rednfast Posted September 18, 2012 Share Posted September 18, 2012 Hiya, I have a problem that when I am cruising (foot steady on gas) in my Mk2 the car seems to miss intermittently, almost like one cylinder is dropping power occasionally. The feeling is similar to dabbing the brake for an instant. There is no change in note in the engine. It does not do this while sitting idle and holding the revs steady, so only happens under load. It is noticeably worse in lower gears, by 4th its almost non existent but still there. Just a note on what has been done to the car recently... New alternator. Single Barrel carb reconditioned at carb shop. Distributor checked over by Quality Rebuilds, both dizzy and vac advance check out fine according to him. Replaced the points and rotor. Coil is a new unit about 3 years old. Set the Dwell (50deg) and Timing (10deg). Starter is in at shop getting fixed atm as it was making a horrible noise (intermittent screeching) for ages after start up (10 mins sometimes). Any ideas would be great, I'm kinda stumped at this point. Quote Link to comment Share on other sites More sharing options...
Rookie Posted September 18, 2012 Share Posted September 18, 2012 Plugs? Quote Link to comment Share on other sites More sharing options...
rednfast Posted September 18, 2012 Author Share Posted September 18, 2012 Changed them twice since this problem started. What plugs should I be using just incase I got the wrong ones? I have Bosch WR7DC+ in there atm with 0.6mm gap. Quote Link to comment Share on other sites More sharing options...
Beaver Posted September 18, 2012 Share Posted September 18, 2012 checked valve clearances? had a simlar issue (although it was accompanied by an audiable missfire) which turned out to be one of the valves set wrong Quote Link to comment Share on other sites More sharing options...
rednfast Posted September 18, 2012 Author Share Posted September 18, 2012 I have set clearances to 0.25mm Inlet, and 0.55mm Ex. Should they be set hot or cold? I am guessing that might make a diff? EDIT: The car is a 1300 mk2 if there is any diff between models? Quote Link to comment Share on other sites More sharing options...
Rookie Posted September 18, 2012 Share Posted September 18, 2012 Is the idle screw set properly? what about the vacuum advance? Quote Link to comment Share on other sites More sharing options...
rednfast Posted September 18, 2012 Author Share Posted September 18, 2012 Idle is set to 900rpm at running temp (about 1/4 on the gauge). Mixture set by winding in till almost stall then back to clean idle and another twist after that. I did notice that after the car has sat for a while after driving and its started while still hot the rpms drop pretty low like 7-800rpm or less maybe, assuming this is because the water gets even hotter after it sits around for a bit? EDIT: Its an auto choke carb. Guy from quality rebuilds said vac advance was fine, and accuracy upto 6k rpm was almost perfect. Quote Link to comment Share on other sites More sharing options...
Rookie Posted September 18, 2012 Share Posted September 18, 2012 Thrown a compression tester at it? What about vacuum leaks? Quote Link to comment Share on other sites More sharing options...
Steelies Posted September 18, 2012 Share Posted September 18, 2012 vac leaks Quote Link to comment Share on other sites More sharing options...
rednfast Posted September 18, 2012 Author Share Posted September 18, 2012 Hadnt thought of that. I did put a new PCV valve on the crankcase vent a while back, as it didnt have one before. It was just venting to atmosphere with the intake bit plugged off. Quote Link to comment Share on other sites More sharing options...
shizzl Posted September 18, 2012 Share Posted September 18, 2012 i had the same issue with my cortina..i replaced the vac lines,and it sorted it.... Quote Link to comment Share on other sites More sharing options...
coldturkey Posted September 18, 2012 Share Posted September 18, 2012 I had a dead similar problem in the past, turned out to be that the lobes were worn down on the shaft of the dizzy meaning my points gaps werent ideal no matter what I set them to and it was missing every so often. Took me a while to figure that one out.. Quote Link to comment Share on other sites More sharing options...
rednfast Posted September 18, 2012 Author Share Posted September 18, 2012 @coldturkey That is interesting I went and checked it... The gap is supposed to be 0.5-0.71mm or so. But when I check the dwell its only at 40deg at 0.71mm gap, so I need to close the gap. Closing to to obtain the correct dwell of 50deg takes it below the minimum of 0.5mm quite alot below, its at like 0.3mm or so. How did you fix that in the end? This is with brand new points btw. Quote Link to comment Share on other sites More sharing options...
coldturkey Posted September 18, 2012 Share Posted September 18, 2012 Yeah, thats the same problem I had. There was not enough variation in the points gap between fully open and fully closed. edit: the lobes were worn down so the shaft was too much like a cylinder...instead of like a square with rounded edges(?) if you get what I mean I fixed it with a new dizzy lol Quote Link to comment Share on other sites More sharing options...
rednfast Posted September 18, 2012 Author Share Posted September 18, 2012 Well mine is pretty square still, I may just have to ignore the dwell and set the gap instead, its possible the dwell meter thing is off. Its pretty old. Once I get the starter back in Ill give these two things a try. Removing the PCV and plugging the inlet manifold. And setting the point gap using feelers rather than dwell meter. Quote Link to comment Share on other sites More sharing options...
shizzl Posted September 18, 2012 Share Posted September 18, 2012 oh yeah, i also reset my timing and cleaned out the PCV. it still has a slight hesitation when its cold but from there on its good as... im gonna rip out the auto choke,i think thats half the issue Quote Link to comment Share on other sites More sharing options...
coldturkey Posted September 18, 2012 Share Posted September 18, 2012 yeah it was still like a square, but it had worn enough for it to be an issue. If you set the points gap a bit on the "narrower" side, check to see if you have an improvement Quote Link to comment Share on other sites More sharing options...
J-W-G Posted September 18, 2012 Share Posted September 18, 2012 Had this exact problem with my mk2 was condenser and vac Quote Link to comment Share on other sites More sharing options...
rednfast Posted September 19, 2012 Author Share Posted September 19, 2012 I chucked the recond starter in, which fixed the unrelated noise problem. Then reset the points gap to 0.6mm, reset the timing. Removed the PCV valve. No difference, still misses while cruising. I guess Ill try rechecking the valve clearance, and do a comp test. Failing that Im gonna head down and get some new vacuum tubes. Quote Link to comment Share on other sites More sharing options...
Beaver Posted September 19, 2012 Share Posted September 19, 2012 may try track down another dizzy to test out? cant hurt for the 5 mins itl take to swap and set timeing again Quote Link to comment Share on other sites More sharing options...
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