Screwed Up Spark Plug Change, Now I've Got A Flashing P0300 CEL

[a1b3c6]

So I followed the guide over on the TrailVoy forum to a T when I went to change my spark plugs. I set the boots back on top of the plugs straight, plugged everything back up, etc.

Or, I thought I did.

I started up my TB and immediately noticed it felt a little rougher than before. I didn't think it was anything too bad...until the CEL started flashing 10 seconds later. Knowing that meant I fucked up big time, I immediately brought up torque to check the light, my rpm, everything. Besides throwing the code and feeling a tiny bit rougher though, everything was normal. It started with an RPM of 1,000, and worked it's way down to 600 (which it did before too). I drove it down my street and back once and it did perfectly fine...no hesitation, or weird noices. Just a little bit louder maybe. I'm not going to be driving it anymore, except to a mechanic. But before I do, do any of you have ANY idea what I did wrong? I mean, I had my phone out following that guide every step of the way, but then I must have messed up somewhere.

 

[jeffro312]

What spark plugs did u use.... Are you sure the connectors to the coils are connected coiled sitted on plugs good.

I would do the job over again. Remove spark plugs put them all back etc try again. Disconnect battery during also clean your throttle body while your at it

 

[a1b3c6]

What spark plugs did u use.... Are you sure the connectors to the coils are connected coiled sitted on plugs good.

I would do the job over again. Remove spark plugs put them all back etc try again. Disconnect battery during also clean your throttle body while your at it

ACDelco 41-103's.

Honestly, I'm not sure about the coils. It felt like they went on okay. I tried to fit the hole directly over the plug, and I didn't have any trouble fitting them on there. IDK how I would know if I screwed it up though.

I know someone who's way more experienced with cars than I am. He offered to redo it tomorrow, so hopefully he can do it right this time.

 

[jeffro312]

Try that

 

[djthumper]

Double check your coil packs and wiring. That is where it is likely to be at this point.

 

[a1b3c6]

Double check your coil packs and wiring. That is where it is likely to be at this point.

I just thought of this, but would it make a difference if I unplugged one of the coil packs to better reach another one? It was just one, so I know I didn't get it mixed up, and I know I plugged it back up before I bolted it down too.

 

[Mooseman]

Check for a code on the misfire. If it says it's a specific cylinder, you might be able to concentrate on it. Also possible one of the coils was installed crooked and missed the plug, which happens. Check the electrical connectors and wires. Maybe while messing with the coils, a wire broke.

Edit: Just noticed you're getting P0300 so it's random.

 

[djthumper]

The P300 flashing is saying that it cannot fully determine which cylinder it is and that you should not keep driving. I would verify that the wire on your number 5 coil pack, or the one you unplugged, is plugged in properly and check the seating of the coil packs.

 

[MAY03LT]

I've done a few of these and for whatever reason I sometimes goof getting the cylinder number one boot on correctly.

 

[02TrailBlazer]

I've done a few of these and for whatever reason I sometimes goof getting the cylinder number one boot on correctly.

I did the same thing last year- never did get the P0301, I guess it can take some time for the computer to decide which one is at fault even if its clearly missing a connection.

 

[HeavyChevy4200]

You may also want to pull the plugs and check them. Perhaps one went in incorrectly gapped or could have a crack in the porcelain.

 

[gmcman]

Just out of curiousity, did you go over all the plugs and make sure you torqued them down? Perhaps you overlooked one.

Did you rinse the top of the motor at any time during the plug change? Easy to get water pooling in a coil pack electrical socket if unplugged.

 

[Sparky]

My money is that a pack is not actually on straight.

 

[a1b3c6]

So, I wound up redoing each spark plug, trying to be more careful of getting them in straight, the coil packs on right, etc. Every one of them went on fine, except for the 5th cylinder. First, the spark plug wouldn't tighten down all the way. It was going in about 3/4 of the way, but then it was so hard to get it to go further I stopped working on it for a minute. I came back and started loosening then tightening it, and that got it to go on what felt like all the way. I put the coil pack on, it went down on it all the way, but with a little more force.

Well, I started it up and it ran perfectly. I mean, no rough idle, silky smooth acceleration, everything. Then the CEL came on after 2-3 miles, but thankfully NOT flashing. I used my OBDII reader and sure enough, it pulled a P0305.

My question is, is this car safe to drive about 20-30 miles? I know someone who has a lot more tools and experience than I do to help me get it in right this time. Like I said, it isn't idling rough, stalling, or doing anything bad like it was first doing. In fact, it rides a little better than it did before I changed the plugs. I still don't know if it'll damage the car though.

 

[Sparky]

If it is not flashing then whatever it is complaining about is a more minor miss and it would likely be OK. Sounds like something may be borked on the head (ouch). Could try clearing the code and see if comes back or if it was just a latent pending code.

 

[a1b3c6]

If it is not flashing then whatever it is complaining about is a more minor miss and it would likely be OK. Sounds like something may be borked on the head (ouch). Could try clearing the code and see if comes back or if it was just a latent pending code.

Yeah, I drove it over to his garage just fine. He started it up and said he couldn't find anything wrong with it, and said it sounded even quieter than before I changed them. He thinks my best bet is to try and drive it a while and see if the code goes away, since that seems to clear it for some people.

I'm thinking about taking a video and posting it here so you guys have an idea of how it's running. It honestly sounds and drives fine.

Edit: Here's the vid:

https://www.youtube.com/watch?v=M9Pgckzh2dE&feature=youtu.be

 

[gmcman]

Did you use a torque wrench to tighten the plugs? Did you apply anti seize to the plug threads?

When the plugs are in their final position, the electrode is in a certain position....this will be uniform across all the plugs.

I don't know if this motor is particularily sensitive to the position but I don't want to keep telling you to remove the plug and possibly tear up the threads.

If the coil pack is hard to seat, the plug may not be all the way seated, and the possible reason for the misfire.

You definitely want to remove the plugs with no more than a luke warm motor. I generally run the motor for about a minute before removing plugs but I believe the rule is to have a cold motor.

 

[coolasice]

So, I wound up redoing each spark plug, trying to be more careful of getting them in straight, the coil packs on right, etc. Every one of them went on fine, except for the 5th cylinder. First, the spark plug wouldn't tighten down all the way. It was going in about 3/4 of the way, but then it was so hard to get it to go further I stopped working on it for a minute. I came back and started loosening then tightening it, and that got it to go on what felt like all the way. I put the coil pack on, it went down on it all the way, but with a little more force.

Could you have cross threaded it?