The C1 test revealed a 25 psi improvement from compression test vs after adding oil to cylinder and red testing. So that is significant improvement.
190 psi to 215 psi…
However what is odd is the same text in Cylinder 5 was almost exactly the same… 190 psi to 210 psi.
This was 20 psi improvement…
The oddity is C5 has no misfires and runs great.
Can just 5 psi make that much difference?
Last I did use RESTORE in the summer oil change. Honestly I thought is cleared up the misfires as CEL stopped coming on for several months… but then we experienced the stall no crank issue. I change oil again in November and did not use RESTORE this time… so I am baffled …
I am always hearing about not being a parts changer… to diagnose it before changing a part…
well that’s all dandy for a hard failure like a vacuum leak, or low fuel pressure, or a hard fault code like P0171, or when Fuel Trims follow a pattern perfectly… but my issue is none of those… and nothing stands out being abnormal… I have eliminated everything except a computer or rebuilding the engine…
Believe it or not I actually have a spare ECU I bought from a scrap yard and had a guy configure it with my VIN number… I am nervous about swapping it out… I know when I do a relearn will be required…
I guess I just had bad luck… before I spend $400 having heads rebuilt and machine shop and replacing it all myself. The would like to know if it’s worth it? I would hate to get to trying everything, having a perfect top of engine, only to realize I need a lower engine rebuild or new engine…
I did see C1 stands out at 25 psi difference, but I missed that C5 has 20 psi diff.
Every time you replace oil, Restore’ effect is gone, so if you tell it helped before, I would dump a bottle into the oil, even if it is not exactly fresh
Restore would definitely have nothing to do with “stall / no crank”
How is your effort to clean/swap injectors going?
Do not make too many changes in one round, it makes it harder to diagnose.
I would not go ECU route until you have injectors sorted.
I did not tackle that yet. I ordered a tool kit to connect injectors and spray/clean them. This week I will clean my old original OEM injectors and if the spray patters look good I will replace them…
I doubt those compression results are the reason for the symptom you are having. While a little less balanced than might be desired, those seem within the normal range of cylinder to cylinder variations to me. I think the specs on my truck’s 302 are only that all the compressions must measure within 25% of each other. There’s no absolute minimum compression number spec’d.
Compression is not your problem.
With 235k miles 190+ dry compression is just fine.
You’re not gonna get misfires until compression drops well below 150.
If the CEL doesn’t come on, and driveability and fuel efficiency are reasonable, I suggest you drive on and get your money’s worth out of the old girl.
OP, do you actually notice some misfiring when driving? Maybe it actually isn’t misfiring, & the misfiring code is due to some problem with the way the computer determines a misfire. The way it usually does it is w/the crank sensor. The computer knows when the spark plug is fired, and it times the crank sensor to see if the spark event accelerates the crankshaft or not. If not then it flags a misfire code. You say you’ve replaced the crank sensor, but there’s always the possibility the new crank sensor is faulty, the crank signal isn’t getting to the computer cleanly, or that the grating the crank sensor senses is the problem.
I replaced crank sensor 1 year ago as a possibility it was causing misfire issues as described. 1 month ago it started having stalk/no crank which led me to start this blog. Fix could be fuel pressure or CPS. I replaced both. I add the .020 shim to COS that was suggested due to bearing wear and gap issues. I hade engine light misfires (no CPS code) but had relearn done anyway…
Since then 2 weeks it does not stall but still misfires at idle or very low speeds. When faster speeds it runs fine with no misfires.
I am sure it’s not the sensor… but maybe the reluctor wheel has an issue…
Took a couple days off. I have a injector tester but need to by some spray cleaner. In addition I did do a Chemical Block Test. Fluid remained blue and nothing indicated any exhaust gases getting into coolant. Just another piece of info.
George thinking about your question on CPS I can confirm the misfire is real because I can hear/ feel it at idle. So it’s not a ghost code from reluctor /CPS miss. It’s not bad lately so not too concerned. Still have not swapped injector but am testing old ones first…
I want to do the injector balance test but do not have a scanner to initiate. I am thinking to connect fuel pressure gauge and record value after disconnecting an injector connector and repeat for all… hope this works?
Will do… the tool arrives tomorrow… it may be next weekend before I test. In addition to above results I will also test the resistance (ohms) I each one as well.
I’m not surprised Eric traced the issue to a faulty injector. I think that is what is going on with this case also. I have previously watched other videos from Eric. I like the way he works and he makes some good videos to help others.
I just tested the fuel injectors. I tested resistance of injector as well as the pressure drop flow rate (or whatever it’s called)…
Remember I am getting a P301 or P300 code and am seeing most misses at idle on 1 and a few on 2.
Resistance in ohms. I did notice I would get .1 ohms movement depending on how firm or where on probe tip I held wire. I tried to record the peak number seen on meter that was stable.
Below are the pressure readings when using the OLLOSUN EM267 pulse meter. Setting on mode 2 medium pulse. Before each test I turned on pump to maximize pressure on rail. In most all instances starting pressure was 45 PSI.
#1 Start 45, End 24, Drop = 21 #3 Start 45, End 24, Drop = 21 #5 Start 45, End 25, Drop = 20 #7 Start 45, End 25, Drop = 20
#2 Start 45, End 22, Drop = 23 #4 Start 45, End 23, Drop = 22 #6 Start 46, End 24, Drop = 22 #8 Start 46, End 24, Drop = 22
I addition I am not sure if it’s normal but after the pulse was initiated and pressure dropped and letting it sit a minute (I noticed this between moving the connector to next injector) that the pressure gauge climbed slightly. For example #4 dropped to 23, but after a minute it read 26. (Pic attached). This wS noticed to occur on all bank 2 injectors. I did not pay attention on bank 1 which I tested first.
