Help me AEU86, you're my only hope

[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!