1.8 GTi running unevenly

When i push the engine up above 50mph, it feels like it is "misfiring/pinking" slightly. Acceleration is fine but just feels uneven.
Does anybody know what this could be?

What fuel are you using?
how old and miles on the ht leads, spark plugs, dissy cap, rotor arm, air filter, fuel filter?
Do you hear a pinking noise under acceleration in a high gear?

Hi Mark. standard unleaded. New air filter last week. I think leads and plugs changed about a year ago.  

Did you have the timing changed to run on unleaded? If not try putting in some super unleaded petrol in, these engines run best on super unleaded.
Even if you did have the timing changed the DX engine runs it best on super unleaded, I tried normal unleaded and played with the timing but I could not get the car to run right and the power did feel a little down.
Have a look at the spark plugs and see what colour they are.
How old is the dissy cap and rotor arm, pop it off  and have a look inside to check the condition of the contacts.

Thanks Mark. Just filled it up with Unleaded too. B***er!
Not sure about dizzy cap and rotor arm. Don't think it's been changed in the 3 years I have owned it.

I would fit a new dissy cap and rotor arm see if that makes any differeance then once most of the fuel is gone try running on super unleaded and see if that makes any differance.
Be careful removing the ht leads from the dissy cap as its easy to break the connection on the ht lead when removing them, I've done it before and had to buy some new leads, just make sure you get the right type of cap as there is a couple to choose from, one with pins to grip the ht lead connection (later cars) and one without (early cars)

more info here.
http://www.vwspares.co.uk/g1electrical.php

 

mark1gls said

I would fit a new dissy cap and rotor arm see if that makes any differeance then once most of the fuel is gone try running on super unleaded and see if that makes any differance.
Be careful removing the ht leads from the dissy cap as its easy to break the connection on the ht lead when removing them, I've done it before and had to buy some new leads, just make sure you get the right type of cap as there is a couple to choose from, one with pins to grip the ht lead connection (later cars) and one without (early cars)

more info here.
http://www.vwspares.co.uk/g1electrical.php

 

Thanks M

Thanks Mark, much appreciated. Is this a good supplier of parts then? It's a 1983 1.8 GTi, so I guess I need part no. VK106 then either EVL090 or EVL096? Should I get some points and condenser too, do you think?
David

Yes I've used them but you do have to pay for postage, you can also get Dissy caps and rotor arms from Euro car parts (and other places) just make sure you get a good brand, Bosch or Beru or the ones to go for, just check the dissy cap looks the same on Euro car parts because it's easy to get the wrong part from them, also if you have a shop near you it's best to order online and collect as I find they charge more if you just turn up at the desk! (I guess they offer a web discount?)

Being an 1983 GTi I don't think your car will have points and a condenser as it should have electronic ignition?

Dissy cap with pins for the connection

http://www.eurocarparts.com/distributor-caps

Rotor arms, there is 2 types one has the rev limiter built into it and the other has no rev limiter you can use either of them but if you have the type with a limiter built in and you replace it with one with out you won't have a limiter but there is no real performance above 6,000 rpm so no point reving the car higher.

http://www.eurocarparts.com/rotor-arms

Dissy cap with pins


End of HT lead for dissy cap with pins


Dissy cap with out pins


 

Just taken my dizzy cap off and removed Rotor arm.


Cap, rotor arm, leads and plugs were replaced 2 years ago when I had a service, but I am not sure of the quality as someone else did this for me

Do you have a picture of the inside of the dissy cap?

How many miles have you done in the last 2 years since they was fitted?

Probably only around 800 miles in past 2 years

From the picture the dissy cap looks fine, there seems to be a little wear/mark on the end of the rotor arm, try cleaning the metal tip with a bit of sand paper/wet and dry etc.. to clean it up.
As they have only done 800 miles they should be fine.
Good excuse to use the car and use up the unleaded petrol in the tank and stick in some super unleaded, it may take a couple of tanks to get rid of all the normal unleaded.

Let us know how you get on and if no better then I would look at replacing the ignition bits (spark plugs, HT leads, dissy cap and rotor arm) for some better quality ones like Bosch stuff (the only stuff I use on mine as it's my daily drive). Then if no better after that I would be looking at timing marks the check the cambelt has been put on right then on to engine timing.
So still some more things to try…..

I've put a new (Beru) Rotor Arm in today which actually fits better than the older, generic one.
Once I have been for a run I will report back. Thanks for your help so far Mark

Update - went for a good run today and it seems to be more like a "flat spot" rather than a misfire. If that makes sense.