Extremely Low Mpg...why???

rideapony · May 21, 2017

Hi all,
I'm appealing to you expertise and suggestions to mi problem.

My MPG es extremely low, I'm not whining just it seems like there must be a problem but hadn't been able to find the root to solve it.

I just filled my tank and got around 9 miles to the gallon in the city!!!

Purposely I drove my ride really easy, like taking off with ease and shifting below 2k rpm.

I have no error codes whatsoever and my timing is about 15 deg.
Fuel regulator is stock and no diafragma ruptured. So everything seem working fine but why my fuel consumption is so high???
My sign has all the details of my setup.

I mean it is a 306 but it seems like it is out of something... Please help!!!

2007_Crown_Vic · May 21, 2017

Does it seem to run rough or have a strong fuel smell at all? I wonder if it is running really rich it maybe a bad O2 sensor or airflow sensor, something like that....

Noobz347 · May 21, 2017

List all modifications

rideapony · May 21, 2017

"Does it seem to run rough or have a strong fuel smell at all?"

Runs fine , there is only a normal slight lumpy idle because the Stage 1 TFS cam and as far as raw fuel smell, It has some raw fuel smell while driving and as I shut it off it in the garage and open the hood the smell is a bit more noticeable.

A bad O2 sensor will trigger an error code, correct? I assume it will be the same for the MAF sensor... I scan the computer and has nothing!!!

I was using an SN95 MAF and tube and I thought maybe that's causing that high fuel consumption. I removed it and installed the stock MAF/Tube setup, reset the computer but didn't make any difference.

I'm stumped and don't know what else to try, Some time ago I took my injectors for cleaning thinking that they could stay open when turning the engine off, but didn't make any difference. the only improvement I saw was that it started right at the turn of the key. before it used to turn a few revolutions in order to fire up, but that was it!!!

I think I asked before if advancing the timing from 10 to 15 degrees would decrease my MPG but but didn't get a definite answer.

So, what else to try?

rideapony · May 21, 2017

... By the way, this is an old problem but latelly I've been so much frustrated and would like to find a fix for it (If there is a fix any way)

jrichker · May 21, 2017

No code 11 (two flashes when the computer dumps the codes)? A perfectly functioning system will always get a code 11, it is the everything is OK code. The 11 code is computer passed its internal self test.
If you don't get an 11, you have computer or wiring problems.
Please check and repost.

rideapony · May 22, 2017

Thank you jrichker, you're always a good source of knowledge

As I mentioned there are no error codes coming out of the ECM.

Every time I run a scan I get code 11 on the "Self test fault code" and code 11 on the "Continuous Memory codes" that means the system is free of errors. That's what makes me really wonder what the heck is going on! I'm absolutely sure there is something wrong because that terrible fuel consumption doesn't seem normal to me, specially when I tried to drive as easy as possible and shifting at relatively low rpm and it just swallows that much fuel.

So what's wrong with my set up, or where to focus to troubleshoot this problem???

Thank you all

General karthief · May 22, 2017

Pull your plugs and see what they look like,
Back your timing off 2 degrees to see if it gets better.
You need to investigate the fuel smell problem, look at your charcoal canister lines, fuel lines etc.
I have a heavy foot every time I drive mine and get 10 to 12 mpg.

Dan02gt · May 22, 2017

I would try O2 sensors. You can get them from Rock Auto for about $20 each. In my experience they will only throw a code if they are "really" bad. If the sensors are marginal you might not see one.

Deleted member 215073 · May 22, 2017

Is it possible having the injectors cleaned ruined them? Are they stock injectors? How old are your O2 sensors?

Mustang5L5 · May 22, 2017

rideapony said:
Every time I run a scan I get code 11 on the "Self test fault code" and code 11 on the "Continuous Memory codes" that means the system is free of errors.

Did you then start the engine and perform the "key on engine running" codes, and a cylinder balance test

rideapony · May 22, 2017

I truly appreciate all your help!

Plugs: Today I'll check the plugs color and condition. I did that not too long ago and they were pretty normal.

The gas smell: I had that smell before I cleaned the injectors, I had the impression that one or more were open at all times but I don't see any smoke out of the pipes. I'm running the skinny injectors, and yes I will inspect all the fuel delivery/return system.

O2 sensors and MAF sensor: I was relying completely on the computer's errors output and diagnostics, but I'm learning that some sensor failures are not kept and registered as errors and that's troubling. I will have to check all the sensors output and see where this takes me. I just don't remember how old any of the sensors are and probably they are downhill already.

I'll post any findings, thank you all again

rideapony · May 22, 2017

First findings:

PLEASE BARE WITH ME...

I ran a KOEO scan and found error codes 81 and 82.
Will these errors affect my fuel economy?

The smog system has been removed for a long time all the hoses going to the two solenoids of the smog system were canceled and the solenoids removed. I inserted two resistors instead of those solenoids and wasn't seeing any errors.
I just plugged those two solenoids without any hoses, will clear the codes and see what happens. But want to go back to the question, will those errors cause MPG suffering?

And by the way, I haven't run a KOER test until I have all the sensors, relays, and solenoids to work properly.

Thank you all!

Mustang5L5 · May 22, 2017

rideapony said:
I ran a KOEO scan and found error codes 81 and 82.
Will these errors affect my fuel economy?

No. Those codes won't affect fuel economy.

The valuable codes will be those run with the engine running codes. That's where you'll see O2 sensor codes and such. You can certainly run them now, no reason to hold off.

All Stock93 · May 22, 2017

I'm kinda late to the game but, have you confirmed you don't have a leak somewhere?

rideapony · May 22, 2017

Yeah that's what I thought about errors 81 and 82. Regarding the O2 sensor I must say they are old, I will try to find a sequence or procedure to test them and see if their output is within specs.

As far as a vacuum leak, that could be another potential cause. I noticed a slight oil leak at the back of the lower intake by cyl No 4. If I spray carb cleaner around there should I expect to have the same change in idle speed??? Or if anyone running the same cam and set up as mine knows how much vacuum should I have if I measure the vacuum with a gauge.

Thank you all!

rideapony · May 22, 2017

Still troubleshooting, I know I might open a can of worms with this, working on the charcoal canister to solve the gas smell issues, I removed the purge solenoid valve which has a flow arrow pointing to engine, but. Let me understand this the vacuum from the intake manifold supposed to suck the vapors to be burned from the charcoal canister as the computer sends ground to the solenoid, correct? At least this is may understanding...

Well when I energized the valve it opens and serves like a check valve (One way flow). The problem is the ad the solenoid is energized, it opens the flow but to the opposite side of the arrow, in other words I have flow from the engine to the charcoal canister, this should be the opposite isn't it??? I think that's why I have that gas smell because the vapors are not being burned.

Anyone have any ideas?

General karthief · May 22, 2017

Charcoal canister: vacuum from intake to purge valve to canister
Vacuum line (rubber) to plastic line back to fuel tank.

http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

rideapony · May 22, 2017

Yeah I have it that way but the problem I see is that there is no flow from the charcoal canister to the intake when the valve opens. It does the opposite, there is flow from the intake to the charcoal canister that's why the intake don't get the fuel vapors stored in the charcoal canister. It is acting like a check valve. I flipped the purge valve 180 degrees and hooked the hoses onto the the fittings and it seems to work fine, no noticeable fuel smell..

Now I'm going to keep troubleshooting the main problem which is extremely high fuel consumption. Right now I'm testing the MAF sensor following be the O2 sensors, will see what I can find there.

Thank you all!

Mustang5L5 · May 22, 2017

The engine side of the check valve will always see vacuum (unless supercharged). The valve opens and draws towards the engine in the direction of the flow arrow.

It's not really supposed to actively flow fuel vapor, it just prevents the pressure in tank from building and prevents hydrocarbon release to atmosphere.

Did you pull engine running codes and see a code 85 for the canister?

Extremely Low Mpg...why???

rideapony

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2007_Crown_Vic

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Noobz347

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rideapony

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rideapony

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jrichker

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rideapony

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General karthief

wonder how much it would cost to ship you a pair

Dan02gt

mazing how much gas smell came from that tiny hole

Deleted member 215073

Mustang5L5

That is…until I whipped out my Bissell

rideapony

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rideapony

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Mustang5L5

That is…until I whipped out my Bissell

All Stock93

rideapony

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rideapony

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General karthief

wonder how much it would cost to ship you a pair

rideapony

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Mustang5L5

That is…until I whipped out my Bissell

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