jas Posted August 1, 2015 Report Share Posted August 1, 2015 Hello Gents, Firstly I will apologise I'm not mechanically minded at all... My 72 Pi 6 had an engine rebuild 2 years ago and have down maybe 5k in it since without any issues. It went in for an oil service and I changed leads to flamethrower red rotor arm plugs etc. When I got it back it seemed fine but started to firstly backfire then mis in low revs in second and third mainly when going through towns etc but would clear when in fourth and higher revs. Had it back and checked out but problem still there, seems more when under load. The metering unit was all reconditioned at same time as engine. It runs fine on the open road its when its in town it feels like the plugs are fouling and it's going off on a cylinder. Does the fact it runs ok on the open road rule anything in or out? Checked the "pulses" from injectors all feel strong. Should I try new coil? Is it getting to much fuel? I'm just little puzzled as it has run fine...could it be something as simple as dodgy lead? Any help appreciated Regards Has Quote Link to post Share on other sites
kcsun Posted August 1, 2015 Report Share Posted August 1, 2015 Have you still got the old parts you changed? Swap them all back and see if the problem disappears If it does systematically change the new bits until you find the culprit There are lots of dodgy parts about now, think everybody has given up on quality over quantity!! Kc Quote Link to post Share on other sites
marki Posted August 1, 2015 Report Share Posted August 1, 2015 Electronic ignition.... Change back to points....Ask me how I know. Quote Link to post Share on other sites
Steves_TR6 Posted August 1, 2015 Report Share Posted August 1, 2015 First rule with classic cars, check what you changed last! Does sound electrical to me, something not right with the new parts,mor you've disturbed something. I had a similar problem with my last tr6, eventually retraced to a LT ignition wire rubbing and intermittently shorting out. Good luck finding the problem Has, let us know how you get on :-) Steve Quote Link to post Share on other sites
jas Posted August 1, 2015 Author Report Share Posted August 1, 2015 How do you know? Quote Link to post Share on other sites
tonytr Posted August 3, 2015 Report Share Posted August 3, 2015 Hi Has I had the same problems and went through everything replacing everything i could As a last ditch attempt i changed back to points from electronic module and hey presto the car flew again as if all the horese where put back I dont know why but i am very happy i went back to points Tony Quote Link to post Share on other sites
Sapphire72 Posted August 3, 2015 Report Share Posted August 3, 2015 Hello Gents, Firstly I will apologise I'm not mechanically minded at all... ..could it be something as simple as dodgy lead? Any help appreciated Regards Has Yes. Pull ignition wire ends off the spark plugs & hold near cylinder head, one at a time. Have assistant crank engine 2-4 turnovers with ignition switch, watch for spark between ignition wire & head. You should see a strong spark. Easier to see in a dark garage. Alternatively, pull spark plugs, look that all tips are consistent colored. Sometimes rotors are not pushed home all the way, same with ignition wire leads. Quote Link to post Share on other sites
Denis Posted August 3, 2015 Report Share Posted August 3, 2015 Yeah, but did you have to leave it blocking the road up! ;-) Quote Link to post Share on other sites
jas Posted August 3, 2015 Author Report Share Posted August 3, 2015 Thanks gents having a look on Wednesday will let you know how I get on... Regards Jas Quote Link to post Share on other sites
Crawfie Posted August 3, 2015 Report Share Posted August 3, 2015 From experience............................. Get rid of any "new Lucas " stuff. HT leads-replaced with copper "bumblebee" leads Coil-My last failure-Lucas Sports Coil-Now replaced with an NGK one Dizzy Cap,Rotor,Condensor,points-Replace with Dizzy Doc stuff. I go to TRshop for any sensors ie temp sender, voltage regulator etc . This is on the recommendation of Stuart. They are extremely helpful. I've bought old stuff to replace new stuff that has failed !!! There is a load of "cr*p" out there. Personal choice, use NGK sparkplugs. Quote Link to post Share on other sites
jas Posted August 3, 2015 Author Report Share Posted August 3, 2015 Thanks again I will report on my progress....! Quote Link to post Share on other sites
jas Posted August 5, 2015 Author Report Share Posted August 5, 2015 Well changed back to old leads and changed rotor arm ( both red ones) problem seems to have gone....touch wood... Quote Link to post Share on other sites
Blue cedar Posted August 5, 2015 Report Share Posted August 5, 2015 Good for you, Has. So what happens if you change and then tested each item one by one, so as to isolate which lead is faulty or rotor ? Maybe just one faulty lead and then you can investigate what is faulty with that item ? You could then jump up and down on the part and get rid of any frustration. Mindful, you may not be bothered ! Cheers Peter Quote Link to post Share on other sites
acaie Posted August 5, 2015 Report Share Posted August 5, 2015 First rule with classic cars, check what you changed last! Does sound electrical to me, something not right with the new parts,mor you've disturbed something. I had a similar problem with my last tr6, eventually retraced to a LT ignition wire rubbing and intermittently shorting out. Good luck finding the problem Has, let us know how you get on :-) Steve The above is the second rule. The first rule is if it ain't broke, don't fix it. Quote Link to post Share on other sites
jas Posted August 5, 2015 Author Report Share Posted August 5, 2015 Gents there is a lot to be said for "if it ain't broke"...may have to do as suggested and test each one individually to satisfy my curiosity now. Many thanks again Jas Ps apologies I typed my name as Has before...specsavers job Quote Link to post Share on other sites
peejay4A Posted August 5, 2015 Report Share Posted August 5, 2015 If it ain't broke, fix it 'til it is. Always worked for me. Quote Link to post Share on other sites
Blue cedar Posted August 5, 2015 Report Share Posted August 5, 2015 Has or Jas ? Good to know that it is a part specific, surely and not something reacting further up or down the line !!!!!! Cheers Peter Quote Link to post Share on other sites
acaie Posted August 5, 2015 Report Share Posted August 5, 2015 If it ain't broke, fix it 'til it is. Always worked for me. I tend to forget that, unlike me, many enjoy the fixing at least as much, and if not more than the driving, judging by the ratio of the hours spent fixing to the hours spent driving. Long may the classic car game remain a broad church. Quote Link to post Share on other sites
jas Posted August 6, 2015 Author Report Share Posted August 6, 2015 Ok so maybe I spoke to soon....filled up car tonight and went out for wee run..stopped after 10 miles car running fine. Continued to next town about 4 or so miles and stopped for ten mins maybe,got back in car missing in all gears again...turned around got onto motorway and it cleared when given blast. Same next town when low running. The car is on points already as I know a couple of comments said to change to them. The coil was hit but not mega hot not sure what it's supposed to be? Going to try changing coil first the dizzy cap if that doesn't work. Could it be fuel pressure? Or bad fuel? Use suoer from same place all the time..Had a couple of small backfires as well. Thanks for any help Jas Quote Link to post Share on other sites
Peter Cobbold Posted August 6, 2015 Report Share Posted August 6, 2015 Fuel filter maybe. Quote Link to post Share on other sites
jas Posted August 6, 2015 Author Report Share Posted August 6, 2015 Hi Peter It was changed recently as well Quote Link to post Share on other sites
Peter Cobbold Posted August 6, 2015 Report Share Posted August 6, 2015 What does the voltage do when in town and misfiring and on the open road at sustained rpm? I'm wondering if the pump is seeing too low voltage when pottering and the fuel pressure dropping. Peter Quote Link to post Share on other sites
jas Posted August 6, 2015 Author Report Share Posted August 6, 2015 I don't think there was much variation from memory Peter but will check it out tomorrow I'm fitting new coil after work see if that makes any difference....will report back.. Regards Jas Quote Link to post Share on other sites
Peter Cobbold Posted August 6, 2015 Report Share Posted August 6, 2015 A duff plug can also seem to be OK at higher rpm and faulter at lower rpm. Lots of rubbish plugs around. Quote Link to post Share on other sites
jas Posted August 7, 2015 Author Report Share Posted August 7, 2015 Changed full set of BP6ES....Both times runs ok for 30 miles or so then starts. It's always starts at low revs and usually when I have stopped somewhere presumably when engine is at hottest? Quote Link to post Share on other sites
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