SamC Posted March 6, 2022 Share Posted March 6, 2022 Hi All, I'm after a bit of a hand diagnosing very rough running please. Hoping peoples collective experience can shortcut my investigations!I went out for a run in my CSR260 today and about 2 miles in it developed a heavy 'misfire'. On acceleration it wasn't clean but wasn't terrible, on part throttle it was horrendous. Jerky, juddery etc. it stalled every time it dropped to idle.I limped back home and took the plugs out, all were thick with soot, and one was heavily corroded on the external portion.This week I've been rebuilding the swirl tower to try and cure a leak, so yesterday it idled for two 10 min periods as I checked the oil level and monitored for leaks. It idled smoothly throughout.So, my first port of call is to replace the plugs, but I suspect they are symptom rather than cause. Any one got a similar experience? I'm curious about the lambda sensor... Link to comment Share on other sites More sharing options...
SM25T Posted March 6, 2022 Share Posted March 6, 2022 Disconnect the lambda sensor. If the engine runs ok, replace it. Link to comment Share on other sites More sharing options...
Area Representative Geoff Brown Posted March 7, 2022 Area Representative Share Posted March 7, 2022 If the plugs are in that condition then suspect other electrical components, their connections & the Lambda sensor.Obviously an annual plug removal, inspection, clean & gap check has dividends ! Link to comment Share on other sites More sharing options...
SamC Posted March 7, 2022 Author Share Posted March 7, 2022 Cheers all! Hopefully I've just got to the bottom of this.New plugs fitted, no change, lambda disconnected no change. Starting from cold it was even more evident just how rich it was running.After a further hunt round I found that the TPS connector had broken (see photo - this was after it had an extra wiggle!). I have only had the car a few weeks and must have knocked it as I was fitting the maintenance charger wiring last week. I suspect the external plug got to that state having lived at a dealer for 5 months over winter.New TPS on order - I'll update here for future reference once it arrives. Link to comment Share on other sites More sharing options...
Andy Doughty Posted March 7, 2022 Share Posted March 7, 2022 It may be worth using copper slip on the plugs as I noticed they a very rusty in your picture. The Duratec's plug cap is not not totally waterproof. You don't want a seizes plug in the alloy head.My engine was getting standing water in the cam cover and this drained down past the plug cap and rusted the plugs.Worse after washing the car. A top cover prevents this.cheers Link to comment Share on other sites More sharing options...
SamC Posted March 7, 2022 Author Share Posted March 7, 2022 Yeah, good call, will do.Cheers! Link to comment Share on other sites More sharing options...
Roadsport06 Posted March 7, 2022 Share Posted March 7, 2022 Watch when torquing spark plugs if you use a grease. Torque settings are usually specified without a grease and you could strip threads if you tighten to that torque using grease Link to comment Share on other sites More sharing options...
7 wonders of the world Posted March 7, 2022 Share Posted March 7, 2022 Duratec uses taper seat plugs so the above wont apply as you install to contact plus 1/8 turn as apposed to crush washer plugs which could be over tightened. Link to comment Share on other sites More sharing options...
aerobod - near CYYC Posted March 7, 2022 Share Posted March 7, 2022 9-11Nm on dry thread taper plug in Duratec. Best to stop moisture getting into plug wells as opposed to putting lubrication on the threads, if possible, as the plugs could loosen due to the lubrication, for the relatively low torque values specified. Link to comment Share on other sites More sharing options...
Area Representative Geoff Brown Posted March 8, 2022 Area Representative Share Posted March 8, 2022 1/8 to 1/4 turn is sufficient with a taper seat & of course no lube on the seat.Or if in doubt tighten till the plug shears then back half a turn !! Link to comment Share on other sites More sharing options...
SamC Posted March 8, 2022 Author Share Posted March 8, 2022 Thanks all.My rule of thumb is to drop the torque ~25-30% when lubricating the thread (inc when using wet loctite). Also, avoiding lubricating the taper/under head on fasteners as that will promote them losing preload.I know many will be despairing at me here and prefer to use 'feel', but I'm very much in the 'torque brigade' on structural/critical parts.I'll also go around the plug sealing and check that they are offering some resistance to water ingress. Link to comment Share on other sites More sharing options...
SamC Posted March 8, 2022 Author Share Posted March 8, 2022 New TPS fitted and (unsurprisingly) runs like a dream.Cheers all! Link to comment Share on other sites More sharing options...
Wrightpayne Posted March 8, 2022 Share Posted March 8, 2022 Well done on the fix.Re seven washing and filling the plug recesses with water - I mostly wash and rinse the bonnet off the car (on the grass) then put it back on the car to wash the rest of the car. Link to comment Share on other sites More sharing options...
SamC Posted March 8, 2022 Author Share Posted March 8, 2022 Good tip thanks, sounds like a sensible technique. Amazingly I haven't actually washed it yet!I've concentrated on cleaning the interior, engine bay, and the rear suspension well.I think I'm subconsciously saving the exterior (and exhaust polish!) as the cherry on the cake! Link to comment Share on other sites More sharing options...
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