Help me AEU86, you're my only hope

[jondee86]

Hey no problem bro We all have different ways of diagnosing and trouble
shooting. Totta and I may not always agree but in the end you get more
information and more possibilities to explore.

This thing you have been doing with the crankcase breather is interesting
too. By pinching the breather you are letting blowby pressure build up inside
the engine. Blowby contains unburned hydrocarbons amongst other things,
and when you release the pressure there will be a rush of "enriched" gas into
the intake manifold which then enters the combustion chambers. It appears
that this creates a rich mixture for a few seconds and this is seen by your
sensor.

This in turn suggests another experiment that you could try. Get 12V from
the battery positive and use it to energise the cold start injector while the
engine is idling. If that does not send your mixture rich, then nothing will

Cheers... jondee86

[totta Crolla]

Hey Jondee. "always the Bridesmaid, never the Bride" we are all but Bridesmaids to you..?

[jondee86]

(03-26-2021 07:01 PM)totta Crolla Wrote:  Hey Jondee. "always the Bridesmaid, never the Bride" we are all but
Bridesmaids to you..?

Geez I hope not !!! We both draw on our own experience when looking to
solve problems and that sometimes takes us down different paths, and that
is the way it should be. There are many ways of getting to the truth and
when one does not work it is good to have alternatives on offer.

Trying to diagnose "engine not running well" problems over the internet can
be a roll of the dice. Over the years I have had more misses than hits, and
while it would be nice to be right all the time, being wrong does not really
bother me because it happens a lot And I learn something from seeing
what the cause of the problem actually was.

The reason I offer suggestions is to encourage the people who are
struggling to get their car running right to keep trying. By persevering they
will learn and eventually triumph !!! Pretty sure that's also the reason why
you are here.

The OP (good Kiwi by his nick) is showing a lot of determination. You can
help with his narrow band setup which is something I have never worked
with. I don't think that makes you a bridesmaid

Cheers... jondee86

[totta Crolla]

Thanks Jondee.
The chap that makes the DTM narrowband units is a good friend of mine and he has been making them since the late 1980's l did the comparison video for him.
It is possible to make a single wire sensor work but unlikely at idle, my original sensor needed at least 2000rpm for 2 minutes before it stabilised and it soon cooled down again.
Nakilad, you can give the heated sensor an initial 'boost' by raising the revs in neutral.

[Nakilad]

(03-26-2021 11:17 PM)jondee86 Wrote:  The OP (good Kiwi by his nick) is showing a lot of determination,

Cheers... jondee86

10/10, Give that man a cigar!

(03-26-2021 07:05 AM)jondee86 Wrote:  This thing you have been doing with the crankcase breather is interesting
too. By pinching the breather you are letting blowby pressure build up inside
the engine. Blowby contains unburned hydrocarbons amongst other things,
and when you release the pressure there will be a rush of "enriched" gas into
the intake manifold which then enters the combustion chambers. It appears
that this creates a rich mixture for a few seconds and this is seen by your
sensor.

This in turn suggests another experiment that you could try. Get 12V from
the battery positive and use it to energise the cold start injector while the
engine is idling. If that does not send your mixture rich, then nothing will

Cheers... jondee86

That was the idea. I have since tried a FWD throttle body on it (you can see a few new videos in the playlist), which has the effect of blocking the breather and that gives some interesting results as well (see below).

Once I take the fuel pressure gauge off and put the cold start fuel line back on again I can try that second idea.

So, I fitted and tested the heated NB sensor this afternoon. Seems to have raised more questions than answers, but totta was right, it clearly reads better than the unheated one, so thanks for that idea totta! Turns out that this says the car is running rich! With some caveats I will try to cover the details, but the videos I added to the playlist here should help with any questions.

First: the gauge says rich, its relatively stable at idle and does not change much when adjusting the CO2 resister up or down, untill it reaches a point where it is completely unstable and jumps around like a mad thing.

If I leave the CO2 resister roughly in the middle, and block the ventilation pipe it shows a stable rich mixture. As soon as I open the breather to atmo, the gauge jumps about again (in one of the vids).

To Note: the throttle body on the car at the moment is from a FWD, therefor attaching the breather hose to the inlet manifold has the effect of blocking it since the vent hole in the throttle body is on the other side. The car has a map sensor so there shouldn't be any un-metered air getting in, but of course the crankcase should be slowly getting pressurized.

So to summarize, adjusting the CO2 still has little to no effect on the mixture, although the change in note of the motor can be heard (rough idle at both full rich and full lean adjustment).

For tomorrow, I will put one of the two RWD throttle bodys back on (don't expect much change from this), remove the fuel pressure gauge and put the cold start injector back on (so I can test jondee86's idea). I have to get a new battery before I do much of a road trip since it seem both of the ones I have here wont hold charge anymore!

[jondee86]

Two things... first, while I have suggested energising the cold start injector
while the engine is running, that would be a last resort action to see if the
sensor/gauge could be forced to show a rich mixture. But as the cold start
injector alone can supply enough fuel to allow the engine to idle with
closed throttle, it would most likely flood the engine unless the throttle
was held open to keep the revs up..

An easier test would be to squirt gasoline or starter fluid into the
throttlebody while the engine is running. That should be all it takes to send
the mixture rich. Probably not even necessary as you have the gauge
working better now with the new sensor.

Second thing, pressurising the crankcase by blocking the vent hose is not
a diagnostic test that I have ever heard of before now While it does
produce a change, running the engine permanently without crankcase
ventilation is not an option as it will lead to oil leaks through gaskets and
seals. Better to let the crankcase breath, either with the RWD throttlebody
or venting to atmosphere.

Third thing (there is always another thing) your fuel pressure gauge is
showing normal pressure and normal reaction to blipping the throttle. So
you are all good there. But I am puzzled as to why the AFR goes lean when
you blip the throttle in your second to last video ?

If I remember correctly, the AFR usually goes rich for a moment after
blipping the throttle, then lean when fuel cut kicks in ? The engine will run
rich after a cold start and then taper back to stoich when warmed up. But
I'm pretty sure that fuel cut is inhibited until the engine gets up to
temperature to avoid cycling due to the high idle caused by the AAV
working. Perhaps Totta can comment on this point.

Cheers... jondee86

[totta Crolla]

ldeally the engine would be up to operating temperature before trying to diagnose fuelling problems and l think Jondee is right to be suspicious of the leaning out when the throttle is blipped, this could be related to engine temperature but there should be an acceleration enrichment via the ecu.
There is some really useful info. in this download pertaining to that mixture screw:
https://jlawson.co.uk/downloads/category/10-mk1 you need the download titled Jeremy Ross....

[jondee86]

Without reading the article again so I may be wrong about this, I seem to
remember that the "mixture screw" was only used on early cars that did not
have an O2 sensor running in closed loop with the ECU for keeping the AFR on
target. I believe that really the only time it should be used is with a CO meter
up the tailpipe for fine tuning exhaust gas emissions.

Cheers... jondee86

[totta Crolla]

Yes Jondee that is correct.

[Nakilad]

(03-27-2021 11:42 PM)jondee86 Wrote:  Second thing, pressurising the crankcase by blocking the vent hose is not
a diagnostic test that I have ever heard of before now While it does
produce a change, running the engine permanently without crankcase
ventilation is not an option as it will lead to oil leaks through gaskets and
seals. Better to let the crankcase breath, either with the RWD throttlebody
or venting to atmosphere.

Third thing (there is always another thing) your fuel pressure gauge is
showing normal pressure and normal reaction to blipping the throttle. So
you are all good there. But I am puzzled as to why the AFR goes lean when
you blip the throttle in your second to last video ?

If I remember correctly, the AFR usually goes rich for a moment after
blipping the throttle, then lean when fuel cut kicks in ? The engine will run
rich after a cold start and then taper back to stoich when warmed up. But
I'm pretty sure that fuel cut is inhibited until the engine gets up to
temperature to avoid cycling due to the high idle caused by the AAV
working. Perhaps Totta can comment on this point.

Cheers... jondee86

If i remember correctly, we used to use the sound and pressure of the air from the breather hose as a crude way of checking for compression ring blow by, and blocking it to locate oil leaks. Its been a while since I worked professionally on cars though, so I might be remembering that wrong.

You are right, the increase in pressure should act like an acceleration pump used on the carb's, richen the mixture to compensate to the sudden change in air coming in. Obviously, it doesnt seem to be doing that.

(03-28-2021 01:37 AM)jondee86 Wrote:  Without reading the article again so I may be wrong about this, I seem to
remember that the "mixture screw" was only used on early cars that did not
have an O2 sensor running in closed loop with the ECU for keeping the AFR on
target. I believe that really the only time it should be used is with a CO meter
up the tailpipe for fine tuning exhaust gas emissions.

Cheers... jondee86

Its an early model car, there is no feedback from the sensor to the ecu, only to the gauge. So its completely open loop.

(03-27-2021 11:58 PM)totta Crolla Wrote:  ldeally the engine would be up to operating temperature before trying to diagnose fuelling problems and l think Jondee is right to be suspicious of the leaning out when the throttle is blipped, this could be related to engine temperature but there should be an acceleration enrichment via the ecu.
There is some really useful info. in this download pertaining to that mixture screw:
https://jlawson.co.uk/downloads/category/10-mk1 you need the download titled Jeremy Ross....

I'll download that and have a read. The mixture leans out with water at 90 and oil at 80 when blipping the throttle so it's still doing it when its warm.

And now onto yesterday adventures:

Three new videos added to the list, Air leak test (just to prove no major air leaks in inlet manifold), adjust full rich to full lean and back again on mixture screw, and finally the first part of something quite weird, I'll get to that in a second. Just to note, these three videos yesterday were made with a RWD throttle body fitted. I have had issues with this one since the rebuild and trying to get a low idle speed. I have another RWD throttle body which I will switch to for the next test. There is no leak from the heated idle speed bypass when the coolant is warm.

Now the funny thing: Disconnecting the jumper battery when engine is running.

Basically, the car requires a jump to start it. Alternator is relatively new and happily charges 14.4 volts at idle. Engine mixture shows rich. Disconnecting the jumper battery causes a change in engine note (perhaps because only one battery to charge instead of two, but i doubt this) and the mixture goes crazy. Reconnect the jumper battery and the mixture shows rich, but is stable. Also, It doesn't look like there are any bad earths as running a jump cable from the battery to the chassis or engine block make any change.

This is repeatable (although not seen in the video as it cut out early). Battery does not hold change, seems like a cell may be damaged, although I am not sure if these two issues are related at all. I tried my second ECU and it did the same thing.

Next steps, fit the other RWD throttle body, get another battery from somewhere (since both the ones I have do not hold charge apparently), and repeat the test and record it properly. With a battery that holds charge i can at least go for a short drive without worrying about getting stuck somewhere. I might also swap the engine loom back over again.

Appreciate you both helping me out here, really helps to keep me going, so cheers for that!