Roy Posted March 21, 2010 Share Posted March 21, 2010 I built a 2.4 to go in my B series but it has a low rev problem. Under 2k it is not firing on all cylinders, once it gets to about 2k and over it is sweet as a nut and pulls like a train. Tickover is uneven because of the occasional spark on the front cylinder. What could be causing this? Spec is: 2.4 Frontera Engine, rebored new pistons adjustable vernier Kent OP234 cam set up as per kent cams instructions New distributor from a 2.2 2.2 Carlton injection system Timing set correctly New plug leads-plus swapped them over and have the same problem. The distributor was new and untested when I fitted it, could it be this or something on the amplifier side of the ignition? Could it be mechanical, ie something wrong with the cylinder (the front one)? Not sure where to start. I took the car round the block today for the first time which highlights the problem, pulling away it misses a little and as the revs build it is fine. Would appreciate some suggestions Quote Link to comment Share on other sites More sharing options...
Shuviteer Posted March 21, 2010 Share Posted March 21, 2010 I've just had a similar problem on a Cav.Turns out it was a dodgy earthing point.Might be worth looking over them all again.Could also be the coil breaking down. Quote Link to comment Share on other sites More sharing options...
manta400john Posted March 21, 2010 Share Posted March 21, 2010 Is it definately an HT misfire. Air intake leak?...this would be apparent at idle/low revs but not higher up the rev range. Where does the servo pipe join the manifold....is it near to no. 1 cylinder? Might be worthwhile blanking this off to test/illiminate,just watch your brakes if test involves driving it!! Or minifold gasket? Whatever's causing it hope you get it sussed. John. Quote Link to comment Share on other sites More sharing options...
mantadoc Posted March 22, 2010 Share Posted March 22, 2010 Are you sure it is always cylinder 1? If so that points to the things cylinder one doesn't have in common with the rest. Plug Plug lead Port on dizzy cap Compression check? Leaky valve having less effect as revs pick up? Rings? Inector Dizzy cam / rotor pickup Rockers Loose nut if not new? Wires to injector......... Quote Link to comment Share on other sites More sharing options...
Roy Posted March 25, 2010 Author Share Posted March 25, 2010 Thanks for your replies guys, just trying to get a weekend to coincide with some non rainy weather and I'm going to hit it with all your suggestions! I know its the front cylinder because I put the light up spark plug covers on and it was onyl that one that stopped flashing, also if you use a strobe light it only accasionally works on lead 1 until you raise the revs. Hoping its not mechanical. Quote Link to comment Share on other sites More sharing options...
mantadoc Posted March 25, 2010 Share Posted March 25, 2010 OK so that points to electrical not internal fault. If tested lead, plug, dizzy cap and rotor arm by substitution then........... I would be very tempted to rotate the dizzy 90 degrees in situ and move the plug leads round 1 position and re - time it and see if the fault moves cylinder, if the fault doesn't you are looking at lobe on the dizzy or chopper. (as long as you are REALLY sure that only cylinder 1 is affected) Electronic dizzy or points???????????????? Quote Link to comment Share on other sites More sharing options...
Roy Posted March 25, 2010 Author Share Posted March 25, 2010 (edited) Carlton 2.2 injection system with Carlton elec dizzy. Got a spare so was thinking of swapping it out just to see........ Edited March 26, 2010 by Roy Quote Link to comment Share on other sites More sharing options...
Roy Posted April 1, 2010 Author Share Posted April 1, 2010 Well as a bit of an update, I found the no1 cylinder had a different type of spark plug in (mixed up from another set that was being used for testing). Changed that but made no difference. Then I noticed froth in the radiator and some mayonnaise in the rocker cover. I did a sniffer test but it came up negative? Could this be condensation from starting and stopping over the year without actually driving the thing? I'm going to flush the engine and drop the oil to see if things improve. Quote Link to comment Share on other sites More sharing options...
Roy Posted April 18, 2010 Author Share Posted April 18, 2010 As an update to this I changed the oil before running it to an mot, it ran OK over there, some pinking under load and missing slightly every now and again. At the MOT we tried altering the timing but it didn't improve anything. It only failed on emissions but afterwards I found a plug lead had been knocked loose when the timing was adjusted! Put it back on and it ran just the same as on the way to the MOT. At home I changed the distributor unit complete - no change. Then checked the came timing on the OP234 cam....103 deg ATDC gave full lift on the front inlet rocker. THats what it should be as per spec of OP234. So its still not right. I've an adjustable vernier on the cam, I was wondering whether to try advancing it a degree or so to see if it helped with the pinking? Quote Link to comment Share on other sites More sharing options...
mantadoc Posted April 18, 2010 Share Posted April 18, 2010 Compression test? Is that cam suited to hydraulic lifters???? You're a way above the base circle so not sure the usual running setting like on a Manta would be correct. Are you sure it is intermittant at low revs? Pull a lead and see. If permanent it could be carrying a cylinder at idle. Lets flip it another way. You're assuming that there is no spark on cylinder no1. As we know you need three things, fuel, air and spark at the right time. On Mantas and probably the carlton injection it isn't sequential (at least not on LE Jetronic). Half the mixture gets squirted at a closed valve and half at an open one (A 4 stroke fires each cylinder every other rotation) so no problem with swapping cyl 1 and 2 injector wiring. Best case disturbing it fixes it worst case you move the fault to cyl two and have your cause and effec. If it stays the same and you have eliminated a possibility. Also never listen to anything I say or type. Quote Link to comment Share on other sites More sharing options...
IanMc Posted April 18, 2010 Share Posted April 18, 2010 Try your old plug leads. One of the ladies at work sweet talked me into fitted a set of new leads on her Mk3 Astra 2.0 Cabrio (not sure why when it seemed to be going OK according to her). I then spent the best part of 3 hours sodding around with them but just could get a good connection to each plug cap (even though her vehicle was specified on the box). I just kept chasing misfires around from cylinder to cylinder. After start up it would run OK for about a minute, then presumably the engine movement caused the lead to slide up the side of the plug and it would start to give random sparking. Put the old ones back on and it ran well again - she got a full refund............ Got to be worth a try. Quote Link to comment Share on other sites More sharing options...
lamchop77 Posted April 19, 2010 Share Posted April 19, 2010 As an update to this I changed the oil before running it to an mot, it ran OK over there, some pinking under load and missing slightly every now and again. At the MOT we tried altering the timing but it didn't improve anything. It only failed on emissions but afterwards I found a plug lead had been knocked loose when the timing was adjusted! Put it back on and it ran just the same as on the way to the MOT. At home I changed the distributor unit complete - no change. Then checked the came timing on the OP234 cam....103 deg ATDC gave full lift on the front inlet rocker. THats what it should be as per spec of OP234. So its still not right. I've an adjustable vernier on the cam, I was wondering whether to try advancing it a degree or so to see if it helped with the pinking? What condition is the plug ono 1 cylinder like if you run it with the misfire and then check NOT revving it until it clears. Is it sooty and black? The big capacity CIH motors (as far as i can gather) need BIG cams for performance. The 234 cam you have fitted will probably be acting like a very mild road cam and is actually designed for the 2.0. I have heard of these 2.4s pulling a contaminated exhaust gases back into the combustion chamber but its usually the overlap on the inlet and exhaust that causes this so moving the timing could help. It's just funny that its on no 1 because usually it would affect all 4??!!?? Does the car lose water at all? I had the rubber ring fail on the front cover which wept through to no 1 cylinder. Steamed like buggery out the exhaust and did have a misfire from time to time. Sorry i'm rambling i'm just racking my brains. If your on hydrualic followers you need to change them. The 234 is a solid lifter cam , a hydrulic cam has a different grind to the ramp angle. HTH Chris Quote Link to comment Share on other sites More sharing options...
mantadoc Posted April 19, 2010 Share Posted April 19, 2010 Did you try rotating the dizzy 90 degrees and moving the plug leads all around one to see if it moves the fault over a cylinder? Also have you had chance to try the injector plug idea? Compression check? I'm back to you need air, fuel, compression and a spark at the right time. Spark and no mixture or compression gets you nothing. That or change the bits you haven't changed. Beware "good spare" distributors that have been stored for years on their sides. Quote Link to comment Share on other sites More sharing options...
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