avg mpg went from 19 to 16 after new coils

[merlon]

I installed visteon coils and left the platinum motorcraft plugs alone. I just bought the car and previous owner said he just changed the plugs and one coil. It's an autozone coil so, I don't trust its reliability. The plugs look clean too, so I believe him.

I instantly had better acceleration and throttle response (yes romping on it affect mpg but gud me the benefit of the doubt) .

I barely get 22/23 mpg on the highway and like 13-15 around town..

It's not ny driving style that's causing bad mpg. I drive the same route everyday, same style...te only thing that changed is the coils.


I always use 91 from chevron or shell.

Sucks to shell out $200 and have mpg go down 15%. Should I just replace plugs? Idk even know what plugs to use, ngk iridiums?

I'm thinking of just throwing old coils back in and only leaving new ones in place of bad ones.

 

[jmtiseo]

Always replace coils and plugs together. Silly question, did you pull the plugs out when you swapped the cops? Don't know if you mean only the plugs' insulators were clean.

If he threw in an autozone coil, what's saying he threw in a plug without checking the gap. I'd go back in there put Motorcraft plugs after checking the gaps and see what happens.

 

[BlackLS06]

You can use regular $3 platinum NGK plugs. Also with good coils the car will run better causing you to drive it harder possibly lowering the mpg.

 

[Kumba]

Reset MPG, go for a 20-minute drive on the interstate, record MPG, reset MPG, drive back. Best way to eliminate the driver issue

 

[merlon]

jmtiseo: I pulled two plugs, they looked fine, but I skipped checking the gap...

BlackLS06: well I can get 8 ngk ix's for about $50 or 8 ngk plats for $25 so if the only difference is change interval ill go with saving 50% and get the plats.

Kumba: I just drove on the freeway to the movies (where I'm at now) and I was getting 23mpg...not exactly as good as others reported 25-29....or is this an avg highway mpg?

 

[Turboguy]

Ha, you beat me to it, my mileage is acting up too. Won't hijack, will start another thread...

 

[Elemino]

You can use regular $3 platinum NGK plugs. Also with good coils the car will run better causing you to drive it harder possibly lowering the mpg.

LOL... that's exactly what happened to my car! New coils and IX plugs... she drives like a dream, just begging for you to bury your foot in the pedal!

 

[regiment1]

Kumba: I just drove on the freeway to the movies (where I'm at now) and I was getting 23mpg...not exactly as good as others reported 25-29....or is this an avg highway mpg?

The best I've ever averaged in 10 years with this car for heavy highway driving is 24 mpg

 

[Elemino]

I did 29 when I bought the car back in Feb with the entire family in the car. The A/C was off (because it didn't work, not because it was Feb. This is Texas), and I had the cruise (speed) control set at 65mph.

 

[jrand]

decrease in MPG would probably be normal because your pcm has to learn new shift parameters due to the new coils. The shift parameter between 4 and 5 is the most important one mpg wise and also the most delicate one to get within spec. Once you have everything fixed/replaced/cleaned, start in D4, get the car up to about 45mph for about 15 seconds then throw it over into D5 and accelerate to 55mph and cruise for 15 seconds. Repeat x5 and your tranny/torque converter "should" have learned the specs for 4-5 shifts and torque converter engage/disengage in 4-5.

You need to let the PCM 're-learn' everytime you clean/replace/fix anything that goes into shift timing (coils/plugs/maf/throttle body/OCTANE RATING come to mind). one of the service manuals i got off ebay says to clear the shift strategies every time you do something like that. easiest way to do it is to unplug your battery for abt 5 mins and follow a prescribed break in procedure. in your case i wouldnt worry about it unless you continue to have problems. there is a specific break-in/learning procedure when you clear shift parameters (or lose them inadvertantly) but i wont even try to post a comprehensive list of all the things you need to do. ill just give the ford answer "just drive it like normal until it learns" but you should know that the procedure is extensive and would probably take 2 hours and 60 miles to complete. there are a ton of sensors that the PCM uses to do everything on this car. PCM 'compensates' for out of spec readings and has to adjust when it suddenly gets different readings. your old coils were probably out of spec but not enough to trip a light, so PCM was compensating.

 

[merlon]

decrease in MPG would probably be normal because your pcm has to learn new shift parameters due to the new coils. The shift parameter between 4 and 5 is the most important one mpg wise and also the most delicate one to get within spec. Once you have everything fixed/replaced/cleaned, start in D4, get the car up to about 45mph for about 15 seconds then throw it over into D5 and accelerate to 55mph and cruise for 15 seconds. Repeat x5 and your tranny/torque converter "should" have learned the specs for 4-5 shifts and torque converter engage/disengage in 4-5.

You need to let the PCM 're-learn' everytime you clean/replace/fix anything that goes into shift timing (coils/plugs/maf/throttle body/OCTANE RATING come to mind). one of the service manuals i got off ebay says to clear the shift strategies every time you do something like that. easiest way to do it is to unplug your battery for abt 5 mins and follow a prescribed break in procedure. in your case i wouldnt worry about it unless you continue to have problems. there is a specific break-in/learning procedure when you clear shift parameters (or lose them inadvertantly) but i wont even try to post a comprehensive list of all the things you need to do. ill just give the ford answer "just drive it like normal until it learns" but you should know that the procedure is extensive and would probably take 2 hours and 60 miles to complete. there are a ton of sensors that the PCM uses to do everything on this car. PCM 'compensates' for out of spec readings and has to adjust when it suddenly gets different readings. your old coils were probably out of spec but not enough to trip a light, so PCM was compensating.

It threw code p0302/0303. primary resistance on those coils was way off from the rest, and instead of buying two at $80ea locally, or two at $45 through rockauto i chose to replace all 8 with visteons.

I cleared codes, but i dont think that resets the pcm. So i shouldve unplugged the battery, and let it relearn that way? The MPG is getting better. I averaged 19 going through the mountains, and around town is pretty good. I always have ac on, and it was getting 19avg before the coil replacments..so i was hoping for 19+ with new coils, ive already run about $100 worth of gas, or 400 miles. (100/$4gal gas = 25 gallons, 400 miles/25=16mpg...boo)

I still will make time to pull the plugs and check gaps, i know they come "pregapped" but that doesnt mean gapped between .039-.044"...worth the 30 minutes of taking of both beauty covers and checking each one.

On another note, i do notice a slight misfire at idle, like small barely noticable hiccups. I can hear it in the exhaust and feel it in when sitting inside. So maybe i didnt seat the coils properly or tighten them enough...idk the misfire was way worse before. So it could just be the plugs.

 

[TooManyToys]

BS.

The only thing the transmission programing relearns are the pressures needed to keep the shift timing within the spec table so that there is no excessive harshness or slip. The engine electronics will adjust the fuel injection and timing to operating conditions, new parts or not.

The 2 hour procedure is the drive cycle to reset all the parameters and checks when the battery is disconnected for the emission control. It does not and should not be done every time there are repairs done to a motor unless the battery was disconnected. Normal driving will reset the drive cycle over a longer time if all the conditions have been met for each section.

*******************

If the plugs were not checked for gap it needs to be done. There have been several threads on this forum where it was later found that the gap out of the box was wrong for this vehicle. The same plug can be used in other motors which may require a different gap. Unless there is only one plug specific to a motor the manufacturer will set the gap to a general spec. If you feel a misfire at idle, it is most likely doing that during higher loads too.

 

[LS4me]

decrease in MPG would probably be normal because your pcm has to learn new shift parameters due to the new coils. The shift parameter between 4 and 5 is the most important one mpg wise and also the most delicate one to get within spec. Once you have everything fixed/replaced/cleaned, start in D4, get the car up to about 45mph for about 15 seconds then throw it over into D5 and accelerate to 55mph and cruise for 15 seconds. Repeat x5 and your tranny/torque converter "should" have learned the specs for 4-5 shifts and torque converter engage/disengage in 4-5.

You need to let the PCM 're-learn' everytime you clean/replace/fix anything that goes into shift timing (coils/plugs/maf/throttle body/OCTANE RATING come to mind). one of the service manuals i got off ebay says to clear the shift strategies every time you do something like that. easiest way to do it is to unplug your battery for abt 5 mins and follow a prescribed break in procedure. in your case i wouldnt worry about it unless you continue to have problems. there is a specific break-in/learning procedure when you clear shift parameters (or lose them inadvertantly) but i wont even try to post a comprehensive list of all the things you need to do. ill just give the ford answer "just drive it like normal until it learns" but you should know that the procedure is extensive and would probably take 2 hours and 60 miles to complete. there are a ton of sensors that the PCM uses to do everything on this car. PCM 'compensates' for out of spec readings and has to adjust when it suddenly gets different readings. your old coils were probably out of spec but not enough to trip a light, so PCM was compensating.

?????? I've NEVER done that after 4 coil/plug changes and my MPG remained the same after each change. In fact, my last one was about 300 miles ago and my mileage hasn't changed.

 

[Elemino]

The only thing I've noticed is that my car will copy my SST habits when I go back to using D5. It's actually pretty nice that it does that.

 

[Upstairs Chris]

This 29 MPG stuff smells like pure bologna to me.:bsflag:

I've driven myself and only myself on the interstate with no luggage or anything else in the car, tires set for better MPG, Shell 93, freshly waxed, new coils, new plugs that were properly gaped, had the cruise on 65, no AC, and windows up.

And got 26 MPG. This was Coming from Morgantown WV, up to Washington PA, and over to Flushing Ohio. Not nearly as flat as Texas, but about as close as you can get around here. My Point being, is that I have attempted to achieve the max efficiency on this car and people routinely get on here and say "Hardy har Har, I get 87 MPG lolz" or something equally non believable.

With that being said, without paying attention to it and usually giving it generous amounts of throttle I get 16-17 for really hard stop and go city driving, right around 20-21 for county back roads, and 24-25 highway.

As far as new coils affecting your MPG goes, mine improved when I replaced them with the same visteions that you got, but then again, my old ones were in water , which is another story altogether. My plugs were NGK platniums but I cant remember which ones, but I checked the gaps and they were all good.

 

[jrand]

BS.

The only thing the transmission programing relearns are the pressures needed to keep the shift timing within the spec table so that there is no excessive harshness or slip. The engine electronics will adjust the fuel injection and timing to operating conditions, new parts or not.

The 2 hour procedure is the drive cycle to reset all the parameters and checks when the battery is disconnected for the emission control. It does not and should not be done every time there are repairs done to a motor unless the battery was disconnected. Normal driving will reset the drive cycle over a longer time if all the conditions have been met for each section.

*******************

If the plugs were not checked for gap it needs to be done. There have been several threads on this forum where it was later found that the gap out of the box was wrong for this vehicle. The same plug can be used in other motors which may require a different gap. Unless there is only one plug specific to a motor the manufacturer will set the gap to a general spec. If you feel a misfire at idle, it is most likely doing that during higher loads too.

haha right bc emissions and fuel economy are not related AT ALL.
I think those sensors and the PCM are doing a little more than you think sir.

OP's issue is either spark plugs or an out of spec "new" coil, but a short term MPG loss over the course of abt 2 hrs / approx 60 miles (longer if you dont do the d4-d5 procedure described in my initial response [or maybe SST, dont have SST, wouldnt know]) after a major component change could be attributed to PCM running tranny in 4 when it could (and should) be running in 5.

 

[TooManyToys]

Of course they do and the adjustments are made right after the sensors get warmed up. They don't need a drive cycle routine and a battery disconnect. And again it's not going to run in a different gear because it has not gone through this cycle. Your making situations up to cover what you stated.

 

[merlon]

Edit;
Getting 18avg....just filled up. Will drive normal, as long as I can....see if that works ....but its Sooo tempting to floor it !

Update

I checked the plugs, they look new. The gaps are all 0.041" and all the coils are tested to be fine. So either i just didnt seat the coil properly or tighten them down enough, or idk? I did install the four on the D-side when it was getting dark. So i only had a lamp to aid in my visibility. But i usually go by feel, when i feel the boot get snugged down on the plug i can bolt it in.

I re-installed everything, car seems to have no more small mis at idle. When i start it up for work in a couple hours ill know for sure (usually happens when it was cold anyways)

Yesterday i was getting decent enough mpg, i drove 60 miles through the mountains and maintained an average of 19.2, which to me is decent. On a straight highway i should see a few more mpg added onto that figure.

Ive burned about 160 miles worth of gas, so ill go fill up and get an actual reading of my averaged miles per gallon since the dash display probably is not 100% accurate. (the one in my mark was pretty close, but not 100%).


On a side not, plug 5 (closest to radiator on driver side) there was oil on the threads...none on the plug, but that kind of worries me a bit. I dont want these new coils shorting out. Does this oil on the thread mean my gaskets are on their way out? Should i get on replacing them, or is this okay?

 

[Elemino]

This 29 MPG stuff smells like pure bologna to me.:bsflag:

Well I also have a K&N air filter in my car... I'm not sure how much that affects anything. I'd do it again just to prove it, but the fact that its over 30 degrees hotter outside in the evening now would surely make a difference.

A friend that used to own a 2000 LS said his grandfather routinely got 29mpg on the highway as well. He never got it himself, because like many of us, he couldn't keep his foot out of the gas.

Now... lets take into account the new vettes and Mustangs claim 24~26mpg on the highway... hmm, doesn't sound so impossible all of a sudden.

The gaps are all 0.041"

I thought the gap was supposed to be .044... I'm pretty sure that's what I used.

 

[TooManyToys]

Merlon,

It sounds like the O-Rings that seal at the sparkplug tunnels are starting to go. When I replaced my valve cover gaskets it was these O-Rings that were the most heat hardened. If you do the valve cover gaskets yourself be sure to first wash the area of the engine block where the dipstick tube fits into as if the dipstick pulls out with its O-Ring out of the block you can get sand down into the oil pan. It also helps to use a Dremmel cut-off wheel to cut down the stud that holds the dipstick in place so you don't have to lift the dipstick too far.

 

[merlon]

Well I also have a K&N air filter in my car... I'm not sure how much that affects anything. I'd do it again just to prove it, but the fact that its over 30 degrees hotter outside in the evening now would surely make a difference.

A friend that used to own a 2000 LS said his grandfather routinely got 29mpg on the highway as well. He never got it himself, because like many of us, he couldn't keep his foot out of the gas.

Now... lets take into account the new vettes and Mustangs claim 24~26mpg on the highway... hmm, doesn't sound so impossible all of a sudden.

I thought the gap was supposed to be .044... I'm pretty sure that's what I used.

I think its 1.0-1.1mm (thats what i remember reading under the hood) which is 0.039-0.0433" on google converter

 

[joegr]

...
I thought the gap was supposed to be .044... I'm pretty sure that's what I used.

.044 is just past the maximum (max is 1.1mm or 0.043"). You want to either set it in the middle, or at the minimum. I find that the minimum seems to work best (1.0mm or 0.039").

http://deneau.info/ls/s6x~us~en~file=s6x37001.htm~gen~ref.htm

 

[joegr]

... but a short term MPG loss over the course of abt 2 hrs / approx 60 miles (longer if you dont do the d4-d5 procedure described in my initial response [or maybe SST, dont have SST, wouldnt know]) after a major component change could be attributed to PCM running tranny in 4 when it could (and should) be running in 5.

Complete bull.

 

[RigsLS]

I did 29 when I bought the car back in Feb with the entire family in the car. The A/C was off (because it didn't work, not because it was Feb. This is Texas), and I had the cruise (speed) control set at 65mph.

Elemino,
I actually noticed this myself aswell.
on longer drives when I'm not in a hurry to get there,
I set the cruise control to just a hair under 2000RPM,
this gives me just around the 100-102KPH. (60'ish MPH)

keeping this up for a few hours, gives me whicked milage.
I've squeezed 595KM out of a tank before.

I don't have mine set to MPH but rather KPH so I wouldn't even want to compare.

Mostly I don't measure my millage, just put more fuel in it.
lead-footing around town throws everything off anyhow.

 

[LS4me]

I got 28mpg, once, driving across Wyoming doing 80ish. You would be surprised how much lower your MPG is with ethanol "enriched" gas. That was my best mileage ever as I was burning real, non-enhanced fuel.