Toyota Tacoma 02 3.4L P0300 P0301 In Cylinder, Crank case, intake , exhaust pressure In Deep Analysis
I have this case study probably too much of images or captures but I wanted to learn more about in cylinder pressure transducer at the same time to develop a method to when used it correctly to make diagnoses faster and accurate.
customer just bought this Tacoma from small car lot about 1 week ago , check engine light is being on and off with engine running Little rough , the first time was diagnose by other technician. but I started my diagnoses here scan for codes and misfire scan data
Engine misfire at light load on scanner cyl 1 only
we initially recommended more diagnoses time as this vehicle had new spark plugs and ignition wires, good quality parts , customer denied as she said the place where she bought it from told her to take it back they will take care of it. now it comes back again after they did cylinder head work ,valve jobs adjustment accordingly to the history and timing belt. now the fault is more often and same dtc than before , customer wanted we to talk to the shop of what kind of job they did, some thing we do not do is be in between customer and other shops, how ever I did exception at this time and they said at the other shop vehicle has cyl 1 only so we removed the cylinder head because blown head gasket is common on this so we decided to sent out both banks but they only did valve seat on rh cylinder head where cyl 1 is , but we did valve adjustment on all of them so I asked so the cylinder head for bank 2 there was not valve seat worked done he said no thee was no issues reported on scanner on that bank. well I said we will continued our diagnoses and you get in touch with the customer.
my first step was to do a relative compression with the Pico scope
two cylinder show low compression I repeated several times this test with same result and I connected the battery maintainer to keep consistence battery voltage during test , fuel pump disable .
I did 4 channel on My Pico scope refer to each channel on scope label where sample was taken from .
on relative compression I definitely I can see cylinder 1 and 2 the humps are lower consistently . note when engine is cold I took this capture
engine warm
well I know my cylinder 1 and 2 are with Lower compression I decided to find out where is this going so I did different channels , pressure wave forms , intake , exhaust, crank case in cylinder pressure transducer on cyl 2 with low compression and cylinder 4 know good cylinder .
but it was not definite for me where the compression was lost , with those capture I decided to do old school static compression test to all cylinder . the result here
cylinder 1 has not bad compression and leak down in comparing with all others , cylinder 2 has 15 to 20 psi less than all others and 35% leak down to intake
I have not had god luck with the in cylinder pressure transducer to detect low compression where is the leak going to , The potential that I have find on it is more for valve train issues , compression to sync spark when no start , with the vacuum and exhaust wave forms I have not play enough as in cylinder but I am trying to , any advised to improve my testing is welcome .
the Tacoma when back to the shop that did the cylinder head job since they are dealing with it customer , car lot and shop , our diagnostic was leak down to intake possible too tight intake valves or sealing issues .
here comes another question in my cylinder wave form I see the exhaust valve is opening at the same degrees than cyl 4(good to compare to cyl 2 with issues) how ever the intake valve is harder to find out opening point to divide if it is too tight or sealing issues at least for what I can see I can be wrong and I wanted to be corrected to who ever has experience on this area . thanks for reading and comments will be welcome.