Engine (EGR Deleted) Solution the hotter combustion chambers?

AeroCoupe · Apr 28, 2026

Comparing at supercrew 4x4 with a panoramic roof and 20" wheels with a tuned Coyote to any Ranger is not apples to apples. I also drive my F150 pretty hard so I am not trying to get really good mpg. I would have picked a different vehicle if I was needing 20+ mpg. There is not at much btu per gallon of E-85 as there is gasoline so you have to use more of it to make the same hp. Great things about it are it runs cooler so you can bump in more timing and like you mentioned it cleans up the back side of the valves. Gen 3 Coyotes have two sets of injectors to direct and behind the valves. Ford did this for a multitude of reasons but one benefit is that it helps with the carbon build up on the back of the intake valves.

PonyGTrider · Apr 28, 2026

86HO5.0 said:
Buy one from Summit/Jegs/LMR. They're about $220 shipped.

DO NOT buy a cheap POS from Aliexpress. They're a knockoff, might as well burn your money.

I’ll plan on that

PonyGTrider · Apr 28, 2026

AeroCoupe said:
Comparing at supercrew 4x4 with a panoramic roof and 20" wheels with a tuned Coyote to any Ranger is not apples to apples. I also drive my F150 pretty hard so I am not trying to get really good mpg. I would have picked a different vehicle if I was needing 20+ mpg. There is not at much btu per gallon of E-85 as there is gasoline so you have to use more of it to make the same hp. Great things about it are it runs cooler so you can bump in more timing and like you mentioned it cleans up the back side of the valves. Gen 3 Coyotes have two sets of injectors to direct and behind the valves. Ford did this for a multitude of reasons but one benefit is that it helps with the carbon build up on the back of the intake valves.

I guess I’m getting your point. In my case I’m having a terrible mpg. Actually I was expecting more criticism like “If you want 20 -25 mpg you have the wrong car better get another car”

I see no wrongdoing trying to get a good decent mpg and a fair performance. Also I don’t see why I can’t get my engine as efficient as possible.

What bothers me is not the filling the tank more often, what really piss me off is that out of ordinary high fuel consumption is not justified by what I have on my build.

AeroCoupe · Apr 29, 2026

That was more directed to 86HO5.0's comment. I will tell you that my Coupe gets about 9 mpg in town but it has a 331 that makes 460ish fwhp and I like how the exhaust sounds so I am not trying to get mpg's out of it either. On the highway at 75 with 3.73's it makes 20 t0 21 mpg. It could also use some time on the dyno as it's been a couple of years since the last tune and I have made some changes. That will not happen until the MS3PRO gets installed which is a ways out.

Regardless I feel like yours should at least make 12-15 mpg city driving and more than that on the highway. The two things you need are an wide band and to send the ECU in to get checked out and any repairs made.

1986-2004 Ford Mustang A9L A9P ECU Repair Service

1986-2004 Ford Mustang A9L A9P ECU Repair Service Engine Computer Repair Please fill out the R&R form here once you've placed your order.ORInclude a note in the box with your order number and vehicle symptoms.A Trusted Product with LIFETIME WARRANTY QUICK TURN AROUND TIMEDomestic and...

www.theecuexchange.com

86HO5.0 · Apr 29, 2026

AeroCoupe said:
Comparing at supercrew 4x4 with a panoramic roof and 20" wheels with a tuned Coyote to any Ranger is not apples to apples. I also drive my F150 pretty hard so I am not trying to get really good mpg. I would have picked a different vehicle if I was needing 20+ mpg. There is not at much btu per gallon of E-85 as there is gasoline so you have to use more of it to make the same hp. Great things about it are it runs cooler so you can bump in more timing and like you mentioned it cleans up the back side of the valves. Gen 3 Coyotes have two sets of injectors to direct and behind the valves. Ford did this for a multitude of reasons but one benefit is that it helps with the carbon build up on the back of the intake valves.

My point was not the gas mileage itself but the % of mileage lost. You stated you were losing 50% MPG, hence my reference of 15% in my own case.

I think you misunderstood my comment.

Have a good day sir!

PonyGTrider · Apr 29, 2026

AeroCoupe said:
That was more directed to 86HO5.0's comment. I will tell you that my Coupe gets about 9 mpg in town but it has a 331 that makes 460ish fwhp and I like how the exhaust sounds so I am not trying to get mpg's out of it either. On the highway at 75 with 3.73's it makes 20 t0 21 mpg. It could also use some time on the dyno as it's been a couple of years since the last tune and I have made some changes. That will not happen until the MS3PRO gets installed which is a ways out.

Regardless I feel like yours should at least make 12-15 mpg city driving and more than that on the highway. The two things you need are an wide band and to send the ECU in to get checked out and any repairs made.

1986-2004 Ford Mustang A9L A9P ECU Repair Service

1986-2004 Ford Mustang A9L A9P ECU Repair Service Engine Computer Repair Please fill out the R&R form here once you've placed your order.ORInclude a note in the box with your order number and vehicle symptoms.A Trusted Product with LIFETIME WARRANTY QUICK TURN AROUND TIMEDomestic and...

www.theecuexchange.com

Sounds good, yeah definitely something is going on with my setup. The excessive fuel consumption is telling me that my engine is completely out of efficiency.
I have two known good ECU’s one that was running all the time and one that I bout manufactured. Both are giving me the same results so what are the chances of both being bad??? Hard to tell.
As for the AFR gauge yes I will look into one.

AeroCoupe · Apr 30, 2026

86HO5.0 said:
My point was not the gas mileage itself but the % of mileage lost. You stated you were losing 50% MPG, hence my reference of 15% in my own case.

I think you misunderstood my comment.

Have a good day sir!

Yup completely misread. Clarification definitely helped and understand what you are saying. I just know that my buddy’s Whippled Mustang gets half the mpg on its E-85 tune vs the 93 octane gas tune. Make more hp on the E-85 due to it running cooler, more timing, and more boost but that’s the advantage of alcohol.

Noobz347 · Apr 30, 2026

I had a Flex-Fuel 1/2 ton Suburban at one point. Probably during the height of the whole Flex-Fuel conversation. We did the math on the 85 vs. gas on the highway and were spending more per mile on E85.

It is [very] noticeable when you're pulling a 35' camper across country.

PonyGTrider · May 1, 2026

Happy Friday guys & gals
I don’t know if I found the smoking gun but I found a very interesting issue here.

So long story short I dismantled the top end in search of potential vacuum leak. Was debating to delete my EGR valve blocking the port at the head but I decided not to do that.
Anyway I assembled everything back making sure I clean perfectly the ends of the block known as the “china walls” and then put a generous bead of ultra black RTV and the put everything back together. Two days later I filled the cooling system and fire it up.
I immediately took vacuum measurements and I got 12 inches of vacuum for this I used the tiny EGR and accessories/reservoir port next the fuel pressure regulator port. So I decided to take a measurement connecting my vacuum gauge inline with the EGR line using a T fitting and what I saw really knocked my nuts off, the vacuum reading dropped to 5 inches! So there was a leak then!!!!!!
But the leak was not at the reservoir or by the dash or at the lines. The leak is at the EGR solenoid. I know I read somewhere that that solenoid is open to the atmosphere but then what happens to my vacuum?? Is that why my fuel pressure regulator is not dropping the pressure and always is running high kicking my fuel economy to the ground????
Now what do I do???? Can I temporarily disable the EGR solenoid vacuum line and see where that takes me?
Can I drive without the EGR vacuum line???

Thank you guys!!!

Noobz347 · May 1, 2026

This?

https://lmr.com/item/LRS-9459A/1987-1993-mustang-egr-control-solenoid

AeroCoupe · May 1, 2026

I stole this out of one of jrichker's posts.

Diagram courtesy of Tmoss & Stang&2birds. (the diagram says 88 GT, but the EGR part is the same for 86-93 Mustangs)

Keep the EGR vacuum line connected and disconnect and plug the lines(s) going to the the two TAB solenoids. You will most likely get a code but this will get you buy and let you prove out what you think it your leak.

PonyGTrider · May 1, 2026

Noobz347 said:
This?

https://lmr.com/item/LRS-9459A/1987-1993-mustang-egr-control-solenoid

That’s the one

PonyGTrider · May 1, 2026

AeroCoupe said:
I stole this out of one of jrichker's posts.

Diagram courtesy of Tmoss & Stang&2birds. (the diagram says 88 GT, but the EGR part is the same for 86-93 Mustangs)

Keep the EGR vacuum line connected and disconnect and plug the lines(s) going to the the two TAB solenoids. You will most likely get a code but this will get you buy and let you prove out what you think it your leak.

Since I have all my anti smog system deleted I don’t have the TAB solenoids connected to the vacuum line I only have the electrical connectors hooked up so I don’t get a code from them.
The only solenoid connected is the EGR solenoid and there is where I lose more than a half of my vacuum and probably that’s why the fuel pressure regulator drops from 40-41 to 39 psi because there is only 5 inches of vacuum. Could that be the source of my pathetic fuel economy?
Can I just put the EGR vacuum line temporarily off for testing????

PonyGTrider · May 1, 2026

Ok here’s a new update:

For a test I disconnected and plugged the EGR vacuum line and installed a vacuum gauge and a fuel pressure gauge then started up the engine I only had ~9.5 inches of vacuum at normal operating temperature why I had 12 inches of vacuum about two hours before???
Anyways, I unplugged the vacuum line from the regulator and my fuel pressure reading was about 44 psi (First photo) then I plugged the vacuum line back to the pressure regulator with about 9.5 inches of vacuum and it only came down to 40 psi (Second photo)
Then just for the sake of it I removed the vacuum line from the pressure regulator plugged it and applied 20 inches of vacuum manually and the fuel pressure only dropped to 38 psi (Third photo)

So why the pressure only dropped six psi when I applied 20 inches of vacuum from 44 psi to 38 psi??? Should I inspect the return line closely for any blockages?????? There is absolutely no fuel smell at the fuel pressure regulator’s vacuum port…

PonyGTrider · May 2, 2026

… Anyone out there can help?

AeroCoupe · May 2, 2026

Read this post by jrichker. He explains how FPR’s work in conjunction with the ECU.

Post in thread 'Adjustable Fuel Pressure Regulator'
https://stangnet.com/mustang-forums/threads/adjustable-fuel-pressure-regulator.871252/post-8755804

PonyGTrider · May 2, 2026

AeroCoupe said:
Read this post by jrichker. He explains how FPR’s work in conjunction with the ECU.

Post in thread 'Adjustable Fuel Pressure Regulator'
https://stangnet.com/mustang-forums/threads/adjustable-fuel-pressure-regulator.871252/post-8755804

Thank you, I’ll review that

PonyGTrider · May 2, 2026

So here is what I found:
The fuel pressure regulator was bad. No leaks just no matter how much vacuum you applied there was no change in fuel pressure as the diaphragm probablyhas hardened. So I replaced it with a good one and when I applied 20 inches of vacuum manually the pressure dropped to 32 psi.
The other problem I found was that EGR solenoid or EVR had a major vacuum leak dropping more than a half of my vacuum, most likely the little plunger got stuck and was venting mora than 50% of my vacuum.
Just for the hell if it I put some very light oil in the ports , shock it and re installed it and so it worked out fine the vacuum bleeding stoped!!!
This was just a quick temporarily fix I have a new EVR order and will be here this coming Monday to replace this old one.
I just filled some gas and should be able to see some progress on my main issue of too high fuel consumption.

Engine (EGR Deleted) Solution the hotter combustion chambers?

AeroCoupe

lube between the nut and the face. I know my lubes

PonyGTrider

PonyGTrider

AeroCoupe

lube between the nut and the face. I know my lubes

1986-2004 Ford Mustang A9L A9P ECU Repair Service

86HO5.0

Active Member

PonyGTrider

1986-2004 Ford Mustang A9L A9P ECU Repair Service

AeroCoupe

lube between the nut and the face. I know my lubes

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

PonyGTrider

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

AeroCoupe

lube between the nut and the face. I know my lubes

PonyGTrider

PonyGTrider

PonyGTrider

PonyGTrider

AeroCoupe

lube between the nut and the face. I know my lubes

PonyGTrider

PonyGTrider

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Engine (EGR Deleted) Solution the hotter combustion chambers?

lube between the nut and the face. I know my lubes

lube between the nut and the face. I know my lubes

Active Member

lube between the nut and the face. I know my lubes

Stangnet Facilities Maint Tech... Er... Janitor

Stangnet Facilities Maint Tech... Er... Janitor

lube between the nut and the face. I know my lubes

lube between the nut and the face. I know my lubes

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