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did you ever get a hold of a $20 fuel pressure tester kit from Harbor Freight, hook it up, lay the hood on it with the gauge facing you in the driver seat at the windshield, drive around and see if the fuel pressure is steady ?
Nope, but this car is dual-fuel - gas and LPG. Acts the same on both fuels, maybe it's a little worse on LPG. So there is little hope here. Where does that fuel pressure tester hook up? Because I quess that it will be a bit of a problem to hook it up
also try gently wiggling wires around while the car is idling and clean the main engine ground
All possible grounds are cleaned and retightened. All five of them, as far as I remember. That was one of the first things I've done. What wires do you mean? There are lots of wires under the hood Plug wires NGK, new and tight. Wires and connectors to that go to the fuel injectors are o.k. I really suspect wiring or connectors too, just don't know where to look, because issue lasts 3 years already, so it seems to me that I've wiggled most of them. Main thing is that this issue doesn't set a CEL. ECU thinks that engine runs good enough Funny thing is that engine runs smooth when driving at higher and constant speed, but idle is sorta rough, car hesitates on slow speeds and when throttle is released and then pushed hard - it seems that engine will tear the engine mounts and jump out - it's that bad.
obviously since it's doing the same thing with the new engine it's clear something not associated with the engine is bad, it really sucks it's not throwing a code, you need to start plugging off evap things by unplugging the sensors and seeing if it runs better after throwing a code, which turns off that system
I've tried to disconnect every vacuum hose that goes into intake manifold and plug the connector to make sure engine does not suck air in - brake booster, PCV, FPR, evap hose, all of them. That did not do much. I've even tried to disconnect every sensor that is on that engine - except CKP/TDC, cause with these unplugged engine does not start It was the same or worse in all cases. Tried to swap with known good MAP, IACV, IAT, O2s, ECT, injectors, block and then clean EGR system and so on
OK so I couldn't do any measurements because my alternator died I'm replacing it on wednesday.
Really, wiggling wires won't make any difference here. It was the first thing I've checked when engine started shaking occasionally on idle. Replaced spark plugs, wires, distributor and cap anyway!
Could be a connector tough. Or even the ECM.
They mention it in almost every troubleshooting instruction in the manual if everything fails: "substitute a known-good ECM/PCM".
EGR? Did you read first post in this topic? EGR was cleaned (EGR plate too in my case) and it is working perfectly. The same as TPS, MAP, O2, PCV and IACV.
This is not such trivial problem.
This is getting really frustrating. Now i have to look at it with oscilloscope. My quess is either air or ignition (timing) problem. MAP sensor should compensate every air leak before the combustion chamber, I didn't check intake manifold with vacuum meter though, just by eye and carburator spray.
The "good" thing is now engine chokes even once on iddle at low rpms when i press gas pedal. Should be easy to pick by oscilloscope if it is an electrical issue.
Can this be because of clogged intake manifold? EGR passages and holes into IM were blocked with carbon, i cleaned that, but maybe there's much more to clean inside IM runners and this causes problems? Is that common on hondas? It's not so simple to take entire IM off and clean it, but maybe it's worth to give it a try?
did you clean the air circuits around the metal intake manifold gasket? those circuits then go to the main hole that's blocked. after that if you got carbon gunk into the hole it goes into the water passage. the egr valve is bolted to the water passage, suggest you unbolt the passage and clean out the carbon that may be stuck there. I now will use a vacuum when cleaning out egr holes because of this. I was blowing straight brake cleaner down into the hole, luckily I also rebuild the water passage seals. those 2 weird looking water passage seals are also prone to leaking coolant fyi.
Did some measurements with oscilloscope:
TPS signal looks perfect
Knock sensor works (i can't tell if it is good for sure)
CKP signal perfect
MAP has some noise at full throttle (low vacuum) but it seems that it is not picked up by ECU
TDC signal perfect
CYP signal perfect
Ignition pulses from ECU ideal
Fuel injectors pulses great (about 3ms at idle)
These signals were taken from the ECU connectors, so they are 100% accurate.
RPM are steady but i definitely get misfires. Engine shakes a bit and vibrates (mounts are ok) but not all the time, just sometimes. The other day i feel notnihg at all. Compresson is 14,3-14,5 Bar on all cylinders.
I hope that this distributor is faulty in some strange way. Im going to test sparking today. I will also repeat knock sensor measurement because i'm not certain about it.
One thing I am pretty sure of - when my car hesitates (feels like something's pulling the car back) timing gets retarded at the same time. I see this on OBD2 scanner when driving. But what makes it pull the timing, I don't know. Maybe because of some sort of misifire, maybe there are other reasons. Only ECU knows why it's pulling timing back
Are you sure about your new knock sensor? Because mine doesn't work at all :D No signal, only high frequency noise which firstly i thought was good (i was drunk btw ). Also checked with multimeter - no continuity whatsoever. So i shortened ECU pin to the ground and went to test ride... and there is a huge difference especially when i touch the gas pedal.
Im coming back in a few days when i replace and measure it again.
When I was trying to disconnect the knock sensor it broke apart. So I soldered broken wires inside to the plate of piezo, glued it with a two component adhesive and checked with oscilloscope on the table. For my knowledge it works fine (waveform depends on how hard I hit it and with what object).
After reinstall I can really notice the difference. Car runs smoother, accelerates with almost no hesitation, has more power and performs much better at low rpms ("traffic situation" You know what I mean) BUT it still shakes 2-3 times at full acceleration and deceleration. So what I did?
I went down the hill, gained some speed and turned ignition off completely. Then on the 2nd-3rd gear I began to press and depress clutch pedal. And bingo! It shakes just the same way. You know what it means? Something is horribly LOOSE in this car. Either engine mounts, transmision or axles (or all of them).
My main problem at the moment is broken hood cord, need to figure out how to open it. After that I'll proceed with the issue.
it should advance timing when u open the throttle ... since its not then something is keeping it from doing that ... like i said i think this is knock sensor related somehow
Ok so I lifted the car today and I've noticed that when I turn the right wheel back and forth (in gear) whole engine and right axle shakes like the way I feel it in the car during driving (just not that strong). I'm really thinking about engine mounts. They might be worn out but not damaged to the point where it is obvious. I am also worried about that inner cv joint on the transmission side play. It shouldn't be that loose.
My 2001 Accord V6 had a bucking engine too and the dealership had to replace the front engine mount and it went away completely the front engine mount is about a hundred bucks plus it usually has a vacuum hose it's for dampening. You know for sure it's the front engine mount if at Park you put it in reverse and it jumps the whole car
04-22-2017, 02:15 AM
Re: Honda Accord 2002 F18B2 bucking/rough idle
Plug wires NGK, new and tight. Wires and connectors to that go to the fuel injectors are o.k. I really suspect wiring or connectors too, just don't know where to look, because issue lasts 3 years already, so it seems to me that I've wiggled most of them. Main thing is that this issue doesn't set a CEL. ECU thinks that engine runs good enough 
I'm replacing it on wednesday.
