coil harness adapter

[340valnt]

I'm having misfiring problems 0300 code once cleared no codes now I thought about building a coil harness adapter to go in between wiring harness and coil harness. 12v source wires only. Idea is to ground one wire per cylinder to see if that is the one missing. My question is will this overheat my coils, cause problems with ecu grounds or something i'm missing. Did a complete hose replacement 3months ago worked great, swapped out maf no change called t3 they seem to think it was injectors on I put a stethescope on them and ohmed them when did hoses and gaskets This is a 96 so its got the good coils. Only run premium gas in it. thanxs

[elwesso]

On a 96 the injectors would definitely be more likely, as 90-96 coils as you said seem to be good, however I wonder if the 96's were close enough to the 97-01 that they may be suspect???

If you want to try and isolate each cylinder, I'd just unplug the connector off each coil. All you'd have to do is take off that little plastic piece off each bank. I don't think what you're suggesting I'd feel comfortable with, I believe all that stuff goes back unfused to the ECU so that means you could short stuff out easily if things didn't go exactly as planned.

If you have a consult or take it to a place that has a consult, you can turn off each cylinder one at a time (power balance test). Maybe a standard OBDII code reader could do that?

Normally if an injector is bad it ohms bad, and if you listened to each one, almost has to be a coil?

[Q451990]

Injectors are certainly more likely. Have you ohm tested them in the last day or two? A good one today can read 300 ohms tomorrow... failures are unpredictable and rapid. Test them while hot... they tend to read closer to spec when cold, even when they're on the way out.

Heath

[340valnt]

thanks guys for getting back to me about killing the cylinders. So you can disconnect the coils while the engine is running with out any problems to the ecu. After considering this and the no codes you can't get a data stream on a obd2. It seems to be misfiring on multiple cyl. I think i'm going to start with the iac. I just found the string on cleaning it and checking the setting. Just so i'm clear. If it is the iac it will be stumbling in the lower rpm range? up to 2000 rpm . Thanks

[Q451990]

I don't think the IAC will cause issues like you're describing... mostly just low idle. I've never pulled the coils with the engine running... I don't know how you'd even keep everything hooked up and be able to access them.

Heath

[340valnt]

i think he meant to disconnect them 1 at a time . That was the reason i was going to make an adapter for access in the harness on top either to disconnect the power 12v supply or break the ground circuit in the ecu either way they won't fire. I wouldn't want to just ground out the coil with the power hooked up i think it would cause the primary windings to run hot. I read on yahoo i think about using a infrared thermometer on the exhaust and check for temperature difference Kinda make sense I might try it. thanks

[elwesso]

So I'm assuming the car has a sort of bouncy idle? If so then it's definitely misfiring.

I think probably if you wanted to unplug the coils individually you would have to unplug one, start the car, then turn it back off to get to the others. Honestly with all that work, I'd be tempted just to take it to the dealer and have them do a power balance test so you know what cylinder it is...... or if the misfire is jumping around which would mean something entirely different.

[340valnt]

yes its rocking the car which has got to be more than 1 What i can't believe is its not kicking any codes that was the reason i was thinking iac If the mixture is way off Aso i didn't say before but it has traction control which involves another throttle valve

[elwesso]

Like Heath said, IAC won't cause a misfire. Anything that goes through the IAC is metered air, so normally when it gets plugged up or sticky it just lets less air in and the idle is low..

I really think that a power balance test is going to really help us out, and probably worth the expense.. Heath, do you know if any of the consult-interface software (like the USB interfaces) can do power balance tests or turn off individual cylinders?

[340valnt]

what would i need to do it with the consult. I checked and i have a female connector + obd2. What are ya'll using in software that will do a power balance.I was looking at ecutalk which cable would i need as there was some confusion over which would work with which serial to usb
thanks

[Q451990]

Nissan Scantech would do individual cylinders, but never a reliable power balance.

Heath