16v miss fire

[bodga]

I'm struggling a bit here, my golf has been fine for years but now its developed a miss fire under load. From cold she drives fine, I never give full throttle until oil temp reaches 50 deg  on the MFA, but as she warms up it starts to miss fire, gradually getting worse. If I don't accelerate hard, there is no problem and she ticks over fine.

I have swapped the dizzy and in tank fuel pump. Spark plugs look good, light tan, beige colour, so in my opinion not over fueling, possibly loosing spark?? I've tested the primary and secondary resistances on the coil and that's OK according to the Haynes bible. Coil was cold though.
Anyone had this problem before? I'm suspecting the high pressure fuel pump but, when I'm giving it full throttle hard and its miss firing, I turn the ign off and on again whilst driving, it resets the fault for about 5 mins and its flying again pulling well with no missfire . Out of gear it revs fine, up hill low revs low speed it will also missfire.
Any help appreciated, its sending me grey!

[Thom89]

Start with a new set of either Bosch or NGK triple electrode plugs, 16v's can be quite touchy, so a good starting point. Also make sure you're using decent fuel, no supermarket stuff, either Shell, BP, etc

Thom

[bodga]

Never thought to change the plugs, but thinking about it they are due. I replaced them in July 2009 when I brought the car. Just ordered NGK triples, there is a sale on again at euro car parts up to 50% off 
Will let you know if it sorts this out.

[bodga]

Replaced the plugs, still the same. 

Anyone know if there is a diode or something In the rotor arms of these distributors? I remember a few years ago my dads rover 414 would just die on him when the car warmed up,  it ended up that the rotor arm was the cause.

[clipperjay]

I would have pulled each plug out and checked for spark against the head first.
If its a strong arc then all is fine with it?
If its dodgy then start checking leads and king lead,dizzy cap, rotor or even a dodgy coil?

[Gambit]

When it starts misfiring how does the rev counter behave? If its very erractic i.e. jumping all over the place randomly then the hall sender inside dizzy is breaking down. It gets worse as car heats up. You can replace hall sender but easier to replace the dizzy in full

Ideally get a lend of a known good dizzy, run it and see does it still miss. If not then hall sender is your problem

[bodga]

I have replaced the dizzy cap and leads, still no joy. 

 The rev counter is fine gambit, does that prove the hall sender is OK? I have a spare dizzy because I replaced mine with one off eBay due to mine leaking oil though the rotor arm shaft. Is there any way of testing the hall sender without damaging it?

I also checked the connections to the temp senders on the side of the head. They all read about the same, (20 ohm difference between the 3 readings) I have swapped the wires on these but haven't been back out in it yet. One of the wires goes to the ECU under the scuttle, I'm presuming has something to do with the electronic advance because a vacuum pipe connects there too. Could that unit be faulty or are they bullet proof?

[Gambit]

If the rev counter aint going haywire when its misfiring then generally not the hall sender.

Was it misfiring with the old dizzy? Stick it back on and give it a run up the road.

Is the ebay dizzy a bosch item? I wouldnt use anything but a bosch dizzy on them

[bodga]

Still struggling with this loss of power folks

I have swapped dizzy, ign amp and the other ECU that the vacumn pipe is connected to. replaced in tank pump, removed and cleaned filter gauze around high pressure pump. timing is spot on with timing lamp. i have replaced fuel pump relay with another, but not new one.

I have found now though as the car warms up and the spluttering starts, if i remove the fuel pump relay and refit whilst im driving (on a private road of course) the fault clears and she is pulling really strong again but this doesnt last long. if i keep doing it though she will be fine for a few minuites.

It has never cut out on me and ticks over fine. Any advise is appreciated

Rev counter is smooth Gambit, its the same on the old dizzy too.

[clipperjay]

When she struggles stop the car dead and check what state the plug tips are in I'm guessing over fueling might be an issues easily check if the plugs are rich or lean?
Has the fuel filter in the back been changed?
Check fuel pump near the back under the car for damaged wires or leaking accumulator?
Worst case a worn valve seat on one cylinder check compression so they are even through one to four?