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VW MKIV-A4 TDIs (VE and PD) This is a general discussion about A4/MkIV Jetta (99.5-~2005), Golf(99.5-2006), and New Beetle(98-2006). Both VE and PD engines are covered here.

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Old August 17th, 2010, 08:35   #1
sps
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Question throttle body reset

the car is vw bora(jetta) 1.9tdi 2004 mark4 model.

how does one do a throttle body reset.

i am told one needs to switch the ignition on for 10 seconds,then switch off ignition-leave for 10 seconds,then start the car.

is this correct or does one have to open the driver door as well?
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Old August 17th, 2010, 13:39   #2
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Um... diesels don't have a throttle body.

The things you have been told sound like old-school glow plug things. To start: you insert the key, turn it to on, wait for the little curly-cue glow plug warning light to go out, then start the engine.

The open the driver's door is an old one from 30 or so years ago when the glow plugs took so long to heat up, that VW started them off as soon as the driver's door was opened. Today's glow plugs are much faster to heat.
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Old August 17th, 2010, 13:46   #3
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Actually, it does have a throttle of sorts. However it is not used as an RPM limiter, and it should reset by simply resetting the adaptation Group 000 in the engine controller.

Was the throttle replaced for a fault? If so, clear the fault(s) first.

The PD's throttle control flap should calibrate itself along with the EGR when the engine is shut off. That is what the buzzing/clicking is after you turn the engine off. Technically you do not even need to start the engine, you can just turn the key on, then back off. That is probably where you heard the procedure from, since 10 seconds should be enough time for the throttle and EGR to self-check.

There is no Basic Settings channel needed for the throttle body like the gas cars, since those rely on the throttle for idle speed, not injection quantity via the fuel injectors.
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Last edited by oilhammer; August 17th, 2010 at 13:51.
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Old August 17th, 2010, 19:12   #4
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Well, shut my mouth!

It sounds like this is the newer version of the anti reversion valve. Or what exactly is it? And since it isn't for rpm control, why would it be called a throttle body?
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Old August 17th, 2010, 23:42   #5
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Quote:
Originally Posted by oilhammer View Post
Actually, it does have a throttle of sorts. However it is not used as an RPM limiter, and it should reset by simply resetting the adaptation Group 000 in the engine controller.

Was the throttle replaced for a fault? If so, clear the fault(s) first.

The PD's throttle control flap should calibrate itself along with the EGR when the engine is shut off. That is what the buzzing/clicking is after you turn the engine off. Technically you do not even need to start the engine, you can just turn the key on, then back off. That is probably where you heard the procedure from, since 10 seconds should be enough time for the throttle and EGR to self-check.

There is no Basic Settings channel needed for the throttle body like the gas cars, since those rely on the throttle for idle speed, not injection quantity via the fuel injectors.
.

thanks

there is no throttle fault.

i was just curious because i heard about the reset procedure on some bmw forum where it said it works on vag cars as well and helped sharpen the throttle response.
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Old August 18th, 2010, 04:17   #6
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Quote:
Originally Posted by Powder Hound View Post
Well, shut my mouth!

It sounds like this is the newer version of the anti reversion valve. Or what exactly is it? And since it isn't for rpm control, why would it be called a throttle body?

People get hung up over semantics, but the basic design and assembly of it is just like the electronic throttles on VAG gas cars. If you set the 2 side by side, you could not really tell the difference.

On the PD diesels, the throttle (technically VAG calls it an 'intake manifold control flap') is primarily for EGR function and catalyst operation. On the CR cars, it is also used for DPF regeneration. Keep in mind the newer diesels run a 'richer' air/fuel ratio than the older ones.

The ECU closes the throttle some when the EGR valve gets opened, to force a higher flow (higher velocity) of EGR into the intake. That higher velocity along with proper ULSD fuel pretty much makes intake clogging a thing of the past. The PDs simply never gunked up intakes like the VE cars did.

It can also allow the engine to force a richer (higher fuel quantity) without pushing the RPMs/output/torque of the engine up, and that extra fuel helps to keep the catalyst hot under certain conditions. The PDs cannot do the post-combustion/exhaust cycle fuel injection like the CRs can, so the only way to get more fuel into the exhaust to keep the catalyst lit off is to increase the IQ. But as you know, in a diesel, if you increase fuel, you increase RPMs. To limit that RPM from going too high under these conditions, the throttle is closed some.

And of course it is used for anti-shudder function at engine shut-down.

There are other (older) diesels that actually use a throttle more like a gas car, that forces vacuum under the throttle plate which acts on a plunger that is directly attached to a fuel metering rod going to the pump. MB used such a system in their diesels for YEARS. It was very similar to a carburetor actually, where vacuum and airflow were employed to meter injected fuel quantities.

Then later MB diesels used them to help keep the engine quieter at lower RPMs (my 1975 240D was one such animal, the throttle plate in the intake manifold was directly mechanically attached to the accelerator pedal, along with the fuel metering lever on the pump).

If you stand next to a CR diesel idling, even with the hood up, (Sprinters especially), you will notice how darn quiet they are. Well, part of that is because CR engines can run the injection timing literally anywhere the ECU needs, and at idle they can be WAY retarded. That way retarded injection timing makes the exhaust catalyst(s) stay hot even at idle, makes the engine quieter, and when used with a throttle (which is partially closed on them at idle) makes the engine even quieter AND smoother because if the engine is not compressing all of the air it could be that high compression won't be being used as much.

For some reason, the myth that 'diesels don't have throttles' keeps on going, despite plenty of them that do use them in some capacity.

Bosch has an excellent book on EDC systems and how they operate, including throttled versions.
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Old August 18th, 2010, 11:02   #7
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Excellent explanation, thank you.
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'00 4dr 5-sp white over black Golf: Sprint 520 nozzles, ABS+ASR, Koni FSD enhanced suspension, vented hood; '00 2dr 5-sp silver over black Golf. DG 5-sp short shifter. Nuthin' special yet.
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Old August 18th, 2010, 13:45   #8
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Quote:
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Excellent explanation, thank you.
Ditto
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Old August 18th, 2010, 13:57   #9
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Quote:
Originally Posted by oilhammer View Post
Bosch has an excellent book on EDC systems and how they operate, including throttled versions.
2X... something to ask Santa for perhaps??!
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Old September 2nd, 2014, 03:53   #10
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As I was driving the engine increased to 5000 rpm by itself. I turned off the engine and pushed in the clutch. It kept running sending out a plume of black smoke until it finally stopped.
Is it possible the throttle plate got stuck open? If not what could have been the cause?
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Old September 2nd, 2014, 03:59   #11
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You experienced a diesel runaway. Does the engine run anymore, or did it totally tooef itself?

Causes for that could be a failed turbocharger or something in the engine proper broke and sent a ton of oil through the breather system. It could also be an injection pump that went rogue, saw that happen not long ago too, and that cost TWO engines!
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Old September 2nd, 2014, 07:26   #12
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Yup, "runaway" is a great search term to try here.. you'll find tons of threads. The engine was likely running on its own oil, which is why turning off the key had no impact.

In general you'll want to:

- pull the glowplugs and crank the motor to eject any remaining liquid oil
- do a compression test, looking for bent rods

Or maybe you got lucky and it was a malfunctioning injection pump, in which case you'll not find any oil in step 1 above. Tons of black smoke suggests oil, however.
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Old September 2nd, 2014, 08:36   #13
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Quote:
Originally Posted by oilhammer View Post
*Interesting bit of text removed*

For some reason, the myth that 'diesels don't have throttles' keeps on going, despite plenty of them that do use them in some capacity.
I think that the myth continues because diesels don't NEED a "throttle". They can be operated 100% by injection alone. The "throttle" is mainly there for all the reasons you said, which aren't to make the engine run, but to make run either better or cleaner.
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Old September 2nd, 2014, 09:37   #14
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Yep, and the manufacturers are experimenting with running gasoline engines without throttles, too, under certain conditions in a super-lean mode. This is still in its infancy, though, and has hit some roadblocks along the way. Search for "HCCI" for more info.
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Old September 2nd, 2014, 10:43   #15
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Quote:
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Yep, and the manufacturers are experimenting with running gasoline engines without throttles, too, under certain conditions in a super-lean mode. This is still in its infancy, though, and has hit some roadblocks along the way. Search for "HCCI" for more info.
I've heard of that before but haven't looked into in detail. Maybe I'll give it a quick googling.
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