Trotsky Posted June 20, 2013 Share Posted June 20, 2013 I have been getting a misfire thru 4 thou to 7 thou revs in 3/4th, doesn't seem to happen in lower gears, checked plugs and one had a light deteriation of the insulator tip so replaced the lot but no difference to the misfire . Engine is c20xe on 45 webers. Carbs recently fettled by Bog brothers in York and a nice job they did too , engine had been running sweet as , revving cleanly and pulling like a train right thru the rev range prior to this misfire problem, could it be the coil pack failing? Is there a way to check coil pack? Any thoughts? Cheers Link to comment Share on other sites More sharing options...
Lee Fowler Posted June 20, 2013 Share Posted June 20, 2013 Could be coil pack but leads give trouble as well. Lee Link to comment Share on other sites More sharing options...
Lee Fowler Posted June 20, 2013 Share Posted June 20, 2013 Might also be a fuel issue if its ok in the lower rev range. Lee Link to comment Share on other sites More sharing options...
kenny. Posted June 20, 2013 Share Posted June 20, 2013 Elimination process Russ, which you've already started with the first suspect....the plugs. As above and what the lads say coil pack and leads next......although I've personally no idea how to check the pack other than trying it on another car. How many miles did the car run perfectly for after the rebuild of the 45s? Link to comment Share on other sites More sharing options...
Trotsky Posted June 20, 2013 Author Share Posted June 20, 2013 Bout 600 miles Kenny.. I know that's an alien figure for you mate 😬 , mostly fast batting. , luckily it didn't develop when I was out giving my mates fire blade a hard time Leads next I spose? Link to comment Share on other sites More sharing options...
kenny. Posted June 20, 2013 Share Posted June 20, 2013 Alien?............I've done more than that in 5 short years 😬 So, obviously the carbs don't seem to be the issue then. Any other lads with a VX near you who'd do a coil pack swap for half an hour? Link to comment Share on other sites More sharing options...
kenny. Posted June 20, 2013 Share Posted June 20, 2013 Russ, do you have a throttle pot fitted or are you on the standard ECU? Link to comment Share on other sites More sharing options...
Trotsky Posted June 20, 2013 Author Share Posted June 20, 2013 None that I know of, no one round here man enough 😬 not that I ever see any other 7 drivers anyway I think I've been black listed coming to think about it , I have never actually met another 7 with an xe engine in all the time I've had it Link to comment Share on other sites More sharing options...
Trotsky Posted June 20, 2013 Author Share Posted June 20, 2013 Throttle pot I think, it's 3 d mapped so presume it must have a throttle pot Link to comment Share on other sites More sharing options...
Jon Stewart Posted June 20, 2013 Share Posted June 20, 2013 What ignition system are you running? Coil pack or distributor? Link to comment Share on other sites More sharing options...
Trotsky Posted June 20, 2013 Author Share Posted June 20, 2013 Coil pack Jon Link to comment Share on other sites More sharing options...
kenny. Posted June 20, 2013 Share Posted June 20, 2013 On my first HPC Russ I had a DTA ECU with the the TPS fitted. Ran great but developed a mid range splutter/hesitancy. Whipped it back to the lad who'd fitted it and apparantly the throttle pot had come loose and moved from it's initial set up parameters. Just wondering????.......seeing as the common denominator is the carb rebuild. Link to comment Share on other sites More sharing options...
Jon Stewart Posted June 20, 2013 Share Posted June 20, 2013 If you're running a coil pack then you would have a mapped 3d ignition which would include throttle pot. Just a process of elimination then really - leads, coil pack, throttle pot, fuel delivery (i've had blocked fuel filters and dodgy fuel pumps give misfires). Link to comment Share on other sites More sharing options...
andy_h Posted June 20, 2013 Share Posted June 20, 2013 If not consistent through rev range then I'd suspect fuel rather than ignition. What fuel pressure are you running and has this changed somehow (by accident or not) as part of carb work? Carbs may not be getting enough fuel at the higher revs. Fuel pump could be on way out also. I changed my Facet pump and fitted a fuel regulator. I had misfire but was through rev range so changed plugs, then leads and was resolved. Link to comment Share on other sites More sharing options...
Trotsky Posted June 20, 2013 Author Share Posted June 20, 2013 Thanks all, I'm babysitting the grandson today, so ill have a butchers in the morning, will check fuel filters and will get a set of new leads, won't harm as I've never replaced these. And I'll take it from there. Link to comment Share on other sites More sharing options...
andy_h Posted June 20, 2013 Share Posted June 20, 2013 I had to get my leads made £ as 'normal' from Halfrouds were too short. Link to comment Share on other sites More sharing options...
Jon Stewart Posted June 20, 2013 Share Posted June 20, 2013 If the coil is mounted in place of the dizzy you should be OK for lead lengths. Link to comment Share on other sites More sharing options...
Bob Simon Posted June 20, 2013 Share Posted June 20, 2013 Try routing the crank sensor cable outside of the plug wire cover. If an HT lead is perishing, the electrical interference with do strange things to the ECU functions. Link to comment Share on other sites More sharing options...
andy_h Posted June 20, 2013 Share Posted June 20, 2013 *arrowup*mine is and were still too short *arrowup*good point re crank lead, mine is over the top but wouldn't this still give a misfire through the rev range? Link to comment Share on other sites More sharing options...
k.russell Posted June 20, 2013 Share Posted June 20, 2013 Check the Venturi bolts under the carbs, I had one fall out and the Venturi was spinning at certain revs, good idea to wire the bolts up, they should have a hole through. Edited by - k.russell on 20 Jun 2013 12:52:07 Link to comment Share on other sites More sharing options...
Mavic82 Posted June 20, 2013 Share Posted June 20, 2013 Three things to check: Lock screw on the carb venturies, experinced on another sevens car recently and was a 30 second fix to weeks of fault finding. Similar issue to yours. Oil level assuming wet sump, has this on mine a number of years ago. the wet sump is very sensitive to oil level Alternator condition and wiring, not something I have had but there are threads on here about it. Regards Guy Link to comment Share on other sites More sharing options...
michaelw Posted June 20, 2013 Share Posted June 20, 2013 I had a similar thing on my VX which has throttle bodies but I suspect uses the same crank sensor which turned out to be the issue. SBD say that the crank sensor fails fairly regularly and sell an unrated one. I think it is probably due to the cable vibrating as the engine moves and because it is next to the exhaust. Trying another sensor is the easiest way to eliminate this but it does need to do it consistently to make sure. The other thing that failed on my car is the sensor wheel itself which is a pressed wheel with teeth in it which cracks and as the revs increase the crack opens, the sensor see's it as another tooth and the engine appears to missfire. This felt like a rev limiter on mine that started at about 6500 and slowly over a few weeks dropped to about 5000 when we found what the problem was but was consistently at the same revs on each journey; you couldn't rev through it. It is reasonably easy to check by taking the sensor out and turning the engine over slowly checking each tooth in turn and checking for a crack. I would check the above - plugs, leads etc - first though. Michael. Link to comment Share on other sites More sharing options...
Trotsky Posted June 20, 2013 Author Share Posted June 20, 2013 I had a similar issue a couple of years ago, similar misfire when accelerating hard and that turned out to be a missing Venturi locking screw, that was the first thing I checked this time but they are all in place, haven't had chance to check if they are tight tho , will do when I get a minute. I have just noticed a tiny crack in the outer of one of the ht leads, just as it bends away from the coil pack, which is sited more or less between the cams so I hopefuly won't have a problem getting correct length replacements. One thing that has always puzzled me , at the rear of the exhaust cam is a ally blanking cap where I presume a distributor would have sat, there is a multi point electrical connection built into it but no wire connected and non hanging anywhere unconnected , what is this for? I'll be having a good old fettle over the weekend starting I think with another butchers at the carbs Venturi screws then onto filters and replacement leads, forecast is sh1te tho so chances of a test run look remote Edited by - Trotsky on 20 Jun 2013 16:48:10 Link to comment Share on other sites More sharing options...
Bob Simon Posted June 20, 2013 Share Posted June 20, 2013 at the rear of the exhaust cam is a ally blanking cap where I presume a distributor would have sat Cam angle sensor for the OEM Bosch EFI. The sensor is still there, but the trigger wheel was probably removed by Caterham or Swindon. Link to comment Share on other sites More sharing options...
Trotsky Posted June 20, 2013 Author Share Posted June 20, 2013 Thanks for that Bob, see if you don't ask you never find out. Link to comment Share on other sites More sharing options...
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