Help needed: Misfires and other CEL's - Detailed account of the situation

[ecarca]

is the number written on the insert, the bit that screws into the chamber which the electrics plug into?

Yes it is!

 

[ecarca]

Excellent work ecarca..!!

Thank you Robert!
Most of the work has been done before but I spent quite a decent amount of time researching the topic, exploring Alfa forums, vendors sites in China and abroad and calling a few local potential suppliers.

There are non Bosch replacements sensor inserts in Europe, readily available on Ebay. The problem in China is that they wanted me to get between 100 and 1000 pcs since I got in touch with the factories directly LOL

This said, I believe that the best is to get a Bosch sensor for years of trouble free enjoyment. The Bosch distributor in China politely told me that this was an OEM part and that they could not sell directly.

So the only way I found to get a decently priced replacement insert (which we can call a sensor since it is the sensor) was to get a complete MAF (housing + sensor) and use the sensor only. The pricing doesn't make sense, it is purely marketing depending on the segment of the cars, so as long as you manage to snap a new one with the right sensor at a good price it is fine.

Emmanuel

 

[CatmanV2]

In the Alfa world, non Bosch parts were generally to be avoided and regarded as having a very short lifespan.

C

 

[hodroyd]

Emmanuel,
That's a common sense approach and well researched, well done..!!
Cheers
R

 

[ecarca]

BAD NEWS!

I received the new MAF, installed it and same problem as before.

So the current bottom line is that the car drives great when the MAF is unplugged and not that great, particularly at low revs when the MAF is plugged.

That is: the car runs perfect in open loop from the ECU preset maps but not in closed loop when it uses the data it collects from the different sensors...

I am not sure what's next. It still could point to a vacuum leak somewhere? Not sure at all...

 

[conaero]

I would suggest you have a split in the intake system post MAF.

If the car runs fine in open loop then poor when metered, it would suggest the mixture it's mixing is being thrown off by additional air coming into the mix post MAF

 

[ecarca]

I checked for leaks already... It's actually quite short there: throttle body and that's about it... Do you have any particular thing you would recheck if you were me?

I got the proper CEL back as well replugging the MAF: misfires. One of my ideas was to purchase 2 new injectors and try to replace 2 on the cylinders that first show misfire codes to see if they are the culprit or not... Still it's strange than there is not the same issue when it's in open loop... It's a headache really.

 

[allandwf]

Could still be another sensor, but not showing faulty. Unplugging the MAF, as said, would force Open Loop control and mask it. Is there any way you can read see real time values?

 

[ecarca]

Yes, I use torque with an obd2 reader.

 

[conaero]

SD2/3 time I think.

 

[ecarca]

The dealer said nothing when I took it to the dealership. They gave me a printout of the codes and that's it. They blamed the misfires on gas and spark plugs, which proved to be completely wrong.... and completely overlooked drivability issues.

So I don't really see how it will be of more help at that stage... I know it's hard to understand but don't think about official dealers or independents the same way you would when you talk about European ones or Chinese ones... There is a real difference in technical competences (their oldest mechanic has 5 years experience) and service level.

No independent that I know of in China has an official computer, so in that sense you could consider there are no "real" specialized indies.

 

[Contigo]

Check the EVAP line, Hoses etc and also injectors which could well be dirty. I saw you had them out and they seemed fine earlier. Does your car run hot?

 

[Contigo]

Did you look at knock sensors too?

 

[hodroyd]

Could be knock sensors, they do knock the power right down..!!

 

[ecarca]

Check the EVAP line, Hoses etc and also injectors which could well be dirty. I saw you had them out and they seemed fine earlier. Does your car run hot?

I want to do a smoke test... I'll see if I have time next week-end. I don't have a smoke machine but I found several DYI solutions that seem to work well.
The car does not run hot, the temps are spot on.

I did not check the knock sensors and don't think I have any issues with these. I think I will first do a thorough vacuum leaks check (not only car cleaner). Since my problem only happens at low revs, it could be a tiny leak, either a cracked tube, an o'ring leaking someplace or even a seal (hopefully not the intake gasket)... A vacuum leak would be masked by the ECU running the default maps when the MAF is unplugged so it is actually quite a serious lead.

If there is nothing coming from there, then I might purchase 2 injectors and replace 2 injectors on bank 1 to see if I still get misfire reports on the cylinders where these are new.

No more ideas than that at this stage. I don't think the problem is too serious but it's very hard to diagnose so far.

 

[hodroyd]

If it is only at low revs it's maybe not the knock sensors..!!

 

[ecarca]

Ok, I will get back to this problem soon. I need to find a place with a smoke machine first. Let's see if there are any vacuum leaks. Other than that, I am thinking of checking the fuel pumps. Could be a dirty pump on one side or something....

Let me know if you have more ideas gents!

Thank you

 

[ecarca]

I checked the fuel pumps, they were a bit dirty but cleaning them did not solve my problem. However I have the feeling that the car generally runs smoother and is more gentle than before.

If I replug the MAF, the car runs rough in the lower RPM. I really think it is a vacuum leak but I cannot find a place with a smoke machine. I need to figure out something.

Here are 2 pics of the fuel pump job

 

[ecarca]

I FINALLY got my hands on a smoke machine and just tried tonight...
Bed news: no leaks! That was the result we already found while testing the vacuum pressure. It is disappointing because I thought I would still find something.

So I am COMPLETELY clueless now. The car works great with the MAF unplugged, and it has this low revs problem with the MAF plugged...

Other than that and 4 the good news: I had the 4 wheels refurbished and most of the small dents and scratches repainted
She is stunning

 

[hodroyd]

Have you tried a new MAF as a temporary measure, if so it sounds maybe like a programming issue in the ECU, or incorrect reading from the MAF..??