Low Power and Rough Idle

tomsawyer

Well-known member
Joined
Dec 28, 2005
Location
Totowa, NJ
TDI
2005 Passat TDI
Hi Everyone, hopefully you can help me out with these 2 issues. I have 2005 Passat TDI w/ 72k.

The first issue is upon cold start up, with the car in drive and foot on the brake, the engine idles not roughly but sort of hiccups at 800 rpm, which seems to be a smooth idle. In neutral or park, there is no hiccup - only in drive with foot on the brake (like at a stop light). As soon as the car warms to normal operating temp, the idle hiccup goes away. I can describe the hiccup as the idle is at 800 rpm then drops suddenly to 780 or 770 rpm, the engine catches itself, then returns to 800 rpm. Happens about every 5 seconds when cold.

The other issue happened for the first time to me when going to the train station. I started the car and went to the DD for a cup of coffee. Everything was fine. I left the car idling for about 5 minutes to go inside. When I came out, put the car in drive, I noticed very low power - almost like the car was running on 2 cylinders. Engine wouldn't go over 2500 rpm. No lights or info came up on the dash and didn't see any strange smoke from behind. I made it to the train station, shut the car off and left it there to go to work. When I got into the car last night, everything worked fine and I had full power going home. Today, I had full power going to the train station.

Any idea what's going on?

Thanks to everyone for their input.
 

aja8888

Top Post Dawg
Joined
Dec 25, 2007
Location
Texas..RETIRED 12/31/17
TDI
Out of TDI's
Issue No.2 is the car went into limp mode. These cars have boost hoses that are prone to holes getting worn in them (rubbing by cables - battery ground cable in particular) and cracking at elbows. Check all the big hoses for those issues. There have been cases where all is good and the car will occasionally go into limp mode and the cause was not determined.

Issue No. 1 is a mystery, but do check all the vacuum hoses for cracks, etc.

Can you scan the car with a VCDS for codes and report back?
 

thundershorts

Top Post Dawg
Joined
Jul 15, 2010
Location
west chester pa
TDI
2015 passat tdi sel premium 2015 golf s tdi gls tdi b5.5, 2002 eurovan,Peugeot 505 td,Citroen cx25 prestige
Do you have the newer ngk glow plugs and ecu flash?
 

tomsawyer

Well-known member
Joined
Dec 28, 2005
Location
Totowa, NJ
TDI
2005 Passat TDI
I had no choice but to take it to the dealer. They told me it had the following code:

P0203N75

I have a cousin that works in the parts dept so he is on the lookout for me (at least trying to protect me as much as he can from the dreaded stealer!).

The tech checked all vacuum hoses, elbows, vacuum leaks, etc and couldn't find anything. He did drive the car and was able to replicate the issue for the low power (they think the hiccup may coincide w/ the same low power issue).

What's interesting is the tech reset the car (not sure exactly what that means but I get the impression they wiped the codes and/or cycled the car (something to that effect) and now after driving for an hour or so, the car has full power and no codes. The tech asked to keep the car until today to drive again to see if the condition would reappear and throw the code.

Your thoughts?
 

rydogg

Veteran Member
Joined
Jan 29, 2008
Location
Indiana
TDI
Passat
P0203 VOLKSWAGEN - Injector Circuit Open Cylinder 3

Possible causes
- Faulty fuel injector 3
- Fuel Injector 3 harness is open or shorted
- Fuel injector 3 circuit poor electrical connection Help with this

When is the code detected?
The P0203 is set if the Engine Control Module (ECM) is detects a low or high voltage drop or resistance at the injector 3.
Symptoms
- Engine Light ON (or Service Engine Soon Warning Light)
- Lack/Loss of Power
- The engine may be harder to start
- Engine hesitation
P0203 VOLKSWAGEN Description
Engine Control Module (ECM) checks the injectors circuit resistance and monitors the voltage drop during normal operation. The ECM will trigger the P0203 code when the resistance or voltage drop at the injector 3 is out of specifications.

I am assuming the issue is somewhere between the N75 valve and your cylinder #3 injector (or your Cylinder #3 injector is bad). "Resetting the car" means that he reset the car's computer back to factory defaults. If it's an electrical gremlin, it could go away but I'd guess that this problem will resurface within an hour of driving.

http://forums.tdiclub.com/showthread.php?t=367606&highlight=N75
 

tomsawyer

Well-known member
Joined
Dec 28, 2005
Location
Totowa, NJ
TDI
2005 Passat TDI
Thanks Rydogg.

I believe that's why they kept the car today. Yesterday, after clearing, the code kept coming back. After reset, they code didn't appear after driving for awhile.

I believe today they planned on driving the car for a longer period to see if it happened again. I'll let everyone know once I hear back.

Thanks again.
 

tomsawyer

Well-known member
Joined
Dec 28, 2005
Location
Totowa, NJ
TDI
2005 Passat TDI
Update - Looks like after performing a "reset" & driving the car again, the tech was able to replicate the low power condition. After getting back to the dealership, the car threw the same code. So, it looks like he's going to change the N75 valve.

Price quoted = $240 parts & labor

Thanks again Rydogg for the info.
 

tomsawyer

Well-known member
Joined
Dec 28, 2005
Location
Totowa, NJ
TDI
2005 Passat TDI
Unfortunately, it looks like the new N75 did not fix the issue.

I picked up the car on Friday and all seemed well on both Friday & Saturday. However, on Sunday, I was getting on the highway so it was under hard acceleration. As the RPM & speed were increasing - all of a sudden, the car jerked just like someone was pulling me from behind, next all the power was gone and then I heard what seemed like a mini backfire. After that, the car went completely into low power mode (no dash lights or other info came up).

I drove the car home and today I called the dealer. I'll be taking it there tomorrow.

If you have any ideas about what's going on, I'd love to hear from you. Also, assuming the car is still in low power mode, will I do any damage driving it to the dealer?

Thanks
 

rydogg

Veteran Member
Joined
Jan 29, 2008
Location
Indiana
TDI
Passat
Sorry to hear that. :(

I think that means you work your way down the list and check your #3 fuel injector. Also, inspect your cam shaft lobes for wear while you're in there.
 

tomsawyer

Well-known member
Joined
Dec 28, 2005
Location
Totowa, NJ
TDI
2005 Passat TDI
Got some news today and not sure how to interpret.

Called the dealer and talked to the service advisor. He didn't seem to have all the facts as probably the technician was doing all the diagnostics which the advisor said was 3 hours, on them.

However, he seemed to indicate that the tech called VW Tech Support for direction. Also, he seemed to feel that the car threw another code this time and the car may need a turbo charger. When I freaked, he said he didn't want to speak out of line and would confirm tomorrow morning with the technician.

Could the car really need a turbo after only 72K?

I will definitely get you the code or codes that came up when he calls me tomorrow.
 

johnboy00

Veteran Member
Joined
Jun 15, 2000
Location
Bridgewater,Ma.,USA
TDI
2005 Passat Wagon, 2004 Jetta, 2003 Jetta wagon
Get it out of there while your wallet still has some meat to it. It sounds like they are taking the plug and chug approach to repairing your vehicle.

You have two gurus who are about an hour away:

TDIJetta99 in port Jervis; http://forums.tdiclub.com/member.php?u=32243

and

Hervster in Montague http://forums.tdiclub.com/member.php?u=38775

One of them should be able to help you out for substantially less $$$ if you can get the vehicle there.
 

thundershorts

Top Post Dawg
Joined
Jul 15, 2010
Location
west chester pa
TDI
2015 passat tdi sel premium 2015 golf s tdi gls tdi b5.5, 2002 eurovan,Peugeot 505 td,Citroen cx25 prestige
I think John is right, dealer is stumped and the turbo replacement is the good indicator. I'd probably see if I could limp over to Harv's and get it fixed, otherwise as John said, you are going to get a big hosing, and not in all likelyhood find the problem and fix it. Why not send Harv a pm?
 

tomsawyer

Well-known member
Joined
Dec 28, 2005
Location
Totowa, NJ
TDI
2005 Passat TDI
I appreciate all your input.

I spoke to Herv yesterday as he was kind enough to pick up the phone as I was leaving a message and told him the whole story thus far. He's really a good dude.

Looks like the strategy is I'll wait for the advisor to call me today to let me know what's going on and of course, I'll let you guys know too. Depending what they tell me, if worse gets to worse, I'll tow the car up to Herv's place and let him analyze/do the work.

The soap opera continues........
 

tomsawyer

Well-known member
Joined
Dec 28, 2005
Location
Totowa, NJ
TDI
2005 Passat TDI
Update on the soap opera -

I made a mistake when I gave the code originally. I gave you P0203 but the code actually was P0234 which they told me was a turbo/supercharger overboost condition. That's what came up last week and they decided to change the N75 valve after checking all the hoses, wires etc and came up with nothing. And, like I said before, the tech was able to duplicate the low power condition. After changing the valve, the car was fine....until -

Now, on Sunday, when the low power condition happened again, the tech pulled the same code. When they pulled the code one time, it said "overboost condition tbd". The other time it said "boost sensor/A circuit briefly occurred mal function". Originally the tech put in 3 hrs and decided to change the N75 valve. Now, he put in another 3 hrs (which I am not getting charged for) after the low power condition reappeared going over all that he'd gone over originally and after resetting, he can't get the car to duplicate the low power condition.

So, now the tech is stumped and apparently called VW for direction and they told him a series of steps to take and now the dealer wants me to authorize 3 hrs labor. After screaming at the service advisor on asking me to pi$$ away $375 on a condition that is currently there, he offered to drive the car home tonight (he lives about 60 miles round trip from the dealer) to see if he can get the code/condition to come up again.

What's funny is this guy lives a couple of towns over from Herv's place so I almost want to tell him to just drive it to his place for me!!!!!

Anyway, not sure what to do now. Let him drive the car home to see if he can get it to happen again and let him deal with it or just go get the car and see if I can get it to happen. If it doesn't happen after 60 miles, maybe it was just a hiccup. But if it does happen, what are they gonna do for another 3 hrs labor assuming the same code comes up?
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis, MO
TDI
There are just too many to list....
You can keep throwing money at them, but they are not going to figure it out. If the boneheads cannot figure out a simple boost problem on a system that is essentially been in use since 1998 what makes you think they'll figure it out today?

I'd get it to someone who actually knows what they are doing. These dealers floor me sometimes. :rolleyes:

The boost control system is DIRT SIMPLE. Like, stupid simple. And on the BHW, it is even simpler than some of the others, because unlike the ALH, BEW, BRM, etc., the BHW only has ONE vacuum circuit.... to the turbocharger! That's IT!!! The EGR is electric, the throttle valve is electric, it has no EGR cooler changeover flap, it has no twin-path intake, nothing but the turbocharger control coming off the brake booster tube from the tandem pump.

You just have a vacuum line, a check valve, the N75, a vacuum reservoir tank, the VNT actuator, and the vent line. That's it. That's the entire boost control system in one sentence. Simple.

Now the charge air tract is a little more convoluted, but hardly impossible to figure out, especially on an automatic car where a quick brake torque can be performed to find boost leaks literally within seconds.
 

tomsawyer

Well-known member
Joined
Dec 28, 2005
Location
Totowa, NJ
TDI
2005 Passat TDI
Hammer - I appreciate your comments, especially since I have absolutely no technical knowledge of this stuff so I'll ask your opinion.

Now that the car has full power and the code thrown the 2nd time is now gone and hasn't been duplicated, what do you recommend I should do? Let the service manager take the car home for the night to see if the car goes into low power or should I just go pick up the car and take my chances?
 

tomsawyer

Well-known member
Joined
Dec 28, 2005
Location
Totowa, NJ
TDI
2005 Passat TDI
Latest update -

I got the car back from the dealer after they could't replicate the low power condition and the car did not throw a code after the tech followed VW procedure after the 2nd low power condition after changing the N75. He cleared the code and it never came back and it operates on full power now.

I've been driving the car all week and I too have not been able to get the car into low power condition.

Now, here's the stupid question -

The 2 times the car went into low power, I was entering the highway and was at full throttle. Now that I've gotten the car back, I know it sounds crazy, but I haven't gone above 2500rpm so I've been driving it very gently. Is it possible that the condition only happens on hard acceleration? I don't pretend to know but I would imagine the turbo and its components have to do more when there's more gas being fed?

I plan on taking the car to Hevster, hopefully this weekend and figured I would do the hard acceleration test once I was close to his place (he's about 50 miles away from me).

Thanks to all who answer.
 

tomsawyer

Well-known member
Joined
Dec 28, 2005
Location
Totowa, NJ
TDI
2005 Passat TDI
Just wanted to give everyone a head's up and to get this documented just in case it hasn't been.

I took the car to Mike Hevner after getting it back from the dealer. Mike went over the whole system - no vacuum leaks, no frayed wires, acuator fine, turbo good, all hoses good. After driving the car with the vagcom, the only issue he could determine was the MAF sensor seemed to mess up, then reset itself (I'm not a tech guy so I may not be explaining things exact). Finally, he was able to get the car to go into limp mode (for the time he had it, it ran on full power).

After all the diagnostics, he decided to change the MAF sensor as all other parts/vagcom readings/diagnostics all checked out.

I've had the car for 2 weeks since and haven't gone into limp mode since getting it back from Mike.

Thanks to all, and especially Hevster!
 

SilverGhost

Veteran Member
Joined
Mar 25, 2005
Location
Back in So Flo - St Lucie
TDI
'05 Golf - totaled :(, wife's '13 Beetle - buy back, TDIless
Huh, that actually sounds like a restricted fuel filter. Only vehicle that i have had set that fault though was a V10 TDI. Most of the other cars just won't shift and have low power, with no MIL. Odd...
 

tomsawyer

Well-known member
Joined
Dec 28, 2005
Location
Totowa, NJ
TDI
2005 Passat TDI
I guess I spoke too soon.....the effin car went into limp mode this morning, approximately 1 month after changing the MAF sensor. Now what???????
 

SilverGhost

Veteran Member
Joined
Mar 25, 2005
Location
Back in So Flo - St Lucie
TDI
'05 Golf - totaled :(, wife's '13 Beetle - buy back, TDIless
Read my post right above yours ^^^ I would try a fuel filter (cause it's easy and relatively cheap), and check for fuel restriction or lack of supply. Over boost fault can be too much air or not enough fuel. So a restricted fuel filter, pinched fuel line, or flaky lift pump could be cause on fuel side.

Jason
 

50harleyrider

Top Post Dawg
Joined
Jun 16, 2007
Location
charleston,wv
TDI
2005 B5.5 TDI/geared BSM, BV43A turbo,stage 2 TDTUNING. 2005 5sp manual passat tdi stage 2 tdtuning,BSM delete. 2015 Passat TDI 6sp manual.
Read my post right above yours ^^^ I would try a fuel filter (cause it's easy and relatively cheap), and check for fuel restriction or lack of supply. Over boost fault can be too much air or not enough fuel. So a restricted fuel filter, pinched fuel line, or flaky lift pump could be cause on fuel side.

Jason
What is the simplest way to check the lift pump and N75? My BHW does the same thing as Tomsawyers and I even swapped the MAF sensor off my wifes' BHW and it still does it from time to time. Mine has a new N75, all vacuum lines checked,turbo cleaned VNT moves freely and has a new silicone vacuum line, fuel filter changed. I still get an overboost code sometimes when it goes limp and no code other times. It sure gets old cycling the key in traffic. Mine is more inclined to go limp when the engine is not fully heated up. Temperature sensors all appear spot on in VAG. I just loaded a stage 2 TDTUNING into it and will see if that helps. Is it a no no to adjust the VNT actuator? Maybe a faulty N75 from IDPARTS? I'm a little hesitant to borrow my wife's N75 as I broke my old one getting it off.
 
Last edited:

tomsawyer

Well-known member
Joined
Dec 28, 2005
Location
Totowa, NJ
TDI
2005 Passat TDI
Just as an fyi -

When my car went into the dealer for the original limp mode condition, I had them change the engine oil, fuel filter and then they determined it was the N75 valve which they changed.

The car went into limp mode again.

Then, I took it to Hevster and he changed the MAF and like Harley, Hevster told me everythinng checked out fine via the VagCom.
 

50harleyrider

Top Post Dawg
Joined
Jun 16, 2007
Location
charleston,wv
TDI
2005 B5.5 TDI/geared BSM, BV43A turbo,stage 2 TDTUNING. 2005 5sp manual passat tdi stage 2 tdtuning,BSM delete. 2015 Passat TDI 6sp manual.
There's something not so obvious going on with these cars. Hopefully Oilhammer or Mike can lead us through it. Was yours fully warmed up your last episode? Mine rarely does it at operating temp.
 

tomsawyer

Well-known member
Joined
Dec 28, 2005
Location
Totowa, NJ
TDI
2005 Passat TDI
I can't remember if mine was completely warmed up as I drove about 3 miles to the local gas station to get a cup of coffee, went inside to get the coffee and let the car idle which was about 3 minutes and then as I went to get back on the highway, it went into limp mode under hard acceleration. If it wasn't at normal op temp, I would assume it was pretty close.

I did the same as you....on the highway, I put the car in neutral, shut it off and then restarted and had full power to complete my journey to the train station!

This morning, I did the same thing. Went to the gas station, got coffee, idled, hard acceleration but this time no limp mode. This is gonna drive me crazy!!!!!
 

SilverGhost

Veteran Member
Joined
Mar 25, 2005
Location
Back in So Flo - St Lucie
TDI
'05 Golf - totaled :(, wife's '13 Beetle - buy back, TDIless
Sorry - I had full write up typed and I thought posted. Don't know what happened to it. I am going to get into detail because both people with this problem seem to have it very intermittently. So not an obvious broken part, but maybe a flaky part that is still working for the most part.

Didn't see the part about the fuel filter. I have been burned by assuming the replaced part was good, just a caution. We'll assume it's ok for now.

You can check the lift pump and transfer pump fuel pressure and delivery volumes. The lift pump is about 0.5BAR I think, and the transfer pump is 10BAR. The delivery rate is dependent on the pressure on the system, so you need to restrict the pump to obtain the correct pressure. Also the voltage at the pump is part of the equation when determining delivery rate. Measure it and use the table of volume delivered and voltage at pump.

There are some specific conditions for the pressure reading on the transfer pump, and it is going to be "fun" to get the gauge on the pump on your Passat. There is a plug you can take out and screw a pressure gauge into. I think the RPM is the main factor in getting 10BAR or more pressure.

Like oil hammer said - air side is simple. Vacuum supply, to N75 control solenoid, to actuator.

Basics first - default position is full boost. Start the engine and the ECM takes over. I believe it pulls the actuator into a no boost position. When throttle is applied and torque is demanded, the ECM releases the actuator to full boost. When boost reaches the level the ECM wants it starts activating N75 to control boost to that level. In practice this is being done in milliseconds and moving constantly.

So for an intermittent over boost I would lean to a mechanical fault somewhere. Is there a strong vacuum supply? No leak from vacuum reservoir? Restriction or lack of restriction in appropriate place in vacuum lines? Actuator moves freely UNDER OPERATING CONDITIONS? Is the actuator starting to move at 8(?)in and fully moved at 18(?)in? N75 is new so I assume it is not at fault.

I'll add more as I think of it

Jason
 

BobZ

Veteran Member
Joined
Jul 6, 2005
Location
Douglassville, PA
TDI
05 Passat tdi, 15 Passat TDI SE auto, 06 Sierra 6.6 DMax
A while back I had a problem (completely unrelated to yours) regarding a fuel pump relay code coming up... Car would shut down, sometimes restart, sometimes not (glow plug light would always come on so I did not feel it could be relay 219 yet again). Replaced fuel pump relay inside car and no improvement. I ended up throwing parts at it and replaced the tandem pump (and relay 219 for the second time). I took notice to the vacuum nipple on the old tandem pump and saw that it would spin with no resistance. The new tandem pump vacuum nipple was secure and would not spin. Since the replacement of the tandem pump, I can count on 1 hand (probably 2 fingers) limp mode overboost/underboost.

Related to your problem - I don't know but it is a vacuum source and I think mine would leak some vacuum there as all my vacuum hoses were replaced and other items always checked out. I remember when I first got the car in 2005, there was a recall on the tandem pump. When I brought it in, they said mine was fine... like everything on this car, if there is a replacement part, it is probably the "new and improved" replacement part. Good luck.
 
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