I have a 2004 ford explorer V6 4.0L. I was having problems with a rough idle when In gear and a little rough when in park. The car would stumble a little when taking off but smooth out the after about 15mph or 10mph. I already removed and regapped the plugs and replaced the wires. I recently ran out of gas put in a gallon of 87 octane went to the gas station and put in 89 octane by accident(wife was talking to me and i wasnt paying attention) I checked for air leaks around the intake and intake manifolds and thats all good. what would cause these problems the only other thing it could be is the MAF sensor. any ideas

Did you check out the code causing the check engine light to be on?

+1, and even if the SES light isn't on still have the codes checked at your local parts store.  That might point you in the right direction at least then you can eliminate cheap things and pray its not the fuel injectors, father-in-laws f-150, different engine though, had to have all of them replaced

+2 for the SES
I have seen alot of probs with the idle air control valve and or just having a dirty throttle body.
If all fails try seafoam. 

The thing that gets me is it didn't start happening after I did the tune up I changed the oil air filter and the plugs after I started it it ran like ish so I removed the bosch +2 plugs and cleaned and regapped the stock motorcraft plugs and tryed again same thing so I replaced the wires no change. Pepboys will check the light for 25 bucks I guess ill do that unless I can't find my scanner.

You now you can't gap platinum plugs right?
If you do, it will brake the tips off and it will run like crap oh and bosch only runs good in a VW

Bosch only runs good in VWs?!?  My jag and Porsche both run great with Bosch injectors and plugs and the merc diesel is still trudging along with Bosch injectors.

Quote from: mach1 on March 31, 2009, 04:53:11 PM
Pepboys will check the light for 25 bucks I guess ill do that unless I can't find my scanner.

Advance Auto Parts will check it for free!!! if there is one by you. They even reset them if you ask nicely =) Pesky gas cap sets my SES off all the time.

http://advanceauto.know-where.com/advance-auto-parts/

Been auto tech for 14 year and never had any luck with Bosch plugs.

Quote from: scottpA_GS on March 31, 2009, 05:32:30 PM

Quote from: mach1 on March 31, 2009, 04:53:11 PM
Pepboys will check the light for 25 bucks I guess ill do that unless I can't find my scanner.

Advance Auto Parts will check it for free!!! if there is one by you. They even reset them if you ask nicely =) Pesky gas cap sets my SES off all the time.

http://advanceauto.know-where.com/advance-auto-parts/

+ a billion, i bought my cheapy scanner from them cause i lived in thier parking lot for a while with my previous truck.  they just tossed me the scanner, i hooked it up and they printed out the results.  Then I would test and test and replace things and scratch my head a little bit then just drove it when it would run and rode the rest of the days

I didnt gap the bosch plugs just regapped the motorcraft plugs.

my police interceptor v8 will ONLY run well with platinum plugs. i tried the others, and it ran like a yugo in a drag race lol. so i pulled them and replaced with specced ones. SO did you try plugs that were called for. or cross referenced?

Quote from: cafeboy on March 31, 2009, 05:33:32 PM
Been auto tech for 14 year and never had any luck with Bosch plugs.

The one thing I will say is that my Dodge truck from way the fuch back when, DID NOT like em at all.

But yeah, my vehicles are practically half bosch and run freaking great.  Actually, I'm pretty sure bosch made the injectors in the Duc too.

IIRC they did. my 924 was in bed with bosch as well lol

So I found my scanner and pulled P0301 Cylinder 1 Misfire. I pulled the plug and it look a bit shoty So I looked through my toolbox and Found a bosch +4 The nut was a bigger size but the size was the same threads the same lengths so I installed and crossed my fingers. What do you know no more missing I cleared the code and took it for a spin all is good check the codes again and no DTC.

hail to the scanner, its awesome when it helps 

silly american cars 


glad to hear you got it fixed......

it was weird how the new plug was damaged from the box and after regapping the stocker it was still wrong sill silly me.

Lots of folks in the parts biz just don't care and drop plugs and other thing on the floor, then sell it to you