Fox T-Bird/Cougar Forums

Technical => Engine Tech => Topic started by: SR71blackbird on February 07, 2012, 12:33:21 PM

Title: baaaaad gas mileage
Post by: SR71blackbird on February 07, 2012, 12:33:21 PM
So i am getting between 10-12mpg. I have stock injectors and stock fuel pressure and rarely get into boost. I dont have the EGR hooked up either. I drive up a steep hill everyday for school but i get to coast down it coming back. Ive never heard of a 4 banger getting this bad of gas mileage. My friends 800hp evo gets about that driving in town. Any suggestions?
Title: baaaaad gas mileage
Post by: T-BirdX3 on February 07, 2012, 12:56:32 PM
That sucks!  :(

I am going to go ahead and ask the obvious questions.

Have you given it a recent quality tune up?
Is there any other symptoms (any stutters, coughs, hiccups, overheating, etc)?
Are the rear brakes holding?
Title: baaaaad gas mileage
Post by: SLEEPER T-BIRD 87 on February 07, 2012, 01:06:00 PM
What are your a/f ratio's like and what tuner?
Title: baaaaad gas mileage
Post by: Haystack on February 07, 2012, 02:09:39 PM
Codes.
Title: baaaaad gas mileage
Post by: SR71blackbird on February 07, 2012, 02:35:26 PM
I gave it a full tune up with the big turbo swap a month ago (besides a fuel filter).
sometimes when i take it out of gear, the RPMs fall to about 500.
My A/R gauge broke so im not sure. Im getting a new put in soon. No tuner yet.
I havent checked the code BUT its been throwing a code after about 20 minutes driving.( ive been super busy with college.)
So im guessing i should get the code checked out first thing huh? and go from there?
Title: baaaaad gas mileage
Post by: Haystack on February 07, 2012, 03:51:49 PM
Well, generally when you want something diagnosed, information relating directly to the cause is the first step. Even if you have to spend 5 minutes at it.

Your check engine light isn't a code, its a hard failure putting the car into limp mode so you can get home.
Title: baaaaad gas mileage
Post by: Soul on February 07, 2012, 04:05:06 PM
If it started with the big turbo, check to make sure VAM isn't being sucked open.

Also Temp Coolant Sensor and Air Charge Temp sensor can do that stuff.

Get codes :P
Title: baaaaad gas mileage
Post by: SR71blackbird on February 07, 2012, 05:48:10 PM
well when the check engine light is on, it drives just the same when its off. My coolant temp gauge shakes alot from time to time lately. Im taking my car into the shop tomorrow to get the codes. I was thinking my check engine light was on because my EGR isnt hooked up which is setting off my check engine.
everything is Motorcraft except the MSD coil for my tune up.
Title: baaaaad gas mileage
Post by: Haystack on February 07, 2012, 07:16:44 PM
Egr will not cause a check engine light. Let us know when we get codes.
Title: baaaaad gas mileage
Post by: Bruce M on February 07, 2012, 07:47:19 PM
That sucks, I thought my ranger was getting bad milage (19 - 20).
Title: baaaaad gas mileage
Post by: SR71blackbird on February 09, 2012, 10:27:49 PM
ALRIGHT i got a few codes!
14- erratic pin signal
23- TPS sensor
25- Knock sensor
34- EGR (took mine off)
41- lean always
65- over changing?

Im thinking the lean and knock is because my big turbo and colder air because of my front mount.
Title: baaaaad gas mileage
Post by: Haystack on February 09, 2012, 11:16:30 PM
14 Pip in the dist bad. This needs fixed. Could be tfi.
23 tps, obviously
25 knock sensor? don't know about these.
34 egr don't worry about this.
41 right side always lean. Generally means bad o2, or injector.
65 overdrive on off not cycled turing test. User error. This doesn't make sense to me. Do you have an electric overdrive onn off switch? If this code was 65 and act is below minimim, that would make a lot more sense.
Title: baaaaad gas mileage
Post by: SR71blackbird on February 09, 2012, 11:44:00 PM
Is the TFI the reason why i have erractic pin signal?
How can i tell if t TPS is bad?
Is the knock sensor ignition timing?
My o2 is brand new so im guessing injector. Would more dense air from the FMIC be doing this though also?
I do not have an over drive switch. Atleast not to my knowledge.
Title: baaaaad gas mileage
Post by: Soul on February 10, 2012, 08:31:16 AM
TPS, poke a wire with voltmeter (the one that goes 1-5 volts) move throttle to open and closed, if there is a dead spot any where its bad.
Title: baaaaad gas mileage
Post by: Chuck W on February 10, 2012, 08:55:06 AM
Get codes.

Also, you said that you swapped turbos.  Since you're running the stock ECU, did you reconnect the orange wire that was originally connected to the old turbo?  It's an O2 ground, and the 2.3T's on stock ECUs will run like ass if it's not connected.
Title: baaaaad gas mileage
Post by: SR71blackbird on February 10, 2012, 10:44:38 AM
Okay thank you soul!
 i have been trying to remember for awhile now to put the orange some where but i also forget! where can i put it? Can i just bolt it down to the engine bay?
Title: baaaaad gas mileage
Post by: Soul on February 10, 2012, 11:22:54 AM
Goes on the turbo housing, it is the ground for o2.

Bolt that on and it will probably solve your issue.

Great catch by Chuck.
Title: baaaaad gas mileage
Post by: SR71blackbird on February 10, 2012, 11:32:02 AM
There is no where for it to go on my turbo housing though. There arent any bolts on my turbo to bolt it down.
Title: baaaaad gas mileage
Post by: Chuck W on February 10, 2012, 11:40:59 AM
There's a place somewhere.  If anything, loosen one of the compressor housing bolts, and attach it there.

Pics of the set-up would help.
Title: baaaaad gas mileage
Post by: SR71blackbird on February 10, 2012, 03:54:11 PM
Okay this is what i did, the wire wasnt long enough to reach to the back of the compressor housing so I took a metal strap and tightened it down pinching the wire to the inlet. I havent driven it yet though. I started Homework instead.
Title: baaaaad gas mileage
Post by: Haystack on February 10, 2012, 10:17:11 PM
Pip erratic signal means the computer isn't always seeing the distributor fire. That is what fires your injectors. It could be your coil, pip inside the dist, or the tfi or associated wiring.

Fix your o2 ground, trouble shoot your tfi, pip and coil. Check voltages, or replace your tps. Double check grounds, and go from there.
Title: baaaaad gas mileage
Post by: SLEEPER T-BIRD 87 on February 10, 2012, 10:18:37 PM
^ along with the other recomendations i suggest you start saving up and get a wideband o2 and some sort of tuner without them your giving up both performance and milage.
Title: baaaaad gas mileage
Post by: SR71blackbird on February 15, 2012, 01:14:56 PM
Is there anything i need to know before a change the TFI? anything i need to be careful of or to watchout for?
Title: baaaaad gas mileage
Post by: Soul on February 15, 2012, 02:47:16 PM
Here is a good resource for some of the stuff we are talking about

http://www.turbotbird.com/techinfo/techarticles.html
Title: baaaaad gas mileage
Post by: Chuck W on February 15, 2012, 03:03:58 PM
So, did you drive it yet after connecting that orange wire?
Title: baaaaad gas mileage
Post by: SR71blackbird on February 15, 2012, 04:09:11 PM
Thank you soul.
Yes i did drive it and it seems to be running better but it jerks when i drive. There use to be a light tint of blue smoke while i drove it but that went away once i grounded the wire.  havent filled it back up yet though to see the gas milegae. I am putting a new TFI on today to see if that stops the jerking. I also put a new coil on aswell but that didnt help the jerking.
Title: baaaaad gas mileage
Post by: SR71blackbird on February 15, 2012, 06:20:41 PM
I changed the TFI and it is running way more smoothly now. i got the codes erased. im hoping they dont come back! I should be filling up here pretty soon and i'll post how im doing with gas consumption
Title: baaaaad gas mileage
Post by: SR71blackbird on February 21, 2012, 12:17:57 PM
I just filled up and got 24.4 MPG!!! i drive it a steep hill once a day on Monday wednesday friday and on tuesday and thursday i drive up that steep hill 3 times! So 9-10 times a week i drive up a steep hill thats pretty long and i get 24.4 MPG. Im pumped!