[adryan16]

The trouble all starts with the word girlfriend. Actually, she's incredible, but her car has a horrible miss. I've been chauffering her around for about the last month, and the car has ran great. The car I'm speaking of is a 95 Lumina with the 3100 engine. She's got papers that say there have been two injectors replaced as well as a set of plug wires replaced, all in the last year. So, I went to go start it after being at the store, and I immediately notice something wrong with it. I put it in gear and feel the horrible chugging. I put it back in park, get out, walk to the back and can hear the exhaust puffin away with unmistakable sound of a miss. Unfortunately we're about 10 miles from home, so I drive it home as is, and call a few guys. The conclusions we've come to is that it could be one of more of the following:
Fuel Injector
Spark Plug
Spark Plug Wire
Ignition Module
Coil
Short in the injector
Dirty or plugged injector

I have a decent amount of mechanical ability; I love working on the old Q-jets and have recently been having a blast working at the flow bench with some old heads. However, this new, fuel injected, computer controlled stuff is beyond me. But if is is one of the above things, I believe that I have the ability to change them all. The one question I have is; how hard is it to change an injector, and what is in all involved in the process? Any help would be appreciated. Thanks!

 

[73oldsman]

Fuel pressure? Fuel filter? Injectors clogged, need cleaning?

 

[97Z28]

is it triggering any DTCs? if its another injector all you have to do is pull the intake off and the injectors are right there... nothing too involved there. did you pull the plugs and see what they looked like? you should be able to tell which cyliner is missing, then go from there.

Can you heat like a snapping noise when its running? one of the plugs or wires could be grounding out and jumping spark.

 

[adryan16]

I doubt that it would be the fuel pump or filter. If it were that, why would it only miss on one cylinder? Dirty injector could be it as well. I think I'll run some Seafoam through it just for safety sake. And that's the other thing; it isn't triggering the check engine soon light or anything. I didn't have a chance to pull the plugs, but like you said, from that I should be able to tell. And, I don't hear that tell-tale snapping of something arcing and grounding out.

So, here's the weirder part. I took it to a guy this morning, just to have it diagnosed. He calls me an hour later, and said he can't get the car to miss at all; it's running perfectly fine. He called it an "intermittent" problem. Obviously it is, but it makes me thingk that now it's not a plug or wire; usually those work or they don't. So, now I guess it could be an injector or coil, possible even a loose wire. I wish I were a bit more educated on this electronic stuff, geez! Thanks for your guys' help.

 

[johnsongrass1]

Might still be an injector pintle sticking. OR a bad computor I've seen do this.


Try unplugging the injectors one at a time while it's missing to find the culprit. IF you can't becuase they are trapped under the intake try ground the appropiate wire at the connector. IF you can't reach the connector at the injector, any place along the harness will do.

 

[adryan16]

Unplugging them; that's a good idea. That's why I come here! I didn't realize a computer could make it miss, but if that's the case, we'll try eliminating the other things first. Thanks for the suggestion. If it does it again, I'll go from there.

 

[97Z28]

it could also be the ignition module or a wire going to the module. most of the time when the module or coil goes it'll go all at once and the car wont start, but i've also seen them cause intermittent problems like you describe.

if it does it again and the other thing with the injectors doesnt show anything, then you can take the module and coil packs to a parts store and they can check it for you.

but from the way you describe the symtoms it sounds like its either a lose wire, or a bare wire thats grounding itself on something. or a faulty or dirty injector.

 

[1931 steve]

I would look at the coil packs or ignition module before the injectors. I have replaced hundreds of coil packs on these engines. Chances are good if you take each plug wire off from the coil pack(s) you will find rusty corrosion under a few of them.

Steve

 

[adryan16]

Okay, I'll check the coil wires. Do you suppose that a little dielectric grease on them after cleaning them up would help matters any? I suppose that that could definitely cause an intermittent problem if the wires sit just a certain way. Another question; I haven't looked too carefully at this engine, so I was wondering where at exactly is the ignition module at, and how do you remove it? It is as simple as the HEI type module or what? Thanks

 

[1931 steve]

so I was wondering where at exactly is the ignition module at, and how do you remove it? It is as simple as the HEI type module or what? Thanks

Its under the coil packs, very easy to replace. If the coil towers are corroded, I would say replace them. If you are getting a intermittent miss fire than why chance it.

Steve

 

[97Z28]

classic symptom of a bad coil pack is the towers will have corrosion on them.

 

[73oldsman]

Yeah it does sound like something ignition wise. I hate the intermittent problems. They always go away at the shop! I do have another forum I go to from time to time for info on my Chevy truck. There is quite a bit of info on there that may also help you. http://chevytruckworld.tenmagazines.com/forums/forum.ten-id-256-n-enginesgasoline

 

[adryan16]

We went and picked it up, and just like he said, it ran fine. I dumped a can of seafoam in the tank just to clean things out. I pulled the coil wires off, and found one of the posts with a little corossion. I bought some dielectric grease and will clean that post off and "lube" it up. Hopefully that will help. Thanks for your guys' help.

 

[97Z28]

the posts usually only corrode when its not being fired, or if its sat for a long period of time. as long as its working fine it doesnt have a chance to rust. so if you clean it off and grease it up and it still misses, pull that coil pack off and have it checked.

 

[1931 steve]

the posts usually only corrode when its not being fired, or if its sat for a long period of time. as long as its working fine it doesnt have a chance to rust. so if you clean it off and grease it up and it still misses, pull that coil pack off and have it checked.

I have seen many coils that have corroded that has been driven everyday, and with no ill driveability concerns
The only thing your going to accomplish by cleaning and lubing the coil tower, is tat the plug wire boot will pop off very easy. Does this thing do it cold or hot?

Steve

 

[adryan16]

After driving about 10 miles, it was driving fine and I shut it off to go into the store. When I came back, about 20 minutes later, then that is when the miss started, right when I started it. I shut it off about 3 more times, and every time it did it as well. So I suppose I could say that it does it when it's hot, but I don't really know if I could say.