Engine Problem

[RWalTDI]

I own a 97 Passat TDI with 102k miles. The other day I notcied that right around 3000RPMs and on there are 2-3 hesitations in the engine.Also, sometimes when starting out in 1st gear the car does not go through the gear smoothly. I get a bouncing effect, which is quite annoying. The car is completely stock and maintained well. I use fuel treatment every time I fill up too. I'm not really too sure of what could be wrong with it, but if someone has an idea or advice it would be appreciated.

 

[QEW rider]

RWalTDI,

I would look at this "problem" sooner then later. I've had a similar problem with my 98' Jetta TDI. The dealer ran through a list of potential problems coming up with a grand total of $4000CDN

, or about $10 in the US

. From different posts it looks to be an oil/turbo issue, with a carbon buildup at the EGR added in for good measure. I'm going in tomorrow (not to the dealer) for the required fix. I will post all the details of my experience later this week.

 

[RWalTDI]

Ok...Thanks.....I'm eager to find out what your mechanic says. I also have looked at FAQ/Performance and it says that it may do that when it is cold and or because the turbo is not working properly, like you have mentioned.

 

[QEW rider]

RWal TDI,

Check out this thread
http://forums.tdiclub.com/NonCGI/ultimatebb.php?ubb=get_topic;f=3;t=009516

I don't think the cold in the major problem, it is darn cold in Toronto today 23F, and I didn't have a problem this morning.

 

[GoFaster]

Regarding the 3000 + rpm "hesitation" during acceleration,

Does it feel like (1) misfire (like a shudder), or does it feel like (2) a smooth dropoff and re-application of power, or does it feel like (3) power drops off a cliff and doesn't return until you go to a different speed and load condition (possibly not until you switch the key off)?

The boost pressure sensor hose issue that was linked to above, will cause (3), and if you get the codes scanned, you'll get "00575 Intake manifold pressure control difference - intermittent".

Fluctuation of boost pressure will cause (2), and the boost control system in these cars has marginal stability in the design. You need a pressure gauge on the boost line to see if this is the problem. I solved it with a mechanical boost controller - there was no other way around it. See the TDIFAQ troubleshooting section on "Fluctuation of boost pressure".

(1) is the toughest nut to crack, but let's not go there until you look into (2) and (3) as necessary.

 

[RWalTDI]

yeah, it feels like a slight drop in power but it regains but then drops off again once to twice more.

 

[BKmetz]

Sounds like a N-75 selenoid valve sticking open.

Brian, 97 Passat TDI

 

[GoFaster]

Yep, it's either that, or the built-in "they're all like that, sir" marginal stability of the boost control system that's causing the boost pressure to fluctuate.

Hint: mechanical boost controller ...

 

[RWalTDI]

So, what do you all suggest I do? I am not a mechanic, so I do not how well I can perform repairs or modifications to my car. I can handle minor or simple tasks, but I do not want to get myself into something I can't fix. Like most people, time and money are factors. I will try anything I think is possible for me to do.

 

[dzcad90]

I'll vote for the N75 as well. It happens to cars of that age, especially with intact CCV systems. Sometimes oil contamination will cause the system to get fouled and not operate smoothly.

 

[lrpavlo]

I had the surging problem with my Passat too. The N75 was @$45 at the dealer. It is located on the firewall above the brake booster...has red, blue, and black hoses comming out of it and an electric plug.
If you feel like you can change it yourself....get the part first because the plastic nipples break off pretty easily (Don't ask how I know!) Push a small flat bladed screw driver into the ends of each of the hoses to loosen them, turn in fingers and pull them off. I'm pretty sure its mounted on a rubber grommet that you lift off.
Take you time....draw a diagram before you begin....its not bad!

 

[GoFaster]

Get someone in your area with a VAG-COM to check the boost pressure. Log requested and actual intake manifold pressure, and solenoid duty cycle, while driving in a way that displays the symptom. It is possible to tell whether the problem involves the N75 solenoid valve if the person using the VAG-COM knows what they are looking at.

 

[Andrei Rinea]

Anyone thought of air in fuel system?
Or anything else (clogged fuel filter) that could prevent proper fuel deliver?

 

[Rickstah]

Greetings,

My '98 A3 (90K) exhibited those same symptoms, plus a marked blip in the smooth idle, more so when cold, it bucked like a horse when you tried to hold it at 16-1800 rpm in third....the dealership replaced the fuel filter, and a lot of the problem went away, but it is still there, only muted in strength. I am getting a LOT more smoke when I accelerate, too...has been happening for several thousand miles, no matter how much fuel treatment I use. They just mumble when I describe the symptoms, and I know they don't lift a finger other than to check for thrown codes...