Hello all. Im really racking my brain here on this car and its really bugging the crap out of me. Hoping an experienced honda tech could give me some experience knowledge to help me get this figured out. So anyways im working on this car for my neighbor. He got it for free and the previous owner said he was told it needs an engine. No more information was given besides there was oil in the cylinder. I have a cylinder one misfire and thats the only dtc's being set. I hook up the scan tool and at idle it does run rough but almost like its just a shimmy from motor mounts maybe. I look at the misfire counters for all 4 cylinders and none are counting. When i rev it to about 2500 rpm cylinder one starts climbing pretty fast. So i started with the basics. Swapped the plugs and coils and misfire did not follow. Checked for spark and all four cylinders had good consistant spark. Next i moved to the injectors. I swapped cylinder 1 and cylinder 2 injectors and no change. My neighbor actually replaced the injector with a new one and also no change. Next i did a compression test. Got the vehicle to operating temperature then ran a compression across all 4 cylinders. cylinder 1 had 175 psi cylinder 2 had about 175 cylinder 3 had about 185 and cylinder 4 was about 178 that all seems good to me so i didnt even try a leak down test at this point. Even knowing this i still decided the pull the valve cover and kinda check valve lash. I only checked cylinder one at tdc cus thats the only problem cylinder and intake and exhaust were within spec. While the engine was running i sprayed carb cleaner around the intake manifold and there was no spike in rpms on the scan tool. ANyone ever experience this sort of issue or know what i should check next? Any help and knowledge would be appreciated. thank you!

 

Leaking valve is my guess. Usually dont show up on a static compression test. (thats ancient testing)

Need to do a relative compression test or better yet a pressure transducer or pressure pulse wave sensor test.(sometimes even an RC test wont show a leaking valve)

 

Thank you for replying to my post. I believe i did figure out the issue. Relative compression would of definitly been a better test. Alot of things would have been bettter tests for me but right now im working out of my garage with minimal diagnostic capabilities because all of my tools are at work and i hate to transfer tools back and forth. Anyways back to what i think it is. Well to begin with my way of checking the injectors was by using a stethoscope to hear to injectors clicking(i know horrible test) but anyways sounded like all injectors were actuating. I didnt like that test so with minimal tools here i decided to pull the fuel rails zip tie all injectors into fuel rail laid a towel over all injectors and cranked the engine over. 2,3,and 4 all had a spot from fuel on the towel. 1 was dry as could be. So i checked the wiring and was reciving battery voltage to both sides of the injector. Seemed good to me. Traced the control wire back to the ecm and was getting battery voltage all the way to the ecm. Seems good to me knowing that this is ground side switched circuit. Well i dont have a noid light kit at home so i decided to use a test light to verify that the pcm was grounded the injector when cranking. Hooked test light to battery posative and back probed injector control wire. No flash of the light. Just to verify my test is correct i back probed 2,3, and 4 injector control wires and performed the same test. Verified all other injectors were grounding in the pcm. So then i got the thinking does honda disable injector when it determines there is a misfire. So i cleared all faults and actually did a ecm reset buy disconnecting battery cables and shorting them together with ingnition lock set to postion 1. Then i performed the same test again and still no injector one flashing. Let me know what you think?

 

Rudimentary for sure,but it sounds like you found the issue.

Youll want to check again at the PCM to determine whether or not there is actually a lack injector control or if you're dealing with a wiring issue. If the PCM is bad,ohm out the injector.(hot and cold) It probably took out the driver.

 

yes I had already done that when I decided pcm had failed. There was battery voltage on the control wire at the pcm. But the pcm will not control injector. I ohm’ed all injectors and I saw no major difference in resistance on all four. That kind of had me baffled because shorted coil windings in injectors are normally what fry the driver in the pcm. So anywho. I got a new(junkyard) pcm. Yes I know bad news bears. But I’m gonna grab my scan tool on Monday swap pcm‘s and I’ll have a definite answer. I’ll post back here to let you know if I verified the repair or wasted my time. Thanks again for your input.

 

In the future, I suggest joining Diagnostic Network. (Diag.net)

It is a professional automotive technicians website that focuses on diag work such as this. Lot of reeeaaaaalllllly smart guys on there.

(This site is mainly DIYers asking for help)

 

This is probably the best thing ive heard all day. Always interested in bouncing ideas back and forth with real capable diagnostic techs about those hard to track down issues. Its like a lifetime supply of technical service bulletins! Thanks DCFIVER!