Thanks George, I will get the numbers again later tonight. You said under all driving conditions on your Toyota the trims stayed within ±10 though right? Mine does not do that, driving steady speed around 2000rpm the long term like to be at just under 10, with the short term, above 10. Wide open throttle they go to almost 20 when I'm driving. I'm going to get started with the running compression test real soon here, just the one cylinder so it shouldn't take too long, I'll let you guys know what I find.

 

I'm looking for fuel trims at idle and 2500 rpm in park.

Watch your graph during full throttle, LTFT goes to a set rich level and STFT shuts off. Its a pre-programmed force rich condition to accelerate. The only time you get to cheat whatever is the Canadian equivalent to the EPA and performance is prioritized over emissions.

Under full throttle acceleration my Toyota forces all fuel trims to display zeros.

George

 

Okay guys, we now have new problems, same cylinder, new day, different problem. No videos yet because I'm going to go out and run the test again on cylinder 1, and maybe another cylinder too but guys. It now makes 155psi MAX static, I saw 70psi idling and 130 snap. The kicker is the pressure will now drop within seconds after shutting off. No other cylinders did this. But on the static test, it seemed to hold the pressure? Very confused, I will be back after more testing.

 

Just sounds like compression gauge's Shrader valve isn't holding pressure every time. That's a problem with the compression gauge itself.

 

Guys, second test idling pressure is 50 PSI! There's something going on here. Snap up to 130psi. Pressure dropped to 0 again after shutting off. I'm not done yet testing out here, I just don't believe this.

 

Yup, your right Les. After testing cylinder 1 a few more times I put it on cylinder 5 and as well got a low compression reading at idle, looks like the Schrader valve went out after the static test on cylinder 1 today because it doesn't hold pressure at all anymore for anything. I will get that replaced and then do it again.

 

Hey Zack, how sure are you where #6 exhaust lifter went after the repairs?

Also, your checks have all been when cold. It is conceivable the lifter is acting up (losing internal pressure and collapsing) only when engine is warmed up thoroughly and oil is thin. So does it idle rough when cold? It's also conceivable that low oil pressure in general could alternatively be a cause, since #1 is the last one to be fed and oil pressure goes down when oil thins out and engine speed goes down. Furthermore, problem appears to be only when idling (time lowest oil pressure). You might also want to do the snap test with the engine fully warmed up and compare to the test when cold. It really sounds like test failed first time, and was OK second time. Could any inconsistency in bad or good snap test be temperature related? What does your oil pressure gauge read cold/hot/idle?

Still I would think a bad lifter would make noises. But can you hear it? Sounds like exhaust is kind of loud in the videos?

Just trying to throw some things out there. Not saying any of this is probable at this point. Just more questions.

 

Hey Les, so I'm not sure at all where the #6 exhaust lifter went after the repairs, I lost track of it while I had it out and it got mixed in with all the others. It's hard to say if it runs better cold or not because here's the thing, when I turn it on cold it will idle high for a few minutes until it warms up, and yes it runs less rough when it idles higher but I'm not sure if the engine is actually running any different? The exhaust is a bit loud from my purposeful exhaust leak at the flange before the muffler, I just took out the gasket (the gasket blew apart when it was misfiring badly about a year and a half ago) and I like the small amount of added noise, it's just right for me. I have the top bolt all the way tight then a few washers where the gasket would go on the bottom bolt so it's an angled opening towards the ground. I will listen more for valvetrain noise, I have to be missing something here. I'll take oil pressure readings later on my way home. Also, get the fuel trims for you George, I just cleared my computer after trying the running compression test so I needed to drive it around a bit. So I replaced the check valve in my compression tester and now it holds pressure again but shows the incorrect pressure reading, yes I replaced it with a tire valve core, they looked identical. But I guess not, what do you think Les, should I continue this battle with the compression tester or go get a new one? I kind of need a working compression tester to keep going here.

 

Zack, exhaust leaks is a known cause of issues with the computer controlling the fuel mix correctly! Some sources say any exhaust leak up front affects O2 sensor readings. Other sources say exhaust leaks ahead of O2 sensors affect the readings. I can say that open headers completely screws up the AFR gauge on my S10 (with o2 sensor 1 foot ahead of opening), rendering it completely useless at idle. Plug it into full exhaust and things change a lot. Another thing to consider. Still this would not affect snap readings. Still trying to focus on them until we can establish the mechanical condition of #1 cylinder.

Yes, you need a working compression tester!! Are you changing the valve up by the gauge, or the valve in the end that screws into the head - or both. There are 2 Schrader valves.

 

Thanks Les, my exhaust leak is right after the last o2 sensor that's behind the cat. I didn't think this would affect o2 sensor readings at all because air shouldn't ever be pulled backward up my exhaust right? Would this still affect the fuel mix, Les? I thought about fixing the exhaust leak just for a bit to see if that's what was causing P0420 when it first came on but came to the realization that the leak is after the last o2 sensor and it's not pulling in any extra air only pushing exhaust out so it shouldn't affect the flow of exhaust past each o2 sensor. Right? So about the compression tester, I replaced the check valve at the end that goes into the head, it had a broken spring. I wasn't aware of this second check valve... I will have a look when I get home, also I noticed another new check valve that came with the kit that's on a different attachment, I think I might try and just take that one and put it in the hose attachment I actually use and see if we can make magic happen again. I have read online at some places the tire valve cores won't work in a compression tester and you need a specific one made for it, do any of you guys have experience with this?