Random power loss "hiccup"

jayceT05

Member
Joined
Oct 21, 2019
Location
British columbia
TDI
2003 jetta
Hey everyone first time tdi owner recently acquired a new to me 2001 tdi alh jetta the car has 306000km on it searched a bunch of forums and cant find one with the exact same symptoms. Sometimes while driving the engine will just all of a sudden drop rpms (the whole car will jerk) for a split second than kick back in doesnt matter what gear I'm in or if I'm going up or down hill. Could be fine and not do it for a week than do it 2 - 3 times within 100km. No check engine light has came on I have replaced fuel filter (was happening prior to this) and noticed alot of air bubbles from fuel filter to pump, not sure if this is normal or not.

As well while driving between 2000 and 3000rpm and you step on it you can feel the motor shaking. More noticeable in 4th and 5th gear. I know it's not tires cause it did it with my old tires and still does it with my new tires as well as dont feel it in steering wheel at all. Read some forums and leaning towards possibly engine mounts? Any help would be appreciated thanks!

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STDOUBT

Veteran Member
Joined
Jul 30, 2007
Location
Portland, effing Oregon
TDI
dos jettas
Welcome!

Our first order of business is to determine when your timing belt was
last changed. Not when you were told it was changed, but proof positive "when", and that it was done properly (new rollers, water pump, etc).
If you have no proof positive that it was done within recommended interval, you need to do it -now-.
Although no CEL comes on, it may still be storing a code(s).
VCDS would help here.
I have noticed that "split second" on rare occasion with my '03 - I call it a heart murmur. I'm not too concerned, but yours seems way more frequent.

Probably not related if it was happening before your FF change, but a lot of bubbles in the fuel line is -not- normal, and may indicate a leak of
air into the fuel system which is at least as common as fuel leaking out.
A common point of air infiltration is the "fuel filter 't'" in the top of the fuel filter. Make sure you replace its o-rings, and maybe if it's original, replace it.
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis, MO
TDI
There are just too many to list....
Replace the Crankshaft Position Sensor. Make certain the mating surface on the block is clean and free of any rust and debris. Do NOT shop around for the cheapest part, either.
 

jayceT05

Member
Joined
Oct 21, 2019
Location
British columbia
TDI
2003 jetta
Welcome!

Our first order of business is to determine when your timing belt was
last changed. Not when you were told it was changed, but proof positive "when", and that it was done properly (new rollers, water pump, etc).
If you have no proof positive that it was done within recommended interval, you need to do it -now-.
Although no CEL comes on, it may still be storing a code(s).
VCDS would help here.
I have noticed that "split second" on rare occasion with my '03 - I call it a heart murmur. I'm not too concerned, but yours seems way more frequent.

Probably not related if it was happening before your FF change, but a lot of bubbles in the fuel line is -not- normal, and may indicate a leak of
air into the fuel system which is at least as common as fuel leaking out.
A common point of air infiltration is the "fuel filter 't'" in the top of the fuel filter. Make sure you replace its o-rings, and maybe if it's original, replace it.
Thanks stdpubt for replying the only proof I have of timing belt being done is a sticker on inside of door says was done 278xxxkm back in 2016.

As far as the T ontop of fuel filter I did replace the o rings on it as it came with fuel filter havnt tried replacing the t itself yet just wanted to get some opinions before I start throwing parts at.
 

BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
Note for all newbies, when you get an answer from oilhammer, you're almost done.
 

Tdijarhead

Top Post Dawg
Joined
Nov 10, 2013
Location
Lawrenceville PA
TDI
2003 TDI Jetta Daughters Car, 2001 TDI Beetle, Wife’s car, 2005 Golf TDI Mine, all 5 spds
Yup change that sensor, first order of business.

Not that you don’t need to be aware of when the belt was done but taking care of that crankshaft sensor will almost certainly fix what your problem is.

Only a Bosch sensor no cheap amazon chinese crap.
 
Last edited:

jayceT05

Member
Joined
Oct 21, 2019
Location
British columbia
TDI
2003 jetta
Replace the Crankshaft Position Sensor. Make certain the mating surface on the block is clean and free of any rust and debris. Do NOT shop around for the cheapest part, either.
Sounds good will give that a try and see if it makes any changes. You thinking this will fix the hiccups while driving or the shaking between 2 and 3000rpm?



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oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis, MO
TDI
There are just too many to list....
If the ECU sees a loss of that signal, but not long enough to flag a DTC, it will "skip" or "hiccup". You won't see it drop on the scan tool data, because the sample rate is too low. You can put a lab scope on the sensor itself and sometimes see it drop out, especially if you can record an event than scroll back through it in slow motion.

This is just an educated guess, but I have seen this happen before. It seems much more common on the BHW engine for some reason, but I have seen it happen on the ALH too.
 

jayceT05

Member
Joined
Oct 21, 2019
Location
British columbia
TDI
2003 jetta
If the ECU sees a loss of that signal, but not long enough to flag a DTC, it will "skip" or "hiccup". You won't see it drop on the scan tool data, because the sample rate is too low. You can put a lab scope on the sensor itself and sometimes see it drop out, especially if you can record an event than scroll back through it in slow motion.



This is just an educated guess, but I have seen this happen before. It seems much more common on the BHW engine for some reason, but I have seen it happen on the ALH too.
So havnt changed that sensor yet as I was out of town working but on the way home glow plug light started flashing and check engine light came on and threw code p1246 and started doing the hiccup alot still think its crank position sensor?


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jayceT05

Member
Joined
Oct 21, 2019
Location
British columbia
TDI
2003 jetta
I think you need a better scan tool.



P1246???
It says p1246 needle lift sensor (g80) implausible signal. I pulled car over side of the road shut it off wiggled wires from number 3 injector cleared code and is running fine now. Was reading some other forums and apparently the number 3 injector the sensor in it screws up not sure if I should remove it and try cleaning it or try a injector cleaner additive would just go get a new injector but vw dealership said the injectors are no longer available same with my parts store (lordco).

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oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis, MO
TDI
There are just too many to list....
Normally the lift sensors do not fail, at least not a high failure item.

Plenty of good core #3 injectors out there though if you look around. I say core because once they are used and removed from an engine, unless they are stored in some sort of oil-based liquid (diesel, kerosene, light motor oil, etc.) they can stick and not work any more (the injector nozzle part). Plus, they really are best to be checked out in sets, so that all four injectors opening pressures are the same, and they have been checked for good spray patterns.

I honestly cannot say what would happen, as I have never seen one of these fail in the way yours is, but it does at least make some sense. The lift sensor is sort of similar to a cam sensor/TDC sensor on other engines. So it along with the crank sensor are what the ECU uses to time everything.
 

jmodge

Top Post Dawg
Joined
Jun 18, 2015
Location
Greenville, MI
TDI
2001 alh Jetta, RC2 w/.205's 5speed daily summer commuter and 2000 alh Jetta 5spd swap, 2" lift, hitch, stage 3 TDtuning w/.216's winter cruiser, 1996 Tacoma ALh
1248 I believe you meant. Mine was doing the same thing, always at approximately 1800 rpm before I replaced a worn sticking vnt mechanism. Doesn’t do it anymore, but It’s a monitoring device, so it could probably mean any number of things. I can’t explain how it relates to my vnt system, other than it has stopped doing it
 

jmodge

Top Post Dawg
Joined
Jun 18, 2015
Location
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TDI
2001 alh Jetta, RC2 w/.205's 5speed daily summer commuter and 2000 alh Jetta 5spd swap, 2" lift, hitch, stage 3 TDtuning w/.216's winter cruiser, 1996 Tacoma ALh
Also in my case the other symptoms were boost lag and overboost, though not enough to throw a code for overboost
 

jayceT05

Member
Joined
Oct 21, 2019
Location
British columbia
TDI
2003 jetta
1248 I believe you meant. Mine was doing the same thing, always at approximately 1800 rpm before I replaced a worn sticking vnt mechanism. Doesn’t do it anymore, but It’s a monitoring device, so it could probably mean any number of things. I can’t explain how it relates to my vnt system, other than it has stopped doing it
P1246


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jmodge

Top Post Dawg
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Jun 18, 2015
Location
Greenville, MI
TDI
2001 alh Jetta, RC2 w/.205's 5speed daily summer commuter and 2000 alh Jetta 5spd swap, 2" lift, hitch, stage 3 TDtuning w/.216's winter cruiser, 1996 Tacoma ALh
Ok, anyway I was wrong on 1248. though I would second Oilhammer’s remark about getting a better scan tool, no offense intended. Just that VCDS is specific to your car and has diagnostic capabilities that your tool doesn’t have. I agree it’s unlikely to be a bad needle lift sensor. The sensor only measures the moment, and possibly duration, fuel is being sent to the injector. Working with the crank sensor to tell the ecu the timing. Those two signals are determining factors on how the ecu controls boost and fueling. VCDS will monitor boost, fueling, and timing
 

jmodge

Top Post Dawg
Joined
Jun 18, 2015
Location
Greenville, MI
TDI
2001 alh Jetta, RC2 w/.205's 5speed daily summer commuter and 2000 alh Jetta 5spd swap, 2" lift, hitch, stage 3 TDtuning w/.216's winter cruiser, 1996 Tacoma ALh
That code is basically telling you something is not in sync or functioning the way the ecu wants it to
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis, MO
TDI
There are just too many to list....
The thing with the generic scan tools is that they often will not give the whole story, which can be very necessary in a proper diagnosis. I see this quite often. They'll show 1 DTC, when in fact the ECU has stored 3 of them. Generic scan tools do not speak Volkswagen very well. Actually, they don't speak ANYTHING very well. But are especially bad on VAG products.
 

jmodge

Top Post Dawg
Joined
Jun 18, 2015
Location
Greenville, MI
TDI
2001 alh Jetta, RC2 w/.205's 5speed daily summer commuter and 2000 alh Jetta 5spd swap, 2" lift, hitch, stage 3 TDtuning w/.216's winter cruiser, 1996 Tacoma ALh
Also if he says it likely is the crank sensor, odds are good
 

jayceT05

Member
Joined
Oct 21, 2019
Location
British columbia
TDI
2003 jetta
The thing with the generic scan tools is that they often will not give the whole story, which can be very necessary in a proper diagnosis. I see this quite often. They'll show 1 DTC, when in fact the ECU has stored 3 of them. Generic scan tools do not speak Volkswagen very well. Actually, they don't speak ANYTHING very well. But are especially bad on VAG products.
Update replaced crank position sensor code came back again. Took it to my buddies shop and hot it scanned with a good snap on code reader still only shows one code (p1246 needle lift sensor (g80) implausible signal - intermittent). Checked all wiring no shorts anywhere.

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jmodge

Top Post Dawg
Joined
Jun 18, 2015
Location
Greenville, MI
TDI
2001 alh Jetta, RC2 w/.205's 5speed daily summer commuter and 2000 alh Jetta 5spd swap, 2" lift, hitch, stage 3 TDtuning w/.216's winter cruiser, 1996 Tacoma ALh
I am going to go over an issue I had that sounds pretty much the same as yours, hopefully it helps you out. Both in finding your problem and understanding the importance of having VCDS. It is not just a code reading tool, it is a troubleshooting tool specific to your car. Nothing like it and I can't imagine working on my car without it. Covers just about everything related engine, body, and ABS controls. For under $400, impressive to me, last you'll here on that, you're choice.

My car seemed to run great, other than a little laggy on boost, fuel mileage was below what I thought it would be and then it developed a "hiccup" along with a needle lift sensor code. Hiccup was always at the same exact rpm, between 1700 and 1800. Could be quite a hard jolt and real annoying. BTW, the sensor resistance can be checked.

I ran a boost log and my actual boost exceeded the reading capability of ny 2bar MAP, which it shouldn't. For the hell of it, I tried another solenoid in place of the N75, my lag disappeared! So I purchased a new one. Well the hiccup and code reappeared. A boost log with VCDS showed my overboost to still exist (no code or limp mode) and at idle my boost actual was not a straight line, looked like a irregular stitch seam. There was signs of an exhaust leak at the turbo so I just pulled it off.

Disconnected the actuator and worked the vnt mechanism, it had a hitch or snag to it. I pulled it apart and the contact points within it were worn on top of it sticking slightly.

My assumption was that the irregular boost line on the VCDS graph at idle was the worn vnt mechanism rattling around and allowing the nozzles to move and allow a very subtle boost variation that was not felt, but picked up by VCDS. Also the sticking vanes and worn contact points accounted for boost lag, and when the N75 overpowered the sticking nozzles, the would snap free and create a boost spike or possibly the worn contact point accounted for most of this.

I pulled the actuator. There is a weep hole in it, and out of that I was able to get quite a bit of rust. probably what fouled or wore my N75. The rod in the bushing was worn also.

Also my exhaust leak was where the cartridge bolted to the manifold, bolts came loose. So after replacing the vnt mechanism, I used a torque wrench to tighten those bolts! A new actuator and set my rod length on the bench with a vacuum gauge.

So, everything back together, car runs great, mileage improved, no code and no hiccup.

Hopefully this helps you in directing your troubleshooting and enlightens you on the virtues of spending your money on VCDS, because I really hate typing.

Best of luck and hope all is well
 

jayceT05

Member
Joined
Oct 21, 2019
Location
British columbia
TDI
2003 jetta
So quick update after all your guys suggestion tried a bunch stuff started putting stanadyne additive into tank and helped the other day started car up to warm up than all of a sudden got code back and was idling very rough (surging).tried driving it still surging. Thinking maybe the injectors are gunked up? Any suggestion would be appreciated was going to take injectors in to get tested here next couple days.


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jayceT05

Member
Joined
Oct 21, 2019
Location
British columbia
TDI
2003 jetta
Another update for everyone that was helping out ended up being the injection pump was starting to go. Installed new one and runs great again. [emoji106][emoji106]

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BBB129

Veteran Member
Joined
Feb 25, 2014
Location
Scottsdale, AZ
TDI
2005 Passat Wagon BHW 2004 Jetta 5 spd BEW - 99.5 jetta 5 speed - 1982 Mercedes 300D Manual 4 spd
The thing with the generic scan tools is that they often will not give the whole story, which can be very necessary in a proper diagnosis. I see this quite often. They'll show 1 DTC, when in fact the ECU has stored 3 of them. Generic scan tools do not speak Volkswagen very well. Actually, they don't speak ANYTHING very well. But are especially bad on VAG products.
So I was looking to get a used #3 injector 2003 ALH as My wires had been spliced previously and seemingly shorted/fried the lift sensor. I’m gathering it wouldn’t be a reliable fix? It’s in limp wonder if it would be ok to drive… I better read up on testing it.
 
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