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| Improvised oscilloscope probe for Automotive ignition analysis. |
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| joeqsmith:
--- Quote from: floobydust on January 04, 2019, 05:35:00 pm ---If possible you can fit an O2 sensor and see each cylinder firing lean/rich to check balance. Maybe joe has tried this. Otherwise you'll blame the ignition system when nothing is wrong with it. --- End quote --- Assuming narrow band, I have not used. The Bosch wideband sensor is slow. 100ms or so. Graphs below show about 1.3 seconds of data. You can see the wideband in the purple trace. The transmission is an auto for 1-2 but requires kill for the other shifts. There is a lot of air and unburned fuel pumping through the motor for that 30ms or so. You can see the wideband does pick it up but its no where near fast enough to see cylinder by cylinder. Second graph shows about a minute of data with the engine sitting without a load. The engine can build a fair bit of pressure on the 2-step. Once off the 2-step, it will tag the upper limiter. Both events can be seen with the wideband. |
| tautech:
Ah, the two step. :clap: Boom, bang, boom. :wtf: 8) All hell breaks loose. ;D Buddies 20B on Meth with 40lb of boost is something that is heard for miles ! >:D Oh yes Joe, I left EGT off the list. :palm: |
| Jim-0000:
I will be driving up to where the car is (two hours away from here) today to assist one of the brothers work on it further. My suggestion to throw away the silicone plug leads and replace with copper was met with some ambivalence. (I am puzzled by this!) I don't want to get too insistent; I am only an onlooker/assistant and not a mechanic. I might have more to report tonight. Jim. |
| mikerj:
--- Quote from: Jim-0000 on January 05, 2019, 09:27:34 pm ---My suggestion to throw away the silicone plug leads and replace with copper was met with some ambivalence. (I am puzzled by this!) --- End quote --- Silicone only refers to the insulation, it's possible to have copper cored HT leads with silicone insulation. It's the carbon string based cores leads that can break down over time. |
| Gregg:
Don’t underestimate possible mechanical problems causing what seems to be an ignition problem. Things like weak valve springs, worn cam lobes, worn rocker shafts, worn or sticking lifters, worn valve guides, sticking valves, timing chain or belt tension / harmonics, worn distributor drive or partially blocked cooling passages to the cylinder head(s). Under load problems are often problems that simply are not noticed under light or no load. For instance the crankcase pressure is much higher under load because of increased blow by and if an intake valve is loose in its guide the mixture to that cylinder can be leaner. Under load exhaust valves get very hot and can grow considerably longer and if the clearance isn’t adequate, the exhaust valve can be held open too long. You stated that it is carbureted; it may be that the power valve isn’t functioning properly making it lean under load; a lean mixture can seem like an ignition problem partly because a lean mix is harder to ignite. A vacuum gauge may help here, a lot of old timers (like myself) swear by them for carbureted engine diagnosis in certain cases. |
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