Slight miss, solenoid resistor (injector resistor) out of spec

[mstgeer]

I have a slight miss I have been trying to diagnose. All mods are in my sig. What I noticed is I can all but eliminate the miss by enrichening the a/f ratio to around 13 at idle with the vpc or the neo. So that lead me to think it is a fuel issue. Tested the solenoid resistor per the tsrm and one leg is out of spec @ 6.8 ohms. Could this be the cause of the miss?

I was thinking of fabricating up a resistor, instead of buying OEM. Bad idea?

 

[3p141592654]

A slightly rich mixture will cure a lot of idle ills. It is unlikely the resistor is bad, or the cause of the problem. I would look for a small vac leak, as this will cause poor idle quality.

 

[mstgeer]

I double checked the resistance of the resistor and got the same results, 2 legs @ 3.8 ohms and 1 @ 6.8 ohms. Would not the higher resistance be cause for lower current at the injector potentially causing it not to pulse properly?

I will search for a vac leak this evening.

 

[3p141592654]

Well, it is out of spec so it should be replaced. Yes, you could try to replace it with an aftermarket 3ohm 50W resistor, but might be easier just to find a used pack, they seem pretty reliable. Personally, I would look for a vac leak first. It doesn't take much. My BOV vac line detached a while back, and that was enough to give me a rough poor quality idle, but otherwise the car drove fine.

If you have a scope, look at the waveform on the 6.8 ohm injectors and compare with a 3 ohm one. If the 6.8 ohm injector has a slower rise time then it could impact your idle.

 

[mstgeer]

3p, thanks for the responses. The scope is a little beyond by abilities, have not used one since airplane mechanics school, many years ago.

I have Dale 3 ohm 50 watt aluminum heat-sink, 1% deviation resistors on the way. I was reading on toymods where a lot of the swap guys are building their own due to issues with the oem 7mgte one.

I have checked and double checked for vac leaks, but will check again. I was hoping the egr cooler gasket repair was going to fix the issue but it did not. Boost does come on a bit quicker / stronger now though.