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Electrical New Codes 29/98/66 - wont run unless MAF unplugged (all volt and ohms checked at maf)

  • Thread starter Thread starter cablegod
  • Start date Start date Nov 5, 2022
C

cablegod

Member
Nov 5, 2022
5
3
13
AA county, MD
Nov 5, 2022
#1
  • Nov 5, 2022
  • #1
Good evening,

I have been reading over the site for the past few days. Ill explain my issue , what ive done and any suggestions from you guys are appreciated.

I have a 91 5.0 that I purchased earlier this year. Mods are: Cobra intake, BBK 70MM TB, BBK shorty headers, off road exhaust . Smog delete, Egr delete.

When I got it the previous owner had the MAF unplugged because he couldnt get it running right. He also told me that he had the ECU replaced because he couldnt figure out the idle problem. When I brought it home, I fixed all vacuum leaks coming from Brake booster and old Egr hoses still hooked up. Now the only vacuum I have hooked up is for vent air control, brake booster, and FPR. All extras are gone. Everything has been fine ever since I fixed all these issues even though me CEL is on. That is until recently.

It started with the car dying when I hit the gas, so I brought it home and now it wont even start unless the MAF is unplugged. Using a code reader I get the same codes ive gotten since day one which are: KOEO 31-81-82-85-84.... but now the new codes I get are 29-66-98.

So VSS and Maf issues.... on with the fun!

I looked around to see what I could do here are my results for volt/ohm checks at the MAF plug/sensor:

Between power and ground getting almost 12 volts
Between MAF Signal and MAF Return getting 15k OHMS
Between MAF and Neg Battery terminal key on is like .7volts and when start car it goes up to 1.2 volts and then the car dies.

------------

Now I am trying to figure out what to look at next. I am thinking about replacing the MAF sensor or Unit completely. Im not sure what housing it is, but its a Ford sensor. Im pretty sure its not even the original because its a E9ZF-xxxxxx-xx and I think it should be a F1 code. Even my BAP sensor is a E7EF-12A644-A1A. I know some things are pieced together on this. What are some techincal suggestions you guys may have for me next since these voltages and ohms seems to check out. Thank you!
 

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor
Admin Dude
Jan 4, 1985
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Nov 5, 2022
#2
  • Nov 5, 2022
  • #2

Cranks OK, but No Start Checklist for Fuel Injected Mustangs

Cranks OK, but No Start Checklist for Fuel Injected 5.0 Mustangs model years 1986-1995 A word about this checklist before you start: it is arranged in a specific order to put the most likely failure items first. That will save you time, energy and money. Start at the top of the list and work...
www.stangnet.com
 

AeroCoupe

lube between the nut and the face. I know my lubes
Founding Member
Oct 28, 2001
5,943
4,058
183
Claremore, OK
Nov 6, 2022
#3
  • Nov 6, 2022
  • #3
Can you post a picture of the MAF? Also, are the injectors the stock 19 lb/hr units? If you do not know what color is the top of the injector? Just trying to see if you have a “calibrated” MAF for larger injectors.
 
C

cablegod

Member
Nov 5, 2022
5
3
13
AA county, MD
Nov 6, 2022
#4
  • Nov 6, 2022
  • #4
I believe they are 19lb. They are orange.
 
C

cablegod

Member
Nov 5, 2022
5
3
13
AA county, MD
Nov 6, 2022
#5
  • Nov 6, 2022
  • #5
cablegod said:
I believe they are 19lb. They are orange.
Click to expand...
 

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AeroCoupe

lube between the nut and the face. I know my lubes
Founding Member
Oct 28, 2001
5,943
4,058
183
Claremore, OK
Nov 6, 2022
#6
  • Nov 6, 2022
  • #6
That appears to be the stock MAF sensor for a 55mm MAF - AFH55-03 is what gives that away. Orange tops are 19 lb/hr so you seem to have the correct injectors.

Do you have another EEC that you can try? If not you probably need to crack the case open on the one in the car and see if you have any issues with the caps or any burnt traces. Seems the common theme here lately has been the processor has an issue and needs to be either repaired by the owner or by shipping it off. Here is a thread on how to replace the caps:

Electrical - EEC-IV Capacitor Replacement Info

Replacing the capacitors in your Fox Mustang EEC? Here is the quick and dirty info you need so that you don't have to look all over the place like I did. I watched every YouTube vid I could find on replacing these 3 caps. I also watched plenty of “how to replace capacitors” in general. I have...
www.stangnet.com

Place most are sending them to get repaired is here:

Ford Mustang 5.0 A9L A9P C3W A3M X3Z ECU Repair Service

Ford Mustang 5.0 A9L A9P C3W A3M X3Z ECUEngine Computer Repair ServicePlease fill out the R&R form here once you've placed your order.A Trusted Product with LIFETIME WARRANTY QUICK TURN AROUND TIMEDomestic and International Shipping available! Our Team is Available Monday - Friday 9am to 5pm...
www.theecuexchange.com
 
Last edited: Nov 6, 2022

nickyb

I gotta say i never painted my nuts, Never Ever
15 Year Member
Apr 3, 2009
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nevada
Nov 6, 2022
#7
  • Nov 6, 2022
  • #7
I'd try cleaning the ma F sensor wire with ma F cleaner. Then if it doesn't help switch out the sensor.
Vss code could be posted wire ,check those . Good luck.
 
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