Golf TDi 90, Very Unsmooth Acceleration After Fitting Box....

[FuNkYcHiCkEn]

Hi all,

I am a newbie after a bit of advice please. I have a Golf TDI 98 90 BHP non PD engine. I needed a bit more power as it seemed really slow, so I fitted a tuning box from Dragon Performance.

First gear is great, bags of accelaration, lots of wheelspin!!!

Change into Second great to start, then drops off, then picks up, then drops off. This happens all the way to over 4K and in 3rd, 4th and 5th.

It seems as though power is cutting in and out even though my foot is buried to the floor!!!!

Could it be a dodgy tuning box, or something wrong with the car? It was pretty slow to start with.

The car is a 1998 model and only covered 18K, previousely owned by my grandad!!!!

Any advice would be appreciated

[SteveC123]

Hi all,

I am a newbie after a bit of advice please. I have a Golf TDI 98 90 BHP non PD engine. I needed a bit more power as it seemed really slow, so I fitted a tuning box from Dragon Performance.

First gear is great, bags of accelaration, lots of wheelspin!!!

Change into Second great to start, then drops off, then picks up, then drops off. This happens all the way to over 4K and in 3rd, 4th and 5th.

It seems as though power is cutting in and out even though my foot is buried to the floor!!!!

Could it be a dodgy tuning box, or something wrong with the car? It was pretty slow to start with.

The car is a 1998 model and only covered 18K, previousely owned by my grandad!!!!

Any advice would be appreciated

I've not (knowingly) used one of Dragonsport boxes, but did you get instructions with it?

Most 'tuning boxes' I've seen / used involve you turning a screw to set the level of resistance the box is using to fool the pump into thinking certain parameters such as fuel temperature and incoming air temperature - if you have it adjusted up too much it'll make the car run like a bag of the proverbial.

However... I suspect going by the symptoms you've described, you might want to get that old favourite checked out, the MAF unit on the air intake pipework - when this goes, it causes bad running as you describe that'll just get worse.

Fitting a tuning box can just highlight an underlying developing problem with the MAF when this is the case.

HTH

[FuNkYcHiCkEn]

Thanks For the advice Steve.

I always thought that the car was extremely slow before I fitted the box, so like you said, there could be an underlying problem...

I have tried adjusting the screw on the box, but it dosen't make a difference to the problem, which either way I turn it!!!

Bearing in mind the car has done such a low mileage, would the MAF really be playing up??

Anyway, I know someone who has access to a VAGCOM system, so I will get the car checked over. Does the MAF always show up if there is a fault, or is it something that does not always show up...

[adamss24]

Thanks For the advice Steve.

I always thought that the car was extremely slow before I fitted the box, so like you said, there could be an underlying problem...

I have tried adjusting the screw on the box, but it dosen't make a difference to the problem, which either way I turn it!!!

Bearing in mind the car has done such a low mileage, would the MAF really be playing up??

Anyway, I know someone who has access to a VAGCOM system, so I will get the car checked over. Does the MAF always show up if there is a fault, or is it something that does not always show up...

A faulty MAF does not allways show up as defective when scanned ! The right way to see if the MAF is faulty is to do a log in third gear while you floor the car over 3000 rpm and then you compare the requested airflow with the delivered airflow and see the log file on a spreadsheet in EXCEL. The req air and metered/delivered air should be closelly following each other. Another way to see if its faulty, do a log as described and then disconect the MAF plug and do another log. If they are identical, then the MAF is shot. Another way to test-but not that accurate-is disconect the MAF and take it for a ride, if it improves or there's no change, replace the MAF. Remember that disconecting the MAF will trip a fault code that will need to be reset. If you planning to keep the tunning box, i suggest you follow the supplied instructions closelly and also you should disconect the battery to initiate basic settings again. See if you have the radio code as you may need it after reconecting the battery. Hope this helps.

[SteveC123]

If you planning to keep the tunning box, i suggest you follow the supplied instructions closelly and also you should disconect the battery to initiate basic settings again.

Interesting... I've not done this when comparing my car with the tuning box and the full remap box I've got - could this be something causing it to use more fuel at the mo, regardless of which I have plugged in or even if I run the car without one?

<Goes off to look for VAG-COM leads on ebay...>

[SteveC123]

Thanks For the advice Steve.

I always thought that the car was extremely slow before I fitted the box, so like you said, there could be an underlying problem...

I have tried adjusting the screw on the box, but it dosen't make a difference to the problem, which either way I turn it!!!

Bearing in mind the car has done such a low mileage, would the MAF really be playing up??

Anyway, I know someone who has access to a VAGCOM system, so I will get the car checked over. Does the MAF always show up if there is a fault, or is it something that does not always show up...

As Adams says, no it doesn't.

However, it does seem to normally be the MAF 99% of the time when a Mk4 isn't running right.

My advice if it is, is read up on how to clean the MAF either in here or on another well known TDI forum, before you resort to buying a new one, as it would appear they can sometimes just need a clean, especially if you've got an airbox that isn't sealing properly.

Avoid a replacement unit off ebay - my experience of these is they quote Bosch part numbers and in the case of when I bought one, they even pictured the unit sitting on a genuine Bosch box, but when the unit turned up it was a blatant pattern part that made the car smoke like a trooper.

A genuine exchange unit from my local main dealers was around £90... but it was the best £90 I've spent 'tuning' a car bar fitting a tuning box. ;-)

The main thing is, get your car running right before fitting any tuning mods such as tuning boxes.

[FuNkYcHiCkEn]

Thanks Steve & Adam for all the advice....

I will get everything checked over in the new year, I will also try the battery thing aswell, might help!!!

I will keep everyone posted anyway....

[FuNkYcHiCkEn]

Just thought I would let everybody know that I have cured the fault!!!!

It was the MAF as suspected, although when I disconnected the old one there was no difference...

I had ordered a pierburg maf for my BMW 320D, so I tried that, it works a dream, the car now goes as it should, even without the tuning box!!!

Thnaks for everyones help...