Alfa Romeo Forum banner

1 - 17 of 17 Posts

·
Registered
Joined
·
5 Posts
Discussion Starter #1
Hello!

car details:
Alfaromeo 156 1997
2.0 TS


So just couple of hours ago got my car fail the emissions test.

I have replaced the lambda sensor about one year ago, and the cat yesterday. Before the cat replacement the lambda sended really garbage data (voltages between 300 - 500mV) and now (more like pwm) -100mV - 1000mV.
Also now it idles much more smoother at around 850rpm, (before it was shifting between 700 - 1100rpm). I can't feel any problems regarding to performance, so the car accelerates normaly, doesn't seems like it might stall, and so on.

only errror code that shows up (before the cat replacement there was always 3 codes, regarding to lamda sensor (integrator over upper limit, intermittent, lambdasond intermittent) but now I only get the "integrator over upper limit, intermittent"

the guy who tested the mot, said that there might be issue with ignition. I have changed the sparkplugs year ago. the idle sounds like that might be the case because its not steady, but more like (
) (the first part, and not my video or car) but not as bad as on the video...

waiting if someone knows more about this...
 

·
Registered
Joined
·
22 Posts
Hi, have the same issue with a jts at the moment. Fault codes for lambdas, so I replaced sensors and cat, but still failed the test. It looks now as if there is an issue with the MAF - just check the connection, clean sensor carefully with contact cleaner and try again. Might be a faulty wire or connection on the way to the ECU, though. H
 

·
Registered
Joined
·
241 Posts
I've written about this before - check your MAF sensor - Ideally try one that you know is working OK. When I had my TS I had a 'lumpy engine', the fault code pointed to lambdas not performing. But as I had it explained by a wiser person that I, if the MAF is not good and throwing garbage data/mixture into the engine management, the lambdas will never cope with incorrect balance as it comes out so shows the error.
 

·
Registered
Joined
·
446 Posts
Wow, 1997 that is older than my 1998 2.0TS. I read/maybe it was just a dream that MAF sensors do age badly, and so all cars with a MAF have some way to compensate for an elderly MAF. This means you need to reset the learned calibration values, and let the ECU figure out new values based on the lamda. Of course this only works if there are absolutley no air leaks upstream of the lambda, and of course no air leaks downstream of the MAF. The CF3 has a pair of lambdas close the engine before the primary cats which helps a lot, but our older CF2 engines only have one lambda, far away, so much more possibiliy of oxygen ingress, you only need a tiny, tiny split in the exhaust to let air in, and 1% air in will upset the learning. So try reseting the cal. values and take the car for an italian tune-up. The Idle position will be reset too, so you might need a bit of accelerator to start it the first time after a ECU reset. The ECU should be able to fix itself given enough time, but the reset will get thing moving considerably faster. Let us know how you get on, and of course if the MAF is really old, it may be outside the calibration range of the ECU altogether, but it sounds to me like you just had a failed sensor, and the ECU needs a bit of learnin'
 

·
Registered
Joined
·
3,732 Posts
How much did it fail by? Do you have the numbers from the part of the test it failed. Was it miles over (indicating a problem to be fixed) or was it only just out.....indicating that a dam good thrashing is needed before the next test!....which is exactly what was needed to get my 159 through the test. Went from being miles over the limit to miles under after a 5 mile thrashing on the A27!
 

·
Registered
Joined
·
9,189 Posts
What make is the lambda? If it's an NTK one .. bin it! Fit a Bosch even the LS615 universal is better that the NTK rubbish (wrong ohm rating to start!).
 

·
Registered
Joined
·
103 Posts
700-1100 rpm is what my brother referred to as "hunting" he had a heavily tuned subaru impreza and the exact same issue occurred, 100% the MAF sensor, once replaced the car idled and fuelled correctly (they only lasted about 5 weeks, but still) so get that replaced, as above.
 

·
Registered
Joined
·
5 Posts
Discussion Starter #8
Okay, thanks for the answers, now I'm going to test the maf values, amd then try to clean it, and measure the values again

The lambda is bosch original.

The values that were wrong were at 2000rpm

CO measured 1.2, accepted 0.2
HC ppm measured 615, accepted 100

I have no clue what the units are...

And how I can reset the ECU?
 

·
Registered
Joined
·
446 Posts
High CO and HC means you are running rich, its usually the other way with intake air leaks. Have you tried to remove the pipe from the air cleaner to the MAF, just to be sure the filter isn't blocked?

The CO is usually by % partial pressure (volume).

I just watched your video again, and it sounds a lot like you are missing on one cylinder. While the car is running you can try disconnecting one of the PRIMARY control plugs to a single spark module. Obviously don't try with the secondary or you'll get a nasty high voltage shock. The CF2 is different to the CF3 since the coil packs are wired up for redundancy, I think 1,4 and 2,3 . Anyway when you remove one of the coil packs from the equation the engine idle should fall by 100 rpm for a bit, but the important thing is that all the coilpacks do the same, If not you have a bad coil pack or spark plug or plug lead or plug resistor. I had a few issues with mine, and carefully removed all the packs and resistors and cleaned them with WD-40. Top tip when you are removing a connector from a live coil pack do it with one hand, keep the other one behind your back, then if you get a shock it does not go accross your chest, you don't want that, it hurts a lot.
 

·
Registered
Joined
·
5 Posts
Discussion Starter #10
Hello and thanks for ansvers!

The video is not from my car, but the sound is kinda similar, I will pe posting video from the actual car and how it sounds as fast as I can. After the last post I tried cleaning the maf, aaaand broke it. After I purchased new, original maf, the hc results didn't change... The guy said that there migt be leaking exhaust valve, so next thing to do is to measure pressures from the cylinders. I really doubt that there is no problem with the valves but we'll see. I have also contact which has other ecu and the whole ignitiion system, so that is the next thing we'll try.

there is picture from the lambda voltages:
933983

the software also says that the stus of the lambda is (changing rapidly) between "cold", "lean" and when I floor the pedal is only time it says "rich"
 

·
Registered
Joined
·
2,553 Posts
Lambda is a ratio- not a real thing.
Similarly, there can be on such thing as a Lambda sensor. Being specific and not being inaccurate can help.

Firstly, on the CF2 engine, the O2 sensor integrator should display lean and then rich within 1 second. If it does not cycle this way as quickly as I hertz, then the O2 sensor is defective. It seems ok in this instance though. It should operate in the 100mV to 900mV range.

Units;
CO is carbon monoxide. Accepted is the maximum limit. Measured is 1.2% which is way too high.
HC ppm is hydrocarbons measured in parts per million. 615 is more than 6 times the limit for unburnt fuel exiting the exhaust. What is the Lambda ratio as measured by the exhaust gas analyser? Clue; It should be between 0.97 and 1.03.

To me it seems the cat is not working but as I have not seen a video of the actual engine working or diagnostic data, it is very hard to suggest anything with a great degree of accuracy.
 

·
Registered
Joined
·
446 Posts
If it were me...I'd like to figure out if this is systematic or cylinder-specific. You can do this by making a known change to each cyclinder one by one. E.G. disconnect an injector, or a spark coil. Check how each cyclinder affects anything you can measure. See if there is a cylinder that behaves differently to the others. If they all do the same thing, then you can be fairly sure it is systematic, such as air leak, low fuel pressure, exhaust problem, ECU, MAF etc. If it is cylinder-specific it could be injector, spark plug, mechanical problem, head gasket etc. Just do the easy/cheap things first, report back here, and we can help.
 

·
Registered
Joined
·
4,333 Posts
Where did you get the cat from?

We’re all used to modern cars with cats that light up easily - but this is a 1998 car with a cat that is 6 ft from the exhaust manifold. My 155 V6 is similar - it will fail the MOT if you drive it to the station, stop it, and then put it on the analyzer 5 minutes later. Drive it up the road, and immediately stick it on the analyser - pass, because the cat has lit up.

After market cats (which my 155 has) are **** at starting up, which is why they are cheap.

A properly working cat will get the CO and HC to the right levels, whatever the engine is doing, The lambda ratio will be miles out, but 600 ppm is nothing. On a V6, you can drop two cylinders and the tail pipe emissions are fine - cats are red hot though.....
 

·
Vendor
Joined
·
45,430 Posts
I've been in a similar situation a few times with customer's cars. Usually when it has an aftermarket cat fitted that is more than a year or two old, it is the cat that is at fault. As RXE says, they don't light up well, but the difference between a pass with an aftermarket cat and a pass with a genuine Alfa cat is usually a 10 fold increase in HC.

I would find a good second hand genuine Alfa cat. If you have someone that can weld it into place, I have one from a 2.5 V6 which would do the job, I fitted one on another 156 TS CF2 about 18 months ago and it has passed two MOTs with flying colours since.
 

·
Registered
Joined
·
5 Posts
Discussion Starter #15
The cat is brand new, but aftermaket. I tried to find original alfa cat, but had no luck. For now I don't have more diagnostic data, as I'm now on my military service and the country is in half lockdown there might be hard time for me to test it more. Also I'm litle suspicious about that chinese delphi software, so I will try the multiecuscan.

here is also the video: MEGA

HTML:
<iframe width="640" height="360" frameborder="0" src="https://mega.nz/embed#!r98XRZzC!wfXWJ9SNzBeup2OlYL6D9aOvOy4OG3iHN2YGRp6rtEU" allowfullscreen ></iframe>
I have good place to do work on the car so that isn't issue, but rn the time is. Haven't yet had ansvers about the cylinder pressures, so I guess that I will get the info when I can test is myself.

I'm pretty sure that last time that I got the test's (my dad got it tested) the cat was "lit up". Regarding to his knowledge about cars (and that you are supposed to "warm it up" before the test).

the errorcode that only now shows up is P0170 which with litle bit of googling says "Fuel trim malfunction (bank 1)" and if I had it right, the bank 1 means cylinders 1 and 4? correct me if that's not right. So those are now the suspected cylinders.

I will update when I get back home and can test it more, cheers!
 

·
Registered
Joined
·
2,553 Posts
Edited;
I originally stated Bosal should be ok but I checked and found CF2 V6 cat is deleted from supply and CF2 TS one is now generic (does not incorporate silencer).
 
1 - 17 of 17 Posts
Top