer me some ideas of what could be going on, or more tests to do???

Thanks

Nigel

[mrzigazaga]

Hi Nigel.


I think most wedges run a bit rich from start up...Its best to drive it about for ten minutes before you take it there...

The EAV is like a choke providing more air and should become closed after a short period of time...Could be why its running rich from start up...

The timing should be around 4-6 running 98ron.

The white plug sensor at the top of the engine may be the "Thermotime" switch and not the CTS...The readings sound wrong for a CTS..Coolant sensor should be brown or could be black if its been changed at some point...Do you have any misfire or hesitation?

[nks350i]

Hi mrzigazaga

Thanks for the reply, had dive around town before test, maybe should have gone the long way round!
I kind of discounting EVA as it should be closed when hot, I could block it off when hot to see if it makes a difference.
I'll probably take the timing back a bit, did it from the book before reading about unleaded changes.
I've not driven it for about 3 years but when i was it did have a very noticeable hesitation when the throttle was pushed down quickly.
The coolant values seem to tie up with the table 80ºC = 300 to 400 Ohms according to the dashboard engine temp was 70ºC when I took this reading, but does sit between 80ºC and 100ºC when used.

The main thing which I can see it requiring to have the CO screw 9.5 turns open to get anywhere near 3.5%, when it apparently should be around 2.5 turns, has it gone too far and having a negative effect. I have checked the bypass and it is clear (poured water through it with screw open).

Nigel

[mrzigazaga]

Mmmmm....I tend not to touch any AFM or plenum screws...what plugs are you running as 7 might be too cold which could cause a richer burn...Also the timing will change the heat build up of the plugs depending where its set...If a spark plug is too cold then you could experience what you are, Especially if they are a couple of used years old.

Maybe whip a couple out and have a look...Check the gap also.

I prefer to use the iridium BPR6EIX...They are more expensive but are a good heat range...My timing is set to 4 degrees and does not like it any higher...However i would not take the timing plate as gospel....

Go for the simple things first....

[HOTTY]

hi Nigel

you seem like a knowledgeable guy, doubt if its going to take you long to figure your problem out but how about........

setting it up to get through the test and put it back for normal use after

(presume your not running on 3 year old petrol)

hotty

[The Hatter]

Looks like you're working through all the workshop manual checks, I assume you've seen Ramon's excellent vintagemodelairplane site.

I had similar problems with my car and eventually diagnosed a dying ECU... in due course it died completely. Best check is to try and get hold of a known good ECU; although it's also possible that the wiring loom is at fault rather than the ECU. Where are you checking the voltage/resistances?

[Chadders75]

Hi, can't offer any help at the moment, but I am going through the same problem and tests. I will let you know if I find anything. MOT in 4 Weeks so need to get to the bottom of it.

Neil

[nks350i]

Had the spark plugs out (apart from no.8) all gaps 0.8 and looking ok - ceramic white, conductors quite clean, outside sooty.
Petrol is new, how would you set it up for the MOT, higher IDLE open CO screw up more? once I've got that I can take my time on some decent runs. I am wondering if there is something going wrong with the ECU as all the tests are coming up ok. All the soot in the exhaust might have been from earlier running. vintagemodelairplane is a good site.

[The Hatter]

Higher idle tends to help with MOT CO/HC, but is masking the problem not solving it.

Have you done the basics such as cleaning the plenum CCV/idle passages and checked for intake/plenum air leaks?

[adam quantrill]

1. Make sure the air allowance back to the intake is working OK. This means the little mushroom on one rocker cover, poke a needle down it, and make sure the brather on the other rocker cover and breather pipe and plenum gallery it attaches to are all clear.

2. If that doesn't help in the past I have put an extra bypass on the air meter to let a little more in, what I did was to trap a flattened 7mm pipe under the jubilee clip on the outlet, just poking out of the air meter into fresh air. This let in enough to get the idle CO down to 1.5%. It doesn't have to stay there of course.

[nks350i]

Checked clean, pulled a blank of the plenum this a big effect om the CO dropped to 0.5 (a bit extreme) to get through looking at fitting a exhaust filter/snubber on to the tube and adjusting to get the proper adjuster in range of 1.5%. Then I can see how it goes.