whats this on the throttle body

[cptkirk 10]

on my 1.8 16v, theres a screw thing on the side of the throttle body....the engine was lumpy revving up and idled at 1100....ive screwed it in and the lumpy has stopped and and its ideling at just under 1000...

 

 

whats it for??? also what normal idle speed?? cant find anything on this

[aide 0]

its the idle adjustment screw, it allows air to bypass the throttle butterfly, from memory valvers idle at around 1100 when warming up then gradually settle to about 800rpm.

[cptkirk 10]

its all the way in and around 900 now??? what other adjustments are they

[Yandards 0]

16v idle when warm should be 950-1050rpm.

 

Idle is higher due to the high compression of engine IIRC.

 

There is a mixture adjustment screw on the fuel metering head (the one on the airbox lid) but you need a long allen key and some exhaust gas analysis equipment before you get to fiddle with that.

Edited January 23, 2012 by Yandards

[Wullie 1]

Found this a while ago which may help, originally written by Fishwick I believe. As Yandards says the best way is to use an exhaust analyser.

 

This problem gets asked about 'quite a bit' on the forums - It applies to the mk2 Golf/Jetta 16v with KR engine.

 

"My mk2 16v cuts out at junctions and idles terribly, I'm at my wit's end"

 

Ok, there are somethings you can check yourself at home.

 

If the ISV is working ,turn ignition on pos2 valve should *buzz*,

 

Make sure it isn't cogged up with oil deposits-either replace it or flush out with carb cleaner.. remove the brass air bleed screw and clean it also. If all that fails .........

Try cleaning out the inlet tracts of oil and the airflow flap. If the engine isn't hunting when cold or hot, the CO is correct. 16Vs run best at 2.0 % CO.

 

To achieve 2.0%, disconnect the famous "red lead" spade connector behind the coil (see fig:1 below) (after the engine is at temp), pull off the breather hose and block the airbox hole. Start the engine and the revs should plummet, if they don't, the idle valve is shagged and you're idling off the bypass screw alone. Now, with the engine running, turn the idle screw (fig: 3) up until you get 950rpm +-50.

 

If the idle wanders or is lumpy (engine visibly rocking), insert your LONG 3mm allen key into the CO screw (fig :2) and turn it anti clock to weaken. Just prior to the engine cutting out, turn the key clockwise in 1/8th turn increments until the idle smooths out. Eventually, the engine should settle to a nice, steady idle. This will be 2.0% or very close to.

 

Switch off and reconnect everything.

 

Take it out for a run and when you dip the clutch, the tacho needle should gently fall to 1000rpm, not plummet. If after all that it's still missing and rough, investigate air leaks around the inlet manifold and the various vacumn hoses.

If you ever need to find the controller for the ISV it's the black box with 'VDO' marked on it that's clipped to the back of the ashtray or (if someones been fiddling), shoved behind the dash in a random fashion!

 

If you're really unlucky and the above instructions don't sort out your particular idling issue,check that the three senders on the end of the head, under the distributor are working, 2 of these control the ISV and the other is the temperature gauge sender - the senders are all the same so as long as your temperature gauge works, you can swap the wires to make sure all 3 senders actually make the temp gauge register, obviously if one doesn't work, there's your faulty sensor.

 

WARNING -The sensors are about £20 from VAG so be careful whilst tightening them, they are tapered thread which means in simple terms that you don't wind them in all the way!

 

Thanks to Kevin Hayward for the original version of this posted on the Club GTI mailing list, many moons ago and GVK who's website I pinched this particular version of the info from

 

[ATTACH=CONFIG]51205[/ATTACH][ATTACH=CONFIG]51212[/ATTACH][ATTACH=CONFIG]51213[/ATTACH]

[cptkirk 10]

nice!!! cheers for that..ill have a do at it...i dont understand what he means buy the tapered sensors tho

[Wullie 1]

The thread on the sensor is not parallel but reduced very slightly toward the tip. It is not really noticeable. Because of this you do not have to tighten it to the shoulder as you would do with a parallel thread.

[cptkirk 10]

got yer, cheers...were best place to get all 3 sensors and the larger one above??

 

scrap yard?? what cars??

[Wullie 1]

I got mine from VW about ten years ago.

[tony_ack 0]

The above guide is excellent and I've used it many times, but there are a few more points to consider...

 

1. Check the throttle cable. When you rev the engine, the throttle should hit a microswitch when returning to idle. On some cars I've seen, the cable is so tight that the microswitch is not triggered when the throttle is released, so the idle valve is not activated.

 

2. Air leaks can cause problems and any unmetered air entering the engine will affect the idle - in addition to the suggestions above, check the injector seals, and also the bakelite injector inserts. On my old 16v I found that the inserts had pretty much disintegrated meaning there wasn't an airtight seal between the inlet manifold and injectors. The brittle injector seats are actually quite worrying as they're right above the inlet valves - so bits of plastic must have been chewed up by the valves and spat out of the back of the exhaust at some point! The inserts are obsolete, but available at Classic Parts, the seals shoudl still be available from VW.

 

3. It might sound weird but it's easy to get to near 2.0% CO by tuning by ear, as long as the timing and idle is right (6deg BTDC, or a little more advance if you're running super, and 1000rpm idle). The engine will just sound 'nice'.

 

4. Also check the wiring to the ISV as well as the temp senders and ISV itself - mine was so old and brittle that three of the wires were broken and the others weren't far behind.

 

5. The CO adjustment screw is super sensitive - just putting the allen key in can stall the car.

[aide 0]

if you're going to keep the valver i'd highly recommend this book, well worth the outlay. it explains the KR (and other) mechanical injection systems in good detail, providing context to a lot of stuff you read on the web.

 

http://books.google.co.uk/books/about/How_to_Tune_and_Modify_Bosch_Fuel_Inject.html?id=fVm0HYHJr4gC&redir_esc=y

[cptkirk 10]

im gunna change the sensors because the muppet who had it before me broke the spades and soldered a piece of wire onto them....whats the bigger one on the side of the rocker cover for???

 

do i need a gun to get it 6%BTDC?? im used to idle being 7-800 lol..ill adjust it up a little...

 

im gunna rip it apart and clean everywhere with carb spary so i know its not blocked....ill get some sensors from the scrapper and then do it on saturday...

 

---------- Post added at 07:33 PM ---------- Previous post was at 07:31 PM ----------

 

y is it called a valver??

[tony_ack 0]

You will need a gun, but don't need a fancy one to set at 6 deg BTDC as there is a mark on the flywheel at 6 deg.

 

Prepare for a long afternoon cleaning out the inlet - not difficult but just time consuming if you do it properly. You might want to get new gaskets for the inlet manifold and throttle body if you're taking it apart

 

'Valver' refers to the number of valves and distinguishes it from the standard MK2 GTI (16 versus 8 in the original GTI). Valvers were the top engine in the MK2 until the G60 came along, though when the Corrado was launched it was the least powerful engine (but still more than powerful enough).

[cptkirk 10]

ive givern her a full service...cleaned the airbox, the flap above, the pipes, the senor on the inlet and the throttle body..still the same...

 

i havent got the inlet manifold off yet..ill be doing that soon to paint it....

 

what else can it be??

[aide 0]

still the same doing what, lumpy, idling too quick/ slow?

[cptkirk 10]

its fine on idle, but lumpy if reved up slowly