Welcome to www.JeepStrokers.com!!
Not yet a registered user? You are required to Register before you can post within this topic.

Map voltage and fuel use.

Performance mods and Advanced Stroker discussion.
Post Reply
rainman2
Posts: 5
Joined: October 22nd, 2018, 8:40 pm
Stroker Displacement: 4.6
Vehicle Year: 1995
Vehicle Make: Jeep
Vehicle Model: Xj

Map voltage and fuel use.

Post by rainman2 » October 22nd, 2018, 8:57 pm

Hello,
Mine is chewing the gas.
The Ngk Oxy sensor is 30,000 Km old
and according to the scanner, it is switching high to low consistently, as you would expect.
Temp sender is working correctly as is the Intake air sender. TPS appears good, smooth/ within spec.
The cat is not blocked
I don't think there is any exhaust leaks, I've looked/ felt/ smelt can't detect any leaks
3 different Map sensors read the same, all good second-hand units.

The only thing i can see is the map Sensor, at warm idle, it reads 1.2- 1.3 volts and reads 4.8 with the engine off. According to the manual specification is warm idle 1.5-2.1 volts, and 4-5 volts with the engine off.

Could this cause excessive fuel use, it runs fine it is just getting bad mileage and the wideband suggests its always running rich.

If the voltage is low how do i fix it

Cummins90
Making Progress
Making Progress
Posts: 74
Joined: May 14th, 2016, 10:29 am
Vehicle Year: 1996
Vehicle Make: Jeep
Vehicle Model: Cherokee

Re: Map voltage and fuel use.

Post by Cummins90 » October 23rd, 2018, 12:31 pm

What do you have? Year make model auto/standard?
What mods do you have? What mpg are you getting and how are you calculating it?

User avatar
Cheromaniac
Senior Member
Senior Member
Posts: 2739
Joined: March 8th, 2008, 12:58 pm
Stroker Displacement: 4563cc
Vehicle Year: 1992
Vehicle Make: Jeep
Vehicle Model: Cherokee
Location: Cyprus
Contact:

Re: Map voltage and fuel use.

Post by Cheromaniac » October 23rd, 2018, 1:12 pm

x2
Plus, which injectors are you using and at what fuel pressure?
1992 XJ 4.6 Stroker - 5MT - Sold :cry: Stroker build-up, Stroker "recipes"
2006 Mustang GT - 5MT - Midlife crisis car :D with Mods

rainman2
Posts: 5
Joined: October 22nd, 2018, 8:40 pm
Stroker Displacement: 4.6
Vehicle Year: 1995
Vehicle Make: Jeep
Vehicle Model: Xj

Re: Map voltage and fuel use.

Post by rainman2 » October 23rd, 2018, 3:49 pm

Sorry,
I thought that would come up as i filled it out in my profile.
95 obd1 xj cherokee 4.6l comp cam 232.
45/38psi fuel pressure running through neon 703 injectors.
AUTO,32"tyres 4:10 ratios
MPG atm: 22l per 100km / 11 mpg
usually, it runs 16l/100km.
its always been rich at WOT but usually pretty good just driving around.

User avatar
Cheromaniac
Senior Member
Senior Member
Posts: 2739
Joined: March 8th, 2008, 12:58 pm
Stroker Displacement: 4563cc
Vehicle Year: 1992
Vehicle Make: Jeep
Vehicle Model: Cherokee
Location: Cyprus
Contact:

Re: Map voltage and fuel use.

Post by Cheromaniac » October 24th, 2018, 2:09 am

Reduce the fuel pressure by 2psi and see how it goes.

Cummins90
Making Progress
Making Progress
Posts: 74
Joined: May 14th, 2016, 10:29 am
Vehicle Year: 1996
Vehicle Make: Jeep
Vehicle Model: Cherokee

Re: Map voltage and fuel use.

Post by Cummins90 » October 24th, 2018, 6:41 am

It runs rich at WOT, which I assume means you have a wideband? My 95 would drop to 12.5 as it hit open loop above 3200rpm. I was never sure if that's what the ecm was programmed to target or if the ecm just would not remap the open loop fuel table while using slightly bigger injectors. I have seen evidence of the obd2 ecm change open loop fuel tables.

rainman2
Posts: 5
Joined: October 22nd, 2018, 8:40 pm
Stroker Displacement: 4.6
Vehicle Year: 1995
Vehicle Make: Jeep
Vehicle Model: Xj

Re: Map voltage and fuel use.

Post by rainman2 » October 24th, 2018, 7:16 pm

yes have wideband ATM.
My understanding is with OBD1 there is no learning at greater than 80% throttle position its all factory memory in open loop north of there.

rainman2
Posts: 5
Joined: October 22nd, 2018, 8:40 pm
Stroker Displacement: 4.6
Vehicle Year: 1995
Vehicle Make: Jeep
Vehicle Model: Xj

Re: Map voltage and fuel use.

Post by rainman2 » November 14th, 2018, 7:40 pm

Turns out #5 &#6 injectors were swapped around. FFS.
Map still reads the same.
Just got 16.4 mpg with 32" muds and a 4.5" lift.
AFR at wot is 12.6. this is with 42psi on the rail. and 703 "neon" injectors. '95 obd1 XJ, auto.

User avatar
Cheromaniac
Senior Member
Senior Member
Posts: 2739
Joined: March 8th, 2008, 12:58 pm
Stroker Displacement: 4563cc
Vehicle Year: 1992
Vehicle Make: Jeep
Vehicle Model: Cherokee
Location: Cyprus
Contact:

Re: Map voltage and fuel use.

Post by Cheromaniac » November 14th, 2018, 10:43 pm

Sounds like you have it pretty well dialed in. A WOT A/F ratio of 12.6 is still slightly rich so you could drop the fuel pressure to 41psi and leave it there.

rainman2
Posts: 5
Joined: October 22nd, 2018, 8:40 pm
Stroker Displacement: 4.6
Vehicle Year: 1995
Vehicle Make: Jeep
Vehicle Model: Xj

Re: Map voltage and fuel use.

Post by rainman2 » November 15th, 2018, 12:29 am

yes, 40 psi gave me 13.1, but i think i will leave it where it is, don't spend much time at wot.
The extra fuel will add a bit of a buffer for pinging on 40*c+ Days.

Post Reply

Who is online

Users browsing this forum: No registered users and 1 guest