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
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.
Joel; Good morning Sir, I hope this reply finds you doing well. Congratulations on the shear amount of testing you completed on this vehicle, you definitely have invested in equipment to better yourself. That being said, I believe you had the answers for your compression loss in your second posted waveform (Relative Compression and Cranking Vacuum). As the pistons for cylinder's #1 & #2…
Jonathan, In your tech help case study, both the good cyl and bad cyl patterns are the same. I was taught that the patterns would be different and that is how you know there is a problem with a cylinder. I am new to this and find looking at the patterns is more of an art than science?
Bentley, read Jonathan Brown's excellent PDF presentation.
I did and that is why I asked the question. In my smog update training which was on in cylinder testing, good cylinders and bad cylinders do not have the same pattern. In Mr Browns PDF on page 11 he overlays a good and a bad cylinder and the patterns are identical, showing you cannot use in cylinder testing to find low compression cylinders, but used a bore scope to see the bad valve. Am I just…
depends of the leaks I have had hard time to see in the in cylinder wave form , yes they are some will show deep pockets while others will not , the pressure transducer measure differences in presure .
I'm with Bentley on this one. The loss of compression has been demonstrated by the relative compression test and cranking compression test, but *not* by the running compression test. Perhaps the sealing issue is intermittent and there was a need to run the running compression test a little bit longer and catch it in the act -- just like the SnapOn transducer did (albeit with questionable signal…
This is from an 06 Ford Escape 3.0 CH B is a FLS on the dipstick tube and the higher crankcase pressure pulses are from the blow-by gases from the fuel washed cyl 2 piston rings. CH C low starter amp draw from cyl 2 CH D is a WPS500 in cyl 2, with 77 psi cranking compression and the vacuum pocket measures 20 inches of vacuum. I put some oil in the cylinder and the compression climbed to 200…
Do you have any capture to share of the injector uneven pulse wid??
Yes, yes, he does! diag.net/msg/m5oq7dsjv0…
The starter amps show the cylinders with the fuel washed piston rings. Normal cold engine injector on time is usually 20ms to 30ms, depending on engine temp. A used PCM fixed it and it ran well.
Bentley; Please let me respond to your question about page 11 of the article I posted. This overlay was made to compare Valve Closing & Valve Opening Events not to Compare Peak Pressures. On page 11 the comparison shows both Cylinder's Exhaust Valve Opening, Maximum Vacuum Point and the Intake Valve Closing all happening at the same time. Using these measuring points a conclusion can be…
I read complete the article , thanks it was a good one.
I understood the patterns were to confirm the valve train, but the vehicle had a compression issue and I was taught that the pattern of a low compression cylinder and a good cylinder would not match on an overlay. So is the point I am missing the fact that these are running waves not cranking waves the therefore they match, if they were cranking than they would not match? Thanks
Thank you sir , for you detailed unswer an explanation
thank you very much for your answer and the case study. there is a wave form/capture I took from your case study same cylinder #1 one capture with snap on and one with pico. .I high lighter the area where the 0 psi should be , and the expansion pockets, here is where snap on transducer shines as a garbage , I still have the snap on transducer but I do not used it for in cylinder as it is garbage…
the customer came in to check another vehicle with misfire but now is a BMW ha, she said the cylinder head was removed and redone the work and the Tacoma is fixed now no more misfire.
Joel, before you do the cylinder leakage testing, attach a rubber glove on the throttle body and a rubber glove over the tailpipe. Also remove the rad cap and put a balloon on the dipstick tube.
I will take your advise , I admire your worked , many capture from you I save it good staff , thank you sir
Joel, this is a fantastic collection of captures. - Regarding attachment 20/37 : Pressure transducers add a small amount of volume to the cylinder, so it is expected to get smaller compression values compared to the gauge. For WPS500 with the supplied hose this can make around 10% difference; sometimes less, sometimes more. Have you compared WPS500 versus the gauge before? - Capture 16/37…
Great posts. Brandon if you are reading these posts ..comment
Brandon is awesome teachers I only have taken 1 class with him , honda technology it was great.
The relative compression test with the vacuum reading shows #3 cylinder cannot pull as much vacuum since the intake valve is leaking on #2 cylinder.
thanks for explaining this is what I need to improve.
Does any body has any type of explanation why the pcm will flag or detect the cyl 1 as current misfire , does it have to do some thing with piston chart? Thank you for your attention.
Joel, the PCM tries to identify cylinder contribution from the CKP (and, possibly, also CMP) signal. If we had the running CKP/CMP signal we could try to analyse what confused the PCM.
Toyota also has spark confirmation from the coil to the PCM to detect misfire. With the lower compression in #2 cylinder could have sparked good and gave confirmation signal. Also have to consider when the Exhaust valve is open on #2 with a leaking intake valve. That can be poisoning the runner for #1 Cylinder with exhaust gasses. That could also be causing the #1 cylinder misfire code.
Robert, thank you for proposing a hypothesis about exhaust gases going back into the intake -- that would be at line II on the attached graph, right? #1 and #2 are on different banks -- are they still close enough for this to happen? Also, for the pulse sensor waveform, did you mean #5 (rather than #3) that did not build as much vacuum as the others (line I)? #3 is busy with compression at that…
When Cylinder 3 is on intake in the last section of the waveform the #1 cylinder is on Compression then power on the first section of the waveform. Both the last section and first two sections did not pull as much vacuum. If you look at overlay of compression and power of #1 it matches up with vacuum readings. With the second section reading the lowest vacuum the engine is on the power stroke…
Have you compared WPS500 versus the gauge before? yes not with the wps because I do not have it , I have different pressure transducer ,my transducer the hose is solid metal , cylinder in question #2 gauge 160 psi, transducer on capture 20 is 140 psi max , I have seen this over and over as you said it takes some volume the hose also I have heard because the hose has not shredded valve can not…
Hi. If you want to try to diagnose these captures using a different tool and technique, contact me and I will provide your files converted to another format and the software to analyze them with. Your procedure for catching the data is not the best for good analysis. Take a look here: youtu.be/fJ5YZxMBXyw
Olle, I think a lot of people here would appreciate you running this dataset through the AutoScope's Px script and showing us screenshots of the results. Thank you.
There are just a few frames and not a lot of data. However, I have attached a screenshot. I cannot upload .mwf files directly. However, I can and did upload a .zip archive containing all of the files for those interested in working with them on their own. The files are in a .rar archive within the .zip archive. Also, here is a link to my Google drive with the folder…
Thank you, Olle. For this dataset the report results seem to be quite confusing: - for the bad cylinder it complains about restricted exhaust at high rpm (even though we know the actual problem is the intake valve leak); - for the good cylinder it complains about "valve timing anomaly" (see attached), even though I can't find that being an issue anywhere on the waveform. So, not sure what…