Hello all, I’m in need of some urgent help on my 2005 500. I literally just finished a tune up and got it running maybe 30 minutes before posting this and I need the car back to full potential by 6 PM do not a lot of sleep tonight for me. The engine light came on for p0303 cylinder 3 misfire so I started cheap because I’m broke until Friday. I replaced all the plugs but not the intake or egr gaskets simply because I didn’t realize the intake had to come off to do the plugs. One reason I’m not the biggest ford fan ever but hey free car so not complaining. It has around 230k miles on it. I cleaned the throttle body while I had the intake off also. Anywho I started it up after priming the fuel line for what seemed like forever and it ran perfect for about 5 minutes then it went back to randomly stumbling. It sounds like a vacuum leak but I can’t find one with the brake clean trick. I swapped all the coils around while I was there just in case the number 3 coil is bad I don’t have to take the intake off again. I just don’t know where to go from here. It ran for about 45 minutes and I put a couple miles on it and no engine light or other warning lights came on. Any help at all would be greatly appreciated!! Thank you in advance!

 

What spark plugs did you use? Fords run much better with Motorcraft plugs, Ive had a few rouge idles that everything looked right then I pull a plug and its a bosch plug, replaced with motorcraft plugs and no problems.
You could always take the intake manifold off again and slowly go over everything making sure its all connected and didnt miss any vac lines.
I wouldnt worry about reusing the EKG gasket. If its high mileage or if there is any obvious wear its good to replaced the intake manifold gasket.
Here is the Ford picture of hoses that connect to the intake manifold along with a numbered list of what each it.

 

I forgot to mention also that until it hits operating temp it runs perfect. And the random stumble is exactly that, random. It comes and goes and when it straightens out it tries to idle upwards of 1000. I don’t remember the plug brand but they were platinum and like $4 a piece

 

Had any luck yet?
I do not believe that ford plugs have a "platinum" level due to there being single spark plug that ford makes for each engine.

 

I had the codes scanned on it yesterday and I have a EGR code, EVAP code, O2 sensor banks 1&2 sensor 1 lean codes. It is running a little bit better than the beginning of this week but it still stumbles. And the plugs were Bosch platinum because I could afford those at the time

 

Yeah 95% sure thats your problem Fords hate Bosch plugs, I dont know why but they really ****ing hate them.
Replace them with motorcraft plugs and I would bet that will fix your issue.
If you dont want to replace them then I wish you good luck with the diag.

 

That’s part of why I’m not the biggest Ford fan ever because of how picky they are although my 99 half ton ran absolutely amazing on E3 plugs. My 500 runs and drives right now so I think ima take that as a sign of leave it alone for now. I just finished up the lower intake gasket on my 3.8 mustang and it decided to **** the bed after about 30 seconds of run time when I started it up.

 

I can't help with why the stumble ... but on using non-Ford spark plugs, I put NGK Iridium plugs earlier this year and it's been running fine.
Here's the link with photos of old original issue plugs after 231,500 miles

https://www.fordforum.com/forum/ford...-photos-41567/

Luck to you...

 

Hi Guys,
I have to admit learning the hard way that Fords do run better with Motorcraft plugs.
There are some questions that come to mind though, and one of them is were the plugs checked for the correct gap before installation, another check is the connector and rubber cover on coil on plug set ups, ? Dirt and poor connections inside the coil boot can take you for a real ride if you are not aware and check those things on reinstallation..

For folks who think all plugs are the same may learn the hard way , some are good and some are, well,, not as good. It is not our intent to poo poo some manufacturer;s products,,,, just to help us be aware that there are differences.

The vehicle manufacturers go through a lot of testing to determine which type plug and gap work best and that is why a specific plug and gap is recommended.
Don't get me wrong, there are good equivalent plugs out there, but the high cost isn't necessarily the best choice. So much for a long winded explanation.

 

I realize we gave you a lot to digest, if you can ,provide the codes you received ?

How this picture can get fuzzy,
We don't know how long the codes you received were in the computer , or if they came about after some work as done and a hose or plug was not on all the way.
What is generally recommended in a case like this is; clear the codes , start fresh and drive the vehicle and see how it performs. Typical drive cycle includes some highway driving and some city driving to give it the opportunity to run some monitors then see just what codes if any are set. Can you do this? If you can , after the drive have the vehicle checked for any codes and post them here. With that info we would have a better idea of what happened and when the codes were set.