nofrills

Hi guys, I've been having a lot of problems with the rx7 recently.. its a 1980 series 1 with a rx4 13b, still with a nikki carb

the car starts first crank, hot or cold. it'll drive nicely until it gets up to temperature, and which point it'll start what sounds like misfiring, a rapid "blurring" sound, and an immediate loss of power. my vacuum gauge still reads 20 inches when this happens, so i don't think it's a seal or spring failing

usually the first time it does it, it'll correct itself after a few seconds (giving me a heads-up that it's time to start looking for somewhere to pull over!) when it kicks in again the car will start to slow down, if i put my foot on the gas it'll start jerking, bunnyhopping almost. if i stop the car at this point and restart it, it'll continue to misfire, and has to be left to cool down.

ive replaced the plugs, leads and distributor cap, and have swapped the coils out for some secondhand ones. i've felt the ignitors and neither seem especially hot... at this stage i'm thinking either the ignitors, or perhaps something with the carb (which has been rebuilt, but I have no idea what work has been carried out to adapt it to a 13b)

any ideas guys?

j9fd3s

iTrader: (3)

assuming the engine is ok, which it probably is. i think it could be either its too lean when its hot, or there is some sort of ignition thing going on. so i have two ideas.

since you've changed the cap/rotor/wires, i'd maybe check the coil voltage, when its cold, and then again when its doing its skipping, maybe there is an intermittent bad connection. could be a failing igniter too.

the other idea is fuel, it might be a weak pump, or some other weird thing. try adding a little more fuel, if you can get it to skip at idle, try richening the idle mixture and see if it does anything

nofrills

hi mate, thanks for the reply

originally once it started giving problems, it wouldnt even idle... having replaced the ignition components, it now idles but will start misfiring as soon as i load the engine up

i thought about the carburetor, but if heat was causing a problem with it, wouldnt it be running far too rich? i've pulled the plugs out and theyre not sooty (or white)

at the moment i've dug out an MSD 5 ignition box which i'll wire in, to take the leading ignitor out of the equation. if it still gives trouble, i'll try swapping them and see what happens.

is there anything in the distributor that gives trouble? i measured the gap in the pickups and it seemed alright..

the pump is old and doesnt sound great, but i checked the fuel levels last time and they were fine. will grab a heat gun and check everything out with a bit of temperature in it.. accelerator pump is another possibility i suppose... geez it could be pretty much anything!

DivinDriver

iTrader: (15)

My money's on a coil or ignitor that's thermalling out; often an open winding in an ignition coil (or a cracked component/connection in an an ignitor) will be fine when cold (the cracked conductor still touching) until thermal expansion sets in and the gap gets opened up.

You mentioned having swapped the coils, so you're right to be thinking ignitor in my book; specifically the lead ignitor, since losing trailing spark is barely noticeable in an operational sense. You can swap them lead/trail to see if the problem changes.

It's possible that a winding in one of the pickup coils in the dizzy could be bad, but thats a lot less common; they are not subjected to much stress, either electrical or mechanical.

t_g_farrell

iTrader: (1)

+1 on the ignition. The SAs have a funky little circuit in that box that holds the ignitors. When
mine went it had similar symptoms and when I took that box apart I saw scorch marks on some
of the board in there. So it was either that circuit or it fired my ignitor in the process. Never
checked the ignitor out, just replaced the whole shebang with a different ignition setup using
GM HEIs and Ford TFI coils.