This sucks

dh03tdi

Active member
Joined
Oct 12, 2020
Location
Kansas
TDI
2003 Jetta
I recently purchased a 2003 Jetta ALH and everything was fine till yesterday. I was on my way to work and this thing started idling like crap. It felt like a gas engine with a misfire. But when you get off idle it felt fine. Plus no CEL which confused the hell out of me. So I did some research when I could during the day and still was confused.

Fast forward to leaving for the day. I leave work, turn on the ramp for highway and just flogged the crap out of this thing. Pulling really well, 25 lbs of boost according to the boost gauge, get to about 105 and decide to let off so I don't get a speeding ticket. Everything is fine until about 8-9 miles from home and boost coming on very slow and not as much as when I got on the highway earlier. A couple more miles down the road, no boost at all. Almost feels like limp mode.

About 2 miles from home the CEL light finally comes on.

I plug the flashzilla into the diag port to get codes. They are:

16502

16686

17964

The 16502 sounds like a coolant temp sensor. Not a big deal.

16686 confuses me as it says cyl # 2 misfire. These things only have compression and fuel. I am hoping this is simple and not a compression issue.

The 17964 could be a few different things from what I have researched. When I got home, I looked around the engine for something that might be unplugged or obvious but did not find anything.

I did not have a lot of time to look over the car as we had things to do last night. I am going to have more time this weekend to check all of the intake hoses and vacuum lines. If I do not find anything there, I will check the actuator and turbo for failure. I suspect maybe the actuator might be sticking or the N75 might have failed but I do not have a hand pump or anything to check these with vacuum.

Sorry for the lengthy post. Any advise would be great and appreciated. Thank you.
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis, MO
TDI
There are just too many to list....
Not sure why a misfire should confuse you, a diesel can misfire just like a gasoline engine.... the only difference is, you can rule out any problem with an ignition system. That leaves compression and fuel.

You may have one problem that caused another. Forget about the low boost for now, does the engine start and idle OK? Turbo function or not, the engine should normally start right up and idle perfectly fine. You may have had a turbo failure that manifested as a bunch of oil in the charge air tract, and it bent a rod or burnt a piston.

I'd first take the charge air tube off the intercooler down low, and see if any oil comes pouring out.
 

dh03tdi

Active member
Joined
Oct 12, 2020
Location
Kansas
TDI
2003 Jetta
Not sure why a misfire should confuse you, a diesel can misfire just like a gasoline engine.... the only difference is, you can rule out any problem with an ignition system. That leaves compression and fuel.

You may have one problem that caused another. Forget about the low boost for now, does the engine start and idle OK? Turbo function or not, the engine should normally start right up and idle perfectly fine. You may have had a turbo failure that manifested as a bunch of oil in the charge air tract, and it bent a rod or burnt a piston.

I'd first take the charge air tube off the intercooler down low, and see if any oil comes pouring out.

It started just fine yesterday leaving work. I could feel a small miss/shake when it was first started in the high idle with the malone tune. I did not drive the car today as I have another car that can be driven. From what I remember, the boost would come up very slowly but the last time I tried before I got home it came up but then dropped like maybe a limp mode kind of thing. I have an appointment to have a shop that specializes in VW TDI here in town but it is not for another week. I was trying to maybe rule a few small things out that I can before that if I can.
 

BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
I'd first take the charge air tube off the intercooler down low, and see if any oil comes pouring out.
Get the covers off, get it up in the air, have a look
Fuel is diesel+air. Air gets way off, they don't run good.
 

braddies

Veteran Member
Joined
Jul 26, 2021
Location
America
TDI
03 golf ALH
With the flashzilla are you able to read fuel temp, coolant temp and ambient temp?
That coolant temp sensor can go bad and will cause issues.
With the motor cold all three temperatures should be within a couple degrees of eachother.

Edit: I only know with vcds engine measuring block 07 will show the temperature output of each of the sensors.
I think when my coolant temp sensor was wonky it told the ECU the coolant was something like -300°f
 
Last edited:

burpod

teh stallionz!!1
Joined
Nov 27, 2004
Location
cape cod, ma
TDI
82 rabbit vnt ahu, 98 jetta vnt ahu, 05 parts car, 88 scirocco.. :/
if the coolant temp is reading very wrong, it can cause serious problems with timing.. especially on that tune depending on what nozzles/pump you have.. you'd best take some various logs, sanity check with vcds all temps when at ambient and while driving.
 

burpod

teh stallionz!!1
Joined
Nov 27, 2004
Location
cape cod, ma
TDI
82 rabbit vnt ahu, 98 jetta vnt ahu, 05 parts car, 88 scirocco.. :/
who knows if it has a dead cylinder. one thing i do know is there's a very good chance that tune is calling for wayyy too much advance. also, if coolant temp is reading, say 10C, so that's what the tune thinks it is, but car's warmed up, it's going to be insanely over-advanced and things don't feel well there lol.
 

dh03tdi

Active member
Joined
Oct 12, 2020
Location
Kansas
TDI
2003 Jetta
It looks like Sunday is supposed to be decent this weekend so I am going to replace the coolant temp sensor. Do you think I should erase the codes? Or just replace the sensor and see if that changes anything?
 

burpod

teh stallionz!!1
Joined
Nov 27, 2004
Location
cape cod, ma
TDI
82 rabbit vnt ahu, 98 jetta vnt ahu, 05 parts car, 88 scirocco.. :/
it's also very possible the contacts of the plug/sensor could just have some random corrosion on them or another wiring issue. i'd see what vcds logs say of what the coolant sensor is reading... check block 007 after it's been sitting overnight and ambient temps are known, and then log for example 011-001-007 during a drive. i've seen one car, that wasn't throwing any codes, but randomly while driving the coolant temps would drop from 90C down to 10C and then sit around 10-20C for a couple minutes then go back up to 90C (during which time the ecu is using completely wrong timing maps). obviously reading wrong. it hasn't been determined yet if it's the sensor or other wiring... that said, if it's an old original sensor, it couldn't hurt to get one anyway for the eventuality, along with any other bits that are useful and inexpensive to have "on the shelf"...
 

dh03tdi

Active member
Joined
Oct 12, 2020
Location
Kansas
TDI
2003 Jetta
it's also very possible the contacts of the plug/sensor could just have some random corrosion on them or another wiring issue. i'd see what vcds logs say of what the coolant sensor is reading... check block 007 after it's been sitting overnight and ambient temps are known, and then log for example 011-001-007 during a drive. i've seen one car, that wasn't throwing any codes, but randomly while driving the coolant temps would drop from 90C down to 10C and then sit around 10-20C for a couple minutes then go back up to 90C (during which time the ecu is using completely wrong timing maps). obviously reading wrong. it hasn't been determined yet if it's the sensor or other wiring... that said, if it's an old original sensor, it couldn't hurt to get one anyway for the eventuality, along with any other bits that are useful and inexpensive to have "on the shelf"...

I am not sure all of the functions of the flashzilla. I will see Sunday if I can indeed look at the coolant temp sensor to see what it is reading as well as a good visual look over all of the wiring and vacuum lines.
 

dh03tdi

Active member
Joined
Oct 12, 2020
Location
Kansas
TDI
2003 Jetta
you need vcds, or at least vcds-lite to log ecu data. it's really 100% essential to having a well running tdi..
I have been looking to find one but not sure which to get. I don't want to spend a bunch of money on it but also don't want one that doesn't do what I need it to.
 

burpod

teh stallionz!!1
Joined
Nov 27, 2004
Location
cape cod, ma
TDI
82 rabbit vnt ahu, 98 jetta vnt ahu, 05 parts car, 88 scirocco.. :/
$200 for the basic vcds will do everything you need for an alh as well as a bew/pd. don't know about the newer stuff tho. its the best $200 you could ever spend if you own a vw
 

dh03tdi

Active member
Joined
Oct 12, 2020
Location
Kansas
TDI
2003 Jetta
$200 for the basic vcds will do everything you need for an alh as well as a bew/pd. don't know about the newer stuff tho. its the best $200 you could ever spend if you own a vw

Is there a particular brand or company that is better then another?
 

burpod

teh stallionz!!1
Joined
Nov 27, 2004
Location
cape cod, ma
TDI
82 rabbit vnt ahu, 98 jetta vnt ahu, 05 parts car, 88 scirocco.. :/
ross-tech.com they're the ones that made it, just buy from them and get the real deal. if you want a truly well running tdi, it's not possible without vcds. the next thing to do is delve into taking logs and see how well your car is really doing... after sorting out any major problems of course lol. especially if it's "tuned". can be a real eye opener, but it can be difficult if you don't have any reference/comparison point of what a truly well-tuned tdi is like to drive... once fuel is added, it's very easy to be fooled into thinking you've got a good thing goin on... ;)
 

dh03tdi

Active member
Joined
Oct 12, 2020
Location
Kansas
TDI
2003 Jetta
ross-tech.com they're the ones that made it, just buy from them and get the real deal. if you want a truly well running tdi, it's not possible without vcds. the next thing to do is delve into taking logs and see how well your car is really doing... after sorting out any major problems of course lol. especially if it's "tuned". can be a real eye opener, but it can be difficult if you don't have any reference/comparison point of what a truly well-tuned tdi is like to drive... once fuel is added, it's very easy to be fooled into thinking you've got a good thing goin on... ;)

I will look into getting this software. I appreciate all of the help. Thank you.
 

Ed27

Veteran Member
Joined
Jan 17, 2019
Location
Florida
TDI
2001 4dr, 2000 2dr Golfs both 5 speed stick
Daughter's car had a similar issue it turned out to be the EGR. A quick careful clean it was like new.
 

dh03tdi

Active member
Joined
Oct 12, 2020
Location
Kansas
TDI
2003 Jetta
I replaced the coolant temp sensor this weekend but I did not clear the codes. Drove it around the block, about 4 miles, and still same issue. I am getting boost now but I think I do need to replace the vacuum lines. The line that goes to the, what I believe to be, the vacuum canister will not stay on and I can here a hissing sound. I push the line onto the canister and still here the hissing but not sure as to where it maybe coming from.

Should I clear the codes?
 

IndigoBlueWagon

TDIClub Enthusiast, Principal IDParts, Vendor , w/
Joined
Aug 16, 2004
Location
South of Boston
TDI
'97 Passat, '99.5 Golf, '02 Jetta Wagon, '15 GSW
Check the fitting on the vacuum pump where the line to the brake booster attaches. Those are tack welded to the pump body and sometimes come adrift.
 

braddies

Veteran Member
Joined
Jul 26, 2021
Location
America
TDI
03 golf ALH
Ooo hissing means you found something! If there's enough slack in that vac line you might be able to cut the last half inch off and reattach
 

dh03tdi

Active member
Joined
Oct 12, 2020
Location
Kansas
TDI
2003 Jetta
Check the fitting on the vacuum pump where the line to the brake booster attaches. Those are tack welded to the pump body and sometimes come adrift.
I will check that hopefully when I get home today.
Clear the codes and see what comes back.

I'd also look at IQ just to rule it out.
I will do this as well.
Ooo hissing means you found something! If there's enough slack in that vac line you might be able to cut the last half inch off and reattach
There wasn't much slack in the one vacuum line that I did notice was kinda hard and wasn't wanting to stay on. I did have a lot of time since the sun was going down last night to really look over all of the line plus I wasn't real keen on sticking my hand down by a hot turbo.
 

dh03tdi

Active member
Joined
Oct 12, 2020
Location
Kansas
TDI
2003 Jetta
Deleted the codes last night. Runs fine but still missing at idle. CEL did not come on on my short drive to pick my son up at the school. I was afraid to drive it to work today. I guess I can try tomorrow and see what happens. Checked the vacuum lines and all look to be at least connected. Boost was good. I did hook up the flashzilla to see what the tune actually was and it said stage 4 hot. When I purchased the car, they told me it was on a stage 2 tune from Malone. Does this sound right?
 

Nevada_TDI

Top Post Dawg
Joined
Aug 17, 2008
Location
Reno, sort of...
TDI
2001 Jetta TDI
You can use a deep socket to partially knurl the nipple down closer to the pump outlet and a wooden dowel or something "soft" to peen it down the rest of the way.
The vacuum doesn't really get hot, silicone will usually stop the rest of the leak.
Are you getting at least 20" of Hg at the pump?
 

turbocharged798

Veteran Member
Joined
May 21, 2009
Location
Ellenville, NY
TDI
99.5 black ALH Jetta;09 Gasser Jetta
Troubleshooting the vacuum system is a waste of time IMO. You have a hard misfire, either fuel or compression. I would start with a compression check first and go from there. Sounds like a bent rod to me.
 

dh03tdi

Active member
Joined
Oct 12, 2020
Location
Kansas
TDI
2003 Jetta
Troubleshooting the vacuum system is a waste of time IMO. You have a hard misfire, either fuel or compression. I would start with a compression check first and go from there. Sounds like a bent rod to me.
I wouldn't think its a bent rod. You would think it would miss all of the time. It only starts missing after it is at normal temps. First start it does not run like that. But on the other hand I am not the smartest person in the world either.
 
Top