Citroen C5 X7 small MAF issue

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grujo93
Posts: 3
Joined: 05 Jul 2024, 21:32

Citroen C5 X7 small MAF issue

Post by grujo93 »

Hello guys, I'm proud owner of the Citroen C5 X7, 1.6hdi engine. I take my cars seriously, and I do kind of preventive maintenance. I like to have well maintained vehicle, ready for any trip.
When I bought car, some 7 months ago, I did regular oil/filters change, and did the timing belt set replacement. It was going perfect, until it started playing games.

*First one was blue smoke and low power. Replaced turbine, smoke disappeared but power still was an issue on any kind of hill or overtaking.
*Next it started with black smoke, my mechanic found bad vacuum hose, replaced it. No black smoke, turbine started working her job. But again, up hill, issue and in my opinion, slow response to throttle.
*Started overtaking lorry up some really big hill, ended up with first gear, from 3rd, 3k RPM, check engine. Stopped by the road. Started car again, check engine was there, but I could go up hill somehow in 3rd gear but barely. On level ground, it was normal.
*Went to mechanic, throttle pedal error, low boost error. Deleted codes, kept monitoring, looked fine.
*Visited mechanic, his Electrician also figured out throttle pedal error, and fixed it. Not showing up anymore.
Then, again, constant incline, for some 2-3km, 70km/h, 4th gear, got depollution error, check engine, no throttle, from 4th to 3rd, then to 2nd, ended by the road in 1st gear and no response to throttle. Restarted car, check engine there, but it accepted throttle and worked. This time, we got overboost error. Cleared it.
*Decided to replace EGR, with new one as well as MAF. BOTH NEW. Once EGR was fitted, I noticed much more profound engine noise. It worked much more quieter and better. But, when cold, it started jerking. Revs going 200-300 up and down, up until the moment, temp bar goes to first bar. From that moment, all seems fine. Drove car, floored it, won't go pass 3k revs, no check engine, no code. Stopped, neutral, you can rev to the red zone with no issue. Drove car again, revs fine up until the moment, I needed to overtake, it would not go over 3k again.

Then, I've replaced MAP as well, to be sure. Delphi one. Same thing. Cold, jerking until first temp bar come on, then jerks disappear. But still, get at some point no rev over 3k. On advice, from one of the mechanics, disconnected new MAF, and drove. CAR WORKS PERFECTLY, pulls like it has more then 110hp. I can overtake, I can go up hill, I can do whatever I want, it GOES. No jerking, no power loss, throttle response perfect.
Connect MAF, we are back into trouble. Tried old MAF as well, connected, same issue. Disconnected, goes perfectly. What I can no figure out, and I noticed, is that the moment I disconnect MAF, turbine can be heard. Connect MAF, turbine goes quiet in neutral. But if I start driving, and going through gears, I can hear turbine working just fine, except for the jerks.

I'm safer driving without MAF at the moment, but I know it is not long term solution.
Did anyone had something similar, since I'm not sure what to look for anymore. I really like the car, and its comfort, but if it keeps like this, I'll sell it.

Any help will be appreciated. Sorry for writing this long, but I believe many details can get better solution when some of you that are experts with Citroen can try to figure out.
steveclv
Posts: 118
Joined: 25 Apr 2024, 14:13
x 7

Re: Citroen C5 X7 small MAF issue

Post by steveclv »

I don't know much about HDi engines but I understand that the engine uses data from multiple sensors and if it cannot read them correctly then it uses some default numbers. So the #1 culprit is likely to be a vacuum leak somewhere and then to test all of the other sensors - IAT, MAP, MAF (which you have changed), Atmospheric Pressure and Fuel Temperauture. All of these feed data to the engine to keep it running correctly.
Do you have a diagbox as that will let you check any fault codes and allow you see what each sensor is providing to the ECU?
grujo93
Posts: 3
Joined: 05 Jul 2024, 21:32

Re: Citroen C5 X7 small MAF issue

Post by grujo93 »

Well, the issue is that it won't actually store any code last two months. It just jerks, looses power, and then works 'fine' for some time. Diagnostic can't see anything stored. Replaced MAF, replaced MAP. Any chance where I can find IAT one under the hood? And since it works fine without MAF, do you happen to know, if MAF is disconnected ECU goes to default values with all the sensors, or just for the MAF? If it goes with all ones, then it makes sense why it is so smooth without it. Maybe it would be good idea to replace vacuum hoses, I guess it is not a big job.
steveclv
Posts: 118
Joined: 25 Apr 2024, 14:13
x 7

Re: Citroen C5 X7 small MAF issue

Post by steveclv »

I would certainly check all of the vacuum hoses and replace them if feasible - you said one had perished so likely others could be leaking.
My 2.0 HDi throws a code when the MAF is disconnected so I don't know why the 1.6 would be different but I think you really need to use Diagbox to monitor the actual live readings of each of the sensors when starting and running the engine.