Thanks for info… putting old ones in on 1 Bank is good idea. Before I do that tomorrow I am going to run the cylinder balance test suggested by “Mustangman” in earlier reply. He indicated to unhook each injector with a vacuum gauge attached and note the RPM drop and vacuum reading after each. It may determine a bad injector based on an extreme anomaly…
If you have a fuel pressure test setup and a way to pulse an injector, the normal way to do a balance test is to pressurize the fuel rail (engine not running) then pulse a single injector a certain number of times, say enough total injector open time so the fuel rail pressure drops 30%. Then re-pressurize & do that same thing for the other injectors, one at a time. Each one should drop the fuel rail pressure the same amount if they are all balanced.
Everyone,
Has anyone had misfires after eliminating the basics? Assuming air intake, fuel supply, compression, spark, and crank/cam timing, exhaust seal, etc are all good What is the strangest or rarest thing anyone has ever seen? Oh I even did noid testing on injector inputs confirming the ECU is firing them…
Could this ultimately be a valve seating, dirty valve, etc? I don’t mind tackling taking heads off and send to shop for rebuild… but I would think the compression / leak down testing is what tells me if valves / rings are good right? My compression testing was good…
Also has anyone seen coils work and fire (Inline spark test good) but not be strong enough for combustion? I would assume if I have coil spark the plug would be the culprit?
A weak spark will definitely cause hard to diagnose intermittent misfiring. I had a problem with my old truck (carbureted and ignition points) over the summer where it wouldn’t start. Cranked ok, but no start. I sprayed some starter spray into the air intake and that seemed to make it want to pop a little, but even with starter spray it still would never start and run even briefly. The spark test revealed a definite spark, but the spark was more orange-ish in color that I’d expect. But it didn’t seem so orange to prevent starting. After totally ruling out fuel system issues I went back to testing the ignition system. Turned out the ignition points weren’t making a low ohm connection and that prevented the coil from fully charging. Sure enough a little filing on the points, resetting the point gap, it did the trick … vroooom … engine started right away. So you might well have a weak spark for some reason.
George that sounds good but I have no way to control the injectors. I guess if I could find an old injector connector I could look up the wiring specs and make an igniter switch. I will check if auto parts makes one for testing.
I would not go very far on idea of any precision control of the injectors with no special equipment.
As for connectors, likely you will find one in auto parts store, but it is much easier to improvise one with a couple of pieces of small plastic tubes (like straws in kids boxed juice) and wires.
This is what I did before, but I’m a “cheapskate” and it was done for one time use, after cleaning my set of injectors it went directly to the trash bin.
I saw the vid on making a tester. I also see there is a $15 system similar that comes with power cables and a plastic orifice to plug in injector and set over spay can… I also found a local injectorrx company that will officially pattern test injectors for $10 each. That might be worth doing on original OEM I removed instead of spending a lot of money on new. But that’s down road if I exhaust all options.
UPDATE - I sealed my bank 1 exhaust leak. While waiting for it to dry I removed plugs 1 & 5 as I am going to swap them along with coils and cables. 1 has most misfires and 5 not misfiring…
Attached is the pics of plugs… 1 on left, 5 on right…
you removed plugs… why not to replace them now?
they are so cheap I see no reason playing “swap them around” game
I understand. I did not change them because I put new plugs in November. I year ago. I am trying to see if anything follows between a good cylinder vs misfire cylinder…
I swapped per last comment, cranked it up, idled until operating temp reached… I can feel a slight misfire. Attached is pic of my scan data. Fuel Trims look good except I would like to see LTFT2 closer to zero (0) like LTFT1 is… but numbers ok.
I still see misfires in C2 and C1 although I don’t understand why C2 shows misfires in “Current” display, while misfires on C1 only shows hits on the “History” display? As I write this is just set a P301 fault code. It never sets a P302.
The new injectors came with new o-rings. I soaked the old ones in B12 for a couple days and the put new o-rings in them before storing them away…
I just ordered this kit to see how the original is injectors are working. While waiting for it I am going to swap injectors between C1 and C5 tomorrow. In addition I am going to recheck compression on C1.
The gaps on those spark plugs look bigger than I’d expect to see. no experience w/your engine configuration, takes so little time, so suggest to double check the spark plug gap is correct.
Seems like a good idea. Some caution about sparks and open flames in order as a fine spray of carb cleaner might be very flammable, even explosive. Also the injector selenoids are pulsed in normal operation, and aren’t designed to be turned on 100% for long periods of time. on for too long could causes them to overheat w/resultant damage. so limit the amount of time the best you can. Best of luck.
I forgot to share. I did check all of them for gap spacing of 0.040… I like this device (see pic) because I just slide as far as it will go and that’s the setting.
My truck’s are gapped 034, 032 for my Corolla, so that’s why 040 looks a little bigger than I’d expect. I have one of those gadgets too, and use it as my go-to plug gap tool.
While I am going to swap injector and try a new cable harness I think I am back to where I was a few months ago… its likely not anything external… but I don’t have high end scopes to monitor all signals…
My gut tells me I have bad valve. Even though my C1 compression is at 170 and meeting specs it’s still lower than the other cylinders which are 190+. I just hope it’s a valve and not a ring… I just read that if smoke puffs out of the oil cap it’s a ring so I will check it…
It’s possible it could be a warn cam lobe but I have remove the head cover and seen the rockers moving for both (all) valves… but I am not sure if that means anything because a warn lobe could just indicate the valves are not opening fully as they did when cam was new…
If I do remove the heads for valve rebuild I will go ahead and replace the camshaft and lifters at same time…
Ok before I go too far I will finish my basics …
Thanks for warning… I did see that on a vid. I will just tap the positive lead on battery a few times and minimize the solenoid open time… a few short spray groupings spaced by a few seconds… but definitely much less frequent than real world…
I 
just finished a compression test on C1. Engine was not hot but I had let it get to operating temp and turned it off. By the time I did the test temp was likely around 150.
ok pics attached.
First test after 7 cycles of starter I maxed at 190 psi…
Then I added a cap full of oil to cylinder and repeated test. After 7 cycles I maxed at 215 psi…
So what does this mean? Shoukd compression be cause of a misfire? Do I have a bad ring?
I am going to test C2 also since it was having some misfires…
Results from C2.
Test 1 - 195psi
Test 2 - after cap of oil added = 202psi
So less improvement with oil added.
I know I am sharing a lot of info. So above C1 was 190 before oil, 215 after oil.
I just test #3 and #5 on same bank.
#3 before oil = 196 psi
#3 after oil = I skipped because it was very difficult to find the thread on this one when installing the pressure cable.
#5 before oil = (see pic) 190 psi
#5 after oil = (see pic) 210
Key takeaway. my #3 and #5 cylinders on same bank do not misfire. The compressions are similar and while the after oil increases #1 by 25 psi it also increased on #5 by 20 psi…
I am going to replace the injector next… but if not injector who votes it’s a ring , verses a bad valve /seat?
Last thing I did today was place this coil pack cable harness on both bank 1 , the bank 2 just to see if it cleared up any misfires… nothing changed…
Thus if it is cabling it’s between bank connector and ECU…
C1 results clearly show worn rings IMHO
I would also suggest that it is not know if they are worn or stuck in their groves, so you might try to chemically clean it and recheck compression
if that does not help - just a wild idea…
if C1 compression is substantially different and this is where you see the majority of misfires, using something like “Restore” would likely give you some compression boost and might allow to let this engine to run a little bit longer.
it is close to quarter million miles after all, so one way or another it is not going to last another 250K miles
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