Thmanx

This is another issue i've had for the last year or so.
Engine is a 01 spec (2005 block), B18C5 I installed 3 years ago. Runs healthy, tuned by Bubba on a S300.


Every time I fill up the car at the pump, the engine has a very hard time to start/sustain idle. The greater the fill up (say a full tank vs 1/2 a tank) the greater the issue.
Engine has a very choppy idle, obvious signs of an over-rich condition.


My assumption is as I'm filling the tank up with fuel, the gasoline vapors in the tank are being pushed through the EVAP system and being dumped into my intake manifold.
Sustaining light throttle for a min or two after fill up, burns up the extra fumes and standard smooth idle continues afterwards.



The engine still has all its OBD2/Emission equipment installed (sans cat) and I was able to pass my Star smog just fine last year using a OBD2B USDM P73 ECU.


The only added hint that may help was a very annoying lean-condition my USDM P73 ECU always caused. If I ran that ECU for more then 2-3 days, the Long-Term fuel trim would eventually max itself out @ over -16% (Short Term in the -20-29's as well).
Giving me an eventual CEL for the fuel trim being to lean, and sometimes a minor leak in the EVAP system. (only at idle, once manifold pressure dropped while under any load, the condition would clear itself up)

I was lucky enough to pass the emission test because I only had one readiness test not ready (the EVAP which takes a few fill ups/drive cycles), and it hadn't been driving long enough to max out the long-term fuel trim which would through a CEL.


O2 sensors are 'new' Acura ones I spent way too much for when the engine was installed 3 years ago. And my OBD2 Scan Tool showed very accurate voltage modulation on the sensor. So the fuel trim was only doing exactly as the O2 sensors were telling it.
(i.e. O2 senses emissions are rich, fuel trim tries to lean the fuel out).



Initially I was running a Walbro fuel pump carried over from my previous supercharged B16A2, and I swapped it out for an OEM spec Denso unit. It helped a little but my Scan tool still showed the Short Term bottoming out its maximum adjustment.



We even -forced- the issue to fix itself by running an adjustable AEM fuel regulator and dropping the pressure to a pitiful 15psi. Which solved the issue @ idle, though obviously starved the engine when ever load was applied. We almost thought some how my OEM injectors (serviced by RC) were flowing 'too well' as if they were 310cc's and not 240cc's.


My initial guess back then was that I had a vacuum leak, but from what it sounds like now; it might be the opposite. (over-rich/EVAP leak into manifold)




What might be causing this? A stuck open EVAP purge valve? or a saturated charcoal canister? Suggestions?

rick_rabies

from reading all this i guessed the same things as you mention at the bottom.
my conclusion would be somethign with evap, check to see if its full? get a new one or do a mod where you cut it open and empty it and clean it out. or purge valve is stuck open. also try different injectors. injectors can give such a headach if they are just even a tad wrong CC or capacity. maybe to back to a walboro pump but a new one.

Thmanx

If memory serves. I even tried putting a vacuum cap over the Intake Manifold where the PCV system attached. It didn't seam to solve my idle/rich problem. Weird...

*Edit* I meant EVAP Vacuum Port

rick_rabies

but your gas tank vapor line still goes to evap can. is your gas tank getting proper ventilation? how old is the evap can?

Thmanx

*I Meant the vacuum port for the EVAP purge system.

Last time I tried that at was many months ago, and I didn't have the rough engine start after idle problem then (just the running too rich at idle with P73 ECU causing a lean out CEL).


I'll have to try it again to see if it clears it up, (which it damn better should, no other way for gas vapors to engine the engine)




As far as the EVAP can/valve; those are all original systems since we bought the car new in 00, (carried over from the D16Y8 engine)