I would replace ALL of the injectors on the vehicle, unless you want to do the job again in the near future.
My OTC injector balance/coil tester is good for testing injector flow on the car(but not pattern of spray) and also will test the coil for shorts
Since you have a scope and you are not a technician I would not worry about buying one

The vertical rise in the current ramp when it is turned on clues you in to the shorted injector - as I point out on the pic below

The only time i use a ohmmeter is when I have a bad short somewhere in the vehicle and I have to power it down

Heres the pic showing where to look for bad injectors - the same effect can be seen in any type of shorted solenoid.
To completely verify an injector you have to flow it, check for shorts and opens, and check the spray pattern. However there are a few tricks with a scantool you can use to ID a fueling problem and narrow it down. Fuel trims are the big tip off here. Im not a gas analyzer guy, but you can also use on of those to verify.

If you really want to learn more about vehicles, I would recommend subscribing to Flatrater.com, and pay a visit also to ATS training - they have a lot of good stuff on there for free. And of course, the absolute best place to learn about scopes is: well you know
your already here
Another good one is Larry Carleys website - aa1 car. But it is geared more towards beginners.
And then you have Motor Magazine, Engine builder magazine, and the list goes on.
Theres a lot of good info on the net - you just have to find it!

Retired wrote on Sep 19^th, 2011 at 11:18am:

Good job ordering six injectors - smart move

I use the Pico or my scantool to verify injector operation (the scantool isnt an exact science on this though)
It really depends on what is closest to me and how fast I need to get the job done

I use my Fluke 87 III for voltage drop testing - it is more accurate than the Pico in that respect, and Its not so easy to blow up, and costs 1/4 as much as the Pico if I do blow it up on one of my stupid days

Retired wrote on Sep 19^th, 2011 at 11:18am:


depends on who you ask  .  scantools have made a big leap, but scoping still plays a major role in other aspects.

crackerclicker wrote on Sep 19^th, 2011 at 7:56pm:

Other aspects?  In what way?  I can see possibly ignition but once it's into the PCM, what do use or even, how do you know since nothing is explained.  As the shop foreman at my Ford dealership stated, "If it ain't in the book, Ford doesn't want us to know".

I've asked them about the operation of what I call their UnIntelligent Four Wheel Drive System.  They couldn't answer and the Ford HotLine said was unavailble.  So I then opened the consule where the 4WD module is and connected a scope to it.  Never believe a sales brochure or even pages at Ford operated sites.

Randy H. wrote on Sep 20^th, 2011 at 12:40am:

If scopes are needed more and more where are the posts for that 2010 Caddie here?  I know what a scope can do but just see their usefulness dwindling on newer vehicles and the lack of posts here on those vehicles seems to prove that.  Don't take this as a personal attack but it seems that the auto manufactures are the cause of this.  I'm not sure if they are trying to force customers to go back to the dealers for service or what?

Being a person that drove around one day with two DMMs going, my Perception in my lap, shifting a 4-speed, I believe in scopes.

These days most technical information is proprietory and not even included in their own manuals.

I used to mention using a scope to electricians at work and they would laugh even though they had access to them. I remember one urnating contest where I suggested using a scope and mechanical lost the battle.  Three days of downtime and $6,000 of percision bearings later, the problem was still there.  The problem turned out to be the cord to a proximity sensor or what you may call a crank sensor which could have been easily diagnosed with a scope or even a DMM used correctly.  We normally had to rebuild something to prove that it wasn't mechanical.  Trial and pay!

Randy H. wrote on Sep 20^th, 2011 at 8:46am:

Hmm, that could indeed be the reason that I see no posts!

You guys never replied if you use dielectric grease "even" if there was none from the factory?

I might get the DRIs tomorrow depending on if LTS shipped the day I ordered.  I decided to try applying power through the injectors and just tapping a ground while using an amp probe and scope.  I started with the worst one.  I wasn't getting anything and discovered that I somehow had the polarity reversed.  I got a square waveform with a width of over 100ms.  I then tried one of the good ones but got the same thing.

I wondered then if I damaged the good one.  I ohm'd both.  The bad one that read 1.2 ohms before, now reads 11.2 ohms and the good one that read 12.2 ohms before , now reads 5.8 ohms.  I could maybe see that I stressed the good one that may have been weak but what happened to the bad one with which the resistance increased?

Retired wrote on Sep 19^th, 2011 at 8:11pm:


first things that come to mind are misfires and no starts.  scan data can be useless on no starts.  and even ford's ids can misidentify a misfiring cylinder.

Retired wrote on Sep 19^th, 2011 at 8:11pm:


you lost me a little here.  i'm guessing you are referring to ford's pip and spout, or even gm's est being internal to the pcm.  doesn't really matter because the coil still needs permission to fire.

Retired wrote on Sep 20^th, 2011 at 6:32am:


hmmm . . . at least until you find yourself needing to look at voltage over time  .

Randy H. wrote on Sep 21^st, 2011 at 1:35am:

I monitored a wireless controled switch output voltage for three days using my Fluke 123.  Part of the power company's interruptible AC service.


Not familiar with the names you metioned but they aren't like the finned rubber seals used on the FP relay.  There is a seal in the connector most of them stuck to the injector when removed, one fell off the rear bank, dropped into the abyss and had to be fished out.  So, I guess the grease isn't needed.

Any comment about the changes in resistance of the injectors?  I'm probably doing things that you just never do as you don't have the time to experiment.  Looking at one of those injector pulsers, it uss a single 500ms pulse, so my quick ground taps shouldn't have damaged them.