Help!! My car has a misfire in it.

[donky4444]

I left the house today and could tell right away something was wrong. It was missing for sure. I had the computer scanned and it is throwing the code Misfire on cylinder 6. Does anybody know which one is cylinder 6? I am thinking I should replace the coil pack and spark plug for at least that cylinder. Any advice would be greatly helpful.

[00Beast]

Sounds like the coil pack. I'm not sure how the N*'s are numbered, but if it's on the back it's going to be a royal PITA.

[donky4444]

That's what I was told. I just picked the car up from getting my tires rotated and it is running perfectly fine. A friend of mine said it may also have been a clogged injector or bad gas. I just put some Lucas fuel injector cleaner in it and filled it up with some Shell Premium gas so hopefully that keeps it running right.

[dpnewfie]

Had the same issue with mine some time ago. The problem was intermitent. Of course, I thought it was bad gas, or clogged injectors. But after replacing the coil pack the problem was fixed.

I hope its just as you said but if it's not and you have to replace the coil pack.....good luck. Its a pain the the butt. IIRC the number 6 cylinder was second from the left as you look at the engine and of course at the rear of the engine.

[donky4444]

The problem came back again today so I put a post on a caddy forum and was told that if you stand in front of the car looking into the engine bay the front bank is 2,4,6,8 so it would be the 3rd one in from the left which made me happy because it is easy to get to. I found the coil pack on GMpartsdirect for about $200 shipped since they come on a plate with all four for the bank. I can't find any parts stores around here that have one in stock, it's a special order part, and GMpartsdirect says it is special order as well and may take an additional 7-10 business days to ship out. I figure I will check with the stealership tomorrow and see if they have any in stock and how much the are going to rape me for it. I will post tomorrow and tell you all what I came up with to fix it.

[harofreak00]

Get it from MonsterPartsOnline. http://www.trademotion.com/partlocator/ ... eid=214632

Usually cheaper prices, and much faster shipping.

[donky4444]

Thank you Haro. That is about $80 cheaper than GM parts direct.

[dpnewfie]

Ah jeez, sorry about that. I should have went and looked to refresh my mind before I commented on the correct location. It was 50k ago. lol

[donky4444]

So Saturday night it ran just fine after I put the fuel treatment and premium gas in it so I took it to Grand Rapids which is about 90 miles round trip and she ran great, even got 21 mpg. Sunday morning I ran to the store and she started missing again. I went to take the coil pack and plug out and the plug was actually loose in the block, I was able to take it out by hand instead of using the ratchet. I put everything back together and made sure the plug was in nice and snug. I drove it to work today with no problems and on the way home the service engine soon light went out. I am hoping that it was just that simple and is fixed now. I guess only time will tell as I keep driving it hoping that it doesn't start missing again.

Thank you to everybody for the help, now lets just keep out fingers crossed.

[CMNTMXR57]

You probably got a P0300 and maybe a specific P0306 (for cylinder #6) then.

Any current DTC (Diagnostic Trouble Code) that triggers your MIL (Malfunction Indicator Lamp) I.E. the check engine light, will clear after 3 consecutive SUCCESSFUL operating cycles. What this means, is now that you found the problem, fixed it, and ran the engine 3 times without a misfire, the PCM clears the current DTC. However, it's still in the history file, and will be there for 40 consecutive SUCCESSFUL operating cycles..

Once it's cleared from the history file, it's as if it never happened.

[jim9706]

I had the same misfire. I took it to a local dealer who still services Pontiac. They checked the plugs and coils and found no problems with either. Then they told me there was a TSB that indicated an engine flush would be needed to remedy the problem. That didn't fix the problem so they then said the car had bad gas" in it so they needed to change the fuel filter. Still no luck. In the end they changed the plugs and that seemed to fix the misfire. Total cost - $518. They did give a $98 credit for the engine flush so the amount I paid was $20 to have the plugs changed!!!!!!!!!!!!!!

I would give up on this car were it not for the very low production numbers and the at thrill i get when I drive it. It's a real love-hate relationship.

[SkiBum1229]

My moms 05 GXP has been having a similar problem the last few days. Sometimes it runs smooth, sometimes not. I checked and there are no codes and no pending codes. I may take a look at the plugs etc. The car has just over 35k on it.

[CMNTMXR57]

Does it do it when it's cold?

[GXPete]

How are all you guys getting the codes of your cars? I know CM has a Tech 2, which I assume is the computer that connects to the car, but it seems like a bunch of you have them? I assume they have gizmos now that just connect to a laptop? Do you have to be a certified tech to get one of those?

[00Beast]

No, you can get inexpensive OBD II code readers. Some here have scanners and scangauges (I have an Aeroforce Scanguage myself). Auto Zone and maybe Advance can also scan codes for free.

[CMNTMXR57]

- GM Tech2 (how I get mine)
- Snap-On has a scanner similar to a Tech2 that they sell.
- AutoTap.
- HPTuners or LS1Edit (or any other "tuning" software will have the ability to read DTC's).
- Cheap code readers at Autozone.
- Or call OnStar if you have the ability.

Etc, etc.

Keep in mind, the cheap code readers are exactly that. Cheap code readers. They won't do much else. In some cases, it may only work with a few certain GM vehicles. The true best tool for the job if you're a mechanical person is a Tech2. It'll work on ANY OBDII GM vehicle, and if you have the CAN module, any '05+ CAN compliant OBDII GM vehicle. I'd follow that by the Snap-On unit. They allow you bi-directional controls and the ability to do troubleshooting by commanding systems/items on/off, monitoring them as you do so, and running test sequences. A tuning software package is great if you like to tweak data tables in your PCM.

[00Beast]

However, for the DIY'er, the Tech II and Snap-On Solus are $1500+. Not justifiable in too many people's car budgets, especially those who only do oil changes and maybe tire rotations.

[GXPete]

Thanks to both of you guys for suggestions. I didn't know there were so many of them out there until I Googled it. Guess I should have done that first, but I value opinions from people that actually use them.

But yeah, I'm the weekend tinkerer, nothing too major, so I'm looking for the most awesome scanner <$100.

[CMNTMXR57]

However, for the DIY'er, the Tech II and Snap-On Solus are $1500+. Not justifiable in too many people's car budgets, especially those who only do oil changes and maybe tire rotations.

I actually picked mine up on LS1Tech for $1,000, including case, multiple cables, and CAN module.

Either way, yes, I agree, it isn't cheap, but the unit pays for itself rather quickly. It's ability to troubleshoot, diagnose (using it's output controls), and testing ability's specific for GM vehicles, are what make it so useful. I take mine everywhere! And between as many GM vehicles I have, has paid for itself 2, 3, 4+ times over. It pays for itself even quicker if you help other people in the GM community. I almost attribute it to another one of my favorite Snap-On ratchets.

But I also completely understand not wanting to spend that much, just for a simple tool. Pete, it all depends on how much you want to get out of it. If you just want a code scanner, than yes, I wouldn't even look at a Tech2.

[GXPete]

Certainly sounds worth the cost. The thing is, CM, you're a tech, so I fully understand how valuable such a tool would be to you, as you can find what's wrong and then fix whatever it is. I'm a network admin at a bank (also a master electrician, but that was my previous career), and while I'm good with my hands and can take anything apart and put it back together, if I had a Tech2, I'd find out what's wrong and then take it to my dealer (if it was involved enough) to fix, and they'd use their tech2 anyway. I just don't have the time to do anything major to it.

My cousin used to have a big GM dealership until '93 when GM started consolidating some of its brands and cut dealerships. I used to tell him he should hire me because I knew computers and I liked working on cars and the two would eventually go hand in hand. He laughed at me. Now he admits I was right as mechanics all have laptops on their work benches; he never would have guessed computers would be so prevalent in the automotive industry. Of course they would, they're part of everything.

At any rate, I appreciate your presence here, as well as everyone else's. I'm getting back into tinkering and having fun doing it.