Eliotlm Posted December 7, 2020 Report Share Posted December 7, 2020 i everyone! This is my first post on the forum. Im sorry if i post this in the wrong spot. I recently purschased a 1999 Volvo v70 2.5t with a misfire. I was getting a p0300 misfire code so my first thought was that a few coils or plugs went bad. I replaced all the plugs, replaced one coil aswell as swapped the coils around, but the issue didnt follow. I determined that im getting No spark from cylinder 2 and 3. I also determined that all injectors were working fine. I cant find any tips on how to diagnose this issue other than that it might be some controle modules inside the pcm. Before starting to rip into the computer i would like to check if there is any way to diagnose of maybe the wires running to the coils have shorted out somewhere. Or IF someone else has had this issue and what they did to solve it. Im sorry if my english isnt that great as i am from Sweden but i hope it is understandable. Link to comment Share on other sites More sharing options...
gdog Posted December 8, 2020 Report Share Posted December 8, 2020 Welcome to VS and your English is fine! So I'm curious; are these old Volvos more popular here (in the USA) than in Sweden? I.e. isn't there a good forum in volvo's native land? In any case, will try to help if I can. Are you sure you're not getting any spark on those two cylinders? If cylinders 2 and 3 were consistently misfiring, I'd expect two more codes (302 and 303) per below. •P0300 Random/Multiple Cylinder Misfire Detected •P0301 Cylinder 1 Misfire Detected •P0302 Cylinder 2 Misfire Detected •P0303 Cylinder 3 Misfire Detected •P0304 Cylinder 4 Misfire Detected •P0305 Cylinder 5 Misfire Detected If you are truly not getting spark on those two cylinders, and the coils are good, then there's either an issue with your wiring harness, or the ECU itself; both of which are generally unlikely. I'd check the compression next and see if those two cylinders are low. Do those two cylinders not fire all the time (at idle and at elevated rpm)? I suspect you may have two dead holes. Link to comment Share on other sites More sharing options...
Eliotlm Posted December 8, 2020 Author Report Share Posted December 8, 2020 7 hours ago, gdog said: Welcome to VS and your English is fine! So I'm curious; are these old Volvos more popular here (in the USA) than in Sweden? I.e. isn't there a good forum in volvo's native land? In any case, will try to help if I can. Are you sure you're not getting any spark on those two cylinders? If cylinders 2 and 3 were consistently misfiring, I'd expect two more codes (302 and 303) per below. •P0300 Random/Multiple Cylinder Misfire Detected •P0301 Cylinder 1 Misfire Detected •P0302 Cylinder 2 Misfire Detected •P0303 Cylinder 3 Misfire Detected •P0304 Cylinder 4 Misfire Detected •P0305 Cylinder 5 Misfire Detected If you are truly not getting spark on those two cylinders, and the coils are good, then there's either an issue with your wiring harness, or the ECU itself; both of which are generally unlikely. I'd check the compression next and see if those two cylinders are low. Do those two cylinders not fire all the time (at idle and at elevated rpm)? I suspect you may have two dead holes. Thanks for your respons! To answer your question, v70's are probably one of THE most Common cars here, thats One of the reasons why i bougt it as parts would be easier to find aswell as People with similar problems, i've used Swedish forums aswell but they arent as active as the English speaking ones, maybe because we simply are fewer people here, i dont know. I also figured that i should've gotten a misfire code on a specific cylinder, someone laid out theory which I dont know wether it is correct or not, he figured that the car maybe was too old to notice misfires in a specific cylinder and throw a p0300 instead of a p0302 and p0303 as it maybe should have. I tested it rather Quick for spark and i Will try it again but im pretty certain that it doesnt spark but that could in theory be that the test spark plug i used was defective. I read One post where someone hade managed to reverse the connector plugs on the cylinder 2 and 3 coils which gave similar symptoms but i think that is unlikely in My case but i Will try that aswell. What do you mean by "two dead holes"? I Will test compression but i didnt som that as i wasnt getting any spark to begin with. Im unsure how to measure if the wires are intact and also how to take Them out. Link to comment Share on other sites More sharing options...
gdog Posted December 8, 2020 Report Share Posted December 8, 2020 11 hours ago, Eliotlm said: What do you mean by "two dead holes"? Means cylinders with little, or no, compression. Link to comment Share on other sites More sharing options...
Eliotlm Posted December 9, 2020 Author Report Share Posted December 9, 2020 10 hours ago, gdog said: Means cylinders with little, or no, compression. I'll check that some day soon but as im getting No spark i Will try to resolve that first Link to comment Share on other sites More sharing options...
Eliotlm Posted December 9, 2020 Author Report Share Posted December 9, 2020 16 hours ago, gdog said: Means cylinders with little, or no, compression. teve I have som Good and some bad news, i replaced 3 of the coils as it turns out One i was testing with also was Broken, i now have spark on all cylinders, which solved the issue with cylinder 2. But I cylinder 3 makes No audible difference as i full the connector plug to the coil whilst running, when i pulled the spark plug it also smelled like gas. In my mind this only leaves one thing, bad compression. I Will test it when i get time. Is that the most likely cause? Is it even worth reparing? Link to comment Share on other sites More sharing options...
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