Air/fuel Swing In Wideband, Car Stutters

[89gtsleeper]

I've been tinkering with my fuel pressure over the last few weeks, ever since I installed a wideband. Car is an 88 5.0 with mass air conversion, vortech blower, cobra intake, edelbrock heads, 42 lb injectors and a brand new fuel tank/Walbro 255 pump. When I first got a view from the wideband, it seemed pretty lean. Idle was around stoich, but no matter what Rpm's and how hard I drive, seems to stay around stoich until decel. Car also had light popping in exhaust and intake occasionally and a small idle problem when cold. Realizing it is too lean to drive on the upper end of the rpm range, I've been slowly increasing fuel pressure over the course of the week. Car has an aeromotive apr.

by the time I had base pressure with vac removed up to about 44-45 from its original setting of 39, things felt generally better while driving, but wideband continued to read about the same in lower Rpm's while driving to and from work. This change was in small increments over the course of about a week. Once I decided the lower rpm driving felt better, I put it on a small highway acceleration pass to see what the wideband would show. I took up to about 3600 Rpm's in third gear and let off. Air/fuel never went richer than 14/1, which makes me uncomfortable still. It ran very strong and nothing felt weird, just the wide band's reading freaked me out. Figured I would need to start troubleshooting the issue and should just drive it home.

I got off the highway and made it to the first stop light, where I sat idling for a few minutes. Once it was green, I hit the gas... Just normal driving, and it spiked all the way rich at 10 to 1, then quickly flopped over to all the way lean at 18 to 1. The car sputtered for a second, then came back toward 14.7 to 1 slowly. As long as the car is continuing to move, it stays around stoich. But every time I come to a complete stop and have to hit the gas, this situation happens again. Doesn't matter if engine is cold or not.

Fuel pressure gauge on the Schrader valve shows pressure that changes as expected when vac line removed and replaced on the regulator. Thought maybe the was an injector issue, but cylinder balance test reads 9, which I believe means no problem detected. Pulled the plugs and they are all pretty uniform. None are wet or oily. Car has really cheap Chinese green top knockoff injectors. Could there be a problem there? What are signs of a problematic regulator? I don't detect gas in its vacuum line.

 

[a91what]

I've been tinkering with my fuel pressure over the last few weeks, ever since I installed a wideband. Car is an 88 5.0 with mass air conversion, vortech blower, cobra intake, edelbrock heads, 42 lb injectors and a brand new fuel tank/Walbro 255 pump. When I first got a view from the wideband, it seemed pretty lean. Idle was around stoich, but no matter what Rpm's and how hard I drive, seems to stay around stoich until decel. Car also had light popping in exhaust and intake occasionally and a small idle problem when cold. Realizing it is too lean to drive on the upper end of the rpm range, I've been slowly increasing fuel pressure over the course of the week. Car has an aeromotive apr.

by the time I had base pressure with vac removed up to about 44-45 from its original setting of 39, things felt generally better while driving, but wideband continued to read about the same in lower Rpm's while driving to and from work. This change was in small increments over the course of about a week. Once I decided the lower rpm driving felt better, I put it on a small highway acceleration pass to see what the wideband would show. I took up to about 3600 Rpm's in third gear and let off. Air/fuel never went richer than 14/1, which makes me uncomfortable still. It ran very strong and nothing felt weird, just the wide band's reading freaked me out. Figured I would need to start troubleshooting the issue and should just drive it home.

I got off the highway and made it to the first stop light, where I sat idling for a few minutes. Once it was green, I hit the gas... Just normal driving, and it spiked all the way rich at 10 to 1, then quickly flopped over to all the way lean at 18 to 1. The car sputtered for a second, then came back toward 14.7 to 1 slowly. As long as the car is continuing to move, it stays around stoich. But every time I come to a complete stop and have to hit the gas, this situation happens again. Doesn't matter if engine is cold or not.

Fuel pressure gauge on the Schrader valve shows pressure that changes as expected when vac line removed and replaced on the regulator. Thought maybe the was an injector issue, but cylinder balance test reads 9, which I believe means no problem detected. Pulled the plugs and they are all pretty uniform. None are wet or oily. Car has really cheap Chinese green top knockoff injectors. Could there be a problem there? What are signs of a problematic regulator? I don't detect gas in its vacuum line.

What WB system are you running?? model # and a pic please. where is it installed in the exhaust stream?
when was the last time the sensor was calibrated?(very important)

What maf are you running?

 

[89gtsleeper]

Also, coil is good, put new spark plugs on just in case, and spark is getting to all cylinders. Also recently put on new cap and rotor. Timing is set to 10 degrees. Ran the codes and came up with something interesting... Most of this is emissions related, and I have gutted all that stuff, so it's not something I am worried about.

KOER = 41944431944431
KOEO = 3181828595 1 29316695

On the koeo, is that a code 66 I'm seeing? I found another thread where a guy was getting 66 (maf) and his symptoms were exactly like these. is it possible that a problem with the maf could cause the problems I'm having?

 

[a91what]

none of this is going to be spark related this is a fuel delivery issue. I need the info I asked for above. without it I am shooting in the wind...
@jrichker for the codes

 

[89gtsleeper]

Wideband is an autometer analog phantom ii. Gauge installed on pillar. Sensor installed on driver's side exhaust. I have shorty headers. Then on the downpipe, the wideband is about 4 " past the stock sensor.

MAF is a pro-m 75 mm calibrated for 42 lb injectors. I looked at it today, and everything looks very clean.

Also, don't know if it matters, but I had new 02 sensors installed while I was getting the wideband installed.

 

[90sickfox]

Is the car tuned and how ?

 

[89gtsleeper]

Wideband sensor drilled into the right hand side of the drives side pipe, clocked at about 2:30. This setup uses the Bosch 4.2 sensor.

 

[89gtsleeper]

No tuning yet. Had it with a tuner for a month and it came back all jacked up. Car has been running pretty well since I yanked his custom chip off and reset the computer. Have an msd btm I'm about to install and going to go old school with fmu potentially, but right now, just relying on stock computer. Don't intend to race this thing anytime soon. Just a daily driver.

 

[89gtsleeper]

My reading about this wideband is that it calibrates the sensor every time the car is started. Here is a link... http://www.autometer.com/2-1-16-analog-wideband-fse-phantom-ii.html

 

[a91what]

try and disconnect the sensor, then power the wb up let it throw the fault code.. power down reconnect the sensor (it needs to be hanging out of the exhaust system) power the sensor back up it should go thru its heating cycle then calibrate.. reinstall the sensor then report back.

I was looking on there website and did not see instructions on how to recalibrate the sensor.... every other WB I have ever worked with this has to be done. if this step was skipped it will never read correctly.

[unless autometer knows something everyone else is not privy to]

 

[a91what]

My reading about this wideband is that it calibrates the sensor every time the car is started. Here is a link... http://www.autometer.com/2-1-16-analog-wideband-fse-phantom-ii.html

I missed that on the website.

 

[a91what]

Hold the BRAKES

you are taking this thing into boost with no FMU or tune... and at a dangerous AFR.
IN BOOST AFR should be at 11.3-12.1
idle 13.8-14.2
cruise 14.4-15.5
wot no boost 12.2-13.1

 

[89gtsleeper]

I'm not getting into boost yet. I totally realize that is a no no for now. I'm just trying to get it healthy at normal driving conditions prior to the install of the fmu and btm. I haven't taken this car past about 3500 Rpm's, I'm notrunning full throttle ever, and I haven't gotten into the boost since pulling the custom chip off the car. My goal is just to work out the baseline kinks, then get the boost ready safety measures in place.

 

[89gtsleeper]

It's been good AFR the last week in cruise, idle, light driving, etc. up until this issue started.

 

[a91what]

It's been good AFR the last week in cruise, idle, light driving, etc. up until this issue started.

What ECU are you running?? I will assume an A9L

 

[a91what]

code 66 is low maf voltage..... try unplugging it and see if the car runs any different.. [don't drive this way] if it seems better its probably the MAF.
pull the NEG batt terminal for 10mins then drive the car pull codes again.

 

[89gtsleeper]

What ECU are you running?? I will assume an A9L

It is an A9L. Previous owner did the mass air swap.

 

[89gtsleeper]

code 66 is low maf voltage..... try unplugging it and see if the car runs any different.. [don't drive this way] if it seems better its probably the MAF.
pull the NEG batt terminal for 10mins then drive the car pull codes again.

I'll give this a shot tomorrow after work. I'll post up the results.

 

[jrichker]

There was no code 66 in your code dump, so chasing that may be a waste of time.

You got a code 41 which is an O2 sensor problem, you said that you replaced the O2 sensors. It it looks like you failed to clear the codes.


You must clear the codes anytime you replace any sensor.

How to clear codes.
Clear the computer codes by disconnecting the battery negative terminal and turn the headlights on. That clears the computer's memory of codes and the adaptive learning data it generates from sensors. Turn the headlights off and reconnect the all sensors including the MAF and anything else you may have disconnected. Then reconnect the battery negative cable.. This clears all spurious codes that may have been generated while troubleshooting problems. This does not fix the code problems, it just gives you a clean slate to start recording what the computer sees happening.

Run the car for at least 30 minutes of normal city driving and dump the codes again to assure that you have fixed the code problem or sensor problem


Just for reference, here is the code 66 test path... Notice that there is a voltage measurement test that you can do to make sure that the MAF is working reasonably well.

Code 66 or 157 MAF below minimum test voltage.

Revised 10-Feb-2014 to add 95-95 Mustang code 157 and 94-95 ECC diagram

Insufficient or no voltage from MAF. Dirty MAF element, bad MAF, bad MAF wiring, missing power to MAF. Check for missing +12 volts on this circuit. Check the two links for a wiring diagram to help you find the red wire for computer power relay switched +12 volts. Check for 12 volts between the red and black wires on the MAF heater (usually pins A & B). while the connector is plugged into the MAF. This may require the use of a couple of safety pins to probe the MAF connector from the back side of it.

Computer connector for 88-93 5.0 Mustangs

Diagrams courtesy of Tmoss and Stang&2Birds

ECC Diagram for 88-90 5.0 Mustangs

ECC Diagram for 91-93 5.0 Mustangs

94-95 Diagram for 94-95 5.0 Mustangs

There are three parts in a MAF: the heater, the sensor element and the amplifier. The heater heats the MAF sensor element causing the resistance to increase. The amplifier buffers the MAF output signal and has a resistor that is laser trimmed to provide an output range compatible with the computer's load tables. Changes in RPM causes the airflow to increase or decrease, changing the voltage output.. The increase of air across the MAF sensor element causes it to cool, allowing more voltage to pass and telling the computer to increase the fuel flow. A decrease in airflow causes the MAF sensor element to get warmer, decreasing the voltage and reducing the fuel flow.

The MAF element is secured by 2 screws & has 1 wiring connector. To clean the element, remove it from the MAF housing and spray it down with electronic parts cleaner or non-inflammable brake parts cleaner (same stuff in a bigger can and cheaper too).

89-90 Model cars: Measure the MAF output at pins C & D on the MAF connector (dark blue/orange and tan/light blue) or at pins 50 & 9 on the computer. Be sure to measure the sensor output by measuring across the pins and not between the pins and ground.

91-95 Model cars: Measure the MAF output at pins C & D on the MAF connector light blue/red and tan/light blue) or at pins 50 & 9 on the computer. Be sure to measure the sensor output by measuring across the pins and not between the pins and ground.


At idle = approximately .6 volt
20 MPH = approximately 1.10 volt
40 MPH = approximately 1.70 volt
60 MPH = approximately 2.10 volt

Check the resistance of the MAF signal wiring. Pin D on the MAF and pin 50 on the computer (dark blue/orange wire) should be less than 2 ohms. Pin C on the MAF and pin 9 on the computer (tan/light blue wire) should be less than 2 ohms.

There should be a minimum of 10K ohms between either pin C or D on the MAF wiring connector and pins A or B. Make your measurement with the MAF disconnected from the wiring harness.

Actually MAF pins C & D float with reference to ground. The signal output of the MAF is a differential amplifier setup. Pins C & D both carry the output signal, but one pin's output is inverted from the other. The difference in signal between C & D is what the computer's input circuit is looking for. The difference in the two outputs helps cancel out electrical noise generated by the ignition system and other components. Since the noise will be of the same polarity, wave shape and magnitude, the differential input of the computer electronically subtracts it from the signal. Then it passes the signal on to an Analog to Digital converter section inside the computer's CPU chip.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel pump, alternator, ignition & A/C wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Computer,. actuator & sensor wiring
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Fuse panel layout
http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif

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

 

[mikestang63]

i'm sure the OP knows this but it is worth saying... get the car dialed in withou the vortech first. Then put the blower belt back on. You don't want to pop a head gasket.