How to test injector function on the car?

[CDMBill]

What is the best way to test for proper injection function on the car?

As posted in some other threads I have been chasing an intermittent dropped cylinder at idle and part throttle. I haven't pushed full throttle under load since the problem appeared as I don't want to detonate that hole and risk hurting the piston or head.

[Matt Cramer]

Re: How to test injector function on the car?

Not much you can do with it on the car, but you can check its resistance with a multimeter for a burned or shorted coil. After making sure it passes that test, if you apply 12 volts to one terminal and ground the other, it'll click and you can hear it.

[CDMBill]

Re: How to test injector function on the car?

I very recently had the injectors cleaned and d flow checked by RCI, so they are solid, I'm chasing this miss and I think the ignition is solid and it seems to be just one hole (#4) so I'm down to lack of fuel given I see a lean spike on one bank on the AFR meter when its running. This problem appeared without other changes so its been hell to find.

[Matt Cramer]

Re: How to test injector function on the car?

Keep in mind that spark misfires also show up as lean, since you have a lot of uncombined oxygen in the exhaust.

[CDMBill]

Re: How to test injector function on the car?

That is where I started so I've put new plugs, new plug wires, moved around the coil trigger wires so a different set of windings was on the #4 hole to see if the problem traveled to another cylinder. So I'm back to the fuel side. And now I'm also working through the mechanical issues, vacuum leaks etc. When I pulled the manifold I found an oil film everywhere but the port floors where the injector sprays except #4 which was messier than all the rest. Plug showed oil fouling as well which is why I was chasing ignition first as you pointed out.

[dieselgeek]

Re: How to test injector function on the car?

That is where I started so I've put new plugs, new plug wires, moved around the coil trigger wires so a different set of windings was on the #4 hole to see if the problem traveled to another cylinder. So I'm back to the fuel side. And now I'm also working through the mechanical issues, vacuum leaks etc. When I pulled the manifold I found an oil film everywhere but the port floors where the injector sprays except #4 which was messier than all the rest. Plug showed oil fouling as well which is why I was chasing ignition first as you pointed out.

something else to look at, take a datalog of it misfiring just to be sure there's not a new noise problem. Get any tach spikes or dropouts? any 12v spikes that seem to match the misfire? etc.
-scott

[horsewidower]

Re: How to test injector function on the car?

And I'm sure you've done the simple diagnostic of swapping the injectors to see if the problem follows.