Possbile MAF Sensor Problem

[Staz]

Hi there,

I own a 2003 Volkswagen Passat PDTDi 130. From time to time it seems to loose power and become more sluggish and a lot less responsive. I also notice that the MPG goes down quite dramatically, however, on other days it will run fine and the MPG returns to normal. Has anyone else on this forum had this type of problem with this particular engine? It has been suggested to me that it could be a possible MAF sensor problem, though no fault codes have shown up when put on the diagnostics. If anyone could help me it would be gratefully appreciated.

Many thanks,

James

[Rolo]

It is probably going into limp mode as a safety measure due to high boost pressure. Does it return to normal if you turn the engine off and back again? Should log a code for overboost though.

[martin1810]

Might be worth replacing the MAF. These can start to fail and not log a fault code. It's not a cheap tryout though. Another possible is a faulty temperature sender. This can screw up fueling and not always show as a code.

[Staz]

Thank you for the replies

Reply to Rolo

A friend of mine who owns an Audi A4 with the same engine suggested this. I tried it, but unfortunately it doesn't make any difference. Sometimes you will feel the problem starting whilst driving the car — it's almost like quick and sudden misfire sensation, and then the car becomes less responsive and I notice the fuel economy going down.

Take care,

Staz

Reply to Martin1810

A temperature sender problem is something I will explore, thank you. I haven't even inquired about the price of replacing the MAF sensor; I'm sure my good mechanic friend will enlighten me if approached. Apart from this little problem, the car Passat is great. I did change the wheels to what I believe are Passat W8 rims which effected the handling slightly — it tends to stray a little on uneven camber — but it looks so much better than what it came with as standard.

Take care,

Staz

[tjompen1968]

Before looking for the hi-tech-problems, check that the basics are ok. I was looking for temp problems and only thought of the sensors at the beginning. I had a faulty thermostat that made my car loose power and become jurky (is that a word?). Depending on the wheather... It had started to keep the temp at 78 deg C instead of 90. The temp gauge in the car showed me 90 which it does due to electronics, approx 75 to 105 deg C shows as 90 deg C. Today I put the VAGCOM on my friends Passat just to check and we found that his thermostat also was busted. The thing I think is that below 80 deg C the car thinks it is still cold and wont give full power and above 80 it says ok to full power??? VAGCOM says that the temp should be between 80 and 105 if I remember correctly.

Well, just an idea since both ours where broken.

[Staz]

Thanks for replying, Tjompen1968,

A broken thermostat is also worth considering, yes. I spoke to my mechanic friend who also thinks that it could be caused by what VAG call a thrust sensor.

Staz

[martin1810]

If it's a thrust sensor problem you will get a fault code when you do a code read. Might be a good idea to get a code read done.

[Staz]

Hi again, Martin1810,

Thank you for the reply. The last time we plugged the Passat into the Stap-on diagnostics no fault codes were logged, which therefore rules out my thrust sensor theory... I'll get there eventually :)

Staz

[Clinterous]

When was your fuel filter last changed? I assume you are not getting any warning lights coming up?

I had sympton vaguely similar to this once. Eventually morphed into an constant misfire and loss of power....and parking on the hard shoulder. The injector loom positioned under the rocker cover needed replacing.

[Staz]

Hi Clinterous,

Looking at the service schedule, the fuel filter was replaced when it was due to be replaced and is not due for replacement for some time. The engine management light doesn't come on during this problem. The injection loom is also something to consider, so thank you for taking the time to reply :)

Regards,

James