1Z/AHU stumbling under part load

[GTiTDi]

thread from the dead!

 

[Abacus]

Help has no time limit.

 

[fixit13]

Thanks Abacus.. crazy timing. I found this post last week and tried it. I was shocked it worked. I came back today to find out where that wire is to cut and there it is.. crazy timing.

I have been fighting this vibration problem for several months, just after doing a full timing belt change. Drove me crazy enough to replace all the motor mounts. Seemed more like a miss, but I just could not track it down and nothing I tried helped, until now.

I am not really worried about loosing my cruise as I never use it. I have a donor car and was thinking about swapping the vss but I suspect it is not the root of the problem.

Thanks again!

 

[bmwM5power]

i tried to disconnect the VSS, it helped with the shudder in low rpm in higher gears but for some reason I started feeling really bad shudder / jolting when I make the right turn and downshifting to 2nd gear, car starts bucking till i give it more throttle. Any idea?
My car has a larger injectors ( from KermaTDI i was told, and everything was balanced), I looked at my Injection Quantity it is at 2.4-2.6 mg/R at the default adaptation value 32768. I was able to only move it to 32668 ( 100 less) which made the IQ 3.2 mg/R. I assume I need to do a "hammer mod" to lower the fuel amount.
If I understand this correctly lowering the adaptation value ( 32768) will raise the IQ value , for ex to 5mg/R , and will reduce fueling, correct?

 

[Houpty GT]

Yes, on the back of the fuse panel you will find two blue electrical connectors that have all white wires going into them.

Look up where the connector is on the CE2 diagram.

Find wire U2/2 and either cut it like other people have, or remove it from the terminal and install it on a switch. I put mine on a switch so I could still use the cruise control when I wanted.

Or you can just simply disconnect one of those single wire blue connectors in the right of the pictures. Once you figure which of the 3 it is, you can mark it for later.

 

[Steve Addy]

Or you can just simply disconnect one of those single wire blue connectors in the right of the pictures. Once you figure which of the 3 it is, you can mark it for later.

None of the cluster wires Abacus et al is talking about connect to those junction blocks so no, the blue block and connectors are a different situation.

The white wires in the cluster harness go directly from fuse box to the cluster without interacting with anything else although there are a couple exceptions to that. The wire in question at U2/2 will need to be disconnected from the big blue fuse block plug, or at least that's about the easiest spot to get to it. I suppose you could remove it from the other plug at the cluster too.

As a side note, is this an affliction that only appears on the B4 or have others experienced this on the Mk3 cars? Very curious about this since this is the first I've heard of it.

As I've said before, important diagnostic info like this ought to be in a sticky somewhere.

Steve

 

[bmwM5power]

so I checked and adjusted the IQ, tried different settings from 2 to 5 mg/R disconnected the VSS and I still get the bucking under partial steady load around 1500rpm or so, in different gears, and I think its worse when fully warmed up, what else should I check? Could this be bad engine mounts? its kind of feel not smooth when shifting or releasing clutch.

 

[cal327]

Has anyone found a way to correct this problem Completely?

 

[Houpty GT]

None of the cluster wires Abacus et al is talking about connect to those junction blocks so no, the blue block and connectors are a different situation.

The white wires in the cluster harness go directly from fuse box to the cluster without interacting with anything else although there are a couple exceptions to that. The wire in question at U2/2 will need to be disconnected from the big blue fuse block plug, or at least that's about the easiest spot to get to it. I suppose you could remove it from the other plug at the cluster too.

Steve

Trust me, it is the blue block and single wire connectors you want. http://forums.tdiclub.com/showthread.php?t=286509
Don't let what you read in books lead you astray.

This shuddering problem happens mostly with tuned 1Z so the 1997 Jettas have this problem also. Disconnecting is not a cure. It is simply a band-aid and leads to other problems in low gears for some people. Disconnecting the VSS from the ECU turns back the injection timing. I would say the root cause is worn valve stems or to much timing advance.

 

[bmwM5power]

I had to play with the IQ a little bit. Disconnecting the VSS in my case was making it worse. I had the shudder in all of the gears almost. Hammer moded the IQ to 5.2mg/R and looks like it liked it, the shudder in low rpms stopped.

 

[Houpty GT]

I had to play with the IQ a little bit. Disconnecting the VSS in my case was making it worse. I had the shudder in all of the gears almost. Hammer moded the IQ to 5.2mg/R and looks like it liked it, the shudder in low rpms stopped.

I was able to manipulate IQ and injector balance to control my shudder for a few years. There is something that wears out (valve guides?) and it cause the shudder to get worse with time.

 

[Abacus]

Not valve guides because mine did it before and after the head replacement I got from Franko6, which was better than new. There was no difference in the shudder with my RC tune. It has gone away with the Malone tune but it smokes a lot more now than with the RC tune.

 

[Steve Addy]

Trust me, it is the blue block and single wire connectors you want. http://forums.tdiclub.com/showthread.php?t=286509
Don't let what you read in books lead you astray.

This shuddering problem happens mostly with tuned 1Z so the 1997 Jettas have this problem also. Disconnecting is not a cure. It is simply a band-aid and leads to other problems in low gears for some people. Disconnecting the VSS from the ECU turns back the injection timing. I would say the root cause is worn valve stems or to much timing advance.

I'm sorry, I misread what was there, yes, the VSS can be disconnected via the blue block single connector but you have to figure out which one it is. The connection that gets it to the cluster harness is done internally at the fuse box at W1 and routed out through U2/2 to the cluster.

My mistake, sorry if I was spreading misinformation, not my intention. I was at first under the impression that it was to discon to the cluster and not to the fuse box. Is there any other adverse consequences to disconnecting it from the entire system vs the cluster only?

Steve

 

[TDIBill]

I had this problem with my 98 Jetta TDI & an Upsolute Tune and with my B4s & Upsolute.

 

[fixit13]

So what did you do to fix it?

 

[fixit13]

I was thrilled to have fixed my problem - https://www.youtube.com/watch?v=6x3S2f5ykVE

Car has ran great but now today 2 weeks later I have a problem Houpty GT mentioned. "It is simply a band-aid and leads to other problems in low gears for some people." Well I guess I am in the some people category and need a new Band-Aid as mine fell off.

New problem is lack of power in 25-35 mph range, some times it will take it sometimes not. No power at low rpms, especially hills, feathering it sometimes helps.

Plugged in the Vag tonight and I am at a loss but see problems.
Temp 132 - timing 60-62 (ok in my book)
IP - will not read! I have been here before and remember putting things back to wher e I started (128) but I get nothing now. (Engine - Login - adaptation - block1) Nothing reads. Somewhat concerning. Another thing that bothers me is when I try to look at IP settings block 13. I have cly1= -2.3 cly2= -2.9 cyl3= -0.2 (cyl 4 is reference from what I understand) So I have a problem with cylinder 3 from what I read.

I could really use some advice.

Thanks guys.

 

[TonyJetta]

When looking at cylinder balance, #3 is the reference:
Vcds / reality
1 / 1
2 / 2
3 / 4

It looks like cylinder balanse for 1 & 2 are WAY off. I would start with a compression check, then probably send the injectors out for pop testing and balancing.

Tony
Sent from my e-diesel fleet

 

[fixit13]

Thanks TonyJetta - I will check compression and go from there. Have a spare set of injectors. A friend with a newer vag was over so I used his to look at my IP and it was at 5.5 - I was able to knock it down to 4.5 but could go no further. I know unrelated to hopefully only an injector problem now. Think I will need to do the hammer mod to get it down but I guess that is a mute point if I have low compression or a bad injector.

Thanks again, you guys are great.

 

[vtpsd]

I'm going to bump this up. I found this thread while trying to diagnose a stumble on throttle tip-in in my AHU swapped audi. It has a tune and big injectors. Runs great, but stumbles mildly when warmed up and under very light throttle conditions. I'v wasted quite a bit of time trying different IQ settings to no avail.

I disconnected the speed sensor, and the car runs PERFECT. I wanted to keep my cruise control so I used a relay that has the signal powered off of the 12v+ from my "cruise on" switch. This relay is used to connect the VSS to the ECU when the cruise is switched on, so cruise will work. If you switch off the cruise, the signal is disconnected and the stumble is avoided.

You never are really at light throttle at low speed when using cruise, so this seems to have completely solved my problem.

 

[ToddA1]

Do you lose your speedometer? Glad you finally got it figured out, but I thought you figured it out, last week.

-Todd

 

[vtpsd]

I don't loose my speedo. The speedo is running off the stock audi wiring, and I just have the ECU tapped off the signal side. My relay just breaks the signal line to the ECU, but the speedometer line remains connected.

 

[greenskeeper]

I'm going to bump this up. I found this thread while trying to diagnose a stumble on throttle tip-in in my AHU swapped audi. It has a tune and big injectors. Runs great, but stumbles mildly when warmed up and under very light throttle conditions. I'v wasted quite a bit of time trying different IQ settings to no avail.

I disconnected the speed sensor, and the car runs PERFECT. I wanted to keep my cruise control so I used a relay that has the signal powered off of the 12v+ from my "cruise on" switch. This relay is used to connect the VSS to the ECU when the cruise is switched on, so cruise will work. If you switch off the cruise, the signal is disconnected and the stumble is avoided.

You never are really at light throttle at low speed when using cruise, so this seems to have completely solved my problem.

see post #18

 

[ToddA1]

I'm guessing you used a standard Bosch style relay? Is the wiring below, correct?

85 ground
86 12v trigger from cruise stalk
87 one side of VSS wire
30 other side of VSS wire

-Todd

 

[vtpsd]

I'm guessing you used a standard Bosch style relay? Is the wiring below, correct?

85 ground
86 12v trigger from cruise stalk
87 one side of VSS wire
30 other side of VSS wire

-Todd

yes, exactly.

 

[vtpsd]

see post #18

doh!!

 

[wyopel]

Just found this thread and tried unplugging the VSS. Sure enough the shudder was gone. So I will also check grounds and likely rewire with switch if nothing changes.

Before I do that though I thought I would ask an obvious question...has anyone tried replacing the VSS with a new one? Is it possible these things go bad and send a dirty signal to the ECU? I suspect the answer is no because the problem seems to be connected to mods like non-stock nozzles...on the other hand it doesn't seem not everyone that upgraded nozzles has the issue. I know IQ setting may also be at play too.

When I unplugged the VSS I also got the flaky fuel gauge. Dose this problem continue when it is rewired with the switch?

 

[Stromaluski]

When I unplugged the VSS I also got the flaky fuel gauge. Dose this problem continue when it is rewired with the switch?

Don't know the answer to the replacement VSS question, but I can certainly answer the fuel gauge question.

The cluster does dampen the fuel gauge quite a bit, but only if it sees the speed signal from the VSS. When you rewire the wire mentioned previously with a switch/relay, you are only interrupting the speed signal to the ECU and not touching the speed signal to the cluster.

Long answer to simply say no, the problem does not continue when the VSS signal is rewired with a switch/relay.

 

[Windex]

It's more of an ECU fuel mapping issue. Once the ECU loses the speed signal, the shudder goes away. As above, there are two wires on these cars - one for the ECU, and the other for the cluster. If you sever just the ECU wire, the car behaves normally wit respect to the speedo and fuel gauge.

Downside is that cruise won't work while the speed signal is cut. Hence the use of a switch by some.

 

[wyopel]

Thanks.
It seems like there are certain nozzle-tune-IQ set ups that more prone to this shudder issue. I would be interested in seeing if there is a pattern that emerges with certain set ups. Or perhaps more importantly what set ups seem to NOT have the shudder. So for the record...

I currently have Titan 502 nozzles with no tune (BK ECU). IQ is currently set around 4.2 and the IP timing just a hair below the middle line (timing belt has stretched a bit since replacing about 12K miles ago). I plan on advancing timing a bit and lower IQ a bit to see what happens. I also have an FA ECU I plan on tuning once I free up some $.

I appreciate the relay work around, and that may be the only solution. However, I assume the shudder returns when you turn on the cruise. Actually I first noticed the shudder when I was cruising around 65 and started going up a slight hill. Would like to find a more complete fix.

 

[Windex]

Bigger nozzles make the part load shudder worse in my experience.

Some tunes completely eliminate the shudder to the point where the ECU speedo wire is left intact.
Other tunes reduce the shudder, but do not eliminate it entirely.

There are not many tuners who can work with the BK ECU, best to keep an eye out for a GQ. The FA requires a bit more work from what I have read (on a B4).