Lumpy / Poor Idling Golf MK4 1.4 16V

Continuing with the guess work......the throttle body on these has a variable resistor which links fuelling to the ECU. As the idle speed is very low anyway, any issues with these causes cutting out.
It may be worth contacting BBA-Reman about this one - they are very helpful.
I had similar issues with an elderly Polo once, and a second hand throttle body cured the idle problem, but gave a misfire further up the rev range :rolleyes:
Just can't win!
John :)
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Dear All

Been a while since I updated this post. I again had a Temperature sensor Failure so bought a Genuine VW Temp Sensor. Car's power returned instantly and the engine ran well at speed BUT still had Poor idling at standstill and really rough idling if on an incline but idling was smooth on a decline.

Today I changed the spark plugs again to Bosch Super 4. The old ones as per the attached pictures look really odd as cyclinder 1 & 2 have the same colour looking at the pics left to right BUT cyclinder 3 & 4 have a diffferent colour! Cycinders 3 & 4 always show a misfire whilst 1 & 2 no mis-fire at all.

Can anyone tell me why the spark plugs look so different? Is there a fue injector problem?
Ye gods - this one is becoming a real hair tearer..... :eek:
I don't think there's a massive problem with those plugs - the triple electrode ones last for ages and there isn't any sign of oiling, which gives a general state of the cylinders and compression.
Remind me - is this a single fuel injector engine (SPFI) or 4 individual injectors?
As for the idling state pointing uphill or downhill I really don't have a clue (so long as the tank has plenty of fuel in) and I'm wondering if this is coincidence......although you seem well convinced so who are we to argue!
One thing is for sure - we haven't hit the problem yet - its just having good and bad days! I'll still go with the throttle body though and would love to see it tested properly, linked up to an oscilloscope really.
Purely a long shot on this guesswork scenario - there's no burning of the wires to the lambda sensor is there? (I've known a few of these being replaced to absolutely no result - but I'm not saying by whom :p )
John :)
Hi Burnerman

Thanks for the reply. The Car engine code is AXP and has 4 Individual Injectors.

I still get Random Mis-Fire and then says its cylinders 3 & 4

VCDS Version: Release 908.0
Data version: 20090830


Address 01: Engine Labels: Redir Fail!
Control Module Part Number: 036 906 032 L
Component and/or Version: ME7.5.10 3869
Software Coding: 00031
Work Shop Code: WSC 00046
Additional Info: WVWZZZ1JZ2B006088 VWZ6Z0A3353858
3 Faults Found:

16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-00 - -
16688 - Cylinder 4: Misfire Detected
P0304 - 35-00 - -
16687 - Cylinder 3: Misfire Detected
P0303 - 35-00 - -

Readiness: 0000 0001

This occurs randomly at any time even whe coming off a motorway or even when stopping at traffic lights. Would a throtttle body cause a mis-fire?? How is a Mis-fire actually calulated by ECU, Coil , Injectors?
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A nightmare, this intermittent misfire can be caused by either a faulty fuel injector or an ignition problem (plugs / caps/ leads etc) - to quote the bloomin' obvious :p
Throttle body problems wont cause a misfire per se (as far as I know) but they can cause the tickover to fall so low that the engine can't run.....whats its tickover speed when its behaving?
John :)
Hi Burnerman

Tick over when its behaving is 760 RPM dead on , no fluctuations. Recap engine has had new Plugs, Plug Leads, Coil, New Air Filter, New Fuel Filter. MAP Cleaned, EGR Valve blanked off no difference so reset back to normal and adapted. Throttle body cleaned 5 times and adapted.

How is a Mis-fire actually calculated by ECU, Coil , Injectors?
Have you had an leak down test done?
Have you had the fuel pressure tested?
Have they removed the cat to do an visual inspection? ( normally only gives trouble at higher speed at first)
One thing you could do yourself is
To swap the injectors around and se if the problem moves with the injectors..

Best Chris..
Hi Chjee

Took it to a local Garage who said Mis fire on cylinders 3 & 4 due to low compression. They think inlet valves are sticking intermittently and want £600 to cure it by reconditioning the head? Not sure if they did leak down or Fuel Pressure test or inspected the Cat.

Once codes are cleared Car runs fine, no mis fires, car has excellant power throughout rev range, mis fires randomly say when coming of the motorway and stopping at the lights or just slowing down in traffic!

Would faulty MAP cause this? I will certainly try swapping injectors around. tried to find any vacuum leask by spraying starter fluid but not found!
OK Problem resolved!! Had the Cylinder Hear Recondition. Engineers found 2 Exhaust Valves badly damaged,1 with Hole in it! The other had split you can see right thru! The other 2 were badly pitted. All 4 Renewed, Valve guides renewed, valve seats renewed and lapped in. Timing Belt and Pump done at the same time. Now car is running superbly perfect idle, engine runs like new and is really quite now! Just running the car in now for the next 200 Miles!

Thanks to everyone for their Help, much appreciated.
Absolutely delighted to hear about that!
Somewhat less than delighted that none of us suggested a compression test :confused:
Enjoy the car - it must be transformed!
John :)
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