[jhazewin]

Hello. I am new to this forum, so I apologize if these questions have been asked before. I have scanned several of the posts and found them extremely helpful and educating, although I have yet found the solution to my issue.

I have a 99.5 Jetta. I purchased it last year with 230k miles on it, now it has 250k. From when I picked it up to present I am getting 42 mpg, which is fine. About 3 weeks ago I experienced lack of power one morning. It was chilly, so I thought it might have been a fuel item. Next morning, same thing. I installed a new fuel filter. After installed, power restored. I thought the problem was solved. Not so fast.

That evening returning from work power was lost. Thought it may be air or debris in the fuel line. Blew out the lines, purged the air. Power returned then left the next morning.

Started to replace all the vacuum hoses. Replaced thermostat (was taking a long time to get to 190 degrees). Cleaned EGR valve. No improvement.

When started cold max RPM is 2000, if running 60 minutes it can get about 3200 RPM. When warm, pedal to the medal speed is 60 MPH. It can do 0-60 in about 2 minutes.

Bottom line, the longer it runs the better it performs however even after one hour it is still not good.

Any ideas ?

Thank you,

Jeff

 

[buggy9]

You said it was air in the lines, did you check the fuel line all the way back to the fuel pickup in the fuel tank? Sometimes bacteria or algae grows in the diesel and you'll see black sludge blocking the fuel line at the pickup.

The turbo could be stuck, are there any error codes?

 

[jhazewin]

Thank you for the reply. I did check the fuel line all the way to the tank, all was clean.

There are no error codes unless I forget to re-connect a sensor.

Jeff

 

[chittychittybangbang]

There's a fuel injection pump problem or turbo problem or MAF problem.

MAF problem is my first guess and it seems to be the most obvious here. Unplug the MAF. On a normal car, power should be lost. On a bad MAF car, power should remain unchanged or get better. If you can't rev high and it's not a fuel problem, it's probably a very bad MAF. Check the MAF FAQ page for more details:
http://www.myturbodiesel.com/1000q_how_to/multi/MAFfaq.htm
http://www.myturbodiesel.com/1000q_how_to/a4/maf.htm

Also remove the rubber "elbow hose" right before the intake manifold and check for intake clogging. No air = no power. This is not just the EGR valve but the intake manifold behind it.
http://www.myturbodiesel.com/1000q_how_to/a4/intake_maniremove.htm
How is engine compression? Make sure to use a diesel specific compression tester. If these are fine then you are looking at some turbo or fuel injection pump problem.

Read the above links and do those tests it will at least set you on the right course.

 

[darren]

RPM is only 2000????? Must be a bad MAF. I hope you got a good deal on a car that only goes up to 2000 RPM?

 

[chittychittybangbang]

Yes, after thinking about it more, it's probably a bad MAF sensor. Today I added some more pics and notes to the artice that should help you diagnose it.

Also a bad accelerator pedal is possible or fuel injector problem.

 

[chittychittybangbang]

Well, I put all of the possible low power causes in 1 article: you can view it here:

http://www.myturbodiesel.com/1000q_how_to/multi/lowpowerfix.htm

I will also make a separate announcement for this article.

 

[jhazewin]

I ordered a new MAF, installed it and the same result.

At startup it will only rev to 2000 rpm, after 10 minutes of idle it will rev to 3200 rpm.

Jeff

 

[chittychittybangbang]

Is the timing correct? When was the timing belt last changed and who did it? If it's off then the injection pump could have skipped a tooth - it often results in a no start. check the timing belt article for details and pics on how to check it.

Check the accelerator pedal. You need the VCDS tool from ross tech to do this. With it, you can see the percent that the accelerator pedal is pressed. It's possible it has failed but the ECU should limit RPM to 1200. It will also let you check the sensors and avoid buying any more unnecessary parts.

 

[AndyPee!!]

Similar prob for me and my Golf TDI mk4 90bhp- im a new poster too- funny how we find the best sites when were in the s""t!! Anyway, my car has been running a dream, quick and responsive, but as its reached another 10000k miles again i had my local garage do an oil/oil filter change, as they always do, i also asked them to change the paper air filter this time as its been a while since its been done-
To cut a long story short, the minute i pulled away from the garage i noticed a lack of pull/power-worst was 2nd, 3rd and 4th, but only 1st felt near normal-im putting my foot down but it just doesnt pull/respond like it should- I took it straight back and the garage denied any knowledge saying it would have been like that and changing the air filter makes no odds-
i opened up the box and looked at the filter-seems ok, couple of greasy finger prints on the paper where the guy put it in-
My first thought was the MAF/Air flow sensor but how, since an hour before it was like a little rocket? it really got me down as i have paid for a service that has done more harm than good...
My friend has a 115bhp tdi air sensor going spare would that work/fit? looks identical?
Help...

 

[LIQUIDSILVER]

Similar prob for me and my Golf TDI mk4 90bhp- im a new poster too- funny how we find the best sites when were in the s""t!! Anyway, my car has been running a dream, quick and responsive, but as its reached another 10000k miles again i had my local garage do an oil/oil filter change, as they always do, i also asked them to change the paper air filter this time as its been a while since its been done-
To cut a long story short, the minute i pulled away from the garage i noticed a lack of pull/power-worst was 2nd, 3rd and 4th, but only 1st felt near normal-im putting my foot down but it just doesnt pull/respond like it should- I took it straight back and the garage denied any knowledge saying it would have been like that and changing the air filter makes no odds-
i opened up the box and looked at the filter-seems ok, couple of greasy finger prints on the paper where the guy put it in-
My first thought was the MAF/Air flow sensor but how, since an hour before it was like a little rocket? it really got me down as i have paid for a service that has done more harm than good...
My friend has a 115bhp tdi air sensor going spare would that work/fit? looks identical?
Help...

Look at the MAFs and compare the part number. If they are the same then yes you know it's compatible. Is your engine 1.9L 90 horsepower ALH? What's his? AJM? AUY? Wikipedia only shows those two for the 115 bhp engine.

 

[AndyPee!!]

Thanks, ill email him and ask-any idea what the actual cause might be on the prob-I cant see how the sensor would have been damaged if it was working so well before the filter change?-i did unplug the MAF sensor and run it round the block but couldnt really tell much difference to be fair-it does rev up to 5100 easily with it plugged in and unplugged-what could they have done at the repair shop which could do so much harm changing the oil and filters?
the car just feels 'blocked up' and 'lumpy' and there just feels so little power/pull there yet im revving so much...

 

[chittychittybangbang]

These cars have sensitive MAFs. Who knows if the shop caused it - it's disturbing the dirt and dust caused it to fail a little more for you to notice. Look through the FAQ articles limp mode and no power. These will help you get started. It's possible your MAF failed at the very top.

 

[AndyPee!!]

thanks, i did notice the old filter was very dirty to be fair-would the sensor ever recover by its self/clear as the dust/dirt subsided through use? would vacuuming the sensor grill remove any loose dust/help things?
looked at the limp mode articles, its not dead or completely unusable, there is just a really huge dip in power through the range-is there a 'how to' on fitting a new sensor/meter?

 

[Fluid]

You could clean it with electronics contact cleaner. This is a safe for sensitive electronics spray. If it doesn't work then it won't cause any harm. If it helps at least you know you found the problem. What you really need is a VCDS ross tech cable to read the maf signal. Heres the how to on MAFs http://myturbodiesel.com/1000q_how_to/a4/maf.htm

 

[AndyPee!!]

thanks-i wondered whether they pulled out/damaged the connection wire? is there any way to tell if the wire to the maf/sensor is ok? (without the diagnostics plug in) if the wire was dis-attached would there be a Check Light?
last time i had a diagnostics they charged £30/$45 which is harsh for 2mins on a laptop...would a complete second hand/used maf be wise?
sorry, last questions, where does that contact cleaner come from and could it be sprayed into the mesh of the sensor or does it have to be disassembled?

 

[jhazewin]

Power has returned!

When I "cleaned the EGR valve", I should have reported I cleaned part of the EGR valve- only the exit side.

Working on the theory "without air there is no power" and the fact that no sensors were throwing codes, I pulled the EGR valve off of the intake and discovered it was almost completely plugged, as was the intake.

After clearing out the blockages and reassembly, power restored.

There is a little smoke, but I will pursue that through the FAQs.

Thank you!!

Jeff

 

[chittychittybangbang]

thanks-i wondered whether they pulled out/damaged the connection wire? is there any way to tell if the wire to the maf/sensor is ok? (without the diagnostics plug in) if the wire was dis-attached would there be a Check Light?
last time i had a diagnostics they charged £30/$45 which is harsh for 2mins on a laptop...would a complete second hand/used maf be wise?
sorry, last questions, where does that contact cleaner come from and could it be sprayed into the mesh of the sensor or does it have to be disassembled?

Follow the wire harness as far as you can. Inspect for rubbing or tears. Look at the plug, you should see the pins - they shouldn't be torn out.

A bad maf doesn't always set a CEL. Contact cleaner can be purchased at any electronics or auto store.

First check the MAF signal before you clean it so that you don't damage a good MAF! If you clean it, remove the MAF from the car so you can thoroughly clean it and then spray the thing hanging down into the airstream. That's it. Don't wipe it down or otherwise mess with it.

 

[AndyPee!!]

Hi checked the cable, it had a split in the outer casing, but wires look intact-cant see where thy join the plug as its shielded-the pins do look ok.....driving the 100 miles to and from work in it today was pitiful-its just got no zip.i dont know whether to go for it and just fork out the £35 for a MAF and chuck it on-if it doesnt work, its only £35, if it does, i have saved the £30 diagnostic fee...??!!

 

[AndyPee!!]

hi not had chance to check the diagnostic but quoted £45 for an MAF...expensive??