B18c4 missfire/fuel issue driving me nuts


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gavgen10

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Jun 29, 2009
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93
hey all, iv had my mb6 vti-s for a few months now, to begin with all was good

then the car developed a hesitation under part throttle, if you were sitting at anyspeed on a light throttle the car would seem to hold back and feel as if it was running out of petrol/misfireing,if you put your foot down it picked up and would accelerate as normal

recently i changed the dizzy as something inside failed and the car would not run(swapped the coilpack but it still would not go so i fitted a known good td86u dizzy from my b18cr civic coupe)

even after changing the dizzy the problem was still there so i purchased some new parts to try to eliminate the hesitation/misfire

dizzy cap
rotor arm
plugs
known good leads
fuel filter
oem airfilter

still the car is missing/holding back under part throttle and on friday it was randomly dropping to running on three cylinders,its back to running on 4 and just holding back/missing slightly now

engine is standard except for a drilled airbox and a decat pipe with oem centre and tail sections

it will empty the expansion bottle on a weekly basis,but once its empty it never losses coolant from the rad,just the bottle so i suspect a leaky bottle rather than HG problem but this combined with missing makes me thing HG, I have no smoke or steam from the exhaust

this problem is at its worst when cruising along trying to drive sensibly but never really does it if you loon about :angry2:

if anyone has any ideas please post as iv been trying to sort this for months, sorry for the story
 
My money is on a faulty 02 sensor. Plug it out and drive car see does the misfire go away
 
my car has almost exactly the same problem except the coolant level, i would also like to know what this problem is.
my first suspicions were the timing as it was over running when i turn the engine off so ive got myself a timing light so im gonna have a go this weekend, but also gonna try changing the same as you have
 
would i be correct in saying that the 02 sensor only controls fuelings at small throttle positions and not at WOT hence why it clears if i give it WOT, or am i mixing o2 with MAP
 
gavgen10 said:
would i be correct in saying that the 02 sensor only controls fuelings at small throttle positions and not at WOT hence why it clears if i give it WOT, or am i mixing o2 with MAP
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Yep the 02 sensor gives feedback to the ecu when in closed loop(part throttle) and the ecu apply's fuel trim as needed. If the 02 sensor was giving a false very rich reading then the ecu is going to pull fuel to try bring the air/fuel mix back to stoich(14.7) I think you could be experiencing a lean misfire. Plug the 02 sensor out and see how it drives then
 
i will try in the morning, so basically its possible my ecu has been leaning the fueling out so far its almost running it out of fuel?

potentially i could melt a piston due to running lean same as on a turbo...now im worried
 
gavgen10 said:
i will try in the morning, so basically its possible my ecu has been leaning the fueling out so far its almost running it out of fuel?

potentially i could melt a piston due to running lean same as on a turbo...now im worried
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Basically too much air not enough fuel. Running lean at part throttle and running lean at WOT, heavy load are two different things. Less likely to cause any damage running lean at part throttle, lite load but not advisable at the same time.
 
i had the same problem, it was the O2 sensor. just unplug it and take it for a drive, if the car is good, then its the o2 sensor
 
unplugged it this morning before my daily drive to work ? what...missfire is gone...you my freind are a genius...now to buy a new lambda sensor...cant believe how much iv spent and nearly parted the car out over a lambda sensor lol

done 40ish miles now without a miss and my cars back to being pretty quick again...feels like vtecs been disconnected for the past month lol
 
Sweet, good to hear ! I was thinking it was to do with the injectors, i guess i was right ( in a way lol..)
 
gavgen10 said:
unplugged it this morning before my daily drive to work ? what...missfire is gone...you my freind are a genius...now to buy a new lambda sensor...cant believe how much iv spent and nearly parted the car out over a lambda sensor lol

done 40ish miles now without a miss and my cars back to being pretty quick again...feels like vtecs been disconnected for the past month lol
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Who the man??:D When you get the new 02 after fitting it remove the negative lead off battery for a min. to reset ecu:nice:
 
gavgen10 said:
ill just pull the backup fuse under the bonnet :p
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Yeah that's what I do but found its easier to tell other people to remove battery cable as most don't know where that fuse is but obviously you do:D
 
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