Fuel injectors!!!! Same problem with mine. 2002 Grand Prix GTP! After replacing coils and mod.. my miss fire was my injectors not getting fuel. Was getting a little gas but not what it was needing! Hope this help bro! Love my GTP!

I had this issue and it ended up being my head gaskets. Good luck to you

Excellent DIY, thanks to your rundown I’ve replaced my own Ignition Coils, Firing Wires and Spark Plugs! Tuned up my own 2008 Grand Prix, saved money and fixed the misfire.

Lower/Upper intake manifold bolts maybe, love your work man!

I installed a remanufactured engine, so it only has about 8 thousand miles on it, and runs very smooth, except I started having issues with it starting intermittently. I narrowed that down to the crankshaft position sensor, replaced it and it's been starting consistently ever since. I've also replaced sensors, cleaned out the throttle body, and that has helped, but it still idles a bit rough, and the scanner shows an aggressive misfire issue. It counts up quickly. Initially, there were no indications of misfiring on any of the cylinders, and no DTC relating to the misfire issue, but today I checked it again, and no DTC, buy it's now showing misfires on nearly all of the cylinders. What I believe might be the problem is that it needs a CASE relearn, which I can only get from the dealer. Scheduling at a dealership is like a 2 week wait time. I don't believe the ECM knows exactly where the crankshaft angle is, so it's out of synchronization. I'm hoping anyway. If that doesn't fix it, then I'll look into the ignition control module next. I don't want to let this go too long as it can have a detrimental effect on my engine.

Like others said bet it’s the fuel injectors. I had same problem on my 07.

To test the coils on these. The best way is to pop off the wires from the coil. Have a buddy crank the engine while you have your fingers between the posts 😮. If it hurts a lot, you've got a good strong coil...

U changed everything I 🤔 it could be. I'm curious if it's the injectors. That's all that's left

I had put gas in my 2006 grand prix that had diesel mixed with it. For obvious reasons my injectors got gunked up leading to the same trouble your having. The next couple tanks I used premium and octane booster and it eventually cleared up. Around the same time I had a bad secondary air pump check valve and upper cooling system elbow leaking. All replaced and no more code

MANNNN I’m having the same damn problems. New spark plugs swapped coils even tried new ignition control module. The misfires come and it goes. It’s mind blowing. I have good compression. Maybe it’s a PCM ISSUE??? Did you get it resolved???

I got a 2008 Grand Prix with a code P0300 and a ticking some coming from the engine when I lift the hood

I'd even check for proper fuel pressure at the rail. Maybe new fuel filter if its low. Also check for any vac leaks that might affect the fuel pressure regulator

Cant say ive ever seen a oem coil on a 3800/3100 family go bad that didnt have rust on the tower post and plug end

I got a question I haven’t really talked to anyone yet about but I do have a older guy helping me with this 3800 superchargered Monte Carlo I notice my gas mileage will jump up and down like it will go from 179 miles up to 208 miles of gas down to 183 what could be the problem in your opinion?

Could be infector but also ive seen valve springs go bad at that mileage. Weak spring cant snap back valve so higher rpm has misfires. Can sometimes find hi leakdown but vaccum gauge best way.

Hey mine doesn't have a misfire I went to auto zone and the little machine showed me literally all green he gave me Lucas lubricant and stuff but it's still doing it later in the day it is only when I start it so do you know what it causing it we have the same car

When was the last time the LIM gaskets were done? I know on my 07 I had a misfire on cyl 6 and cyl 2 was the problem. The previous owner put 5 new standard plugs in and left cyl 2 on the original plug which was fouled out after 172k miles. Moral of that story was perhaps there might be another problem on another cylinder and it’s causing the code to show on another cylinder.

I did. Crank shaft sensor. Cam shaft sensor. Coils and IGN cont mod. N still have a miss fire

Mines a 95 and im having the same problem n it act like it wants to shut off

Literally just picked up the same car in color and year. Mine has 127k. Looking for the update video

I'm trying to figure out why mine in misfiring 😢

Hey man gotta question for u by the fuse box there is a two pin plug with an orange and red wire mine is unplugged and is kinda missing what is it so I can find the parts to replace it? I have tons of electronical issues ?

Just curious, did you ever find that misfire? Im sort of in the same boat with my 04'. Diffrence is that Im getting a flash check engine light when I get on the throttle. I replaced coils, fire wires, spark plugs runs a lil' better but that flash check engine still comes on...

Check the injectors

Ive got a miss at high load, high rpm on my NA 3800. No code, just a loss of power. Driving around normally you would never know until you get on the gas… Could it be one if these? I don’t have hp tuners so I can’t use that to troubleshoot 🤔

KZfaqr NanoBytesInc is having the same issue

Hi Bro! ¿Can i ask you something? I've some problems with my Grand prix GT supercharged, i need to see where is conected the two back pressure sensors, actually have one sensor conected to de valve purge, but, i see that the other pressure sensor is not connected to some place, my problem is " reduced engine power " and i cant resolve that, really i love my GT so i would like to have a solution 😔

What software you using on laptop

I’m having same problem on my Grand Prix I change icm coils wires spark plugs how did you fix it

Misfire with no code??

Having same problem with the same color car and model lol I did all plugs all wires even went to pull apart and took 3 different modules and I got a misfire but urs is at acceleration mines is at idle it Shakes very rough and when I floor it my engine boost goes all the way to the max then my check engine light blinks?

I'd check your injectors out.

How's the abs working My cars a 2006 grand prix gt supercharged 120kms same code dealer said plugs I did them and fit didnt go away it was randomly at idel Otherwise the car ran mint Then 2 weeks ago the abs light goes on and the car pulses the abs on almost every time you press the brake And they said 600 buvks that it was a front wheel bearing I think he's nuts So I bought a brand new 2022 corolla se cvt loaded tint Rims I will never own a gm car again They went bankrupt in 2007 and there quality was terrible Now I have everything

I have a P0305 can’t find

did you find it?

My 06 grand prix is having that same problem po300 I changed spark plugs, spark plug wires, coil packs, ignition module and fuel injectors and it's still showing up po300 I'm at a complete lost on what to do next.