Ok, heres the thing, I had no problems with rpm spikes at all. Then recently I went to go start the car and i'm getting serious rpm spikes. So bad that its almost impossible to start. I dont know what I have changed but sometimes I could even hear the injectors firing when the engine wasnt even cranking meaning I was getting a tach signal without my distributor even turning. I'm using an electronic distributor. Do you think it could be a faulty ignitor or something to do with the coil? I took the spark plug leads off the plugs and I still got some rpm signal when cranking, is this right? Common sense tells me it isnt because the coil shouldnt fire if the circuit is not complete. Im only running leading spark at the moment and my tach signal is off the leading coil. Can an ignitor or coil go faulty and cause this kind of problem or would they just die completely?

Any help would be appreciated.
Thanks

 

Hey, its painful isn't it!

Firstly the idea to remove the lead/sparkplug isn't going to remove the 'ignition noise' because the lead/coil should still arc out to the car body. You could try removing the power from the leading coil and see if the noise still occurs. It could be the starter motor or alternator as a noise source.

I think most likely would be that you need to clean your grounds with a file/sandpaper, and make sure your engine is really well grounded to the battery.

Have you got a resistor in your coil -ve to pin 24 path? I guess you could check the resistance between the coil -ve and the end of the wire going to pin24 on the db37 after the resistor. You will need to desolder the wire going into pin24 or unplug the socket and jam the probe into the female socket.

Check all your other grounding related to the ecu and electrical.

 

Thanks for the input. I think I will go search around thoroughly and check all my grounds and connections. The strange thing is how I had no spikes at all and now suddenly I have a large amount. I tried 22kOHM, 33KOHM and 47KOMH resistors on the signal wire and they didnt help so it seems something serious has changed. So difficult to diagnose these things I hope i can figure it out before it affects my mental health .

 

And just to give you and idea of how bad the problem is here are some logs. The first one is how it used to look at idle. Dont mind the slightly zig zaggy rpm line, thats just from the bridgeport's brap brap idle. The second one is of how it is now when I actually got it to start. As you can see, the spikes are huge and very frequent.

 

46257 RPM! damn.... you must have that thing balanced very well!