car engine ramblings- low compression symptoms

[steveo3002]

yeah ..tried everything cept another loom and the engine

loom ive checked pin to pin with a mates car , all checks out as far as well can tell , sensor readings are getting to the ecu , all earths ok

 

[steveo3002]

The Bosch dizzy has a diagram of a circuit you build on the net to test them

the advance comes from the ecu , as far as i know (correct me if not) the dizzy hall sender isnt much more than a switch , theres a disc that spins with 4 cut outs that trigger it as goes around?...kinda either works or doesnt , have tried spares on it too

 

[130]

picture of rotor arm required.

 

[steveo3002]

https://www.ebay.co.uk/itm/Bosch-Di...m=153027768522&_trksid=p2045573.c100507.m3226

like so ..its new

 

[130]

Right, typically the bosch dizzy that gets advance from the ECU does not have a hall effect in it. The rotor arm is usually asymmetric but seeing as 20 years+ has passed anything can be fitter, a lot of one type fits all around...………….


They typically get timing from a crank sensor in that case, so you cannot easily mess up the timing with dizzy and the arm is asymmetric so it is by the pin regardless of advance.

On those the dizzy is usually empty, had no vacuum advance and if you grip the rotor arm you cannot rotate it in either direction as they have no springs inside to go wrong over time.
Different combinations are available in transitional periods though.

Check if the spindle turns, if it is fixed then no advance internally to go wrong. I've had 3 old ones go bad on the shelf back in the day just from lying down

 

[steveo3002]

no vac advance , with the dizzy off you can spin it in either direction

no crank sensor on this

 

[130]

with the dizzy off you can spin it in either direction

That's not what I asked and the answer you gave is the same for any dizzy whether solid spindle or with internal advance in that scenario, but doing a random google I expect it may be a straight shaft with no internal advance, in which case the dizzy should probably be set by static marks

 

[steveo3002]

ask me again i dont understand

with it off the rotor spins freely either way...with it on the engine it turns with the cam shaft as its keyed to it , rotor arm is keyed to the dizzy shaft

 

[130]

On those the dizzy is usually empty, had no vacuum advance and if you grip the rotor arm you cannot rotate it in either direction as they have no springs inside to go wrong over time.
Different combinations are available in transitional periods though.

Check if the spindle turns, if it is fixed then no advance internally to go wrong. I've had 3 old ones go bad on the shelf back in the day just from lying down

I expect it will be solid shaft if you check

 

[slim_boy_fat]

doesnt have one

What decides the mixture then? I'd be looking at the air supply. Sounds like on little throttle openings it's struggling. That's assuming you've checked things like the fuel filter etc?

 

[130]

AFM
Air Flow Meter
A flap with a resistor on from the 1960s onwards.

 

[steveo3002]

yep like this here

 

[130]

Except you are never meant to adjust an AFM internally though whn used with the old Jetronic on Alfas and Mantas there are many references to 5 teeth over on the cog helping pickup. There is a plug for adjusting them with the lid on that should be considered sealed for life

 

[optima21]

the engine is using digifant injection, there is an airflow meter, throttle position sensor and narrowband lambda for adjusting the mixture strength based on the speed indicated by the hall effect sender in the distributor.

 

[octo0072000]

can you swop the whole distributor etc inc cap leads from a known good working one to test it out

 

[steveo3002]

i have done and no change

 

[mr haynes]

Are there any timing marks you can monitor? Not advancing correctly at idle will throw mixture out
Is there a tps?

 

[steveo3002]

is a tps...diag machine confirms its working

i have timing marks on the bottom pulley...what are you saying , see if theyre jumping around at idle?

 

[ajlelectronics]

On the Ford 2.9i if you disconnect the AFMs, it drops to a default setting which would smooth out the idle if there were a problem with the AFM. What does your engine do?

The Nissan AFM is a hot wire type which needs cleaning with brake cleaner from time to time. Car washing water gets in due to a design issue. Not sure which type you have though. Any help?

 

[steveo3002]

doesnt run with the afm undone