dobbo Posted 12January, 2023 Report Share Posted 12January, 2023 Went from Swansea to Mooney Mooney via the M1 on Wednesday in my 1980 928 and about halfway there it started misfiring on 1 or 2 cylinders under load. Was doing about 120kmh and up some decent climbs engine temp was normal and if I backed off or was going downhill it was'nt as bad. Had lunch at the Bowlo (car had cooled down) and went home via the old road at 60 to 80kmh and it ran a lot better but was misfiring a bit when I got back on the M1 and was doing 100 to 110kmh. Sounds like spark breaking down as had happened in 2019 when I replaced the plug leads it rectified the issue. So the leads are only a bit over two years old and done only about 12000kms. At the same time I checked the dizzy cap and rotor and they seemed ok and the coil looks original. The green wire has been affected by heat but thats fairly normal for an old 928. Do the 928 brains trust think it's time to replace the coil or could the leads have gone bad after such a short time. I don't want to spend another $500 on Buru leads again if I don't have to. I also replaced the sparkplugs when I fitted the new leads advice welcome. Quote Link to comment Share on other sites More sharing options...
LeeM Posted 12January, 2023 Report Share Posted 12January, 2023 Plugs I reckon. Different kinda vehicle, but my Hiace van was doing the same, and the RAA diagnosed a misfire in cylinder one. I pulled the plug out, and the electrode was missing 😅🙄 Quote Link to comment Share on other sites More sharing options...
Buchanan Automotive Posted 12January, 2023 Report Share Posted 12January, 2023 Install new spark plugs and re-test tomo 1 Quote Link to comment Share on other sites More sharing options...
dobbo Posted 14January, 2023 Author Report Share Posted 14January, 2023 Thanks lads will chase some new plugs up next week. Quote Link to comment Share on other sites More sharing options...
OZ930 Posted 15January, 2023 Report Share Posted 15January, 2023 Have you tried pulling one plug lead off at a time to isolate which plug is playing up? Yeatesy and tomo 2 Quote Link to comment Share on other sites More sharing options...
dobbo Posted 16January, 2023 Author Report Share Posted 16January, 2023 Oz it only happens under high load and when hot. Went for a 30k drive yesterday to try and replicate the fault and it did not play up. Have not had time to check plugs yet. Quote Link to comment Share on other sites More sharing options...
DaveO90S4 Posted 17January, 2023 Report Share Posted 17January, 2023 Hi Dobbo - in the time it took you to do your 30km drive you coukd have replaced all spark plugs, couldn’t you? Quote Link to comment Share on other sites More sharing options...
dobbo Posted 17January, 2023 Author Report Share Posted 17January, 2023 Dave have not purchased new plugs yet. Rain forecast for Thursday Friday so will replace them then. Quote Link to comment Share on other sites More sharing options...
dobbo Posted 21January, 2023 Author Report Share Posted 21January, 2023 Replaced plugs on Friday. Went from Chinese made BOSCH WR8DC to Thai made NGK BPR6ES. Old plugs were white with a slight grey colour about half to a third away round the insulator indicating a lean condition. Questions is it a 3mm allen key that fits the air\fuel ajustment screw. Which direction to richen it up and by how much. Note car starts,idles and did run fine only hiccup was misfire under heavy load and prolonged high speed. Quote Link to comment Share on other sites More sharing options...
DaveO90S4 Posted 22January, 2023 Report Share Posted 22January, 2023 On 21/01/2023 at 20:43, dobbo said: Replaced plugs on Friday. Went from Chinese made BOSCH WR8DC to Thai made NGK BPR6ES. Old plugs were white with a slight grey colour about half to a third away round the insulator indicating a lean condition. Questions is it a 3mm allen key that fits the air\fuel ajustment screw. Which direction to richen it up and by how much. Note car starts,idles and did run fine only hiccup was misfire under heavy load and prolonged high speed. Quote Link to comment Share on other sites More sharing options...
P-Kay Posted 23January, 2023 Report Share Posted 23January, 2023 On 21/01/2023 at 21:43, dobbo said: Replaced plugs on Friday. Went from Chinese made BOSCH WR8DC to Thai made NGK BPR6ES. Old plugs were white with a slight grey colour about half to a third away round the insulator indicating a lean condition. Questions is it a 3mm allen key that fits the air\fuel ajustment screw. Which direction to richen it up and by how much. Note car starts,idles and did run fine only hiccup was misfire under heavy load and prolonged high speed. Clockwise is rich - make sure you ONLY do small increments https://jimsbasementworkshop.com/CIS/pages/test_mixtures.html Quote Link to comment Share on other sites More sharing options...
OZ930 Posted 23January, 2023 Report Share Posted 23January, 2023 Have you checked the fuel filter ? Quote Link to comment Share on other sites More sharing options...
dobbo Posted 23January, 2023 Author Report Share Posted 23January, 2023 Thanks P-Kay will chase up long allen key when I come back from holidays so will update next month. Oz fuel filter not due for change for another 3000ks. The filter in the fuel distributer is seized in and I have'nt been able to get it out even with a few hits from a chisel. If adjustment fails will go down filter replacement route and may have to take top off fuel distributer as a last resort. From memory I tried flushing out the FD filter from the outside with WD40 years ago. Any advice or tips welcome however leaving for Perth tomorrow so won't be able to reply till next month. Quote Link to comment Share on other sites More sharing options...
dobbo Posted 15March, 2023 Author Report Share Posted 15March, 2023 Turned mixture screw CW half a turn. Took car on short test drive and ran ok. Will check sparkplugs after a few longer runs. Quote Link to comment Share on other sites More sharing options...
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