Resolving Loss-of-Power Issues in the Volkswagen TDI

Updated on January 17, 2019

Volkswagen diesel cars such as the TDI can experience a loss of power. This could be temporary or more permanent, depending on the cause. Two possible causes are computer-imposed "limp mode," and the MAF sensor, which is just a small distance from the air cleaner.

Limp Mode Symptoms

Limp mode is a safety function when the car computer detects a serious malfunction of some sort serious enough. There is NO signal to the driver, just this odd feeling. It feels like you have the E-brake on, or something is holding you back. On a flat road, it will be subtle; it is much more obvious when trying to climb or get onto a highway. Your engine light may or may not be on. Most cars in this mode will seldom go above 2000 RPM, but limp mode will let you slowly accelerate to 40-50 mph. It will take much longer than normal.

Troubleshooting Cause of Sluggish Performance

The only way to find out the cause for this limping is to use a VCDS computer to hook up to the car and see what the codes are. Vacuum leaks are known to cause it because the car may stumble or buck. However, the problem might be a boost issue, EGR, exhaust leak, clogged fuel pump, bad MAF sensor, or sticking vanes in the turbo from soot. So, you really do need the code to make a determination.

The arrow points to the top connector of the MAF, which is a section. The top connector can be disconnected with special tool
The arrow points to the top connector of the MAF, which is a section. The top connector can be disconnected with special tool
This is a MAF sensor for many VW TDI models
This is a MAF sensor for many VW TDI models

The MAF (Mass Air Flow) Sensor

A bad or going-bad MAF can cause the loss of power. These are usually good to 70K miles.

Symptoms of a Bad MAF Sensor

A bad MAF sensor might produce a sudden reduction in car power, but the normal failure mode is a gradual loss of power over weeks. Your engine light may come on if the sensor only has intermittent failure. If power is restored by shutting the car off and turning it back on, you are in limp mode.

If you are not sure whether it is bad, simply rev the engine to 5100 RPM while in park or neutral. If the MAF is bad, you will not be able to do it. If the MAF has not failed totally, you should be able to do it. You can also unplug the plug connector. The ECU will then replace the faulty signal with a default value. If the car has more power or is unchanged, the MAF is definitely bad. If the engine check light is on, it may reset when the connector is disconnected and reconnected.

Cause of MAF Sensor Issues

One cause of a bad MAF is that you have used an aftermarket air cleaner that fails to keep oil residue away from it. Even a little residue will cause the sensor to fail. They are sensitive.

Time and Cost to Repair a Mass Air Flow Sensor

The time to change a MAF is not longer than 30 min. The cost of a MAF is anywhere from $140 to $200. The MAF base is held onto by two screws. Once removed, disconnect the top connector to the MAF and install a new one. To remove the top connector you will need a special tool to remove the two screws.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

Questions & Answers

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      • perrya profile imageAUTHOR

        perrya 

        7 days ago

        If B is true, sounds like it IS the MAF, which is a very finicky part. If dust is in it, you could trigger limp mode. I once had to replace it twice before all was fine. But, have you let VW diagnose with their deep scan computer? You might be shocked at what causes limp mode.

      • profile image

        06 A4 TDI PD 

        11 days ago

        I'm at a complete loss trying to diagnose this car. It behaves exactly like you've described the limp mode: like someone threw the torque out the window, never going above 2K rpm, barely getting out of its own way.

        So far I've ruled out MAF, vacuum leak, n75 valve, vnt actuator and vnt mechanism.

        Weirdest part is that:

        a) 1 out of 5 times or so, when pressing on gas pedal, it works properly until the gas pedal is let go.

        b) it drives MUCH better, almost near normal with MAF disconnected.

      • perrya profile imageAUTHOR

        perrya 

        2 weeks ago

        You may be in limp mode for some reason. If you turn off the engine for 10-20 seconds, limp mode goes away, but as you drive again, it happens again. There must be a code about why limp mode is being triggered. The VW dealers have a much more thorough computer to obtain the codes.

      • profile image

        2015 Golf GTD 

        2 weeks ago

        I have had 3-4 times this odd sensation of loosing boost power. I dont know if it went into limp mode or not. It has always happened on aggressive city drives when there are many stop and goes. So far i have checked engine error codes but nothing has come up. It usually goes away when i stop the car and turn off the engine. I also get inconsistent boosting at times where there is no full loss of power but is just slightly underperforming while other times i get huge turbo boosts in second and third.

      • perrya profile imageAUTHOR

        perrya 

        3 weeks ago

        Since you removed the MAF, the engine light came on and will impact how fast you can go . The glo light may mean you need to replace the the glow plugs which are like spark plugs

      • profile image

        Sanchit 

        3 weeks ago

        My golf 1.9(Diesel engine) having issue of lack of power while accelerating.

        I removed MAF connector now it’s performance improved but it’s glow plug light and engine light is on (does it mean bad MAF)

      • perrya profile imageAUTHOR

        perrya 

        6 weeks ago

        I had to replace my MAF a few times, it is a very sensitive part and any particle or dust on it can create a fault code.

      • profile image

        Jeff 

        6 weeks ago

        The car will drive better when I unplugged my mass airflow sensor so I bought a new one and put it on but I'm still having the same problem any ideas would help

      • perrya profile imageAUTHOR

        perrya 

        2 months ago

        You just may need a new oxygen sensor or maybe your CAT is partially blocked.

      • profile image

        @tabs 

        2 months ago

        Hi, i drive VW Mk5 1.9 Tdi and have following code; P0234 i know its about turbo supercharger overboost or something. Secondly, it has emissions workshop light on. i did check for turbo problem and believe waste gate might be the problem and coming to emissions, i cannot see or detect any leak on vacuum pipes. What could be the course?.

      • perrya profile imageAUTHOR

        perrya 

        2 months ago

        I would pull the engine codes from the computer and see what they say. Limp mode is a protective mode so your car cannot go about 50 mph or so. It could several things.

      • profile image

        Maiana 

        2 months ago

        Hi my car has had an issue with energy loss the last couple of times I've driven for more than 2 hrs on motorway , only when going up hill

        Today it changed and I was in limp mode for about an hour until I go at home

        Think it's the MAF .?

      • perrya profile imageAUTHOR

        perrya 

        2 months ago

        Not sure, I never had this issue.

      • profile image

        Jors Viljoen 

        2 months ago

        During low engine refs, for example when slow down to enter the driveway and changed to 2nd gear, the engine cut out on my 1.9 tdi golf 5. New glow plugs have been installed 1500kms ago.

      • perrya profile imageAUTHOR

        perrya 

        3 months ago

        Vibration in neutral means the flywheel is lose inside the tranny! Bad sign, time for a new one

      • profile image

        Amit Mukhedkar 

        3 months ago

        Sir i have Polo diesel engine 1.2 litter i get this type of light symbolÔ×┐ and lots of engine vibration when my car is neutral or in addling mode it blinks sometimes when Air condition is trun on.Sometimes i drop pickup on 1st gear but later it goes fine. But i do feel performance is poor. Guys please help me out to slove my problems

      • perrya profile imageAUTHOR

        perrya 

        5 months ago

        Have the engine compression checked, if OK, the car is slower going up hills, a bit under powered.

      • profile image

        Waqs 

        5 months ago

        Hi i bought golf mk5 08 78k drives good but hard to pick up spewd especially on motorway nd hills anyone can suggest me what could be the cause please as i spent a lot of money

      • perrya profile imageAUTHOR

        perrya 

        5 months ago

        You might need new glow plugs, which are like spark plugs, or some new plug wires attached to them

      • profile image

        Hatem 

        5 months ago

        Hi i have golf 7 gtd some times i lose the power the glow light is flasinge engine light not limp when i restar engine all is good the problem code 029900 plzas help me please help me

      • profile image

        Rudzani 

        6 months ago

        I have polo classic TDI 1.9,the engine was steeped off,they put it together wen they start it runs for 6 secondsand stop,at dashboard show wire light blinking,wat is the problem?

      • profile image

        William 

        15 months ago

        Yes Armando. Check a youtube video on what you are trying to do. If you are comfortable following the instructions then go for it. If not, go to a mechanic. A MAF can be changed in church clothes in under an hour with a screwdriver and large mouth pliers.

      • profile image

        armando 

        16 months ago

        can i service my 2000 vw jetta 1.9tdi turbo

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