car is bucking like a bull on steroids....

i have a 99.5 jetta tdi. today, i noticed that the car was "bucking" like crazy while driving. the rpms were fluttering all over the place. it has done this in the past. it has been raining all week and the roads are flooded... could this be a factor, or poor fuel?

I would tend to say it's fuel related, but if it keeps up, give us some more info so we can get to the bottom of it...

-Rich

I had some RPM differences while accelerating and while on cruise. My N75 was 'sticky'.

check your air filter for water.

check your air filter for water.

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Also check the snowscreen and clean if necessary. There is a spring-loaded trap door on the side of the ductwork that has the snowscreen and it's designed to get pulled open by the airflow in case the snowscreen becomes totally blocked. It's a safety "relief valve" feature, but it would take nearly a total blockage of the screen for this door to get pulled open by the airflow. It has a rather strong spring. It's possible that the snowscreen is blocked and the door is flapping open and closed.

The engine needs to breathe and is gasping for breath!


~ n1das

Also look at the (clear) fuel line from the fuel filter to the engine. Are there large bubbles in the line as the engine runs? Small (tiny) bubbles are normal. Large bubbles, as if the fuel were "foaming", would indicate a leak somewhere, allowing air to get in.

I'm thinking fuel starvation or intake air starvation (like in my previous post).


~ n1das

i checked the air filter, that was fine. my car does not have a snow-screen... i removed it. im thinking fuel related, i have always had issues with air in the fuel lines but it does not seem to be any worse than it has been in the past as far as air bubbles. today... seems to be driving fine thus far, i will keep everyone updated. thanks for the info.

I had the same thing to me on my return trip from Mother's Day weekend. It was raining outside and all that. The car starting to buck for about an hour. After that it stopped raining and all is well. I wasn't sure what the problem was. I got home and hooked up the VAG-COM and got 16485 MAF Sensor (G70) Imlausible Signal. After about 5 startups on the car, I checked again and there was no fault code. The check engine never came on.

I told the dealer about it. They can't do anything since there never was a CEL. I am just noting it and waiting for another rain.

Then I started to think that I did drove in the rain for about 4 hours before and never had that about two years earlier. Not sure what it is but I am keeping that in mind.

i have a 99.5 jetta tdi. today, i noticed that the car was "bucking" like crazy while driving. the rpms were fluttering all over the place. it has done this in the past. it has been raining all week and the roads are flooded... could this be a factor, or poor fuel?

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My first thought was that you got a batch of bad diesel. Do you go to the same station to fill up ? Maybe water got in their diesel tanks ?

Secondly, how flooded are you ? If you are driving around such that your muffler is submerged (or water got inside the muffler and couldn't drain out), then I would think that it would cause enough back pressure to mess around with the turbo and engine - are the RPMs fluctuating lower than they should be , or are they revving higher than they should be ? If lower, then I'm guessing your engine is choking cause it can't get rid of it's exhaust at the speed it was designed to.

Just my thoughts ?

The day after this began, I bought some power service diesel supplement and added it to the half tank of diesel i had left. Then I filled my tank with diesel at a different station. It stopped bucking almost immediately. Suggestions? I have 88,000 miles on the car and have not yet replaced my timing belt or glow plug system. Could this have anything to do with it?

ttt

As far as the bucking, if it ain't broke, don't fix it.

If the timing belt breaks, you will not have any more bucking problems. (Except for that last nasty one.)

You replace timing belts by milage. If you let it go longer, you are either lucky or you are not. (Go to Vegas a lot? )

Glow plugs either work or they do not.

It's probably water got in to your diesel tank. I used to have similar issue and it was because of flooding. So, i fixed it fast, cos I could not hear how my baby sounds like your bull on steroids ... it was terrible.

LanaW said:

It's probably water got in to your diesel tank. I used to have similar issue and it was because of flooding. So, i fixed it fast, cos I could not hear how my baby sounds like your bull on steroids ... it was terrible.

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15 year old thread you posted in...

Wasn't clear what the fix was, but I experienced this with the wife's car about a year ago. With the car running I stopped and pulled the plug on the MAF and it instantly settled down. Totally crapped out MAF. For sure I'd thought that the engine was trashing itself! Not a common failure on the MAF, but, as I witnessed, it CAN happen.

So, LanaW, how'd you get a Polo into the USofA, or are you just trolling us?

Just wondering...

PH

PS: Holy Necrothreads, Batman!

Since it cleared up in one day, 15 years ago, it was likely wet electronics, almost certainly in the ECU. I did this to mine, 18 years ago washing the engine bay.