I have been driven demented chasing down ignition issues, mainly sluggish performance over 1bar boost, feels like it drops down to 4-3/4 cyls under boost. Normally coil packs would be suspect but i have five new ones in mine so i knew they were good. I had wrongly assumed the POS units either worked or they didn't, but after swapping them out and driving for a few days, then swapping to another set i noticed some perform better than others. Basically you can have a weak POS channel that runs fine at idle/daily driving, but starts to break down under load. i.e. when you put your foot down in anger.
They are basically a switch, they connect/disconnect the ground for the coils. On the 4 pin connector Pin2 is the common earth, this is what each of the coil packs are connected to when triggered. Pin1, 3, 4 are the three input pins from the ECU and from what i have read the ECU outputs a 3.3-5v signal to trigger them. The three pin connector are the connections to each of the coil pack ground connections.
Having sat down and stabbed them with a multimeter i started to see a pattern emerge. In the chart below i refer to the ECU Inputs on the four pin connector as the Inputs, and the coil pack connections on the three pin connector as the Outputs. I have colour coded the list to make it more obvious which ones are good, bad, and suspect. The Notes column is what i knew about the POS units before i started testing. The rest should be obvious
In short set your multimeter to measure resistance (ohms), connect the black lead of your multimeter to the common earth (Pin 2 on the four pin connector), and then probe each of the three pins on the three pin connector. If you get 0, i.e. nothing, no continuity, they are good, if you get any reading at all its pooched.
I went a step further and measured the resistance with the POS triggered with a 2.5v power source but that didn't tell me anything i didn't already know. Likewise measuring the (Ground to Input), and (Output to Input) resistance didn't tell me anything either, other than identifying a broken wire on POS X1. That unit died spontaneously on our 93 S4 so i knew it was dead to start with, hence i cracked it open in the name of science. Point of interest, the clear potting compound is actually a gel thats soft and sticky, wasnt expecting that when i stuck my finger in.
If you have any spare POS units and a multimeter to hand please post up your findings. If you know the health the POS unit to start with all the better. I am 90% sure i have found a quick and reliable way to diagnose their health, just need others to verify it.
Cheers,
Mark
p.s. I sorted the list based on age, oldest at the bottom and newest up the top. Coincidence, i think not
They are basically a switch, they connect/disconnect the ground for the coils. On the 4 pin connector Pin2 is the common earth, this is what each of the coil packs are connected to when triggered. Pin1, 3, 4 are the three input pins from the ECU and from what i have read the ECU outputs a 3.3-5v signal to trigger them. The three pin connector are the connections to each of the coil pack ground connections.
Having sat down and stabbed them with a multimeter i started to see a pattern emerge. In the chart below i refer to the ECU Inputs on the four pin connector as the Inputs, and the coil pack connections on the three pin connector as the Outputs. I have colour coded the list to make it more obvious which ones are good, bad, and suspect. The Notes column is what i knew about the POS units before i started testing. The rest should be obvious
In short set your multimeter to measure resistance (ohms), connect the black lead of your multimeter to the common earth (Pin 2 on the four pin connector), and then probe each of the three pins on the three pin connector. If you get 0, i.e. nothing, no continuity, they are good, if you get any reading at all its pooched.
I went a step further and measured the resistance with the POS triggered with a 2.5v power source but that didn't tell me anything i didn't already know. Likewise measuring the (Ground to Input), and (Output to Input) resistance didn't tell me anything either, other than identifying a broken wire on POS X1. That unit died spontaneously on our 93 S4 so i knew it was dead to start with, hence i cracked it open in the name of science. Point of interest, the clear potting compound is actually a gel thats soft and sticky, wasnt expecting that when i stuck my finger in.
If you have any spare POS units and a multimeter to hand please post up your findings. If you know the health the POS unit to start with all the better. I am 90% sure i have found a quick and reliable way to diagnose their health, just need others to verify it.
Cheers,
Mark
p.s. I sorted the list based on age, oldest at the bottom and newest up the top. Coincidence, i think not
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