Stuttering/Stumbling under load and flashing SES

[MC05XLS]

So I've finally gotten around to changing my spark plugs, and it's good that I did as the ones I pulled were pretty well baked. During this upgrade, I installed Bosch Platinum +4 plugs, a K&N air filter to fit the factory intake, and an oil change to Mobil 1 5w30 full synthetic, in my 2005 XLS 4.0 V6 (FFV VIN letter K)

I changed the oil and installed the K&N first, as it was getting late, and didn't want to be working on plugs in the dark. But when I went to work the next day, as I was getting on the highway, the SES light started flashing slowly, and I noticed a change in engine performance. Once I got on level ground, engine performance leveled out, and the SES went out.

Next overpass, the engine stumbled again, the SES flashed, and something with the engine changed again, and it ran smooth.

The stumbling and stuttering kept on doing this both nights I worked.

Yesterday I installed the new spark plugs, and went out for a test drive. I'm still having the same problem. But, the problem is less than it was before I installed the plugs. I had to drive to Houston today, and I was hoping that between going over and coming back, maybe the computer would finally adjust and it would act right, but that didn't help. I disconnected the battery when I installed the plugs, and left it off for about an hour after, to clear the error codes. After my test drive, and seeing not much change with my problem, I disconnected the battery over night.

So now I have know clue what to do. Do I need to remap the ECU, and if so what program do I need and where can I find it? Would disconnecting the MAF sensor fix the problem?

One thing I've noticed, is I've gained about 1.5MPG average and at 65MPH on level ground the tach is now staying around 2,000RPM instead of between 2,750 - 3,000RPM. I'm not sure if that helps with diagnosis tho.

Please help!

 

[moto-mexican]

I had the same problem a while back. I just changed the plugs out with bosch platinums and it went away for good. If you already changed yours I'm not sure what could be wrong unless its something with the +4 plugs

 

[aldive]

Have you:
(1) scanned for trouble code(s)?
(2) checked the fuel pressure?

 

[MC05XLS]

I had the same problem a while back. I just changed the plugs out with bosch platinums and it went away for good. If you already changed yours I'm not sure what could be wrong unless its something with the +4 plugs

Well it started when I installed the air filter, and the new plugs only helped it a little bit.

 

[MC05XLS]

Have you:
(1) scanned for trouble code(s)?
(2) checked the fuel pressure?

I don't have a scan tool and autozone says they can't scan my 05 due to some block Ford has on the computer. This is what they've told me in the past.

I've not yet checked fuel pressure. Honestly I'm not sure how to do that. But I've not had an issue until I put in the k&n air filter.

 

[aldive]

Is it possible that you dislodged a vacuum hose when doing the K&N?

Further, Bosh plugs do not do well in these motors.

 

[aklmfreak]

my 2000 sport had a real bad stuttering problem after i changed my air filter because i FORGOT to reconnect the MAF sensor (dont remember why i disconnected it anyway). if you can, get someone to check the trouble codes with a code reader, that should help you narrow it down

the RPM change suggests something in the transmission? maybe its having trouble going into OD or something

I've also been told that you have to flush your oil system before you switch to synthetic oil, otherwise when it mixes with the old oil under the engine heat it will make paraffin wax.... i'm not sure about that, but it's just what i've heard

 

[aldive]

I've also been told that you have to flush your oil system before you switch to synthetic oil, otherwise when it mixes with the old oil under the engine heat it will make paraffin wax.... i'm not sure about that, but it's just what i've heard

You were told utter nonsense.

Its perfectly safe to mix dino and synthetic oil.

 

[aklmfreak]

You were told utter nonsense.

Its perfectly safe to mix dino and synthetic oil.

ok thanks for clearing that up, it didnt really sound like it made sense.....

 

[MC05XLS]

Is it possible that you dislodged a vacuum hose when doing the K&N?

Further, Bosh plugs do not do well in these motors.

I'm not sure about the vacuum hose. I'll have to check that when I get home from work. I double checked the MAF sensor last night to be sure I'd not forgotten to plug it back in and it was fine.

I've had other people with the same engine using these plugs before and never have an issue. Like I said, it's fine at highway speed, just hard acceleration and uphill causes it to give me problems.

 

[aldive]

I've had other people with the same engine using these plugs before and never have an issue.

Look around this site and you will see that the Bosch plugs are not recommended.

 

[MC05XLS]

Look around this site and you will see that the Bosch plugs are not recommended.

Yeah I know. But having local friends that use them on their 4.0, and my issue started after I installed the air filter but before the plugs, I need to investigate the vacuum hose you suggested. I had to take the lid off the air box to install the gasket for the filter, I probably did knock something loose.

 

[MC05XLS]

So I finally managed to get to the shop. He ran the diagnostic and did some investigating, and said it's a blown coil pack. I have an extended warranty, so it has to be an OEM replacement part. This has to come in from Houston and won't be in till around 3pm.

Al, I asked the mechanic about using Bosch plugs, and he said he's never had a problem with them in any engine. I asked him point blank if that was what caused the coil to fail, and he said no. I showed him the old plugs that were in it when I bought the truck, and he says the way they were burned, it most likely has something to do with the previous owner's driving habits, and the truck having been abused.
Which also explains why I see signs of body work that didn't show up on Carfax.

Oh well. It buys me some time before I need to upgrade coils and wires.
Next step? New all-terrain tires.

 

[eXcali]

It's also not uncommon for the oil from the k&n to cause problems with your MAF sensor. Just needs a good spray of brake cleaner on the sensor and let it dry to clean it up. I've also heard bad stories about the bosch +4.

 

[MC05XLS]

Well come to find out, this issue was my fault. I cracked the #3 plug when I put it in (right side, back cylinder) but in my defense, it was a pain to get to. Warranty still covered me, and the dealer had a new +4 brought in from the parts house for me. Very nice people at Silsbee Ford.

The thirty minute drive home, and my 40 minute commute to work at 4am showed what i'd hoped. My instant fuel economy has gone up from the 18.6-19.4 range to 20.5-21.3 range. Roads are wet so I'm not able to test performance, but the Ex didn't seem to rev up as much going over the overpasses, and maintains a lower rpm at highway speeds.

I'm not as worried about performance as I am mileage, so at this point, I'm satisfied. 2-3 mpg instant doesn't sound like much, but with a 19 gallon tank, ever little bit counts. I'll know more at the next fill up.

 

[F1EA]

I'm having a kinda similar issue with my '03 V6. The SES light came on a few days ago, then turned off by itself... now its on again.

There is some stuttering on the 1,300 - 1,500 RPM range (everything is fine above 2k RPM) and i feel kindof a rough idle. Air filter is OEM, less than 3,000 miles old...

Will check the plugs and while at it wanna check on the MAF.
Question: How do I check and clean the MAF sensor??

(by the way I have heard platinum plugs are not the best for these engines)

 

[MC05XLS]

I'm having a kinda similar issue with my '03 V6. The SES light came on a few days ago, then turned off by itself... now its on again.

There is some stuttering on the 1,300 - 1,500 RPM range (everything is fine above 2k RPM) and i feel kindof a rough idle. Air filter is OEM, less than 3,000 miles old...

Will check the plugs and while at it wanna check on the MAF.
Question: How do I check and clean the MAF sensor??

(by the way I have heard platinum plugs are not the best for these engines)

Hi,
The MAF sensor is located on the plenum connected to the top half of the air box. You should be able to disconnect the plug and remove 2 screws holding it in. You're looking for dirt and oil buildup on the sensor. If I remember correctly, I think I was told brake cleaner would work, but I'd defer to a member like Aldive to be sure.

 

[aklmfreak]

Hi,
The MAF sensor is located on the plenum connected to the top half of the air box. You should be able to disconnect the plug and remove 2 screws holding it in. You're looking for dirt and oil buildup on the sensor. If I remember correctly, I think I was told brake cleaner would work, but I'd defer to a member like Aldive to be sure.

Advance Auto Parts and other auto parts stores sell a cleaner designed for MAF sensors. it's just called MAF Sensor Cleaner

 

[F1EA]

it's just called MAF Sensor Cleaner

I wonder what it does
I think Electric Contact Cleaner also does the work...

 

[aldive]

I think Electric Contact Cleaner also does the work...

It does.