for some reason, my car has some post fuel issues. maybe every 3 times i take my foot off the gas it keeps giving some fuel and the air fuel sill stay from stoich to somewhere in the 20s or 30s as it keeps floating around before finally shutting those injectors off and going to lean air. sometimes it will keep giving fuel for at least 4 or 5 seconds.

im going to be breaking in a new motor tomorrow and i dont know if i should be concerned about that post fuel washing oil off the cyls and screwing up my ring seal? if so what can i do about it. ive tried 2 different sets of injectors so far to no help

 

If your seeing 20-30 AFR with a wideband AFR gauge that is very lean not rich. That is a fuel cut-off situation. Now if you had AFRs in the 7-9s that would be considered a fuel dump.

What ecu are you using and what if any base map are you running on it?

 

i should be more specific. the air fuel will sometimes fluctuate between somewhere in the teens to twenty or thirty before it shuts itself off and goes lean. it is enough to notice the car buck slightly.


it used to do it on a stock ecu and stock injectors. it continued when i swapped to an rtp neptune with stock injectors as well as currently running rc310s and the rtp. the car itself is a 92 teg.

 

AFRs in the high teens, twenties and thirties is not a rich mixture, it's extremely lean.

Honda ECUs do this when they receive certain signals. A high manifold vacuum (MAP) in conjunction with a low throttle position % (0-10% TPS) and high rpms (VSS) will cause the ECU to shut off the injectors and throw the AFRs into the high teens low 20s until the RPMs & manifold vacuum come back down to a certain number. It's called a deceleration fuel cut.

Now if your seeing this throughout the full range of throttle, from closed throttle to WOT. I would look into your fuel delivery as a possible cause of the lean problem.

What wideband O2 sensor and gauge are you using to read your AFRs and has this car been dyno tuned?

 

using an lm-1 with the bosch sensor i think its the lsu4. i didnt get to the dyno yet. i street tuned a map on the stock motor, drove it around for a few months and am now just bolting in the new high compression motor which hasnt run yet.

the air fuel behaves fine everywhere else in the rpm range and that street tune was totally smooth and felt like stock except for certain times when i take my foot off the gas and decel with this aforementioned possible post fuel issue.


again my biggest question is will the extra fuel (even if its just a little bit) is that enough wash the oil off the cyl walls and impede proper ring sealing

 

With AFRs in the 20-30s your not getting any extra fuel so you should be ok. As long as these readings are only seen on deceleration. As I mentioned above lean decel is normal and should not cause your new engine any harm.

 

I would strongly suggest taking it to a dyno for the engine break-in and tune

 

When you take your foot off the gas pedal, does it still feel like it's throttled a little and makes misfiring/popping noises?

You may want to check to make sure that your column 1 load value is less than the lowest amount of pressure the motor will ever see. If the column 1 load value is greater than the immediate throttle release and cruise down pressure, then the ECU won't know what to do and it keeps outputting.

I would also check your fully closed TPS voltage and that the software is synch'd with the voltage if possible.

 

ok, i cut down the fuel in the 26" vacuum column. new motor is in, fired up, ran till the fan cycled then oil changed. gonna take it for a spin soon and see how it does. right now i got the idle at like 13.9-14.3:1 and its smooth as stock at 900 rpms, brian crower st2 cams, about 11.5:1 compression.


i was having problems with my laptop itself. i bought a replacement chinese battery and it was making my computer run like ****. went back to an oe dell battery and its gravy currently.


ill get it on they dyno at some point soon in the next few weeks, but its my daily so im really not looking for ***** out power or going to go around flooring and redlining it much at all

 

This is how a AFG reads, X amount of oxygen to 1 part fuel. So like GhostAccord has been saying, you do not have a "post fuel" problem.

 

ive come to realize that. my original conception of post fuel was anytime the injector was not shut off and still giving fuel when your foot is off the gas. i was wrong. now my clutch isnt working properly. go figure