Hey Guys

I have a old BMW 1983,, and it is running bad,, runs great just sitting there at 800 rpm when i give it gas it starts missing bad and no power ,, I found the coil wire going to the cap bad ,dirty, cleand it up and it still missing when i give it gas ,, with no power, so its been a long time that i have had to work on a old coil system ,, what i was wondering if the coil is bad or going bad , will this make it miss under load ?? i just dont rember . like i said at 800 rpm,s it runs smooth just like it should. .
thanks

 

Have you pulled all the plugs out and checked them? A bad coil wire like that means you were not getting a hot spark and you could have a fouled plug/plugs, the contacts inside the cap could be burned, more bad plug wires...etc....

Check to see if all the plugs are firing, if you find a dead cylinder and swapping plugs doesn't help, then you need to check compression.... You could have a weak coil but I would check all the above before I bought any parts.

 

yep i did that ,, cant find any this wrong , this is what i did to day with the car,, i pulled the car out last week and got it back on the road ,, was running great up to this point untill i washed it and cleand the motor ,, yep sprayed it down with cleaner and water ,, but not a hard stream ,, went to start it to move it and would not start ,, fooled with the cap and wires that is when i found the drity coil wire to the cap ,, dryed and cleaned and now it starts but like i said under power it misses so bad it wount pull the car , I guess tomarow i will try to get a new coil wire and try that ,

 

Something I have seen a time or two ( dozen )

someone with the best of intentions washes his/her engine, with a gentle spray ( 4000 psi washer ) and then it won't start. So, you dry off the plug wires, coil wire, coil, and try again. And it won't start. So you remove the cap, and see moisture. You wipe it dry, maybe blow it out with WD-40 or other equally useless commercially available product. Now all is well, you start the car, it runs well, then you shut it off. Next time you start it, it idles, but off idle it pukes,sputters,farts, misses, etc. So, having cleaned the igntion system, you assume it HAS to be something else.

This is where it gets tricky. You remove the cap and... moisture. Because there was still some built up in the lower distributor unit.

I have seen this go on for a couple days after a good washing, and yeah, its a pain in the butt.

Also look for carbon tracking on the inside of the cap. Oxidation on the pins inside the cap, and believe it or not, after a shower, spark will follow cracks that you can't even see, from one post to the next.

Good luck

 

Yeah, if it acted up after a wash, I'd let it sit on a warm day with the cap off, and maybe the wires off.

Once it is bone dry, hit everything with contact cleaner, blow dry, then dielectric grease.

 

All the answers so far are good. Another thing that can cause this is a capacitor (condenser) going bad. Have you pulled a spark plug wire off and checked the spark? Is it a big fat blue spark, or is it weak and yellow?

 

I once had a 240Z that had similar problems. I too had cleaned the engine bay ever so gently. Went thru all that you have done and still had recurring problem getting engine to run under load. Come to find out that I had inadvertantly sprayed the external ballast resistor (little ceramic looking thing with 2 wires). I guess the water provided a means for it to short out and ruined it. Put a new one on and problem was cured. Myself, a mechanic buddy and a couple of "Z experts" took 3 days to find.

Rotsa Ruck

Gary

 

yes if the coil is bad it will miss under load

 

Thanks guys for all the help .. it was the coil ,, I had changed one part at time as i got them , started with the plug wires , then the cap, i had tested the coil and realy could not tell if it was good or not , last i had changed was the coil and bammmmmm ran like new again ,, who knew bmw parts are had to come by ,, well 1983 parts are lol
thanks