Hello all,
I've been lurking here for the past week trying to sort out my problem. haven't found a solution yet. Here is the history.
Bought an '89 civic 1.5 with a blown head gasket a year ago. rebuilt the bottom end with new ring, rod and main bearings, water pump and timing belt. Had a cel a couple days after (comes on randomly while driving), but performance never impacted. about a month ago I used an injecter cleaner (in tank) and there after my bucking problem started. At speed it is powerful and smooth as glass. but stopping at a light it will buck violently (and stall) if I don't flutter the gas to pick up the RPMs. It does it when going up a hill without down shifting,and around curves where I never had to down shift before. The code flashing (after a reset) appears to be 1 -O2 sensor. it flashes count: *1,2*1,2*1,2* etc. Am I reading it correctly. I replaced the air & fuel filter, spark plugs, valve clearance, PCV, distributer cap and rotar button. Flushed the IAC , but still problem persists.

 

used some seafoam in the vacuum line as has been described here and saw white smoke in the vicinity of the O2 sensor or the down pipe joint. every time I tried to see where it was coming from it was too disipated to pin point. I did not replace the O-ring at the joint when I rebuilt the engine. could this cause the issue or contribute to O2 sensor code, and therefore the bucking.

 

Do you have two O2 sensors? Codes 1 and 2 correspond to O2 sensors A and B on a B16A engine.

Sounds like you have a leak in the exhaust manifold, likely from the missing O-ring. This would interfere with proper O2 sensor function. Fix this problem before considering replacing the O2 sensor(s). I don't think this is causing the bucking problem, however.

You may want to check for an intake air or vacuum leak, adjust the idle screw, and clean the EACV for the bucking problem.

 

I believe there is only one O2 sensor. I have already bought a generic one from Auto Zone and had planned on replacing it . I cleaned the IAC But not soaking it over night (I think you call it something different from what my book calls it) . What is it about the injecter cleaners that adversely affect the IAC? It was running great prior to this. There is an o-ring in the exhaust flange but it is the original. I will install a new o-ring when I pull the exahaust maniford to replace the O2 sensor. Can't get the sensor out with out the flats beginning to round off

 

Your problem does also fit with clogged fuel injectors. Maybe the Seafoam treatment freed up a lot of debris in the fuel system and intake manifold.

 

can the injectors be cleaned. How are they removed after the retaining clips are removed. I have two injectors on the throttle body.

 

Two injectors on the throttle body?

The diagram may help for fuel injector disassembly. I don't know if they can be cleaned but it might be worth inspecting them.

 

yes two injectors. I have a dual-piont fuel injection system. I did not find a pic in the downloaded manual, however there is one on page 4-15 (lower right corner) of my Haynes manual: 1984 thru 1991. do you just pull them out? I removed the clip and they would not budge. nothing there to really grab on to with out the risk of damaging them other than the meter check in the book, what else would I be looking for? I once heard that injecters could be cleaned in an ultra-sonic cleaner.

 

update. Have pulled the exhaust man. and changed the O2 sensor. the O-ring between t he man. and header pipe was leaking( saw carbon traces extending beyond the o-ring to the outside of the flange), replaced it with a new one. pulled the EACV and soaked it overnight, lubed it in the morning before reinstall. Disconnected the neg battery cable to clear the ecu. started up, topped off and purged thecooling system. let idle for twenty min. test drove. No CEL present this time, however the bucking is still there. the RPMs flutter slightly at idle (when up to temp)- from 500 To 800. Since this started after using the cleaner, could it be a fouled pressure regulator and/or injectors. Has anyone pulled th e injectors from a dual point system? can they be cleaned?