No ECU light in service mode

[Chas54]

Looking for any comments if anyone spots something or could advise:-
Here are results of checking the ECM pin voltages with a engine at temperature , running and then stopped with the ignition on.I havent included any voltages taht are within the stated target figures in EMJ4
Ignition on but engine stopped
Pin A10 VSS signal seems to be 12v with little variation seen . But still within stated range
Pin C13 TPS signal 0.42-- despite the fact i adjusted it mildy warm , when engine hot its risen from 0.4 to 0.42 still within range

Engine running

Pin A4 secondary throttle solenoid 0.37V target is 0.2
Pin A10 VSS signal input didnt see much change despite steering position
Pin B9 Engine position target of 0.5v actually swinging between 0.2 and 1.1V
Pin B12 EGR sensor input target 1v to 4v actual reading was 5.05V
Pin D5 bypass control cct target 4.5v actual 4.8v
Pin D7 target stated as 50 to 999 i'm guessing this means 0.5v to 0.999v . Actual reading fluctuating between 0.6 and 0.06.

21oct O2 sensor voltage drop.zip

Ive stripped back the O2 sensor plug at the sensor side and measured voltages there. the 12v supply is good and the voltage being returned is the same as at the D7 pin.

The engine is still hunting up and down and running a little rough and uneven.

I have again checked the base line timing in the service mode ..

I still get concerned about the wasted spark . With the strobe attached to No4 lead by the inductive clamp i see an engine speed spark (once every revolution). If i put the clamp on No1 lead i only see the one spark at half engine speed ( presumably at the top of the compression stroke) and that doesnt appear once every few revs . It sounds like its at the point the engine revs drop for a second.
I did swap all the leads about and even swapped the coils to the other cylinders. Still the same though.

I know there is one noisy tappet when the engines cold but it does quieten when warm . Sounds like No2 and the compression test is good so i don't think there's a valve problem .

I may have to try a continuous monitor of the O2 signal at the sensor plug as i'm not convinced it always returns a sensible voltage.

Any comment much appreciated .
i am attaching a short elanscan data set from my final run today , i think the 02 voltage drops off but also when the car was reved , on returning to idle the engine stumbled a bit as the vacuum didnt recover.

[KenS]

Hi, not an expert on elanscan plots, but something happens just before the 500 seconds, the battery voltage shows shows a dramatic drop-off to near zero volts - could something be breaking down ? I am sure someone will know more on this. edit - were you measuring pin voltages at this time? maybe this was caused by probing rather than the actual problem? Another edit - or was the engine switched off and restarted - which thinking about it makes more sense (and the knock counter gets reset)

[KenS]

Looking through the scan data a bit more carefully, I guess the event around 500 seconds was due to the engine being restarted and not an effect of a problem. The O2 sensor data looks quite static compared to mine:

chas54 o2 sensor.jpg

Chas54 O2 sensor data

kens o2 sensor.jpg

My (KenS) O2 sensor data


Can anyone put some reason for the difference? Is the sensor data valid for the conditions it sees, or is there an O2 sensor/connection fault ?

[Chas54]

Thanks Ken

I stopped the engine then restarted.

Looking at you O2 sensor signal voltage compared with min, it looks like mine is definitely acting differently. The voltage is a lot lower on mine.

I am wondering if running so rich for so long has affected its performance .

[KenS]

Hopefully Simon will make some comment on the O2 sensor plot. I believe the 3 wire O2 sensor puts its sensed voltage out on the sensors Black wire (to Grey in the loom), and is reliant on the O2 senosor casing to manifold threaded connection for its earth reference. Might be worth checking that the sensor thread does make a good connection - i.e. is there a good low resistance path from sensor case to chassis/engine ?

[Chas54]

Thanks Ken.

Ive checked again for voltage at the wing plug for the O" sensor and checked it at the ECM D7 and they correspond closely but intially were very low 0.06 . But whilst playing about with other bits waiting for it all to warm up, the voltage at the socket started reporting 0.8 v . Looking at the elanscan trace now its working well .

The car was difficult to start and wouldnt idle -- the scan will show when i eventually wedged a piece of card under the throttle stop screw and the TPS goes to 0.48v . Vacuum a but poor as well.

Once warmed up at 1640 secs i switch the dapinky switch to service mode and the IAC sets itself to 20 during my idle air screw adjustment. During the period in service mode the revs can be seen rising and falling along with the vacuum and i cant figure out why. At 2030 seconds i return to normal mode . The fluctuation is a lot less then .

Ive decided i will lash out and buy a new coil for 1 & 4 . I dont like the missing spark on the strobe every now and then on N0.1 . I cant see it being the ignition module as thats only in play bellow 800 revs.

Again i've attached todays scan which has a number of engine stops before it all gets more stable.

Comments much appreciated.

good O2 VOLTS.zip