misfire
It's possible. No leak down was done. I don't have the compression number of that cylinder but the guy looking at it said it was really good. He also found it odd that the engine pulled awesome vacuum and didn't fluctuate
He also couldn't actually see a miss on his test equipment.
I wonder... if I pulled all 4 plugs. I'd think if the trims show a possible fueling issue that one plug would be different than the rest. Ah, I'll start with some logging.
If the compression was good then there is no need for a leak down test or wet test. But what are the numbers? Usually if you ask someone what their fuel pressure is and they say good then they did not even check fuel pressure. Otherwise they will say 40 psi at idle (or what ever it was). Since the misfire code was on cylinder
#1 I would want to know what the compression readings were for that cylinder and a known good one like # 5 which is the first cylinder on the drivers side. I would also like to know what the first compression pulse looked like, it should hit 50 psi if the test is being done right(good battery, open throttle plate, etc.) and if the cylinder's compression is good. Also a running compression test could check for sticking valves or valve spring problems (but a fluctuating vacuum reading would also point that out). To do running compression test pull cylinder
#1 spark plug out and install compression tester, start engine and then release the pressure from the compression tester gauge with the little button on it and then let go of the button and see what the compression comes up to. Compare it to cylinder
#5 on the other bank. If both compression and running compresion tests pass there can be no leaks so no leak down test or wet test is needed.
If compression test fails and wet test brings up compression significantly more than the good cylinder wet test does then the rings are shot.
If compression test fails and leakdown fails(more than 20%) there will be air escaping from 1. intake 2. exhaust 3.crankcase 4.cooling system 5.side of engine between cylinder and block.
If compression test fails and leakdown passes then it could be a slightly bent connecting rod, worn camshaft lobe, bent pushrod, loose rocker arm etc. Another words the valves would not be opening fully or the piston is not coming up as far as it should.
A misfire on one cylinder is either caused by compression, spark, or A/F mixture problem on one cylinder. You need concrete test results to rule out two of the three and you will know which one it is. Don't assume that new spark plugs are good either, I was thrown off by a defective spark plug once. Check the resistance of the plug from the metal end where the wire attaches to the center electrode and make sure it has some sort of continuity or resistance reading. If you get a reading on the spark plug of OL or what ever your meter reads when the leads are not hooked up to anything means the spark plug is open and is defective. Instead of installing a new spark plug move the one from cyl 1 to another cylinder and see if the misfire changes cylinders. Do that with the wire also. When you change something make sure you disconnect the battery for 10 minutes and then reattach so the PCM's memory is cleared. Then drive it up to 60 and decelerate to 40 without stepping on the brakes three or four times. Then if the engine still runs rough hope a misfire code comes back to let you know if it changed cylinders or not.
And let us know about those STFT's and LTFT's.
Do the heads!!
lol
still blows my mind a obd2 provides sooo much info...something something FUEL TRIMS??
