ukpete

This is a question and answer!!!

I had the common misfiring problem under load!! its a 94 black rose auto convertible. I made a check list based on this forums Q and A...to help me track this problem down..ie leads, fuel pressure, plugs, opti etc etc

The symptons were:

Misfiring when engine warmed up mostly, sometimes cold!!
It used to stumble and pink loudly when accelerator floored
and back fired thro exhausts
OK when acc was gently pressed
Used to miss at tick over (not all the time)
Seemed ok at high speeds, but a real bugger in heavy traffic, engine rocking, revs up and down. had to put into neutral, to ease rocking

plus points were...it did not stall...used to start 1st time, no codes,
Oxy sensors were changed last year, fuel pressure ok

When checking the battery it had full 12 volts, but noticed a leak coming from positive terminal!! to end this story, fitted a new battery, all problems disappeared!!! what a result. Old battery was 4 years old but showed little signs of problems, I presume it did not have enough energy to keep the engine electrics going...worth a go if you have similar problems in the future all the best Peter:

pcolt94

I glad you are good because these are classic opti symptoms fitting the mold. Hard to believe a battery could cause that, I will keep my fingers crossed for you.

ukpete

Just to update you all, have run the car over several miles, in hot weather, wet weather, heavy traffic and it runs spot on. No more stumbling, misfires, or back firing at all...So please check your batteries before anything else, even if the voltage reads ok,,especially if the car has been idle for a while, bye for now ukpete

Nico

I guess you have a broken connection to the plates. I had that with a battery as well. When making contact, all ok. When driving the vibration made the connection coming loose. This can give a lot of problems. When the battery charges, a bad contact will give rise to quite severe voltage spikes because the regulator inside the generator can not follow the fast current changes. These spike really can upsett the electronics. In addition to that, it may give sparks inside the battery wich even can result in a battery explosion. With the bad battery I had I even saw the sparks inside though the translucent housing when starting. That actually gave me the clue of the strange behaviour of the charging circuit. I had luck that it didn´explode.