honda_killer Posted June 13, 2009 Share Posted June 13, 2009 to start off with i have a 1984 300zx turbo running megasquirt 2 extra 3.0. i have been running megasquirt for about a week now with a miss (ignition) i believe. the miss is in the rpm range of 1500 to 2500. so today i pulled my plugs and found one wet black plug and five white plugs. determined to find this miss i have done a compression check, swapped injectors around, checked the plug wire resistance also the cap. i ohmed out the injectors and the wiring to MegaSquirt. everything i have checked looks good. any advice would be helpful thanks in advance Quote Link to comment Share on other sites More sharing options...
dan5138 Posted June 13, 2009 Share Posted June 13, 2009 Old injectors or new ones? just because everything ohms out doesn't mean the injector is mechanicaly sound. When I first got my 280Z it ran really rough. The injectors more or less dribbled instead of atomizing the fuel. Just food for thought. Quote Link to comment Share on other sites More sharing options...
honda_killer Posted June 13, 2009 Author Share Posted June 13, 2009 old injector. i had thought the same and tryed changing the injectors around and the problem did not follow the injector. Quote Link to comment Share on other sites More sharing options...
jeffer949 Posted June 13, 2009 Share Posted June 13, 2009 The white means they are lean. The one dark one might mean that you have some bad oil control rings. Quote Link to comment Share on other sites More sharing options...
softopz Posted June 13, 2009 Share Posted June 13, 2009 check if that black plug is getting spark. Quote Link to comment Share on other sites More sharing options...
honda_killer Posted June 13, 2009 Author Share Posted June 13, 2009 plug has spark, just had the heads off not long ago. cylender walls had no deep schoring in them. any way to check without pulling the motor apart. Quote Link to comment Share on other sites More sharing options...
Flexicoker Posted June 13, 2009 Share Posted June 13, 2009 Have you cleaned the injectors? You need to open the injector (I think megasquirt has an injector test thing) and then spray B-12 chemtool through the injector backwards and forwards. Quote Link to comment Share on other sites More sharing options...
randy 77zt Posted June 14, 2009 Share Posted June 14, 2009 compression test then do a cylinder leak down test.or you could be getting some oil from an external source(intake manifold gaskit,valve guides) Quote Link to comment Share on other sites More sharing options...
honda_killer Posted June 15, 2009 Author Share Posted June 15, 2009 i did a cmpression test and all cylinders were within specs around 180PSI. the whole motor has been regasketed plus valve guide seals. i'll get back to you on results of the leakdown test. appreciate all the help guys. Quote Link to comment Share on other sites More sharing options...
Guest Rolling Parts Posted June 15, 2009 Share Posted June 15, 2009 I'd start by fixing the over-lean condition first. Lean and turbo is not a great thing to have together. The one black plug and miss could be as simple as having one bad spark plug. You can move the plugs around and see if the condition follows the plug... Quote Link to comment Share on other sites More sharing options...
honda_killer Posted June 16, 2009 Author Share Posted June 16, 2009 tryed two different sets of plugs condition stayed in same cylinder Quote Link to comment Share on other sites More sharing options...
WizardBlack Posted June 16, 2009 Share Posted June 16, 2009 Since you have MS, you are running batch ignition and waste fire, no? It has to be the engine itself if you swapped plugs and swapped injectors and it stayed at the same hole. Did you swap plug wires as well? Maybe a dopey wire? Rolling parts: The car most likely does not have a lean condition. He is probably tuning with a wideband that is reading all cyclinders. The one rich cylinder's exhaust mixes with the lean ones to average out to stoich according to the sensor. Once the one cylinder starts burning it's mix like it should, he will show lean and know how much to enrich the tune to adjust. I'm sure he knows not to boost while it's behaving in such a way. Quote Link to comment Share on other sites More sharing options...
honda_killer Posted June 17, 2009 Author Share Posted June 17, 2009 the only reason i feel that this is a problem with megasquirt. is because the only thing i have done is pulled the motor out, painted and resealed. the motor ran with no problems for about two years till megasquirt and injectors. today im going to try going back to the stock ecu, wiring, and injectors. and yes i did change wires Quote Link to comment Share on other sites More sharing options...
Guest Rolling Parts Posted June 17, 2009 Share Posted June 17, 2009 It's NOT megasquirt causing a problem in the single cylinder since it's batch fired injection. Since you've only run MS for a week, you need to tune it by enriching the fuel map. The engine is telling you it's LEAN so do whatever it takes to fix that real situation in the engine. Since Megasquirt is 100 times better at adjustability than the 1984 "electronics" are then I don't see why you'd want to yank it out at this time. Use the MS adjustability, that's the only strong point of installing a programmable ECU in the first place. You have a first year 300ZX V6 turbo engine and one cylinder is not like the others. You've tested compression and swapped out injectors, plugs, plug wires and confirmed spark. If spark and compression are perfect, then your 1984 oil control ring on that one piston might be the first one to let go. You probably just never noticed it before since the old engine controls were so coarse and just masked the problem. Now that you are running so lean across the board you can actually see the one bad cylinder on the plugs? Quote Link to comment Share on other sites More sharing options...
WizardBlack Posted June 17, 2009 Share Posted June 17, 2009 the only reason i feel that this is a problem with megasquirt. is because the only thing i have done is pulled the motor out, painted and resealed. the motor ran with no problems for about two years till megasquirt and injectors. today im going to try going back to the stock ecu, wiring, and injectors. and yes i did change wires Listen to what we're saying, though. The MS doesn't control a cylinder individually in any aspect. It could be your wiring/wires/plugs/injectors or the cylinder itself. MS is practically incapable of fouling up a single cylinder on a 6-cyl install. Nothing is sequential. Quote Link to comment Share on other sites More sharing options...
honda_killer Posted June 18, 2009 Author Share Posted June 18, 2009 (edited) i understand i had just thaught that the miss was making it foul out. well i pulled the motor apart and this is what i found. i just want to say thanks for all the help guys Edited June 18, 2009 by honda_killer add Quote Link to comment Share on other sites More sharing options...
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