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I've had a 2000 Ford Focus for about 3 years now, and ever since I bought it it's had the following problem.  Sometimes, while accelerating, the transmission is slow to shift up and the engine runs a bit, also the radio momentarily turns off, and if the head lights are on they flicker.  When decelerating there's sometimes a startling jolt from the engine, along with the said electrical problems.  What's strange is that the car can go 2 or 3 weeks without any of these problems, and then out of no where they'll occur 50+ times in 1 trip.  Any ideas?  

until someone comes up with an idea... or a fix...

i think autozone.com  has wiring diagrams for that... in their repair info section.. when logged in...


but i would think a printed factory service manual would be a better thing to have on this one...    

start with the ground wires...    clean the cable ends at the battery...    with the battery out.. follow the ground cable...  take the bolts out that attach it to the engine block.. use a stainless steel tooth brush from a hardware store to clean the ring terminal on the end... clean the bolts that hold them to the block... clean the block face where the bolts fit...

there is another wire or two that connect the battery ground to the body...   remember.. the engine is sitting on rubber mounts.. so it is mostly isolated from the body...

dirty ground wires are the cause of may evils on cars...

light bulbs in your house will not work if one wire is loose...  think of how you car operates...

and ben franklin got it wrong.. electrons flow from negative to positive... so the engine and body are full of electrons...  loose ground... no power can get to that part...    with the electronics in new cars...  everything has to be properly grounded...  or stuff will not work.. or go intermittent...  and. don't forget.... the engine control computer is grounded directly to the motor...  not to the body or battery... loose grounds... dirty grounds... intermittent grounds...

oh... and a 99 cent pack of spark plug thread anti seize on the ground side fasteners really help prevent corrosion from rearing its head later...


now. before you put the battery back in...    follow the positive battery wires over to the relay block...    there are usually maxi fuses on the end of the relay block...  i have on other cars had these come loose... causing all kinds of problems...  

the one more thing... figure out which circuits are affected... see if they get power from a single source...  

all this work will take possibly an hour or two...  

really hot water will wash the corrosion off the battery top... do not use baking soda on the battery top....  it will get into the battery and ruin it...  use baking soda only in a plastic throw away cup  with hot water to dip the battery cable ends in ... just bend them down into the cup....   then wash with hot water... then wire brush them...