Gas Mileage is deplorable

93GTDIN · 09-22-2002, 02:44 PM

I get 10 mpg mostly highway miles.

I am getting sick of coughing up 20 bucks every 4 days for gas.

I have replaced EGR, O2 sensors, and IAC valve in the last 2 weeks.

These have made no difference.

Idle is still bad in neutral, but fine when in drive with A/C on (doesnt surge then). This may be unrelated, but i figured i'd provide all possible information.

I'm all out of ideas and i'm ready to stab myself with a fork.

A/f Gauge reads lean/stoich most of the time

Pings up hills in hot weather

fuel pressure set at about 35 psi at idle

vacuum is 10-11 in hg at idle in gear

timing is about 18 degrees (ish)

car stalls when I put it into gear when warm.

Is my cam to much for the automatic? (TFS Stage 1)
Specs:
* Advertised Duration: 275 intake/279 exhaust
* Duration at .050 in. lift: 221 intake/225 exhaust
* Gross valve lift: .499 in. intake/.510 in. exhaust
* Lobe Separation: 112 degrees

Please help me, i'm losing my faith in ford!

88workcar · 09-22-2002, 02:53 PM

What gears, what stall, what speed on average, what RPM. Is your speed odom, correct? Not related to the problem, what does it run?

HotRoddin · 09-22-2002, 04:48 PM

Did this happen all of a sudden or after you changed something ?

It sounds like a vacuum leak?

Have you tried backing the timing off a bit ? At 10 to 1 compression your kinda on the edge of what you can run on street gas, thats why i wondered if its been ok then this happened all of a sudden ?

I know i'm showing my age but this is the down side of EFI ... it complicates things when it comes to troubleshooting because you have this computer trying to correct things and you can get into a big loop that makes it hard to find problems. You need a genius at reading error codes like Pkrwud !

Easy cold starting and idle quality huh ? ... hmmm... I still like to open the hood and see an engine instead of a big pile of vacuum hoses and wiring and sensors !!

Whew ... hand me that fork after you're done

93GTDIN · 09-22-2002, 04:50 PM

stall: stock
gears: 3.27
odo and speedo work fine

problem started when I put in the new motor.

Where besides vacuum hoses can I have a vacuum leak?

HotRoddin · 09-22-2002, 05:09 PM

Quote:

Originally posted by 93GTDIN
Where besides vacuum hoses can I have a vacuum leak?

Anywhere around the intake manifold ... brake booster ... any of the connectors that the vacuum hoses attach to.

Make sure the spout connector is in tight.

I'd take a timing light and make sure the timing is changing with engine speed and throttle.

Have you read the error codes ? Are you even getting any error codes ?

93GTDIN · 09-22-2002, 05:12 PM

ignition profile eratic is the only code I get.

A while ago after a tuneup I had a terrible idle surge that rendered the car undriveable. I pulled off the upper and made a new gasket for it, tightened the snot out of it and the car was driveable again, but vacuum is still horrible.

I need help.

HotRoddin · 09-22-2002, 05:27 PM

Go read the post called "Vacuum reading at idle?" Chris (PkrWud) has a reply with a wealth of info on diagnosis with vacuum guage... it might help you ?

There is a way to test for a vacuum leak with a propane torch ... I believe you just turn it on (Unlit) and go around all the intake areas where you might have a vacuum leak and if you get near a leak the idle will noticably increase?? Don't quote me on that one cause i've never done it and not sure if those instructions are right ... i'm working from memory which i don't have much of !!

One of you EFI guys or girls can jump in anytime ??? Before i lead 93GTDIN down the wrong path ??

Agent_4573 · 09-22-2002, 07:40 PM

I haven't heard about that on all the vaccuum fittings, just on the intake side. I've tried it on the maf, throttle body, upper to lower gasket, stuff like that. I'm not sure if you spray the vacuum tree on the fire wall the the idle will go up. Also you can do it with just about anything that has aerosel in it. I prefer a can of GumOut cuz even if i don't have a leak(idle increases), it leaves my engine nice and clean after i wipe it off.

93GTDIN · 09-22-2002, 10:04 PM

I've tried that with a can of throttle body cleaner before, no apparent leaks. Not to mention it evaporates from heat the instant it gets near the metal.

Skyman · 09-22-2002, 10:22 PM

Your injectors are a little big in my opinion, but I doubt theyre causing that much of a problem.

Hmmm, this is a tough one.... How much gas do you have to give your car to maintain steady speed? 10mpg is terrible, mine gets 21 freeway....

Also 18deg timing w/ 10:1 sounds a little high, try 15.

Sky

93GTDIN · 09-22-2002, 10:25 PM

I've tried backing off the timing but the idle gets even worse when I retard it. On the highway, I barely have to push it in half an inch. If that. Very little. About the same as stock.

93GTDIN · 09-23-2002, 12:02 AM

Anyone Else Have any ideas?

Agent_4573 · 09-23-2002, 08:20 AM

Have u checked the car for fuel leaks? Maybe your not burning it, maybe your leaving it on the ground as you drive.

Mach 1 · 09-23-2002, 10:41 AM

My combination is also an AOD, but i have non-lockup, 2800 rpm stall converter and 4.10 gears.

My gas mileage is also very terrible. Its hard for me to get an accurate reading, because my odometer/speedometer is not accurate as I have the speedo gear for a 3.73 installed in the tranny, but im running 4.10s.

I would guess Im getting somewhere between 10- 15 around town, the same on the highway.

This is a good indicator of how inefficient the AOD is, as t-5 guys are getting twice the mileage of us AOD guys with similar engine mods.

Do you have the correct 3.27 speedo gear for your 3.27 gears? And also, tire size will affect the accuracy of your odometer, which can throw off your MPG calculations.

Also sounds like your combination is a little mismatched. you need some gears and a converter for that thing, although this probably wouldnt help your mileage concerns?

Whats the power band of that cam? You should get a converter to stall up into that range. This could help. Sounds like you have some other issues also...stalling when warm, rough idle in nuetral. Get those problems fixed first, then see what happens with your gas mileage.

I would look for fuel leaks everywhere as already mentioned.

Also your vacuum seems a little low for the fairly average size trick flow stage 1 cam, which by the way, should work well with an AOD.

gotta run...good luck

302 LX Eric · 09-23-2002, 01:03 PM

Was your cam installed straight-up?

E

93GTDIN · 09-23-2002, 06:02 PM

if by straight up you mean not adv. or ret., then yes, it was.

I would love to solve my idle surging problems and what have you, but i'm so exhausted i don tknow what could be the problem anymore.

93GTDIN · 09-23-2002, 06:03 PM

Also, the 3.27's came stock

Mach 1 · 09-23-2002, 06:21 PM

idle surge problems are common on modified stangs and sometimes impossible to solve. The only thing i havent tried yet to fix mine is a modified computer chip.

09-22-2002, 02:44 PM	#1
93GTDIN Registered Member Join Date: Jan 2001 Location: Live music capital of the world, TX Posts: 324	Gas Mileage is deplorable I get 10 mpg mostly highway miles. I am getting sick of coughing up 20 bucks every 4 days for gas. I have replaced EGR, O2 sensors, and IAC valve in the last 2 weeks. These have made no difference. Idle is still bad in neutral, but fine when in drive with A/C on (doesnt surge then). This may be unrelated, but i figured i'd provide all possible information. I'm all out of ideas and i'm ready to stab myself with a fork. A/f Gauge reads lean/stoich most of the time Pings up hills in hot weather fuel pressure set at about 35 psi at idle vacuum is 10-11 in hg at idle in gear timing is about 18 degrees (ish) car stalls when I put it into gear when warm. Is my cam to much for the automatic? (TFS Stage 1) Specs: * Advertised Duration: 275 intake/279 exhaust * Duration at .050 in. lift: 221 intake/225 exhaust * Gross valve lift: .499 in. intake/.510 in. exhaust * Lobe Separation: 112 degrees Please help me, i'm losing my faith in ford! __________________ 96 Cobra - a bit too stock. 14.0 @ 101

09-22-2002, 02:53 PM	#2
88workcar Registered Member Join Date: Oct 1999 Location: Pierre Part, La. U.S.A. Posts: 1,850	What gears, what stall, what speed on average, what RPM. Is your speed odom, correct? Not related to the problem, what does it run? __________________ 88workcar 1988 Mustang LX 342. 417rwhp @ 6800. 28 X 10 ET Drag, 4.30s, 10.69 @ 126.43 1.42 60ft. 11.13 @ 127.7 on BFGs 1.72 60ft Rice Hater # 42 To be old and wise, You must first be young and stupid I'm somewhere in tthe middle.

09-22-2002, 04:50 PM	#4
93GTDIN Registered Member Join Date: Jan 2001 Location: Live music capital of the world, TX Posts: 324	stall: stock gears: 3.27 odo and speedo work fine problem started when I put in the new motor. Where besides vacuum hoses can I have a vacuum leak? __________________ 96 Cobra - a bit too stock. 14.0 @ 101

09-22-2002, 05:12 PM	#6
93GTDIN Registered Member Join Date: Jan 2001 Location: Live music capital of the world, TX Posts: 324	ignition profile eratic is the only code I get. A while ago after a tuneup I had a terrible idle surge that rendered the car undriveable. I pulled off the upper and made a new gasket for it, tightened the snot out of it and the car was driveable again, but vacuum is still horrible. I need help. __________________ 96 Cobra - a bit too stock. 14.0 @ 101

09-22-2002, 07:40 PM	#8
Agent_4573 Registered Member Join Date: May 2002 Location: New Jersey Posts: 375	I haven't heard about that on all the vaccuum fittings, just on the intake side. I've tried it on the maf, throttle body, upper to lower gasket, stuff like that. I'm not sure if you spray the vacuum tree on the fire wall the the idle will go up. Also you can do it with just about anything that has aerosel in it. I prefer a can of GumOut cuz even if i don't have a leak(idle increases), it leaves my engine nice and clean after i wipe it off. __________________ '89 LX 5.0, off-road h pipe, flowmaster muffs, underdrive pulleys, rebuilt WC T-5, King Cobra Clutch, 65mm throttle body, Explorer Upper/GT40 lower, Lakewood Rear Lift Bars. 76mm C&L Mass air w/ inlet pipe, Twisted wedge heads w/ stage 2 port,polish, MAC equal length shorties, Billet AFPR, 255LPH fuel pump, fresh low end w/ 10.5:1 compression. If anyone ever wants to go to Raceway Park in Englishtown New Jersey, give me a shout. RICER HATERS CLUB MEMBER 87! www.ricehatersclub.com

09-22-2002, 04:48 PM	#3
HotRoddin cranky old man Join Date: Sep 2001 Location: Longview Texas Posts: 683	Did this happen all of a sudden or after you changed something ? It sounds like a vacuum leak? Have you tried backing the timing off a bit ? At 10 to 1 compression your kinda on the edge of what you can run on street gas, thats why i wondered if its been ok then this happened all of a sudden ? I know i'm showing my age but this is the down side of EFI ... it complicates things when it comes to troubleshooting because you have this computer trying to correct things and you can get into a big loop that makes it hard to find problems. You need a genius at reading error codes like Pkrwud ! Easy cold starting and idle quality huh ? ... hmmm... I still like to open the hood and see an engine instead of a big pile of vacuum hoses and wiring and sensors !! Whew ... hand me that fork after you're done

09-22-2002, 05:27 PM	#7
HotRoddin cranky old man Join Date: Sep 2001 Location: Longview Texas Posts: 683	Go read the post called "Vacuum reading at idle?" Chris (PkrWud) has a reply with a wealth of info on diagnosis with vacuum guage... it might help you ? There is a way to test for a vacuum leak with a propane torch ... I believe you just turn it on (Unlit) and go around all the intake areas where you might have a vacuum leak and if you get near a leak the idle will noticably increase?? Don't quote me on that one cause i've never done it and not sure if those instructions are right ... i'm working from memory which i don't have much of !! One of you EFI guys or girls can jump in anytime ??? Before i lead 93GTDIN down the wrong path ??

09-22-2002, 10:04 PM	#9
93GTDIN Registered Member Join Date: Jan 2001 Location: Live music capital of the world, TX Posts: 324	I've tried that with a can of throttle body cleaner before, no apparent leaks. Not to mention it evaporates from heat the instant it gets near the metal. __________________ 96 Cobra - a bit too stock. 14.0 @ 101

09-22-2002, 10:22 PM	#10
Skyman I need 110mph Trap Speed! Join Date: Feb 1999 Location: So, CA Posts: 4,315	Your injectors are a little big in my opinion, but I doubt theyre causing that much of a problem. Hmmm, this is a tough one.... How much gas do you have to give your car to maintain steady speed? 10mpg is terrible, mine gets 21 freeway.... Also 18deg timing w/ 10:1 sounds a little high, try 15. Sky __________________ 2001 BMW M3 6spd 12.79@108 RIP ---- 1993 Notch w/ 98 4V 4.6 Fasttt... -1989 Saleen Mustang #406- 12.32@109 -1999 Black Cobra Coupe- JBA Shorties, Bassani Cat-X, Magnaflow 3", Pulleys, 85mm Pro-M, Ported Intake, Soild Rear w/ 4.30s, Tubular Front End, X2C arms, 13lb batt, few others.

09-22-2002, 10:25 PM	#11
93GTDIN Registered Member Join Date: Jan 2001 Location: Live music capital of the world, TX Posts: 324	I've tried backing off the timing but the idle gets even worse when I retard it. On the highway, I barely have to push it in half an inch. If that. Very little. About the same as stock. __________________ 96 Cobra - a bit too stock. 14.0 @ 101

09-23-2002, 12:02 AM	#12
93GTDIN Registered Member Join Date: Jan 2001 Location: Live music capital of the world, TX Posts: 324	Anyone Else Have any ideas? __________________ 96 Cobra - a bit too stock. 14.0 @ 101

09-23-2002, 08:20 AM	#13
Agent_4573 Registered Member Join Date: May 2002 Location: New Jersey Posts: 375	Have u checked the car for fuel leaks? Maybe your not burning it, maybe your leaving it on the ground as you drive. __________________ '89 LX 5.0, off-road h pipe, flowmaster muffs, underdrive pulleys, rebuilt WC T-5, King Cobra Clutch, 65mm throttle body, Explorer Upper/GT40 lower, Lakewood Rear Lift Bars. 76mm C&L Mass air w/ inlet pipe, Twisted wedge heads w/ stage 2 port,polish, MAC equal length shorties, Billet AFPR, 255LPH fuel pump, fresh low end w/ 10.5:1 compression. If anyone ever wants to go to Raceway Park in Englishtown New Jersey, give me a shout. RICER HATERS CLUB MEMBER 87! www.ricehatersclub.com

09-23-2002, 10:41 AM	#14
Mach 1 Registered Member Join Date: May 1999 Location: Georgia Posts: 3,866	My combination is also an AOD, but i have non-lockup, 2800 rpm stall converter and 4.10 gears. My gas mileage is also very terrible. Its hard for me to get an accurate reading, because my odometer/speedometer is not accurate as I have the speedo gear for a 3.73 installed in the tranny, but im running 4.10s. I would guess Im getting somewhere between 10- 15 around town, the same on the highway. This is a good indicator of how inefficient the AOD is, as t-5 guys are getting twice the mileage of us AOD guys with similar engine mods. Do you have the correct 3.27 speedo gear for your 3.27 gears? And also, tire size will affect the accuracy of your odometer, which can throw off your MPG calculations. Also sounds like your combination is a little mismatched. you need some gears and a converter for that thing, although this probably wouldnt help your mileage concerns? Whats the power band of that cam? You should get a converter to stall up into that range. This could help. Sounds like you have some other issues also...stalling when warm, rough idle in nuetral. Get those problems fixed first, then see what happens with your gas mileage. I would look for fuel leaks everywhere as already mentioned. Also your vacuum seems a little low for the fairly average size trick flow stage 1 cam, which by the way, should work well with an AOD. gotta run...good luck __________________ 2002 GT 1993 GT (SOLD) '93 Mustang GT RHC member #142

09-23-2002, 01:03 PM	#15
302 LX Eric or '331 LX Eric' Join Date: Jan 1999 Location: Columbus, Ohio Posts: 2,142	Was your cam installed straight-up? E __________________ 1991 5.0 LX Coupe - 40,750 miles 331 cu. in. / Tremec 3550 / BFG Drag Radials 12.22 @ 114.31 mph - w/1.89 60'

09-23-2002, 06:02 PM	#16
93GTDIN Registered Member Join Date: Jan 2001 Location: Live music capital of the world, TX Posts: 324	if by straight up you mean not adv. or ret., then yes, it was. I would love to solve my idle surging problems and what have you, but i'm so exhausted i don tknow what could be the problem anymore. __________________ 96 Cobra - a bit too stock. 14.0 @ 101

09-23-2002, 06:03 PM	#17
93GTDIN Registered Member Join Date: Jan 2001 Location: Live music capital of the world, TX Posts: 324	Also, the 3.27's came stock __________________ 96 Cobra - a bit too stock. 14.0 @ 101

09-23-2002, 06:21 PM	#18
Mach 1 Registered Member Join Date: May 1999 Location: Georgia Posts: 3,866	idle surge problems are common on modified stangs and sometimes impossible to solve. The only thing i havent tried yet to fix mine is a modified computer chip. __________________ 2002 GT 1993 GT (SOLD) '93 Mustang GT RHC member #142

Thread Tools
Show Printable Version Email this Page
Display Modes	Rate This Thread
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode	Rate This Thread:

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Gas mileage?	Nixon1	Windsor Power	17	08-07-2003 01:43 PM
Gas Mileage	Jacob_M	Blue Oval Lounge	5	01-28-2002 12:11 AM
which mods hurt gas mileage?	acidangel316	Windsor Power	5	06-20-2001 09:59 PM
really bad gas mileage???	green94droptop	Windsor Power	22	05-22-2001 01:12 AM
5.4 TRITON V-8 FUEL MILEAGE	FASTFRANK	Small Ponies	1	03-27-1999 11:28 AM