Cyl 1 missfire

[01OhioAlero]

So I was driving my car and a cel came up randomly. Car ran fine so I drove it around for a while then went and got the code read and it came up p0301 missfire on cyl 1. I have no idea what it could be since it runs fine, smooth as butter, no lack of power but I have noticed bas gas mileage since it came on. I have new injectors,plugs and wires so I dont think its any of them. So the only thing left is the coils, do any of you guys know how to test them?

[03Alerosil]

It may not be a coil. Could be a mechanical issue or a manifold leak.

[01OhioAlero]

I know its not a manifold leak for sure. What kind of mechanical issue could it be? It doesnt shake or lose power or drop rpms, just the light and bad mileage.

[03Alerosil]

Could still be an injector issue. Mechanical could be a cam going bad so the lobe isn't as tall as it needs to be so the valve isn't opening as much as it needs too. It may also be a faulty spark plug of ignition system part. Just because its a new part doesn't always mean it's 100% good

[Nas Escobar]

Coil
Plug cable
Spark plug itself
stuck/bad injector

You can always swap out the coil since it's right there in front of you however if that doesn't cure the issue, then it's something else.

Since you mention all but the coil is new, did you cross them? A crossed plug on the same coil won't be as bad as crossing plugs between 2 coils.

[01OhioAlero]

Huh tested plugs and wires good. Got a new coil, still has the code. How would I check the injectors?

[Nas Escobar]

Check the ohm rating on each fuel injector with a multimeter. You put the multimeter at the lowest setting (200 ohm or so, at least that's what it is on my Walmart special multimeter) and check the reading. You put the tips of the positive and negative on one pin. I dont think it matters which one touches neg and pos, but if you don't get a reading one way, do the other. It should be 12.0 or somewhere close to it. If it drops to 9.9 or below, then you have a bad injector. I'd also check the fuel pressure regulator and do a compression test on the engine. The tool can be rented at the parts store, all you do is disconnect the coil's fuse, the fuel pumps fuse and crank the engine for each cylinder to see the compression. The compression should be above 100 or so and all cylinders should read similarly. A bad one will be the one with the lowest rating. Usually the gauge will be red in the reading where it is considered a bad compression rating.

Doing the fuel injector ohm rating will not tell you whether or not its' stuck however you can gauge if it's weak or not. A weak injector usually indicates inadequate fuel being given to that cylinder.

[rustyballs_69]

How do you know its not a manifold leak?

[01OhioAlero]

Wel the code went away randomly. I dont think I have a manifold leak cause they were just done a few months ago and no milky oil, low coolant, etc.

[rustyballs_69]

A vacuum leak from a cracked upper intake manifold will cause a misfire. Those intakes are notorious for cracking if they are tightened a bit too much.

[01OhioAlero]

Never thought of that. Should have when my lower cracked from tightening to much and my uppers been off a few times..Besides visual inspection is there any way to pinpoint a vacuum leak?

[Nas Escobar]

Originally Posted by 01OhioAlero

Never thought of that. Should have when my lower cracked from tightening to much and my uppers been off a few times..Besides visual inspection is there any way to pinpoint a vacuum leak?

Spray carb cleaner where air can get in. If Air is getting in, the engine will surge or stumble when it takes in the carb cleaner. That's how I found my LIMG leak on my Cutlass Supreme.

[rustyballs_69]

Since its only cylinder 1 that misfires if there was a crack it would around the the bolt by the alt. Like Nas said, just spray it with brake or carb cleaner.