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Troubleshoot Miss on #3 cylinder

1814 Views 24 Replies 6 Participants Last post by  Ronbuell
Spent some time on finding the miss today. Just for kicks, I swapped out all injectors on the passenger side. Idle is up some but still missing. Kept pulling wires until found that #3 offers no change in the miss, so whatever is going on, its #3.

The done to list: Plug wires, spark plugs, rotor cap, button, swapped out know good injectors, put in unknown injector harness.

So can I put a voltmeter or ohmeter on the injecotr plug to see if it is getting a signal?

I'm suspecting the Salt&Pepper connectors, but other suggestions, offers, tests to try, all appreciated.
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You can check it with a noid-lite or a 12vdc test light...attach it to both pins and check for a dim blink at the test light, engine it between 2 injector plugs....and yeah, salt & pepper conn's are recommended to be checked. Hope this helps.
Spread out the pins on the salt and pepper conns... nothing. Still misses. Getting to #3 is a pain, under the throttle section of the manifold.
You could also check if it's "clicking" with a thin metal rod (ice pick, small philips screwdriver) and check for its vibration engine idling. Use one of the known good injectors as a baseline. You should "feel it clicking" (pulsing)...check #3 and compare with the KG injector....this is a crude way of simulating a fuel injector quick probe tool like the one you'll find at:

Hope this helps.
get a 9 dollar stethascope from a parts store or Harbour freight and listen to it with that. Then check the plug wire....
FE, I swapped out the plug wire from my car and it made no dif... still missed... thanks. I was hoping that would do it too! Joel, Now the probe idea sounds good. Looks like a nice Friday evening under the hood.
On 2006-04-07 15:49, Ronbuell wrote:
FE, I swapped out the plug wire from my car and it made no dif... still missed... thanks. I was hoping that would do it too! Joel, Now the probe idea sounds good. Looks like a nice Friday evening under the hood.
LOL....welcome to my world...FE's idea with the stethoscope is another alternative, very reliable too....Let us know what you find out though. GL
OK, so here goes it. Used a Stethoscope, verified that #3 is not working, no clicking. Go to the box of stuff and pull out an old injector and old harness. Clipped the end off of old harness and plugged it up to 9V power and it was clicking, so I guessed it would work, but could be plugged up. Anyway, 15 minutes later had the old #3 out and tested it, no clicking on power source. Out with the old, in with the "new" old injector. Not missing as bad, but still not right either. No power down the street. Ran out of time, could possibly be another injector because I didnt' get to check all of them. I'm beginning to think I've got a vacuum leak somewhere also.

<font size=-1>[ This Message was edited by: Ronbuell on 4/11/06 9:15am ]</font>

<font size=-1>[ This Message was edited by: Ronbuell on 4/11/06 9:16am ]</font>
Compression is good, 150 to 160 on all. But the car did sit up for 3 years. I'm wondering if I've got a stuck intake valve or lifter... only way to check is remove the valve covers and turn it over. Guess that's next. Will post.
Just to make sure, I changed out all sparkplugs, Motorcraft, for Autolite. Still missing. All injectors were probed and sounded like they are working, hear ticking when probed.

<font size=-1>[ This Message was edited by: Ronbuell on 4/21/06 11:31am ]</font>
If you had a stuck valve it would sound BAD, bad enough to notice it.

Go to a shop and borrow a noid light for Ford injectors, or maybe a parts store has one you can rent or use in the parking lot. I'm betting you have intermittant signals getting to the injectors from a wiring issue.

Thanks FE. Never heard of NOID night except thru this post. I thought it was one of those things that when put close to a wire, will flash to signal working. I did use a stethescope on the injectors and they are clicking... all of them... nice rythimic, tic, tic, tic. So on the hope it was a bad plugs, I changed all the plugs. No change. All the old plugs came out sooted black, so I'm thinking the computer is going over to a default closed loop due to some bad signal received. The bad part is someone has removed the smog pump, and not all the stuff is hooked up on the emissions. I think my code reader will do a test while running so that's on the docket for today too, but I've got to read more in the instructions on how to do it. I'm also thinking about just pluggin in the mass air computer harness just to see what happens, even though its got some plugs that don't match the car. Thanks to all who are following this thread and contributing.
Well, tried to swap in the 91 computer harness, not enough stuff plugs in to make it run... couldn't even get the fuel pump to run, so put it back like it was. Thinking on a lark its a vacuum leak, I plugged in a gauge and got 10 at idle, 20 at 2000, so I guess its not that. Ran out of time.

I'm just about frustrated enough to swap it to carb and be done with it.

<font size=-1>[ This Message was edited by: Ronbuell on 4/24/06 8:05am ]</font>
If you run a 13726548 firing order cam, make sure you keep #1 and #3 wires seperated, not next to each other. I have seen a piston with a hole in it from crossfiring wires. Just thought i`d mention it.
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I definately know about that, running wires adjacent to eachother is a no-no. I was checking out the injector kit cleaners today and went by an Express Oil change. They were having a special on the injector cleaning so I took it in there to see what they could do with it. While its there, I'm getting the brakes blead as well.

The mentioned one that I have not experienced, and that's a leak in the brake booster. That would have a vacuum leak and cause the rought idle as well as a hard peddle which is what it has. I'll know in the morning what he found!
Sorry..what year? I have an '87 and went through a similiar incident in which the ecm fried, had changed the ignition module x2, map sensorx2, temp sensors and ecm and car still ran with 10" vacuum at idle and smoked and ran so rich it sounded like a top fuel dragster...fix was new ground batt cable and 2-10ga. ground wires running to the body from the batt. .
Oh man, what an inspiration !!! never occured to me that it was grounding issue. I did replace the starter wire (long one). The way you describe yours is very close to mine. Has a lope at idle, pull 10" vacuum, running rich. I'll give that a try.
Thanks, Ron
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