Re: [doc] Erratic

[Nick Tomlinson <nickandkathryntomlinson@xxxx>]

Hi All, not been on here for a while as my wife's been in hospital for an op but is now on the mend. Should still be there for NEC though..
 
Here goes - Unplug the oxygen and sensor but still leave the frequency valve connected. This should give the freq valve a fixed duty cycle.
If the engine now idles OK, use an oscilloscope on the oxygen sensor and see if it switches OK (should be a square wave between 200mV and 800mV with frequency of approx 1Hz). If the waveform appears sinusoidal and not near these limits then the oxygen sensor is not switching fast enough causing incorrect slow feedback to the lambda ecu.
 
If the above checks out OK then check for any vacuum leaks on the engine before any adjustment.
I did this on mine by spraying WD40 around the inlet manifold gaskets with the engine running. Any leaks would be noted in a sudden rise or dip in engine revs. If any are found then repair the leaks before adjustment.
 
I found on mine too that the plug for the CO adjustment on the fuel distributor (near the big main sensor flap) was missing causing an air bleed effect too.
 
If you have a cat bypass you could leave the oxygen sensor unplugged and set the CO to 1.3-1.5% to run in open loop mode and reconnect the oxygen sensor. The CO should drop to less then 0.3%.

There should be a copy of the bosch fuel injection article I posted onto the news-group that covers
 
It's always hard to diagnose a problem without looking at the car but hope this gives some help on what to look for. Hope this helps for starters.
 
If you're going to the NEC I could point these bits out on the engine for you and what meter to connect to the diagnostic plug on the engine.
 
Regards,
 
Nick and (poorly) Kathryn.

pastyman@xxxx wrote:


Hi all

I am experiencing a problem with erratic idle/engine speed,the problem stops if the frequency valve is unplugged.The car thens appears to run a bit rich but has a steady idle.
If I reconnect the frequency valve everything is perfect for usually 1/2 hrto 1hr before the problems start and it starts increasing/decreasing.
Has anyone got any ideas to point me in the right direction??

Thanks

Alistair 
11622

P.S 
Just received photos,newspaper articles regarding the purchasing/painting of my car from its first owner in Belfast who bought it at the Culloden auction,its amazing what you can do with 118000!!



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