Indication Of A Failing Cts

[pug_ham 244 3 Cars]

I took my car for its MOT yesterday (passed with a couple of minor advisories ) but the main thing it failed on was the emissions (again) until we adjusted it low enough to pass.

 

I've also had a couple of pm's from Phil cti who is also running the same MP3.1 ecu from the ZX & had problems getting his car through the emissions on its MOT who has spoken to Welshpug about his car which only just scraped through afaik. Book figures (according to haynes) for the XU9 ZX Volcane with MP3.1 is 1.0-2.0% CO vol at idle.

 

I'm wondering if it might be a sign of a failing Coolant Temp Sensor because the CO was never stable for the time of the emissions test & only going outside the 3.5% limit for the closing seconds of the test causing it to fail.

 

When they first tested mine yesterday it was warm enough for the low speed cooling fan to cut in & failed at just over 4% iirc but second test the fans were on high & it had dropped to 3.7% still a fail but closer.

 

After the tester had gone round the rest of the car picking a couple of minor advisories (wrong colour bulbs for year of car manufacture(Xenon type!!), headlight aim, front number plate cracked through a letter & NSR wheel bearing slight noise) I asked if I coudl borrow the tester to adjust the co.

 

When I started it back up plugged into the machine (cooling fans off), it was hovering around 3-3.4% so it would've passed but I adjusted it down on the CO pot to just inder 3% & we started the MOT emissions test again which it failed :angry @ 3.53% for the last few seconds of the test. In between the tester recalibration for the second test I tweaked the CO pot again & this time it passed @ 3.15%.

 

This is the only problem I've had with my car running on MP3.1 annually at MOT time, getting it through the emissions test. Last year it went through after some adjustment @ 2.63% but nothing has changed between then & now except its done ~2k over the year.

 

Anyone else think this could be a sign of a failing CTS & a new one might control the emissions better?

 

I'm going to rig up a test lead so I can monitor the CTS resistance as the coolant temperature changes & see if its within the book figures for it, if not I'll swap it for a new one before next May.

 

Graham.

[welshpug 1,657]

I remember checking recently what the emissions pass figure was for mine back in January 2008 (its been off the road this year) and I was surprised to see it had actually failed first time round at 7.5% amusingly it drove fine.

 

It passed after being adjusted down to 3.15% by my tester, and had since then returned very good economy, and done an RR pull at a corrected 129.8bhp/123lbft.

 

From memory I think its the same sender as the Jetronic system, much like the 1.9 MI16 so the resistance specifications are easy to find, definitely something I would check for next time, not sure if there are any checks that could be made to the mixture pot though?

[steve@cornwall 100]

Had this at recent mot on my Seat - going fine until the closing seconds of the test when it just rose for no apparrent reason.Only thing I knew was not right with the car was that the ig. timing was too advanced (every little helps with 50 bhp) After retarding the ignition it sailed through. May help ?

[pug_ham 244 3 Cars]

I remember checking recently what the emissions pass figure was for mine back in January 2008 (its been off the road this year) and I was surprised to see it had actually failed first time round at 7.5% amusingly it drove fine.

 

It passed after being adjusted down to 3.15% by my tester, and had since then returned very good economy, and done an RR pull at a corrected 129.8bhp/123lbft.

 

From memory I think its the same sender as the Jetronic system, much like the 1.9 MI16 so the resistance specifications are easy to find, definitely something I would check for next time, not sure if there are any checks that could be made to the mixture pot though?

Yeah, its odd.

 

Mine always drives fine & doesn't smell rich at idle but the CO has always been over the limits for the MOT each year since fiting, highest I've seen is 4.5% iirc & it wouldn't come below 3.5 so I went to chipwizards & he adjusted the idle map to drop the CO for free.

 

I agree the sender is the same sopec for most of the Pugs, changes colour for either blue or green but still gives the same readings.

 

With regards top checs for the CO pot I foudn this on Autodata;

• CO adjustment resistor;
  Checking supply voltage.
   
  Pin 3 & earth > 5v approx
   
  
• check ignition switched off
  
• Disconnect CO adjustment resistor multi plug.
  
• switch on ignition.
  
• Check voltage between harness & multiplug terminal & earth.
   
  Checking voltage;
   
  Technical data; (typical)
   
  Terminals 1 & 2 > 0.5-1.2v approx.
   
  
• Ensure ignition siwtched off.
  
• Do not disconnect multiplug. Access CO adjustment resistor multiplug terminals.
  
• Switch ignition on.
  
• Turn CO adjustment resistor from stop to stop.
  
• Check voltage between CO adjustment resistor terminals.
  
• Voltage change should be smooth
  
• If voltage is not as speicified, check wiring.
  

Graham.

[welshpug 1,657]

Cheers Graham, should have remembered stuff like this is available from Autodata, I have a copy but it wont work as my computer needs a rebuild

 

The most important bit for the mixture pot then is

Terminals 1 & 2 > 0.5-1.2v approx.