Honda Accord - Slight Miss At Idle - Case Study
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Date: 2020-08-05
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Comments and reviews: 10
Steve
The cranking waveforms show much more difference between cyl 1 and 5 than the running ones, probably because at low cranking speed there is more time for air to leak out of the cylinder during the compression and expansion strokes. The cranking test also has atmospheric pressure at the start of the compression (due to WOT rather than idle manifold vacuum) so the cylinder pressures will be higher, increasing the amount of leakage. On the cyl5 cranking trace the pressure at the bottom of the expansion stroke is lower than at the bottom of the intake stroke, if the pressure is lower and the volume of the cylinder is the same (piston at BDC in both cases) then physics says there must be less air in the cylinder by the end of the expansion stroke - as there is no combustion you would expect the compression and expansion strokes to cancel out (you take a fixed amount of air at BDC intake, compress it to TDC firing, then expand it again to BDC expansion and end up back where you started. assuming a slightly idealised case where the intake valve closes exactly at BDC and the exhaust valve also opens exactly at BDC. I don't think the pressure trace can tell you where the leak is (inlet valve, ex valve, rings) - just that there is/isn't a leak.
Thanks for sharing the scope data, really interesting to have a look at
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The cranking waveforms show much more difference between cyl 1 and 5 than the running ones, probably because at low cranking speed there is more time for air to leak out of the cylinder during the compression and expansion strokes. The cranking test also has atmospheric pressure at the start of the compression (due to WOT rather than idle manifold vacuum) so the cylinder pressures will be higher, increasing the amount of leakage. On the cyl5 cranking trace the pressure at the bottom of the expansion stroke is lower than at the bottom of the intake stroke, if the pressure is lower and the volume of the cylinder is the same (piston at BDC in both cases) then physics says there must be less air in the cylinder by the end of the expansion stroke - as there is no combustion you would expect the compression and expansion strokes to cancel out (you take a fixed amount of air at BDC intake, compress it to TDC firing, then expand it again to BDC expansion and end up back where you started. assuming a slightly idealised case where the intake valve closes exactly at BDC and the exhaust valve also opens exactly at BDC. I don't think the pressure trace can tell you where the leak is (inlet valve, ex valve, rings) - just that there is/isn't a leak.
Thanks for sharing the scope data, really interesting to have a look at
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Mike
Your catch phrase If I can do it, you do it only applies to about 0. 000001% of the population, at least in regards to evaluating transducer voltages during an ICE compression cycle to determine gas-sealing blow-by viability. You give humanity too much credit.
You should think about getting a teaching degree if your arthritis proves overly problematic - you're a natural. I'd think you'd find it highly-rewarding to pass your knowledge to the next generation of vehicle technicians.
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Your catch phrase If I can do it, you do it only applies to about 0. 000001% of the population, at least in regards to evaluating transducer voltages during an ICE compression cycle to determine gas-sealing blow-by viability. You give humanity too much credit.
You should think about getting a teaching degree if your arthritis proves overly problematic - you're a natural. I'd think you'd find it highly-rewarding to pass your knowledge to the next generation of vehicle technicians.
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John
You are an intensely intelligent human being sir. I literally know zilch about automotive work but am mechanically inclined, since watching your videos I have been inspired to replace the leaky valve cover gasket on my car as well as the VVT solenoid for the intake side. Learned an incredible amount from you, thank you so much for such great videos Eric O!
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You are an intensely intelligent human being sir. I literally know zilch about automotive work but am mechanically inclined, since watching your videos I have been inspired to replace the leaky valve cover gasket on my car as well as the VVT solenoid for the intake side. Learned an incredible amount from you, thank you so much for such great videos Eric O!
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Blue
I wonder if anyone would know what the problem is with my 2006 Toyota Tacoma TRD brakes
Brake pedal travels, not spongy. I have bled the system 4 times over and checked the master cylinder and it is 100%. I am hoping it is not the ABS pump problem. There is not Engine check light on or anything. Heeeeellllllpppppp. :-)
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I wonder if anyone would know what the problem is with my 2006 Toyota Tacoma TRD brakes
Brake pedal travels, not spongy. I have bled the system 4 times over and checked the master cylinder and it is 100%. I am hoping it is not the ABS pump problem. There is not Engine check light on or anything. Heeeeellllllpppppp. :-)
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Johnny
When you put the smoke machine on the cylinder, did you have to have it at top dead center? I'm suspicious of my exhaust valve cylinder 8 on my Silverado 07 can I just take out my spark plug and immediately stick the smoke machine there or I have to turn the crank? Thanks.
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When you put the smoke machine on the cylinder, did you have to have it at top dead center? I'm suspicious of my exhaust valve cylinder 8 on my Silverado 07 can I just take out my spark plug and immediately stick the smoke machine there or I have to turn the crank? Thanks.
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Gregg
I bet the high current draw in the cylinder AFTER the faulty cylinder is due to the starter motor fighting the vacuum to pull cylinder 5 (leaker) down to BDC. If you're losing air charge in that cylinder, the starter will have to work a little harder to bring it down.
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I bet the high current draw in the cylinder AFTER the faulty cylinder is due to the starter motor fighting the vacuum to pull cylinder 5 (leaker) down to BDC. If you're losing air charge in that cylinder, the starter will have to work a little harder to bring it down.
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autos
Hey bud. FYI, I don't know if you noticed on the video but on this particular morning, you forgot your beard at home. Just thought I'd let you know in case rubbing it while you think was part of your diagnostic procedure or whatever.
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Hey bud. FYI, I don't know if you noticed on the video but on this particular morning, you forgot your beard at home. Just thought I'd let you know in case rubbing it while you think was part of your diagnostic procedure or whatever.
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bob
Pinched nerve. Stand under the hot shower, putting the water on to the shoulder area. The hydration regeneration is the key. Men Lift too heavy weights, and over reach because they can. There's your problem ( Lady)
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Pinched nerve. Stand under the hot shower, putting the water on to the shoulder area. The hydration regeneration is the key. Men Lift too heavy weights, and over reach because they can. There's your problem ( Lady)
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Jonathon
Jeeze Eric! So used to seeing the bearded shows. This one you look like a 20somethin-with early greyingwisdom whiskers! Lol. Comical seeing your facial expressions without the hair covering the smoocher!
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Jeeze Eric! So used to seeing the bearded shows. This one you look like a 20somethin-with early greyingwisdom whiskers! Lol. Comical seeing your facial expressions without the hair covering the smoocher!
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Steve
mr o after that ridgeline that the dealer screw up telling her she needed to replace you had the head fixed the engine was just fine. i was waiting to find out how that persons hondoo was working.
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mr o after that ridgeline that the dealer screw up telling her she needed to replace you had the head fixed the engine was just fine. i was waiting to find out how that persons hondoo was working.
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