(Multiple) Problems with Golf IV 1.8 GLS (+whinge).

[aintgotitmusthaveit]

For the past 3 months, my 99 Golf GLS (1.8 ltr 20V) has been:

- Trying to idle at 400-600 RPM, yielding a very rough idle (and stalling on cold mornings).
- Jerking - almost bunny-hopping - when feathering the throttle near the off-throttle condition (while trying to maintain the speed limit).
- Refusal to step-up the engine idle for increased load (i.e. air-conditioning on means the vehicle will more than likely stall).

The problem is causing the ECU to shut-down other functions:
- The cruise control will not set.
- The air-conditioning compressor does not remain active for any length of time (meaning you get moderately cold air at best).

The car has been to Essendon Volkswagen, Barloworld Volkswagen (Glen Waverley) and South Yarra Volkswagen. The things that have been done/suggested are:

- Change from Shell V-Power (98 RON) to BP Ultimate (98 RON) fuel.
- Innumberable ECU resets.
- Changed over a vacuum line.
- Cleaned the throttle body.
- Replaced the MAF.

Car is still the same, and I am sick of shelling out cash, and dealing with the arrogance of the Volkswagen service departments. The issue is not throwing an error code, so they seem competely inept at fixing the problem.

Any suggestions on what it could be guys? At the very least, maybe a suggestion for where I should take it?

Cheers.

[fuzion]

If your in Sydney i would highly recommend Sebastian from EuroAutomotive on 0410-541-322. He's located just out near Parramatta in Girraween.

Also on here under the nickname bug_racer

sounds like a dilemma instead of issues lol.. if your in another city im sure someone else could recommend someone for you

[Golf Loon]

Fuzion, he is obviously in Melbourne, you didnt read that post properly.

How about the temp / choke sensor on the engine? That would not throw up an error code and could cause those probs.

[Jmac]

Ok couple of classis signs there and believe it or not its very easy to rectify.
Firstly the cruise and the bunny hopping is your Brake pedal switch mate.
Ill try and explain - When you press the brake the switch cuts off the fuel (which you are getting) and of course switches off the cruise!! Try that and its about $30 from VW. You might have another fault there but fix this one first and make the thing driveable the ont othe next thing mate. Try VAGCOM and check the brake peadl switch function , but my money is on that.
Jmac

[Bug_racer]

hmmmm

Its seems so obvious I had to post : Throttle body

[Jmac]

Lets all jump without checking what the Ecu is giving and recieving, geez this makes me laugh sometimes and again i have fell into the trap. Its this, no its this , no its this, connect Vag com or similar and check the measured values , fault codes and the likes. Clean the throttle body and reset Throttle body, obvious or not obvious.
My 2c
Jmac

[aintgotitmusthaveit]

Lets all jump without checking what the Ecu is giving and recieving, geez this makes me laugh sometimes and again i have fell into the trap. Its this, no its this , no its this, connect Vag com or similar and check the measured values , fault codes and the likes. Clean the throttle body and reset Throttle body, obvious or not obvious.
My 2c
Jmac

Thanks for the replies! I forgot to mention, this problem is somewhat sporadic - occurring roughly 80% of the time. Sometimes you start up the car and it runs perfectly - the idle is a smooth 800 RPM, the air-conditioning is cold and the cruise control is functional. Start it up again, and it's back to cr*p.

I connected up VAG-COM for the first time yesterday - these were the three fault codes pertinent to the engine:

• 17967 - Throttle Valve Control Part ( J338 ): Fault in basic settings
  P1559 - 35-10 - - - Intermittent
• 17973 - Throttle Actuator ( J338 ): Lower Stop not Reached
  P1565 - 35-10 - - - Intermittent
• 16486 - Mass Air Flow Sensor ( G70 ): Signal too Low
  P0102 - 35-10 - - - Intermittent

No fault codes were found relating to the ABS Brakes.

I'm new to VAG-COM, so still need to work out how to check measured values. My previous post indicated the issue was not throwing a code - this was based on what Volkswagen has told me.

I also forgot to mention that Barloworld Volkswagen Glen Waverley did clean the throttle body and reset the ECU, stating the problem was grit not allowing the throttle body to return to the lower stop (i.e. sucking air at idle).

Any further comments and suggestion while I delve deeper with VAG-COM?

Cheers.

[Jmac]

Sounds like they havent done the throttle body correctly. Clean it again mate yourself then you know its done, then with VAGCOM with the IGN ON ONLY not running go into basic settings (04) then select 60 end this will run the throttle body adaption. IGN OFF take the key out and then redo an ign cycle ( start the engine and all should be well) Forgot to mention take a note of the current faults logged and clear them before you do the above procedure.
Drive the vehicle and then recheck codes.
Airmass one sounds like the conector has been unplugged at one stage.
See how you go , if the throttle body doesnt realign then you might be up for a new Throttle body
Jmac

[Bug_racer]

I dont understand how a brake pedal switch causes bunny hopping ? Ive never seen brake switches that have failed cause that . Also it doesnt cut fuel it actually controls the motor inside the throttle body shutting it down and making it go back to the idle position , if it was to cut fuel then the car would stall as a car can not run with no fuel going into the combustion chamber , and on a safety note with the braking system that if the car is not running then you will loose vacuum which in turn will cause you to loose brake booster support so brake pedal will go rock hard .

Ok couple of classis signs there and believe it or not its very easy to rectify.
Firstly the cruise and the bunny hopping is your Brake pedal switch mate.
Ill try and explain - When you press the brake the switch cuts off the fuel (which you are getting) and of course switches off the cruise!! Try that and its about $30 from VW. You might have another fault there but fix this one first and make the thing driveable the ont othe next thing mate. Try VAGCOM and check the brake peadl switch function , but my money is on that.
Jmac

He initially has told me enough information for me to correctly guess whats wrong with the car , yes a Vag-com scan will help but when you have done a few dozen with the same faults then a vag-com scan will only confirm what problems there are with the car , Im happy to go through all the problems and explain its relationship with the throttle body .

Lets all jump without checking what the Ecu is giving and recieving, geez this makes me laugh sometimes and again i have fell into the trap. Its this, no its this , no its this, connect Vag com or similar and check the measured values , fault codes and the likes. Clean the throttle body and reset Throttle body, obvious or not obvious.
My 2c
Jmac

- Trying to idle at 400-600 RPM, yielding a very rough idle (and stalling on cold mornings).
Throttle body controls the idle on the vehicle , it basically has a Throttle position sensor (TPS) which is sent to the ECU to determine where the butterfly is positioned

- Jerking - almost bunny-hopping - when feathering the throttle near the off-throttle condition (while trying to maintain the speed limit).
The car uses Mass air-flow , lambda probe , knock sensors , coolant temp sensors , intake temp sensor (mainly on turbo cars and this is seperate from the intake temp sensor in the MAF) , Exhaust temperature sender (once again usually turbo cars ) , crank angle sensor , cam position sensor and most importantly the throttle body to determine outside air temp , incoming air temp , incoming air speed and engine load . If the throttle body is not correct in its postion in relation to the other sensors then the ecu will send out signals based on what information it receives . Part throttle and cruise are important to the operation of smooth running with the throttle body , whereas the MAF is more important on full throttle .

- Refusal to step-up the engine idle for increased load (i.e. air-conditioning on means the vehicle will more than likely stall).
Once again if the throttle body has failed any small increments required in load will not be able to be carried out by the throttle body due to the rheostat inside not operating correctly


The problem is causing the ECU to shut-down other functions:
- The cruise control will not set.
Cruise control works through the throttle body by using the motor that controls the butterfly to control engine speed
- The air-conditioning compressor does not remain active for any length of time (meaning you get moderately cold air at best).
Any issues in regards to the engine running the vehicle will shut down the A/C system . On later vehicles it shuts down the A/C system and also has the coolant fans running on constantly


I hope that answers peoples questions , I could be wrong but too many things wrong that all point to the one part . A second hand throttle body is about $300 and worth a shot

[Jmac]

Ok , firstly been around these for a long time to and i know u need fuel for the enigine to run. I had a Porsche cayenne that had a 1J0 switch ( same as golf) and i was malfunctioning ( and not found on a simple scan) it was closing down the vehicle and of course this too is linked to the cruise. I agree totally about the throttle body and its great that you have taken the time to explain in depth, and like yourself i have diagnosed dozens that too have been throttle body. I also know a simple scan doesnt find faults and im an advocate for this. A quick question and i trust we are having a technical discussion here which i appreciate being a tech myself ,always seeing new stuff and having other peoples views is good brain fodder. The Golf 4 Australian delivered model is cable controlled and not Torque controlled (Drive by wire) now how is the brake pedal incorporated to this when depressed. To go further when manaully testing the switch right foot throttle and left foot braking, the throttle is manually open, braking at the same time shuts the engine down - What then???? I understand if it is Torque controlled which is out of the drivers hands.
Cheers

[Jmac]

To add to the above i have had a look at my VW notes to find and correct me if im wrong and im sure you will that both the Clutch pedal and brake pedal switches when depressed send a signal to the ecu to REDUCE the amount of fuel injected, as we know the engine still needs fuel and air. They both also disable the throttle damper facility and thus close off the throttle quicker, and as also noted above im very open to technical debate , and on the topic of Torque control override that comment as this doesnt matter where the throttle is when the fuel is Reduced and when you manually test this you can clearly tell the juice is being reduced, just like a diesel has unlimited air and fuel is the thing controlled ( and by the way this is the way VAG ar going to go with later technology) feels like the fuel filter has partially blocked for a few seconds, i am more than happy to challenge this. Vehicles with EPC do in fact work differently and when the switch FAILS it sets an idle default.
CHeers again

[aintgotitmusthaveit]

Thanks Jmac and Bug_racer. Signs do seem to be pointing towards the throttle body.

First I'll try Jmac's suggestion of clean/recalibrate. If that fails I'll seek out a second-hand throttle body. I'm just a little slow at getting things done at the moment (with my preferred hand in a sling after shoulder reconstruction).

Cheers guys!

[Bug_racer]

The only issue with the fuel being trimmed is that it also does this when driving and you completely let go of the accelerator it shuts down the injectors until it senses load again . The main emphasis here is that the the throttle body is faulty and all the signs have pointed to this as the fault . Using all the symptoms and my experience for me its quite obvious its the throttle body

[aintgotitmusthaveit]

Secondhand throttle body was fitted on Tuesday - and the car has been running right since. If it's still all good by the end of the week, I'll call the problem sorted.

Thanks Jmac and Bug_racer.

[Jmac]

Great stuff mate good to hear!!!!