Ek9 NCT Emissions Failure

[soxturf]

Hi folks,

Unfortunately my car has failed the NCT (Irish equivalent of MOT) due to an emissions failure. (Its failing on high idle).

I originally thought it was the cat an replaced it with a new cat but still no joy.

After it failed the second time, the nct tester said that the emissions are fluctuating wildly, both up an down, above and under the required limit.

I replaced the 02 sensor an reset the ECU. I checked the voltage of the new 02 sensor an it is staying between 0.5 and 0.7. Obviously it should be fluctuating between 0.1 & 0.9. Just incase the new 02 sensor was faulty, I tried another new 02 sensor an checked the voltage again. It is still staying between 0.5 & 0.7. When I let the car out or accelerate hard, the voltage can manage to go outside the 0.5 to 0.7 range, but for the most part, especially when just idling, it is staying stuck between 0.5 & 0.7 meaning it is telling the car it's running rich an needs to lean up, which it obviously is not doing properly as the emissions fluctuate wildly an then it fails on high co2 meaning running rich.

Has anyone else ever seen their 02 sensor behave this way or had the same problem?

I own the car 13 years an never plan to sell it so this is cracking me up. Its not my daily, so now its just sitting in shed connected to trickle charger. Really want to get it back on road as I have big plans for it.

 

[Civicfacelift]

Is there an additive you can put in petrol just for test ? or a more restrictive exhaust ?

That's just covering the problem though, if its running rich you will need to find the real cause.

 

[ScottEk9]

Hi folks,

Unfortunately my car has failed the NCT (Irish equivalent of MOT) due to an emissions failure. (Its failing on high idle).

I originally thought it was the cat an replaced it with a new cat but still no joy.

After it failed the second time, the nct tester said that the emissions are fluctuating wildly, both up an down, above and under the required limit.

I replaced the 02 sensor an reset the ECU. I checked the voltage of the new 02 sensor an it is staying between 0.5 and 0.7. Obviously it should be fluctuating between 0.1 & 0.9. Just incase the new 02 sensor was faulty, I tried another new 02 sensor an checked the voltage again. It is still staying between 0.5 & 0.7. When I let the car out or accelerate hard, the voltage can manage to go outside the 0.5 to 0.7 range, but for the most part, especially when just idling, it is staying stuck between 0.5 & 0.7 meaning it is telling the car it's running rich an needs to lean up, which it obviously is not doing properly as the emissions fluctuate wildly an then it fails on high co2 meaning running rich.

Has anyone else ever seen their 02 sensor behave this way or had the same problem?

I own the car 13 years an never plan to sell it so this is cracking me up. Its not my daily, so now its just sitting in shed connected to trickle charger. Really want to get it back on road as I have big plans for it.

Did you find the problem? Be good to know for future reference.

 

[civicx3]

If you've tried different 02 sensors and they're both within range i would of thought its something else

Make sure the cat is hot, a cold or warm cat wont work properly and is it brand new or just new to the car? Aftermarket cats suck from what ive seen and dont last long, i killed a new one within a year

All fuel and air intake sensors wired correctly?

 

[soxturf]

Is there an additive you can put in petrol just for test ? or a more restrictive exhaust ?

That's just covering the problem though, if its running rich you will need to find the real cause.

Hi mate, an additive might help if it was just barely above the limit and staying constant but wouldn't do anything for something like this. Even with a more restrictive exhaust, it still fluctuating so wildly that I don't think it would work. But yeah, like you said, I wanna fix the problem, not mask it

 

[soxturf]

If you've tried different 02 sensors and they're both within range i would of thought its something else

Make sure the cat is hot, a cold or warm cat wont work properly and is it brand new or just new to the car? Aftermarket cats suck from what ive seen and dont last long, i killed a new one within a year

All fuel and air intake sensors wired correctly?

Hi mate, yeah what I was saying about the O2 sensor its that it should be fluctuating between 0.1 - 0.9, mine is only fluctuating between 0.5 and 0.7 so there is something wrong there but the problem is not with the O2 sensor itself as I have tried two new ones and both are doing the exact same thing.

When the car first failed the test I thought it was the CAT so I replaced it with a brand new aftermarket one. I know the CAT is good though as I used a reputable exhaust place in Ireland, and when my car previously failed the NCT about 5 years ago on emissions, I used their CATs to fix it and it went through every NCT until now (last time it failed on emissions it was normal though and it was clear the old CAT had failed as the emissions were remaining constantly high on high idle).

Thinking it was the CAT this time again, I replaced it and had it retested and it failed again, it was only after this I said to the tester that I was surprised as I had just replaced the cat, and this is when he said he does not think it is the CAT as the emissions are fluctuating so wildly there is clearly something else wrong.

I am about to embark down the road of checking all fuel and air intake sensors over the coming weeks/months and hopefully find the issue but I was just hoping that someone may have seen this issue happen before where the O2 sensor stays hovering around 0.5-0.7 and share what they done to fix it. Living in dream world I know haha

 

[soxturf]

Did you find the problem? Be good to know for future reference.

Hi mate, no not yet, been working alot so have not had the chance to start checking properly but if I do find what it is, I will be sure to update so that the forum has it miss taking the car out at weekends so much at the moment! ha

 

[soxturf]

Hi Guys,

Apologies, I forgot to provide an update to this post. The good news is that the emissions are now fixed and the car is NCT'd, and was back on the road since last May 2022.

Unfortunately I cannot pinpoint exactly what was causing the emissions problem. In the end, I upgraded the injectors to Honda RDX OEM 410CC Injectors and had the car mapped with a socketed obd1 ECU & jumper harness by AP Performance (Vtec6000 on here). After this, the emissions problem was completely gone and the car went straight through the NCT. I should also note after mapping, the O2 sensor which had previously been showing up as stuck (despite being replaced etc), started fluctuating correctly again.

There was no guarantee that having the car mapped would fix the emissions problem but it was a risk I was willing to take, as I had planned on having the car mapped anyway. As an added bonus to fixing the emissions, on the stock ECU, bhp had dropped to 169bhp over the years, and after mapping, bhp is now 182bhp. Engine/Internals are completely stock so I am very happy with this.

As some of you may have seen elsewhere on here, car is now undergoing a full restoration (it currently sits as a bare chassis after Vapour blasting, and should be fully restored anytime between February to May 2023 in time for summer. I look forward to writing a full restoration thread once finalised.

 

[terry_em1]

My EM1 got tested in November and failed on emissions too. No engine light, so I assume the O2 sensor is working. I'm getting a new exhaust made up and having a brand new high flow cat welded in. Hopefully that and a good service sorts it.

 

[ScottEk9]

Hi Guys,

Apologies, I forgot to provide an update to this post. The good news is that the emissions are now fixed and the car is NCT'd, and was back on the road since last May 2022.

Unfortunately I cannot pinpoint exactly what was causing the emissions problem. In the end, I upgraded the injectors to Honda RDX OEM 410CC Injectors and had the car mapped with a socketed obd1 ECU & jumper harness by AP Performance (Vtec6000 on here). After this, the emissions problem was completely gone and the car went straight through the NCT. I should also note after mapping, the O2 sensor which had previously been showing up as stuck (despite being replaced etc), started fluctuating correctly again.

There was no guarantee that having the car mapped would fix the emissions problem but it was a risk I was willing to take, as I had planned on having the car mapped anyway. As an added bonus to fixing the emissions, on the stock ECU, bhp had dropped to 169bhp over the years, and after mapping, bhp is now 182bhp. Engine/Internals are completely stock so I am very happy with this.

As some of you may have seen elsewhere on here, car is now undergoing a full restoration (it currently sits as a bare chassis after Vapour blasting, and should be fully restored anytime between February to May 2023 in time for summer. I look forward to writing a full restoration thread once finalised.

Hi,did need to buy a Hondata to map you ek9?or just the harness for the car to be mapped? I'm not too clued on ECU MAP side .

 

[soxturf]

My EM1 got tested in November and failed on emissions too. No engine light, so I assume the O2 sensor is working. I'm getting a new exhaust made up and having a brand new high flow cat welded in. Hopefully that and a good service sorts it.

Hi mate, I would not assume the O2 sensor is working just because there is no engine light.

When my o2 senor was 'stuck' and not fluctuating between .1 & .9 like it should, there was also no engine light (not even a code being thrown up when I connected it to diagnostics).

I would definitely check it before getting an exhaust made up as that could be a huge expense and still not solve your problem.

 

[soxturf]

Hi,did need to buy a Hondata to map you ek9?or just the harness for the car to be mapped? I'm not too clued on ECU MAP side .

Hi mate, this will sound ridiculous but I am not 100% sure the brand of the ECU which was used. The reason for this is because I paid 'AP Performance' or 'Vtec6000' as he is better known on here, to both supply & fit both the socketed ECU & jumper harness & new injectors.

I believe it was a Hondata S300 ECU he used (this is what he suggested when I first contacted him) and the reason I don't actually know the specific ECU used, is because he is known as one of the most respected 'Mappers' on this forum and in Ireland, so I trusted whatever he thought was best to go with.

I would go check it for you now, but my car is stripped at the moment and I do not have access to the parts as they are in my mates warehouse.

 

[ScottEk9]

Hi mate, this will sound ridiculous but I am not 100% sure the brand of the ECU which was used. The reason for this is because I paid 'AP Performance' or 'Vtec6000' as he is better known on here, to both supply & fit both the socketed ECU & jumper harness & new injectors.

I believe it was a Hondata S300 ECU he used (this is what he suggested when I first contacted him) and the reason I don't actually know the specific ECU used, is because he is known as one of the most respected 'Mappers' on this forum and in Ireland, so I trusted whatever he thought was best to go with.

I would go check it for you now, but my car is stripped at the moment and I do not have access to the parts as they are in my mates warehouse.

OK ,no problem . I'm thinking of going down a similar route ,and wasn't sure what's involved .
Cheers