Engine stumbles during low RPM acceleration

[93twodoorLX]

as title suggests this problem started for the first time 2 days ago, engine has 118,000 miles on it. and yes i have already researched and narrowed my probable causes. haynes manual and other sources (honda-tech, cb7-t) suggest that it could either be a

-vaccum leak, (unlikely)

-fuel system malfunction checked resistor box ohms and they are within range, checked injector resistance and they all between 2.6 and 2.7, this may or may not be an issue, ohms should be between 1.5-2.5

-EGR valve could be but again unlikely

ignition timing- unlikely because i set it and check it myself and it is between 16 and 18 degrees BTDC because i run 89 and sometimes 93 but i could try backing it down and see if that works.

fuel filter clogged- unlikely but possible, I changed it about 2 years ago and dont think it would be f'd up so soon

spark plugs fouled- checked them all and they all look identical with brownish color and no build-up no white spots, and no corrosion

Oxygen sensor faulty- not too sure, I unpluged it and drove around with it unplugged and plroblem persists so i dont think it is faulty O2 reading considering the ECU was in open loop correct?? no signal means open loop fuel map right??

so this is all i have in front of me, I dont have too much knowledge of this being a common fault for CB7s or not but just try to bounce some ideas off of me, It idles fine. it pulls hard but between 1500 and 2500-3000 RPM it stumbles under load. just so annoying lol

-sean

[old honda tek]

make shure the sparkplug tubes dont have oil ,when was the last time you replaced the plug wires ,i use only ngk wires .......

[Shag Wagon]

EGR ports clean? I am having a similar problem but I blocked off my egr for the tune I have and could be causing issues.

[EJX_Michael]

I had the same stuttering/stumbling situation about 3 months ago. I replaced the o2 with a denso and got a new distributor and havent had the problem since.

Try leaving the o2 unplugged and reset the ecu and see if the issue stops.

Make sure to reset it again if you replace anything.

[93twodoorLX]

bump to the top. i replaced the dizzy and it helped but it still stumbles when applying the throttle in higher gear and lower RPMs. def. seems to me like an ignition problem to me. unplugged the O2 to run in open loop but it doesnt seem to help, so im doubting but not ruling out the O2 as the culprit. probably gonna get new plugs and see how that does then maybe some new wires although mine arent more than 2 or 3 years old

anyone else ever had this problem, i know someone has.

-sean

[cloudasc]

Plug the vacuum line going from the egr to the intake with a screw, a cel will eventually come on, but thats one way to test if its the egr system causing the problem. If unplugging the o2 sensor didn't address the problem, then i'm pretty sure your o2 sensor is still ok, thats what leaves me to believe its the egr system.

[old honda tek]

if you are running cheapplug wires and they are 2 yrs old their junk get some ngk wires and make shure the tubes arnt filled with oil.......

[93twodoorLX]

ok well i replaced the O2 sensor AND thats not it, I blocked off my EGR with a plate that i had and thats not it. New dizzy new rotor, thats not it. plugs and wires are NGK and not that old so doubting that, but i am gonna get new plugs anyway and maybe try swaping wires to see anyway. all else has checked out only thing i have left to change is the fuel filter but again it isnt more than 4 years old so I'd be pissed to find out that its that.

Ugh im losing my mind, nothing is working.

P.s. IACV is good Ohms are within spec. and i just cleaned it

-sean

[cloudasc]

Have you done any checking/diagnosing of the map sensor? Have you tried another ecu? Theres really not much left to check that I can think of.

[whitejdmcb7]

check fuel pressure

[93twodoorLX]

going to check the map sensor and replace a couple fuel injectors with spares i have and see what that ends me up with.

p.s. replace the fuel filter today since it is cheap and easy and that wasnt it. unplugged #2 cylinder fuel injector and idle didnt change so im going to change that one tomorrow

-sean