adam r.s.t

hello,i have an 83 xr3,it has a misfire problem which is very random,i replaced plugs&leads was fine for a few days,then started again,it pops and bangs,sometimes i have to pull over&try it again after 10mins,i have replaced dizzy cap&arm,again fine for a while,then same thing,with the car running i have taken air filter off&held my hand over carb to try to get any crap out,changed the fuel filter next to the carb and also the coil,yesterday it was fine,today i cant get it off drive as its missing so badly,any ideas help would be much appreciated as its doin my head in now!!thanks adam

stevo123

You have done the basics already, the xr3 does not suffer with missfires a lot in my experience. I have seen broken down leads that dance with blue sparks when it's dark and short out onto the head but your's sounds worse than that. Have you considered it may not be electrical, you may have a sticky or burnt valve. Get yourself a compression tester and, with the ignition coil disconnected and the throttle fully open, turn the engine over on the key. Count how many rotations it takes to reach max pressure in each cylinder. Should take no more than a couple of seconds and you should be looking for between 150-180 ish psi. A stuck or burnt valve will see none or very little pressure build up. As you take out the plugs one of them may still be wet thus giving you a clue as to which cylinder is the duff one.

Finally you have got the leads on 1-2-4-2, anticlockwise looking at the dizzy cap? Set the engine to TDC and make sure the rotor arm is pointing at number one plug also.

Best of luck - you just can't beat a nice Mk3 IMO.

adam r.s.t

thank you,i will get a tester as it did seem like it was jumpin a bit earlier when i was tryin to start it???also did u mean 1-2-4-3 with the leads??

Rax

iTrader: (1)

1342 I would of thought.Check the coil,wipe around the top of it to see if its cracked.Had this on a few cars cortina,astra gte,metro I only saw one as it was pitch black.Would run fine somes time until warm.Other than that dizzy,ignition amp maybe ?.

stevo123

1-3-4-2 for sure.

Although I think that the OHV engines of that eara were 1-2-4-3 though so that might be were you are getting that from.

Mrbump

I had the same problem a while ago on my 81 X-reg, I changed the dizzy as my problem was the 2 cables coming out of it were on there last legs and weren't far away from snapping, I alson changed the cap and rotor arm, and fingers crossed its been fine mate look at the 2 cables coming out the dizzy, sounds electrical.
Joe