Intermittent Engine Misfire Toyota 20r

[Fsharp]

So I've got the Toyota 20r with an HEI ignition module running off the magnetic pickup in the stock distributor. The HEI ignition module I'm using is a Pertronix Flame Thrower III with a Pertronix Flame Thrower III coil as well. I've previously posted about this engine so it might be familiar to you. Stock Toyota Ignitior modules are very expensive is why I went with this setup.

It's got new plugs, wires, cap, and rotor. Total ignition timing at 800 rpm is about 10 degrees.

What's happening is that every few seconds the engine has a misfire or two. It happens at idle and when the engines revved to 1500-2000 rpm. It seems to be an ignition problem since, with the timing light on, the timing light doesn't flash when the engine misfires.

I've checked all of the connections to the coil, and the ignition module. The air gap for the distributor pickup coil is between 0.006 and 0.008. I'm wondering what could be the cause of my misfire. I'm going to pick up a cheap coil at Autozone tomorrow to see if it's the coil. Any thoughts or suggestions as to what could be the cause?

 

[The_Eric]

Go back and re-read your last thread- I posted some diagnostics you can do with the test light and multi meter. It'll work here too.

Is the test light blinking and the coil not firing? If so, then the coil or it's B+ is wonky. If not then the module has or it's trigger is questionable. So then is the pickup coil putting out a steady signal? If so then module. If not then pick up coil.

You have a simple system- so it's just process of elimination. It may help to use an older analog meter to catch blips in the pickup coil as I don't know if the digital meters will read quick enough.

 

[expat]

How much did the Petronix stuff cost?

I run Toyota ignightors on both my Toyota and Triumph. So long as you shield them from heat (like unshielded headers) they are very, very reliable.

 

[HerrStig]

You may need a scope to catch those blips. With aftermarket systems there's always the chance that the firing pulses from the coil or the pulse to the coil primary is interfering with the signal from the pickup in the distributor. Are you using "RF supression" ignition wire?

 

[Fsharp]

Originally Posted By: The_Eric
Go back and re-read your last thread- I posted some diagnostics you can do with the test light and multi meter. It'll work here too.

Is the test light blinking and the coil not firing? If so, then the coil or it's B+ is wonky. If not then the module has or it's trigger is questionable. So then is the pickup coil putting out a steady signal? If so then module. If not then pick up coil.

You have a simple system- so it's just process of elimination. It may help to use an older analog meter to catch blips in the pickup coil as I don't know if the digital meters will read quick enough.


It's very hard to tell if the test light between B and C continues blinking when the misfire occurs because the light blinks on and off so fast.

I have a digital multimeter. I will see about using an analog one, maybe an oscilloscope like someone else mentioned.
I'm going to try another coil so see if that makes a difference and take it back if it doesn't. I'll also recheck all connections.

Originally Posted By: HerrStig
You may need a scope to catch those blips. With aftermarket systems there's always the chance that the firing pulses from the coil or the pulse to the coil primary is interfering with the signal from the pickup in the distributor. Are you using "RF supression" ignition wire?

I'm using an NGK spark plug wire set http://www.lceperformance.com/NGK-Spark-Plug-Wire-Set-20R-22R-RE-RET-1978-1992-p/1083032.htm

I'm using regular primary wire to and from the distributor pickup and to the coil from the HEI module.