Nearly sorted out my rough running 16v... One last bit of help required!

[Conker]

Spent all day trying to solve my rough running problems.  I've searched and searched the forum but can't find the actual answer I'm looking for...

Symptom: General lack of power and popping missfire/erratic revs between 1500 and 2000 revs (when engine is hot or cold).

Based on info I've found in the forum I've changed dizzy cap, plugs, leads, rotor arm, and a full tank of V-Power fuel. I've also quickly cleaned the ISV with carb cleaner.

Now, two questions...

1) If I disconnect the red spade connector on the ignition coil, the popping miss-fire completely goes away, but then the car seems to run roughly and I think i can hear "pinking" at high revs. Rubjonny calls this red connector "famous" in his 16v timing guide  -  But what does it do?

Rubjonny: To achieve 2.0%, disconnect the famous "red lead" spade connector behind the coil ...

2)  How do I "clean" the throttle body - Do I have to competely remove it???


Cheers for any help.

[clipperjay]

There is a ground and a postive also a spade or hoop which is an earth strap from what I can recall on the top of the coil itself. It might be worth buying a new coil as they get very hot sometimes if left on ignition. The earth strap can be replaced also if needed. Does yours have a plastic cover if it does take it off and check the state of the top coil. Mines in bits from heat and age which started to give me partial spark or weak spark throught the dizzy.

Your symptoms sound like a possible Lamda problem have you disconnect the plug to see if she runs better?

Get carb cleaner and spray into throttle body or ISV, but cleaning your ISV doesn't mean its not knackered mate. The piston could be clogged and its running on piston screw or limp mode as I call it no power and low hunting. Go and find yourself a MKIII 16V ISV from breaker yards cheaper than VAG. 
Don't worry about over spraying with carb cleaner as its designed to burn up into the head and will do no harm.

[Leon R]

Is it a mk2 16v?

Does the car rev past 2k and pull ok? If not check your cambelt timing, dizzy, then cam/cam, but before you take the inlet off check the Pins on the plug of the ECU for corrosion and check the TCI too, the ECU and TCI control the igntion timing on valvers.

Check your TB switch, that the mechanism makes good contact and you can hear it click when you open and release it too. To clean the tb, squirt carb or brake cleaner as ClipperJay said. I'd give the whole breather system a clean tho from crankcase breather pipe/inlet trunk.

Another test you could try doing is with a timing light, connect the clamp on the king lead and point the light on the inside bonnet to watch for a good pattern when the fault occurs. (i looked directly at the light  ) When my TCI was packing in, there was gaps in the pattern so i knew it was an electrical fault.

Hope that helps a bit

[VeeDubGTI16v]

also check that the swittch on the throttlebody is actually being closed when you release the throttle! your accelerator cable might be sticking as well.

[Conker]

Thanks for the suggestions, i'll try them out later today.

Answers to questions you asked... Yes its a Mk2 16v, it does rev freely all the way to the red line, but doesn't pull that strongly.

Just to add a bit more detail - With the red spade connector on the coil disconnected it pulls strong but sounds like a lawnmower until 2000rpm. With it connected it has a miss-fire/erratic revs between 1500 and 2000 rpm.

By the way, this is the connector I'm on about:

[clipperjay]

That should be connected to the coil regardless so your coil is up the creek buddy!
J

[Conker]

Cheers Clipperjay,  hopefully that will solve it as its only a £30 part from euro car parts.  I've checked and theres no lambda sensor - perhaps thats on 8v's.

[clipperjay]

Not to put a damper on things mate, but I know that on Ktronic systems the ISV plug is very close to that coil plug it might be the ISV plug mate I would still get a second hand ISV off a MKIII just to be sure. I'm used to 8V digi's, but reckon that plug looks like ISV plug. Can you trace it? I say that becuase there is a plug on your coil already which I carelessly didn't look properly. Sorry dude!
J

[Conker]

I think its the ISV plug. The coil looks like an antique so I'll change that anyway as well - Can't do any harm!.

[clipperjay]

Yeah it should buzz and vibrate when its pluged in.
My coil looks like this. I'm awaiting for the part tomorrow £25.00
You can see its cracked on top!