Possible clogged/dirty injector causing P0300 Random Misfire?

[Clooney]

Ill try to keep this brief but a little backstory.

I bought 2 cans of BG 44k platinum last week. One can was put in on an empty tank refuel at 21 gallons with 93 octane( I never run anything but 87 in it). A couple days later I was reading users who were stating its best to be used at half a tank. So I put the other can in at half a tank. Later on that day I replaced the ignition switch in the steering column. Started it and let it run for about 5 minutes, came back out and it had shut off. When I restarted it, it was running bad and popped an SES light. Code was P0300 and nothing else. So I topped the gas tank off again thinking the BG 44k was too concentrated. Still it ran like crap for hours after that. So I decided to pop out the plugs thinking they became fouled out. One plug in #6 was extremely saturated with that cleaner. I replaced all plugs with new 41-103 AC Delcos. Still, it ran like crap, so I thought maybe its a coil pack. So i replaced #6 coil pack..still no change in the way it was running. So I started disconnecting coils, one after the other to listen for a difference in the way it ran. Turns out Cylinders 4 5 and 6 are not firing. Tested those coils and plugs, they are firing perfectly but nothing inside the chamber is igniting.

So now my attention is on the injectors being clogged up from too much BG 44k at once. I ran a seafoam clean through the brake booster hose and it acted like it was trying run right, but i only used a 3rd of the can and after letting it soak for 30 minutes, it went back to running like crap.

I have 2 questions on this,

1. Is there a way to diagnose the injectors without removing the intake manifold?
2. The truck still runs, although rough as hell, will it hurt the motor to drive it 40 miles to my mechanic?

 

[Mooseman]

1. Is there a way to diagnose the injectors without removing the intake manifold?

If you have the equipment, do an injector balance test. This will tell you if all the injectors are firing at the same rate.

2. The truck still runs, although rough as hell, will it hurt the motor to drive it 40 miles to my mechanic?

Running it too much like this could damage the cat. It might be OK for the one run.

 

[gmcman]

Also sounds like your plugs are fuel fouled.

Can you give some history on the vehicle? How long has this random misfire been going on?

How many miles are on the plugs? Are the plugs AC Delco 41-103?

If that were mine, and the plugs are old, I would start with a fresh set of plugs.

 

[Mooseman]

He did say he replaced them with the proper Delcos.

Another thing to do is a compression check. And what prompted you to use the BG44K to begin with?

 

[budwich]

what are you saying / doing when you wrote this: "So I started disconnecting coils, one after the other to listen for a difference in the way it ran. Turns out Cylinders 4 5 and 6 are not firing. Tested those coils and plugs, they are firing perfectly but nothing inside the chamber is igniting."
How did you determine they are firing perfectly but nothing inside the chamber is igniting???? Further, I rather doubt that your engine would run without 3 of the six cylinders working. As previously asked by others, why did you start down the path of "cleaning the engine internals"? You should probably do some compression testing before doing anything else besides being towed to a "full service" mechanic.

 

[Clooney]

He did say he replaced them with the proper Delcos.

Another thing to do is a compression check. And what prompted you to use the BG44K to begin with?

I typically run seafoam through the tank at oil change time. This weekend I had planned on doing that but I read other TB owners stating that BG44K was the stuff to beat. So I bought 2 cans then did some more digging on how to properly use it. It was all preventative maintenance mainly and i feel it is totally my fault, apparently that BG44K works better than it should.

Edit: the truck has a little over 187K miles on it.

 

[Mooseman]

It is supposedly potent stuff. Hopefully you didn't damage the injectors by doubling the dose on a half tank of gas. The bast way to check is an injector balance test.

 

[Clooney]

what are you saying / doing when you wrote this: "So I started disconnecting coils, one after the other to listen for a difference in the way it ran. Turns out Cylinders 4 5 and 6 are not firing. Tested those coils and plugs, they are firing perfectly but nothing inside the chamber is igniting."
How did you determine they are firing perfectly but nothing inside the chamber is igniting???? Further, I rather doubt that your engine would run without 3 of the six cylinders working. As previously asked by others, why did you start down the path of "cleaning the engine internals"? You should probably do some compression testing before doing anything else besides being towed to a "full service" mechanic.

Believe it or not, I pulled each coil and plug out and put the plug in the boot one at a time on cylinders 4,5, and 6. The coil/plug was outside of the engine when we tested each one My brother and I saw with our own eyes that i turned the key, the truck started and each plug fired fine. They weren't weak sparks either, they were bright blue and very loud. I couldn't test cylinders 1,2, and 3 because it wouldn't run like that. I have no idea why it runs like that but it does.

Doesn't matter why I started down the path of "cleaning the internals" at this point but with 187K miles, a previous owner who neglected it, no service records and some random rough idling sitting at stop lights i thought it was time.

 

[budwich]

the purpose of the "history" is to understand where you / your vehicle has "travelled" in this journey so that people can understand what has happened before, IF anything.

So you appear to have confirmed good spark on each of the plugs, that's good. It would appear that you have lost compression in some of those cylinders if the plugs are remaining wet. You should ensure that they are clean / dry before doing much more. It would be a good idea to do a compression test to confirm "mechanical sanity" of the cylinders. Maybe someone has some ideas on any link between the numbers of cylinders that you indicate have issue and motor design... it might provide further clues. Maybe the variable valve timing sensor / solenoid has an issue... guess.

 

[Clooney]

the purpose of the "history" is to understand where you / your vehicle has "travelled" in this journey so that people can understand what has happened before, IF anything.

So you appear to have confirmed good spark on each of the plugs, that's good. It would appear that you have lost compression in some of those cylinders if the plugs are remaining wet. You should ensure that they are clean / dry before doing much more. It would be a good idea to do a compression test to confirm "mechanical sanity" of the cylinders. Maybe someone has some ideas on any link between the numbers of cylinders that you indicate have issue and motor design... it might provide further clues. Maybe the variable valve timing sensor / solenoid has an issue... guess.

The problem is that those 3 plugs are not wet, they dont even smell like gas. Before i replaced the plugs, the number 6 plug was covered in a slimy almost greasy substance that smelled like that BG44K and not gas.

So theoretically, if 3 cylinders were not getting gas but the other 3 were, the truck would still run, but it would be really rough.....check! Code P0300 means "Random Misfire", since this code means the computer cannot tell you which one is misfiring or it would have presented a P0301,02,03, and so on....check!! Process of elimination tells me to now focus on the injectors, but a compression check is easy enough to rule out before tearing off the intake manifold.

 

[budwich]

sorry I must have misread somewhere that they were wet.

One thing, the code, p300, is a "high level" code to indicate the system is detecting misfires. You need to monitor the misfires per cylinder with live data to determine what cylinders are impacted.... the individual cylinder counts will give you a better idea of which are having problems. The reason that you aren't seeing a p30X code is that the individual cylinder misfire isn't high enough to see the particular code for the cylinder. It would still be misfiring and you will see counts show up.

 

[Clooney]

Ok so I was able to get this to my mechanic over the weekend.

Come to find out that only cylinders 4 & 5 were not firing. And the reason why is absolutely stupid on my part.

The BG44K did its job, and did it well. The initial problem that resulted in a stall and rough idling afterwards was due to the BG44K fouling out #6 spark plug. Instead of changing just the one plug, I replaced them all. When I reconnected the coils to test it, I crossed up cylinders 4 and 5's coil wires. This created the illusion to me that the issue was still the same leading me to believe the injectors might be plugged. Thankfully my mechanic was smart enough to think I may have made a stupid mistake since the wires weren't marked and they were both the same size in length. As soon as he switched the connectors, the truck ran like a top.

Lesson to be learned, if you take off all of the coil connectors at once, mark cylinder 4 & 5 wires before proceeding any further, they are literally the same size.

 

[Mooseman]

Just one of those moments. I didn't even think it was possible to mix them up since the wires are a set length. I'm gonna have to check that out next time I'm in there. Thanks for letting us know.