2004 Pontiac Sunfire Misfire On Cylinder Four

I have a 2004 Pontiac Sunfire, and its got a Valve 4 misfire. I have changed the spark plugs, plug wires, coil pack and distributor. What else can I do.

I think you mean cylinder 4 misfire, but that’s ok. Since you have changed most of the ignition components, I would say the misfire is not ignition related. You could possibly have a bad fuel injector, or worse, a loss of compression in that cylinder which could be due to sticking valves in the cylinder head or other associated problems. I’d recommend doing a compression test just to make sure that’s ok to start with.

Yes that’s what I mean. Sorry.

No Problem. Do you have a compression tester that you can check compression on all the cylinders with?

To be honest I would have to check with my husband hes been doing the work but we are just stuck that’s all. do you have any idea what it would cost to get the valves in the cylinder head fixed if that may be the problem. The misfire only starts after 4000 RPM.

Well if it is a cylinder head problem, you would be looking at upwards of $1000 or more to fix. If the cylinder head is in bad shape, it may need to be replaced which will just cost even more. Worst case scenario would be about $2000. Whether the car is still worth that much or worth putting that much money into to fix would be up to you.

If i took the car to a mechanic should they be able to tell me what exactly it is?

Yes a mechanic can do some detailed diagnostics and tell you exactly what is wrong. Like I said earlier, it could be something as simple a bad fuel injector which would be much less expensive to fix. Either way, it does need to be checked out to find out the exact cause of your misfire.

I don’t know if it matters but it only misfires when it gets to 4000 RPM.

That would be something to tell the mechanic if you drop the car off at a shop. But the misfire may be also occurring at lower rpms and you’re just not feeling it. That’s why it may be best to have a professional look at it or take it for a drive. A scanner can be of great help in diagnosing as well, and if you don’t have one, at least a shop would be able to use one on your vehicle to watch the misfires as they happen.

Okay thank you very much for all your help!!!

You’re welcome! Glad to be of assistance, have a nice night.

I just have one more thing sorry, my husband told me that when he pulled out the plugs in the first cylinder, there was no end on the plug. Would that be a problem too?

Yes that would be a problem and that cylinder should have been misfiring as well.

At first it was a random misfire and when we changed the plugs and coil pack it went to cylinder 4. How do i tell what cylinder is what?

Well maybe he should recheck his work. Possibly he caused a problem during installation. Recheck the spark plug gaps and make sure ignition wires are fully seated.

He has put 2 different sets in.

As you stand at the front of the vehicle, cylinder #1 is at the far left side of the engine and then they work towards the right…2,3,4. I’d recommend getting it to someone who knows what they are doing to really get it diagnosed properly.

OK that’s the one that was missing the end.

Now if he can get a compression tester what should it be and if its low whats that mean.

You want to normally want to see around 150psi per cylinder on the compression gauge. If it is lower than about 125 psi, or much lower than that, you have a big problem.

Thanks again!!


Engine Swap

Hi. I have a 2004 Pontiac Sunfire and it needs a motor i found a 2.2L out of a 2007 Chevy Cobalt. I was wondering if it will fit my car.

While those motors are very similar, the 2007 engine will not work in a 2004 vehicle. There are some differences that won’t match up.

What are the differences.

Sensor locations, different types of sensors from 04 to 07, the wiring harness would not match up, computer programming, power steering and A/C, etc…

Can you tell me what motors will fit my car.

The best bet would be to stick with the same year, but the newest that will work is 2005. If you can find a donor car such as a cavalier or another Sunfire from 2002 to 2005, that would work.


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