ISUBIEXI

I'm not getting much for input on my other thread so I figured I would start a new one in a better location.
My wife's car is a 1999 Civic Sedan, swapped in a B20 a little over 2 years ago. It ran really well for 2 years, very few issues, idle was a little rougher than I would hope but with an innovative mount that may have just been expected. It was running a Stock p75 for all of that time, car was great. I think about 4-6 months ago the car start to inconsistently drop rpms at idle and started to stall. All of the information is below but the work around at this point is raising the idle to 1k and removing the Vacuum line on the fuel regulator. This keeps the car from stalling but its still extremely rough at idle. Chipped p28 has given the best results so far but that's most likely since I raised the idle in the tune. The car is perfect and no power loss above 1100rpm as far as I can tell. I may have to hook up a wide band and vacuum gauge to keep a better eye on things but I hesitate since this is my wife's daily and if its not hidden well may invite unwanted attention. I really regret letting the muffler shop talking me out of the second O2 bung when we were working on the exhaust, that bung would have made things easy.

I have tried.
3 Different ECU's
New Distributor
New IACV
New Throttle Body and Gasket
New MAP
New TPS
New Injectors
New Plugs
New fuel regulator
New Fuel filter/fuel line from filter to rail.
Cleaned up the wiring on the OBDII A/B adapter
Removed Header and put on stock Manifold
Timing perfect
Swapped in the Stock Fuel rail.
Checked Valve Lash, everything was in spec
I want to pull the fuel rail again and add another spacer, I installed the stock rail initially with no spacer and the injectors bottomed out in the rail. I added a fender washer as a spacer but its not as thick as the spacers I have seen on other fuel rails. I doubt that would be an issue since the car runs smoothly at higher rpm but honestly I'm not sure what else to do. It would have been much cheaper just to pick up another b20 for $350 and swap it in. I'm sure I have dropped at least $600-$700 in parts trying to fix this issue. Its been at least 4-5 months with no change better or worse.

Using a Stock p75. if I leave the vacuum on the fuel regulator it will idle around 900 then suddenly stutter drop and stall. With the vacuum unplugged it idles at 1000 and drops to about 500-700 but does not stall. This is not IACV surging, its a non consistent issue. Its worse when the car is warmed up.
Using a chipped p28(B20 tune) it ran smoother but there was definitely still a miss/inconsistency at idle. You can see the exhaust/engine rattle when its doing it.
I hear a strange noise around the distributor/transmission. The noise occurs when the idle drops, kind of a rattling noise, the car still stalls with the clutch in. I am trying to determine if the sound occurs when the clutch is pushed in, it may be 2 different issues. I need to drain the Transmission and look for metal.

Any Ideas?

Guess I can try creating a different vacuum leak and leaving the fuel regulator plugged in to see if that makes a difference.

tony_2018

there suppose to be a spacer of some sort before installing the rails, kinda hard to remember, but it has to be set up the same way an LS has. Another thing is if it sounds like its backfiring you'll either have to look at the spray pattern of each injector and see if the distributor is ohm checked within spec with the FSM. Also did you re-pin the crank sensor properly if you're running an obd2 ecu? It looks for that.

ISUBIEXI

OBD1 ECU. P75. I have 2 of those and the chipped p28. Same result. I want to actually plug in a OBD2 P75 and see if I can get some better diagnostics.
The rail does have spacing but I did want to go back in and add a little more. Honestly I feel like we would have issues in higher revs if there was not enough fuel flow but this is definitely on my list of things to correct. I found 2 out of 3 of the oem style spacers.. not sure what engine they came off of but I do have them.

There is no backfire, more like a miss.
I have tried 2 sets of injectors, the current set was new. Same issue. I have used 2 different distributors.

I'm guessing the next step would be to pull out the ohm meter and start looking at things. Its just been such an odd issue.

HondaPartsHero

JRCivic1

What about the possibility of a couple of fuel injector plugs being out of order ??? The ground color for injectors 1 thru 4 beginning at the cam gear end of the rail would be Brown, Red, Blue and Yellow.

ISUBIEXI

I'm pretty sure that's not the issue. Car runs great outside of idle. The injectors are taped up in order and the harness is not modified outside of minor fixes. Maybe a bad ground or something. I guess I could try a new harness.

Ill double check the colors when I get a chance. My wife is still daily driving the car so its hard to get any time to work on it.

ISUBIEXI

I disconnected the Fog lights and Amp and so far the idle is fixed. I think it may have been a short in the fogs, I never stopped to figure out why they stopped working.
Car is for sale if anyone is interested.