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Resolving Loss-of-Power Issues in the Volkswagen TDI

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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.

Comments

perrya (author) on August 20, 2020:

There are many VW things that can put your car into limp mode, things that might seem unrelated. When you pull over and turn off engine for a minute, the system resets until limp mode resumes. You need to find out the engine codes to determine what needs to be looked at. The VW dealers have a machine that pulls all the VW codes, others will not. It is worth the one time cost.

Mo on August 19, 2020:

While driving 60-70mph usually okay any faster and goes into limp mode, if i turn off and back on it goes back to normal, very alarming when trying to overtake, what could be the problem? Also goes into limp after slowing down after a motorway journey, have to turn off and on again

allen on August 17, 2020:

vw t4 25tdi when driving engine revs go .engine still ticking over no power from the pedal until i switch the key on and off then revs come back please help

Karim on August 07, 2020:

Hi Perrya,

I am driving VW Touran 1.9 TDI, it drives fine locally but notice when take it to motorway, RPM not passes over 3 and if I put my foot down then some times it goes to idle mode. When turn off and turn back on then drives as expected

Can you assist me what can be a root cause please?

Thanks

Karim

perrya (author) on July 31, 2020:

Nana-at the very least and it is easy, replace all the glow plugs with new ones. As to no turbo after 2nd gear, what are other warning lights on the dash? Have you done a computer check for engine codes? Sounds like the car goes into limp mode to protect itself. Engine codes will tell you what the trouble is-get them from a VW shop.

Nana on July 28, 2020:

Hi, to everyone I'm Nana from south Africa thanks to everyone with your questions and your answers i have 2006 passat TDI 2.0L after replacing the engine it looses power from 2nd gear i mean turbo shuts off and a glow plug warning light comes up followed by engine management sign what can be the cause please.

perrya (author) on July 23, 2020:

You still may need a new fuel pump, if there is a turbo, then a new turbo. Sudden loss of power seems to be a turbo related thing. There must be some other codes?

Tapologo on July 19, 2020:

Hi have a question , my vw jetta 2015 just lost power while driving , i went to besides the road and turn it off. Tried to start the car again just cranks , i put scaner just got a code saying fuel pressure low. Checked from fuel pump all the eay to the engine and there was diesel up to the engine checked some sensors . Pliz what could be the problem ?

Collen on July 15, 2020:

I have problem with my polo 1.9 tdi .does nt reving .

Phala on June 18, 2020:

Lack of power n refuses to start sometimes

perrya (author) on May 19, 2020:

Try changing the glow plugs. There many things that can cause limp mode, some seem unrelated.

perrya (author) on May 18, 2020:

Defective glow plugs? Switch them out and see if the issue remains, Of course, fix the fault also, as many conditions can trigger limp mode even things you might not think would.

simon siddells on May 17, 2020:

Hi from Auckland New Zealand!

I have a 2006 A3 2.0l tdi. Runs perfectly well EXCEPT when I take off in the morning and drive up the hill outside our garage, it goes into limp mode if I put my foot down a bit. Only does this in the morning when it is cold. No other time. Turbo always works when it is warm and it runs like a dream. I have had the diagnostic test done and says turbo boost fault. There are obviously lots of potential issues that limp mode can be caused by but does anyone have an idea why just when it is cold?

Thanks

Gemmaingl on January 30, 2020:

I’ve gotta VW Tiguan, 59 plate. I was driving on the motorway at 70mph and the car glow plug light started flashing and lost power, pulled over turned it on, the light on dash isn’t there anymore but car is permanently in limp mode. Took to the garage and code saying boost pressure came up. Garage cleared the code but car still in limp mode, I’ve took it to a VW specialist who hooked it up for codes, no codes found. They’ve said it’s the turbo! My husband doesn’t think that is the problem because of many reasons, it’s been to 4 different garages and now feel like they are all just taking my money. And help?

perrya (author) on January 13, 2020:

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.

06 A4 TDI PD on January 10, 2020:

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 (author) on January 05, 2020:

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.

2015 Golf GTD on January 04, 2020:

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 (author) on December 26, 2019:

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

Sanchit on December 25, 2019:

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 (author) on December 09, 2019:

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.

Jeff on December 08, 2019:

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 (author) on November 08, 2019:

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

@tabs on November 07, 2019:

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 (author) on November 07, 2019:

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.

Maiana on November 05, 2019:

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 (author) on November 02, 2019:

Not sure, I never had this issue.

Jors Viljoen on November 01, 2019:

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 (author) on October 21, 2019:

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

Amit Mukhedkar on October 20, 2019:

Sir i have Polo diesel engine 1.2 litter i get this type of light symbol➿ 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 (author) on August 18, 2019:

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

Waqs on August 18, 2019:

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 (author) on August 11, 2019:

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

Hatem on August 11, 2019:

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

Rudzani on June 25, 2019:

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?

William on October 22, 2018:

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.

armando on September 19, 2018:

can i service my 2000 vw jetta 1.9tdi turbo

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