C8 2.0HDI power issues and engine light on

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bestoday
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C8 2.0HDI power issues and engine light on

Post by bestoday »

Hi all..
Never posted before, so bare with me.. I have a C8 2.0HDI with 145K miles. Properly serviced with Turbo replaced at 90K.

Initially, problems started 10 minutes after starting, engine would falter when accelerating in any gear, then give a little jump, falter again and jump, and do this several times. There may or may not be little spurt of white smoke from the exhaust. It may be Ok for a few minutes, then do it all over again. It would eventually stop doing it, if it was more than a 30 minute journey or after 3-5 or more shorter drives of say 10-15 min's.
Then it would be OK again for a long while, then reoccur again usually after an irregular number of miles , approx. between 400 to 700 miles completed.
After a bit of investigating, someone suggested that the reason was that it only happened on FAP regeneration, when the ECU decides it needs it.
On regeneration, it closes the normally open doser valve, and opens the normally closed one, to bypass the intercooler to allow hotter air into the intake. However, they suggested that the normally closed one isn't opening for some reason, so the ECU compensates and opens the normal intercooler one again so not to starve the engine of air. This is what causes the jumping forward on acceleration.
Armed with this, I took off the doser valve unit from the intake and had a look. I noticed the lower one was covered in oil (Spill from oil changes) and vacuum pipe was very loose & slippy, cleaned it all up, cut some of the contaminated vacuum pipe off. Checked its operation by sucking on it and although it appeared to open, I felt it was alot stiffer than the other one. Each valve has a factory set torx adjusting screw. Would adjusting these help in any way? I then took off and tested the solenoids (difficult to do) that control it and compared and tested both and appeared to operate the same. My conclusion was that the lower doser valve was too stiff for the vacuum to open it, but I won't know for sure until the next regen. Any thoughts on this?
While I was there, I replaced the air filter and cleaned the MAF and housing with a soft brush and electronic cleaner.
This is why I am posting.
Now I get an amber engine light on startup, so I suspect I may have damaged the MAF. After startup, if I unplug it, it appears to make no difference to idling. Should it? Does that mean, its not being recognized,
and that the ECU is using a default map to run the engine? After unplugging the MAF, and restarting a few times the engine light appears to go out, but comes back on after a few minutes.
Car starts fine, sounds fine and engine appears to sound even smoother than before, but has slow acceleration response, especially at higher revs. It gets there eventually, but it does it at its own pace.
Long shot, but has anyone got a clear image or part schematic close up of what the OEM Siemens MAF No: 9632215280 should look like?
I suspect a component may be missing from two terminals, but can't be sure. Before I invest in a new one.
Also, I have read that some some types of air filters can cause this problem? Now that I think of it, I had an engine light after the last time I serviced & changed the air filter. Both Mann air filters. When I had the codes checked, they said the only code was a brake switch fault which they reset. Light kept appearing for a while on startup, but eventually it seemed to go away itself.
Really sorry for long post.
Thanks in advance for any advice.
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Re: C8 2.0HDI power issues and engine light on

Post by GiveMeABreak »

Hi and welcome.

By actually using a brush on the MAF you may have damaged it - these things are uber sensitive and normally just need some special MAF cleaner. Anything else may leave residue on the wire or damage it.
Please Don't PM Me For Technical Help

Marc
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