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Showing results for tags 'misfire'.
Hi everyone, I've got a really confusing idling issue that I just cannot find the solution to. It's on a Mk3 Spitfire (FD engine) 1300. The engine seems to have developed an irregular misfire and/or very rough idle (please see the two videos below, as they show it better than I can explain!) which I cannot seem to remedy, no matter what I do. The revs can vary wildly (sometimes as much as between 1500-3000rpm) running fast or nearly stalling, with no apparent pattern as to when it will/won't misfire. I have swapped in and out various components (list below) and re-set and adjusted the timing, mixture, and idle speed screw settings every which way I think I can with no results. There is good supply of fuel to the carbs, and the car has run well on this same tank of fuel before (so I don't think it's contaminated) and a good spark from each plug. If I had to describe it (and I am clutching at straws at this point), I would say it seems like the timing is maybe 'wandering', with the time of spark meaning the odd late/early/missed detonation. It's an AC Delco distributor. I don't have much knowledge about distributors, but could the centrifugal weights sticking cause this sort of issue? I haven't had chance to get my timing light out yet to see if there is anything noticeable there. Video 1 (Revs) Video 2 (Engine bay) I have swapped around and used various different combinations of the following components: - HT Leads (old set & new club supplied set) - Plugs (original Champion N9YCC & new Bosch WR7DC+) - Condenser (original & two new ones) - Points (original & club supplied set) - Distributor cap (original & club supplied) - Rotor arm (original & club supplied) - Coil (original & new Bosch) I have recently replaced the following: - Float chamber needle valves and floats. Also cleaned thoroughly, breather hole clear, valves moving freely, appears to be good fuel flow. - Air filters. I have reverted back to standard from the K&Ns I had fitted before, until I can get things running right. I have been running without air filters while trying to get the idle to settle. - Cable from coil to points (had no effect) - Cable from distributor base plate to outer casing (replacing the cloth covered original, had no effect) I have also done the following engine jobs, but before this problem arose (so hopefully won't be a part of it): - Replace manifold gasket and seal with blue Hylomar - Replace and seal around carb/manifold gaskets with Loctite 574 - Thoroughly clean and check carbs, needles, jets, etc. - Fuel pump - All fuel lines, mostly rigid copper line with Codan R9 flexible hoses in the necessary places. - In-line fuel filters (glass), one after tank, one after pump. Both appear full with good fuel flow. Any thoughts greatly appreciated... Matt
Hi all, trying to sort a misfire out on my Gt6 mk1. Initially I thought it was the coil, had a good read of the posts on here, and thought I’d covered everything. So open to suggestions really. it happens when hot, on a day like today, car starts to lose power, eventually coughing, spluttering and finally backfiring when under load. Let it cool down all fine again for a bit. I’ve looked at the ballast situation, looked at my wiring and no obvious signs of ballast resistor or wire, straight forward white/red from starter to fuse board, white to coil from ignoition. No pink flecks or white and yellow wires so have assumed not ballast. Changed to a good quality coil of 4.5ohm, same imp as rubbish inter motor one that was on there ( on local tuners advice, it’s the only one he had! ) changed back to points and condenser, to check the module, still got the problem? I’ve assumed it’s not fuel as I’ve had this problem before and you don’t get all the backfiring ‘popping’ stuff with the power drop. The engine has only covered a few thousand miles since rebuild, but the only thing I didn’t touch was the distributor. It does appear to have a slightly wobbly base plate, I was considering replacing with an complete electronic unit from the club shop if the module was found faulty, but I don’t think that’s the problem as the points proved. Was planning to take it to SEM next weekend, but not looking to hopeful at the moment. ☹️ As always any help appreciated. Thanks hag
Can anyone help with regard to a problem I cannot resolve. I have a 1972 GT6. Apart from sports exhaust and K&N filters the engine is pretty much standard. The engine has developed a problem when it gets to full operating temperature. Starting up and running while warming up it is fine. After about 10 to 15 milles and under load the engine looses power and runs very roughly. I have to ease of the throttle and allow the car to accelerate very slowly and even then it is constantly missing. If I stop and allow it to cool a bit it runs smoothly again until it heats up. The carbs were replaced about two years ago and colourtune shows them to be set correctly. The timing is correct. I have fitted new HT leads, coil, distributor cap and rotor arm. All made no difference. The car has electronic ignition. I have just set all the valve clearances and although the car then started running better the old problem came back after 30 or 40 miles. I am running out of ideas and getting fed up of buying new parts that make no difference. Anyone got any ideas where I should look next? Thanks.