Greetings everybody,

After some time since my last post, I've managed to swap spark plugs, clean the ignition coils, new air filter, cleaned the throttle body (looked very clean anyways), and taped many "holes" that I found on the underside of the "accordion" intake hose, using two complete rolls of 3m electrical vinyl tape. I could hear air blowing in when giving the car a bit of throttle, so that was an air leak for sure over there.

I took the car to pass emissions again, and the outcome has been the same: Lambda emissions too high, too much oxygen coming out the exhaust.
So I have been checking fuel trims again, and I beleive the ECM is substracting fuel as before, so basically nothing has changed.

We are about to take the cat to the official dealer and let them deal with it... But before we do that, I thought maybe I could get some help here about it.

1. Both upstream O2 sensors are new.
2. One ignition coil died when I swapped spark plugs, was in very bad shape, so replaced with a new one.
3. No error codes reported by the ECM.
4. Performance and smoothness seems to be perfect, no hesitation, no strange stuff, etc...
5. Doesnt look/sound like there's any exhaust leak.
6. CO emissions are perfect.

• Should I swap the other 7 ignition coils to ensure every cylinder is getting the same voltage?

Here are two pictures I took, before and after the spark plug swap and intake leak fix:


Before



After

So would this make sense?:

1. Check for exhaust leaks (smoke machine?)
2. Check for air hoses leaks
3. MAF sensor possibly bad?
4. Swap both downstream lambda sensors?

King regards from Spain.

 

I don't see a problem with the fuel trims. Even if they were in the teens the ECU could compensate. Do you get a P1111 or a P1000 code? It may be that you have not accumulated enough drive cycles if it's P1000.

 

No codes reported by the ECU.

Thanks for your reply!

 

There's something wrong there. The P1000/P1111 readiness monitor should always be logged by the ECU.

 

The OBDII reader is an Autel Autolink AL619, and it reports no pending nor stored codes...
I have never seen the P1000/P1111 codes in the reader.

Aside from that, here are the lambda emissions as reported at the "technical vehicle inspection" (government test center):

First test: Lambda = 1,060 (CO emissions were high, but got fixed after swapping upstream o2 sensors)
Second test: Lambda = 1,504 (after upstream o2 sensors swap for new ones)
Third test: Lamda = 1,203 (after new air filter, intake leak repair)

- The acceptable range for lambda emissions here is between 0,97 – 1,03.

If fuel trims are inside a proper operating range, then, there's a leak somewhere at the intake or the exhaust?

 

Negative trims means that, according to the o2 sensors, the effective amount of fuel is too high, and the feedback dictates that the amount of fuel be reduced. Positive trims is the opposite, fuel has to be added because there seem to not be enough, typically because of air leaks.

You are fighting a situation where there seems to be too much fuel. As opposed to air leaks, there are not too many scenarios where that happens: can be uncontrolled release of fuel in the intake, like from the evap system (purge valve, etc.), or a faulty air flow meter. I suppose there are more far fetched scenarios where your fuel pressure regulator is leaking fuel in the intake, or engine oil contaminated with fuel, etc.

I would start with a cleaning of the AFM with the proper spray. The AFM is in a cavity. Fill it with cleaner, leave it be a while, then do it again. The more visible "pill" is the air temp sensor. If the cleaning is successful (keep your expectations low on this one), you should start seeing positive short term trims eventually driving the long term trims back towards zero.

Next, look at just throwing money at a new AFM. I believe the earlier parts are unfortunately more $$, but this sensor is sort of critical to the whole emissions scheme.

You can also try and see what you can do with the evap. Normally, it is heavily monitored and there are codes when it fails. Maybe try and find a way to temporarily cap the line from the purge valve (located in the driver side wheel well) and see if it helps.

Best of luck, keep us posted.

 

Updated news:

After cleaning the MAF, or also called AFM, I have new fuel trims displayed:

IDLE:

• SFT1: 0%
• LFT1: 2,3%
• SFT2: 0%
• LFT2: 3%

2000 RPM:

• SFT1: 25%
• LFT1: -13%
• SFT2: 25%
• LFT2: -13%

This looks like better fuel trims than before?

Also, I used the method of covering the exhaust pipes with cloths for a few seconds, and found that the car wouldnt stall or sound anything near stalling, and there was smoke coming out somewhere else... between the last silencer and the left tail pipe, at the top, where it cant be seen directly.
Could this exhaust leak be the reason the exhaust is getting more oxygen and so Lambda is higher during the emissions test?

Thanks a lot for you reply, fmertz.

 

This leak seems too far to really mess with the on-board lambda sensors (midway down the converters), but could definitely mess with the readings off of the tailpipe sensor at the emissions station.

 

Good news everyone!
After finding and sealing all the "micro leaks" at the exhaust system (specially around the joints), the "vehicle technical inspection" (formely ITV at Spain) has given the positive test pass. The Lambda mixture is perfect now at the exhaust as sensed by their equipment and they told me that any leak at the exhaust causes lambda to give wrong readings and so fail the test.

Another happy cat now running great on the road again

If for some reason this post could help others in the future, I will resume the points learnt:

1. Swapping both upstream O2 sensors made CO emissions "perfect" (I had these codes: P1646 and P1647).
2. Sealing exhaust micro leaks fixed lambda readings (along intake leak fix while fuel trim readings were useful to check mixture).

Thanks to everyone for helping me out on this matter!

 

Yup... If you have time (inspection wise) get a simple and generic code reader the will BT to your phone. If you have no light and the p1111 code the car should pass as is. Those values look fine... What the inspector probably saw was a p1000 code which just means the car is not diagnostic-ly ready for inspection.

IMHO, self vulcanizing black tape will give a better and longer lasting result on the intake tube. Stuff is a little tough to work with (loves itself - you'll see, lol) but if the surface of the tube is spanking clean, it'll stick to and seal them air grabbing holes better than regular adhesive tape...

EDIT - I wrote before I saw you solved it AND before I saw you live in Spain! Probably much higher standards there for y'all? In NYC, I've never even had them put anything in the tailpipe. They look at the dash, plug in the car, and if all is green, they slap a sticker on it.