Got an irritating slight misfire most noticeable at 2000 or less rpm in top just when you accelerate gently. Check about everything I can think of. The engine has one shiny new looking O2 sensor that flashes really quick on the diagnostic. The other looks old and makes flashes very slowly but still manages 5 or whatever per 10 seconds.

 

Is this the lazy O2 sensor causing the problem or is the problem somewhere else?

when my O2 sensors were knackered I had a stumbling / misfire feeling when on the motorway in top, accelarating gently between 2k-3k rpms. If you then go WOT at 2000 rpm it'll pull fine as the ECU doesn't use O2 readings at WOT. Try that to see if that helps pinpointing it...

Thanks Jaffa

 

Sounds exactly like it. Foot down it goes like a bat out of hell. Its just at light throttle its not right.

 

O2 sensors are more than a hundred a piece arent they? Just dont want to blow that if its not that. The odds are the slow old dirty one is duff. I just couldnt figure out how it affects the engine - does it mean those 3 cylinders richen up too much under some conditions?

Yes it means one side will be running rich or lean, if disconnected it will run rich by default.

Thanks Jaffa

 

Sounds exactly like it. Foot down it goes like a bat out of hell. Its just at light throttle its not right.

 

O2 sensors are more than a hundred a piece arent they? Just dont want to blow that if its not that. The odds are the slow old dirty one is duff. I just couldnt figure out how it affects the engine - does it mean those 3 cylinders richen up too much under some conditions?

 

does sound right then, to make you feel happier mine's been nice and smooth since putting new O2 sensors in ;) You can get them cheaper from the states too

Nissan wants £107 each for O2 sensors. Being a good Scot I thought make damn sure first. Checked and cleaned all the connections to the suspect O2 sensor again and now it flashes as fast as the other on the diagnostics. Also got the LHS connector off the PTU and put it straight back on thinking it would freshen the connection - it really ran like crap after that just showing how sensitive these things are, especially the LHS one. Forced now to take the PTU off altogether to clean it properly and found the two lower screws wouldnt come out because the female part was rotating in the cam belt cover. Forced the blighters out and cleaned all the green off the connectors. Smeared em with vaseline before refitting. Decided to do the same with the CAS as well. All these connectors were thick with green. Today its been faultless and now pulls itself up the incline to my drive without any throttle. Over 30 miles or so I couldnt make it misfire. Smooth as silk. It might actually be cured.

 

I've had my Z more than three years and just did not appreciate how bad these connections can get. Anyone with hesitations misfires and the like wants to pull apart and clean every connector to, PTU, O2 sensors, CAS, TPS, MAS and Temp sensors. Then maybe the plug and injector connectors. Beware brittle plastics and wires. Also getting these connectors apart I use a littly tiny screwdriver to pull up the wire locking thingys.

 

Here maybe endeth the lesson otherwise its back to a new O2 sensor.

If you do need 02 sensors get onto....

 

http://www.courtesyparts.com/z32/z32_oem_popular-engineelectrical.html

 

Half way down the page.

 

both sides gor abot £70 + Carridge

 

All the best

 

Rich;)