My 94 UK Auto went for it's MOT yesterday and failed on emissions. At fast idle it was putting out 6.84% :eek:

 

Now normally i'd stick it on Datascan (which i have) to diagnose, but, datascan refuses to work with this particuar car - it works fine with my other zed.

 

So how can I diagnose what's causing the problem without computer diagnostics. I've done the basic ECU code check and get an all clear 55

Swap the ecu from your other zed and re-run the test.

 

Jeff TT

Try this http://www.300zx-twinturbo.com/tech/co/co.html

Swap the ecu from your other zed and re-run the test.

 

Jeff TT

 

My other Zed is a manual. Does a manual ecu work in an Auto? I'd prefer not to have to cannibalise my other one. Might make more problems for myself.

 

Try this http://www.300zx-twinturbo.com/tech/co/co.html

 

Could do this - but it's only a short term fix, not identifying the real problem. I wouldn't know if it had brought it down sufficiently before the re-test. 6.84% is pretty high.

My other Zed is a manual. Does a manual ecu work in an Auto? I'd prefer not to have to cannibalise my other one. Might make more problems for myself.

 

No what I meant was to identify the fault swap the ecu`s so the diagnostic system will work.

 

For the purpose of checking for faults ETC. swapping the ecu`s will workok, however the autobox will not change correctly with a manual ecu so its a temp only plan.

 

 

Jeff TT

Try this http://www.300zx-twinturbo.com/tech/co/co.html

 

This works. My emissions were OTT until I pulled that little pipe off and she flew through last year. Make sure it is taken off before taking for an MOT -you will not notice any difference with it disconnected.

This works. My emissions were OTT until I pulled that little pipe off and she flew through last year. Make sure it is taken off before taking for an MOT -you will not notice any difference with it disconnected.

 

Might have to do this as a quick and dirty way through the MOT as I only had 10 working days to get it retested.

 

I have been on to the guys at Blazt who supplied the cable used with Datascan. They have been very helpful and have agreed to send me a new replacement cable very cheaply.

Checked the car today using Datascan. One o2 sensor reports a value of 6 the other a value of 1. This doesn't change when the engine is revved above 2K. It also doesn't change if they are unplugged.

 

Is it normal for them both to fail? Is there anything else to check before buying two new ones?

the o2's are often broken on zeds but they don't fail your mot as you are not tested for lambda...or rather you shouldnt be tested....the z32 is a non-cat test....tell the mot centre to look in the MOT book they will see your zed isnt listed so they cant test for lambda...it doesnt matter even if your cats are still in...its still a non cat test

cheers

the o2's are often broken on zeds but they don't fail your mot as you are not tested for lambda...or rather you shouldnt be tested....the z32 is a non-cat test....tell the mot centre to look in the MOT book they will see your zed isnt listed so they cant test for lambda...it doesnt matter even if your cats are still in...its still a non cat test

cheers

 

I think if mine had been tested correctly it still would of failed with emissions of 6.84%. The non cat test limit is 3.5% ish i think

 

Would failed o2 sensors cause the emissions to go this high?

I think if mine had been tested correctly it still would of failed with emissions of 6.84%. The non cat test limit is 3.5% ish i think

 

Would failed o2 sensors cause the emissions to go this high?

 

hard to say mate.....from my experiance a lack of regular maintenance will often be the cause of emission fails....basics like sparks, air filters...bla bla....your car is it running stock? or has it been modded?

It's running stock.

 

It's gone in for its re-test today and i've removed a pipe of the balance bar so hopefully that will (temporarily) do the trick.

Well......................did it work? Let us all know the out come.

Well it passed the MOT but not because of removing the pipe.

 

Because they tested it properly this time as a non-cat car it only has to acheive under 3.5% at idle which it did :D At a fast idle it was still hitting 6%

 

So its passed, but not running as should. I'm going to run more diags on it over the weekend, but will prob have to replace the o2 sensors as a minimum.

there you go bud....uncle uno saves the day :D