Injector Diagnostic Question

S

Some Car Guy

Registered
I have one injector showing "YES" for open/short in the computer. It changes back and forth to "NO". I'm guessing this means it is bad but maybe it is just showing it pulsing normally. I tend to think it is a problem since the others aren't moving but I don't want to throw a new one in there if I'm missing something here.

The car is a '97 and it is still bucking after sorting out misfires in the ignition. There aren't anymore misfires but the problem has remained.
 
You can mechanically test the injector to see if its working properly using a stethascope. (NOT A SCREWDRIVER, don't be cheap, hehe) You should hear a steady "tick tick tick" from it. If it doesn't "fire" then it will show an open/short to the computer. You should be able to hear this.....but this doesn't necessarily mean its bad. One way to test it without spending money is to switch its position on the fuel rail and see if the "YES" switches cylinders. If it does, then you have a bad injector, if it doesn't, then you may have wiring issues.
 
the injectors are pretty easy to replace. there should be a few small bolts holding the fuel rail down to the manifold they are about a 8 or 10mm head. once you have these bolts out of witch ever side the bad injector is on just take some sort of pry bar and VERY SLOWLY pry the fuel rail up. pry the front up a little then move to the back and just keep working it up slow untill it pops up. some of the injectors will stay in the manifold and some will come with the fuel rail. then all you have to do is unplug the wires going to them and swap holes with the injectors. make sure all of the o rings are still on the injectors some times they will come off and stay in the intake or the rail (witch ever end they came out of) just take a pick or a small screw driver and pick them out and slide them back on the injectors. then set the fuel rail back on top of the injectors just enough to get the bolts started and let the bolts pull the rail down on the injectors as you tighten them. make sure they all go in the holes and that they dont miss because you will break them if you dont. after the bolts are tight just plug the wires back into the injectors and your done. the bolts dont have to be super tight but tight enough they wont back out.

hope this helps and good luck on your quest for the bad guy!
 
The fuel rail bolts are 8mm and its easier to disconnect the connectors while the fuel rail is still bolted on. :)

Also...don't tighten the bolts down to seal the injectors, use your hand and push down on the fuel rail directly over the injector, one at a time. The bolts can pull the rail down at an angle and could tear an o-ring.
 
Ok guys thanks.

I'm not sure when I will get to do this. Time is short.

I did pull the connector to the injector showing the switching thing on the computer and the car hardly ran at all on the way to get gas about 1 mile from here.

I reconnected it and it is at least running like it was.
 
Lol...you're not supposed to unplug it THEN drive it, haha. You drove to the gas station on 7 cylinders, haha.
 
I've heard of guys taking the plug wire off a dead cylinder and getting by without fixing the engine.

I'm begining to wonder about other 7 plugs. Maybe they only misfire under a load. I'll have to hook the computer up and do some driving. I really can't figure out why after all this I only got a code ONE time. It's not like that time it had a new problem.:confused:
 
A misfire under load is a plug boot/wire 90% of the time. An injector isn't going to do this, they either clog, or don't work at all. A coil usually just fails. A plug usually just wears out and you'll get a rough idle.

I think in another post you said you've changed your plugs and boots?
 
There is another thread on here where we're talking about fuel injectors.

Since you have access to a scanner, I recommend you swap the injector with the one next to it and then try checking the circuit on the scanner again. See if the issue follows the injector, or it stays on the same cylinder. This will point you in the right direction.

Also...we're basing all these repairs of the simple symptom you gave us....."bucking". Can you elaborate more...what speed...how much throttle....cold...hot....only on Mondays?
 
UPDATE-

Was able to take laptop on road with me today.

Injectors didn't show anything this time.

Reopened misfire section. Saw quite a show.

Apparently at least 3 coils are weak. At this point I'm thinking they work sometimes, which is why they show good for a spell and I think it is something else.

After awhile I noticed the # 1 injector again showed a back and forth YES to NO. # 2 also showed this as well.

I've been doing some reading all over the net and came across something that suggests that the computer will not send fuel in when it sees a major cluster of misfires.

Those two cylinders were the worst two for misfires, so there may be some merit to that.


I need to get some coils and go under the hood again. I would like to find a good brand as the one I replaced last week was a replacement itself.

I would also like to know for sure why those injectors are doing that.

And bucking is just that - a big miss and the car jerks what feels like back and forth. Like a horse trying to throw you off. Does it cold or hot, randomly. No problems at times.
 
Guess it wouldn't hurt. By tommorrow I will have 4 new total in this engine. No telling how long the new China stuff will last. How much you want for them?
 
One thing you could do to either rule in or out the coils is to swap them on the cylinders to see if the "miss" follows the coils.

$15 each shipped?
 
UPDATE-

Installed 3 new coils and all is well. If they had just shown bad when I replaced that one it wouldn't have led me astray.

I need to rescan and see if that injector thing still shows. I'd just like to know because I like to know crap like that.
 
J said:
One thing you could do to either rule in or out the coils is to swap them on the cylinders to see if the "miss" follows the coils.

$15 each shipped?
Click to expand...

That isn't a bad deal. I'll let you know.

I'm thinking about getting a set of MSD coils at the moment. I'm having hard time with the fact I have saw so many MSD boxes fail on old cars. I would like to have 8 new QUALITY coils in there so I don't have to go down this road again anytime soon.

I won't buy anything that says ACCEL on it and that is the other choice I have come across so far. I think Granitelli makes a set though.
 
I would like to thank everyone who chipped in with advise on my problem.

Anything electrical can drive you insane so all the input helped.:)
 
Yep

I highly reccommend that anybody with a laptop get Auto Tap. I bought a GM one a few years ago to work on my Trans Am and it was about 150 bucks. I then got a Ford one a couple years back, used for 100.

I think for around 400 they sell a model that will work with anything at all OBD II.

Also, on a side note, I found that Jegs sells Granitelli coils pretty cheap. You can get a stock type(I'm sure a China part) replacement set of 8 for about two bills. For 300 you can go to a 40,000 + volt coil. Stock coils are something like 25,000 volts. I'm not sure a mostly stock Mark would need the upgrade but hey...
and they come with the boots.
They don't list them for our year cars but they will fit. If you go to AutoZones website, it lists the same coil for a 97 Mark as an 03 Mustang Cobra.
 
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