Changed plugs, gas milage took a dump

[americanuck]

Hey all,

So im halfway decent around tools and maintenance. Normally basic maintenance on all my cars I’m happy to do. I got a new to me 21 with 160k km (100k miles). Got it for practically nothing, and it ran great.

I was getting about 11/100km on each fill up using premium.

Since it was due for service, I got out the tools and changed the plugs and engine air filter. And wow… now I’m getting 12-13/100km. I used motorcraft plugs and I do know that 21 had two types of plugs. Mine is job 1 and I verified as I pulled one out that it matched what I put back

I’m not getting any error codes and I took off the boots and checked everything. Just anecdotally it feels like there is less power.

I’m tempted to just get all new plugs, boots, coils, the whole thing. But money. Anybody smarter than me have any troubleshooting or thoughts?

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[Mosey]

You don’t specify directly, but I am guessing you have a 3.5L Ecoboost? Have you noticed any change in the engine roughness-wise? How many tanks of gas have you run thru to come up with your post plugs number?

 

[americanuck]

Oops. You’re right.

It’s a 3.5. I’ve gone through 4 full ups so far. The last fill up was 13.1.

Plugs seemed to have gone in nicely with no issues. It has always idled rough, so I don’t think it’s gotten any worse.

I would just think that if it was a plug or coil issue, there wood be some code?

The only other thing I’ve noticed, on occasion, a bit of white coming out of the exhaust. Not full on scary white. Just some white while idling. If that makes sense.

 

[Mosey]

One thing you could do is to determine the position of the spark plug gap with respect to the intake valves. If any gap is facing directly away you could just replace that plug with another. I have a Job 2 2021 PB with the new plug design. These are indexed plugs and they are designed to always have the gap facing the intake (or 90‘ either way).

For the white smoke from the exhaust, does it smell strongly of gas?

Edit. Did you observe/check the gap?

 

[Gros Ventre]

Indexing and such things can make a difference. On a Suburban I ran for 30 years, I ran some "tests" where every 50,000 miles I used different brand plugs to determine if there was one that gave better performance. I could not tell the difference across any of the plugs I tried.

 

[americanuck]

I didn’t check the gap. Mainly because everything I read screamed at me not to touch the gap. But they didn’t seem drastically out of whack. But easy enough to pull out and check.

Didn’t really smell any different. I lingered near the exhaust for a minute to try to smell anything, but didn’t get anything. Just normal exhaust smells.

For the position of the gap, pardon my ignorance, but how would one check for that?

 

[Mosey]

With the plug in the plug socket mark the top of your racket extension where the plug gap points. Then reinstall and torque. Recheck the mark and see where it fell with respect to the intake.

 

[Mosey]

BTW, have you noticed any loss of coolant?

 

[americanuck]

Gotcha. Thank you for the advice! That’s exactly what I was looking for. I’m gonna pull them all, double check the gap, see where they land when I reinstall.

 

[americanuck]

BTW, have you noticed any loss of coolant?

No, that was one of my first concerns, especially with the smoke I saw.
I’ve been keeping an eye on that, just in case.

 

[JCsTruck]

Did you use the correct heat range on the plug. Could effect ignition timing and cause the computer to scale back timing resulting in worse fuel economy and less power. Also check the air box hose connections to make sure they are not leaking.

 

[XLT22]

What plugs did you use and where did you get them? Fakes are rampant which is why I only buy them direct from Ford now.

 

[Billflangjr]

Hey all,

So im halfway decent around tools and maintenance. Normally basic maintenance on all my cars I’m happy to do. I got a new to me 21 with 160k km (100k miles). Got it for practically nothing, and it ran great.

I was getting about 11/100km on each fill up using premium.

Since it was due for service, I got out the tools and changed the plugs and engine air filter. And wow… now I’m getting 12-13/100km. I used motorcraft plugs and I do know that 21 had two types of plugs. Mine is job 1 and I verified as I pulled one out that it matched what I put back

I’m not getting any error codes and I took off the boots and checked everything. Just anecdotally it feels like there is less power.

I’m tempted to just get all new plugs, boots, coils, the whole thing. But money. Anybody smarter than me have any troubleshooting or thoughts?

Where did you buy the plugs , auto parts store or on line ?

 

[americanuck]

I got the plugs from my local dealership. The air filter was apparently on back order. But I’m gonna replace that with oem once they get them back.

 

[Davexxxx]

I was getting about 11/100km on each fill up using premium.

And wow… now I’m getting 12-13/100km.

Maybe I'm missing something obvious, need more coffee or something but that is an increase in mileage, not a dump.

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