jrichker, I got one for ya! Anyone?

[D347643]

I replaced all the harnesses in my 86 with ones out of a 90 and 91 gt. The car runs and drives fine but my A/f ratio's at idle and part throttle are ridiculous! It averages about 18:1 and gets as rich as 16:1 if im lucky. Ive done a lot of datalogging and the WOT ratio's are dead on and hardely need any adjustment. I just installed a AFM PMS and on the main screen it shows dif engine readings, the problem is for injector duty cycle and and pulse rate it shows zero for both!.. I checked my plugs and they are black, when you stand next to my car while its idling it burns your eyes from all the unburnt gas (i assume) I want to say that my injectors arent cycling but im not sure. Also the A/f ratios were like that long before I installed the pms and even when i try to lean out the cranking fuel it has a really hard time starting even with my foot to the floor. Anyone have any ideas what it could be? Im only pulling 10 inch of merc with my advanced stage 1 cam btw.

thanks to anyone that gives me some ideas.

Drew

 

[jrichker]

Must be something wrong with the PMS to get zero pluse rate and duty cycle. If that were true, the engine would not run.

The symtoms you are getting ( very rich) don't match up with the ratio's you posted (very lean).

The stock A/F is 14.7:1 at cruse, with it going leaner with the use of the EGR. Really rich gets you down into the 12:1 range or lower. With 16:1 or 18:1, you are in the very lean range, not rich.

Make sure you aren't getting any codes. Your post didn't mention any, but it would be a good idea to make sure there are no ECT problems.
ACT & ECT test data:

Use Pin 46 on the computer for ground for both ECT & ACT to get most accurate readings.

Pin 7 on the computer - ECT signal in. at 176 degrees F it should be .80 volts

Pin 25 on the computer - ACT signal in. at 50 degrees F it should be 3.5 volts. It is a good number if the ACT is mounted in the inlet airbox. If it is mounted in the lower intake manifold, the voltage readings will be lower because of the heat transfer.

Voltages may be measured across the ECT/ACT by probing the connector from the rear. Use care in doing it so that you don't damage the wiring or connector.

Here's the table :

68 degrees F = 3.02 v
86 degrees F = 2.62 v
104 degrees F = 2.16 v
122 degrees F = 1.72 v
140 degrees F = 1.35 v
158 degrees F = 1.04 v
176 degrees F = .80 v
194 degrees F = .61

Note that all resistance tests must be done with power off. Measuring resistance with a circuit powered on will give false readings and possibly damage the meter.

Ohms measures at the computer with the computer disconnected, or at the sensor with the sensor disconnected.
50 degrees F = 58.75 K ohms
68 degrees F = 37.30 K ohms
86 degrees F = 27.27 K ohms
104 degrees F = 16.15 K ohms
122 degrees F = 10.97 K ohms
140 degrees F = 7.60 K ohms
158 degrees F = 5.37 K ohms
176 degrees F = 3.84 K ohms
194 degrees F = 2.80 K ohms


I would start by looking at the MAF and making sure that it is working correctly. C&L MAF's don't work well for everyone.

Code 66 MAF below minimum test voltage.
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.

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.

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).

The MAF output varies with RPM which causes the airflow to increase or decease. 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. 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.

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 and ground.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host)

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif

http://www.autozone.com/servlet/UiB...s/en_us/0900823d/80/19/59/5a/0900823d8019595a

 

[D347643]

Yes I understand that, My symptoms are from running too rich, yet my A/f ratios are very lean, its crazy. I got a code a few months back that says I hit my adaptibve lean limit. This would make sense being that the comp is reading too lean and trying to compensate by richening the mixture up, correct? My MAF is putting out .75 at idle. I had the crazy A/F ratios before I installed the pms and on the PMs main screen it tells me the temperatures that my computer is reading from the ECT. It's pretty much dead on with my aftermarket gauge. My o2's are reading very lean also, my right is always zero unless I rev the car or WOT. My left is around .2 and always pretty much stays lean at idle. I checked my plugs and they are black, my o2's are brand new. Its crazy!

Drew

 

[jrichker]

The O2 voltage is low, I would expect to see .4 volts. You might think about replacing the O2 sensors if you haven't already done so.

 

[D347643]

the o2's are brand new

 

[D347643]

i have tried to change the global fuel and idle fuel up to 40 percent with the pms and it will hardely change anything to the A/F. I know its not the pms at fault cause it had this super lean a/F before I installed it. Its crazy, reading super lean but the exhaust smells really really rich. Another thing, when i snap the throttle my A/F will take take a plunge down to almsot 12/1 and then go back up to 16 or 17. Isnt that a sign of being too lean? Im going to try and switch my maf meter with a pro-m. You have any more ideas?

thanks

Drew

 

[GREYFOX4INCH]

if i was trying to fix that problem, i might as well send the car to the scrap yard cuz i dont have a clue what the heck you guys are talking about, damn.
if i could only find a machanic that is this good i would be all set!
there all idiots.
good luck D347643! hope you get that fixed.

 

[D347643]

haha i have all new harnesses in my car and swapped over to newer style dash and interior. no way its going to the scrap yard, lol.

 

[D347643]

any more ideas?

 

[jrichker]

O2 sensor ground? It is an orange wire in the engine fuel injector wiring harness.

Beyond that, I am running out of answers.

 

[Maryland Stang]

Call Andersen Ford and tell them what you're doing. They should be able to help.

 

[D347643]

yeah i checked the orange ground, resistance from pin 49 to body ground is 0.0. ground is good. as for AFM i had these whacked A/F ratios before i installed the PMS. I already talked to Rick about the fuel trim problem.