Engine 93 Mustang GT, Code 41/91, KOER Cylinder ID shows 6 and not 8

79MercCapri93

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May 12, 2012
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Cleaned the connectors, used dielectric grease on them, and still getting 41/91. I have my other EGR on the car currently and the CEL comes on way more often then before. It comes on while driving both to and from work now, rather then just on my way home.

I am going to use the block off plate and the CEL plug eliminator for the EGR for a short stint. That way i can get a better idea of where this issue is stemming from and to try and rule out the EGR being the source of the problem. Would it be worth trying to using some RTV under the TPS sensor? When i did the smoke test there was smoke coming out from around not, and want to rule that out as an issue as well.

All of my spark plugs look great with the exception of them being white.
 
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79MercCapri93

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@jrichker

I have been trying to scour the forums and using google searches but for some reason i cannot find previous posts you made and was hoping you might be able to retrieve a little easier then me.

Disregard this part jrichker, i searched using the forums rather than google and found it quite quickly. (I remember reading a post about lower intake slipped gasket and something created by I believe you and Tmoss for trying to do a test for this without pulling the entire intake to check.)

I was also looking for a post on how to test the 02's to insure they are actually being "heated" to rule out that possibility of a bad fusible link. Or can i just probe both sides of the wire in the harness around the fusible link with the key forward and see if there is 12vdc? Thank you for all of your help!
 
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79MercCapri93

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Got home this morning and changed out the EGR for the delete plate and eliminator plug. I also checked the PCV grommet and it was way loose. I dont know why it never crossed my mind before, but i dont remember getting a 41/91 before, but i changed the TPS, PCV, Grommet, and Wire Mesh all at the same time a couple of weeks ago. Im hoping that this has finally fixed the issue and if so i can put my EGR back on and see if all is well with that to. Did not get to drive my car today, but I will be tomorrow, so wish me luck!
 
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79MercCapri93

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Excitement short lived, CEL came on right before I got home. 33,41,91. Wont be able to drive it again until Wednesday.

But eliminating the EGR did not solve the problem. Any other thoughts on what could be causing the car to run lean?
 

General karthief

wonder how much it would cost to ship you a pair
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This is a long shot, actually two.
seems to me that the lean condition is happening during the cruise mode (?) And maybe you need to inspect the vacuum line from the purge solenoid to the fuel tank. This may involve dropping the tank. Also on another stang I worked on had a problem with the air idle control valve hanging open, but this effected the idle on that car too.
I will also mention that a deteriorating lower intake gasket was a problem on my car, I have had my intake off soooo many times in the past that I could do it in my sleep, and likely the reason I call it the exxon valdez because the last time I didn't get the back rail sealed up good and it leaks from there.
Yeah, I was asleep on that one.
 

79MercCapri93

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Yeah to me it seems to occur just as I come out of a cruising speed.

I replaced a section of the vapor line by the rear axle that had been pinched, and use clamps and rubber fuel line to fix that. It was about a 1 inch section where the exhaust pinched it. I now have dumps so that shouldn’t be an issue anymore.
 

79MercCapri93

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May 12, 2012
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I sprayed air intake cleaner around my TPS and noticed a very slight change in the idle ( i had to spray directly at the base of the TPS and a couple of seconds later the idle would change), so i put some silicone around it as a "test" and drove it to work today to see if that does anything. Really don't have the money to buy a whole new TB, so if this does end up fixing the issue, then im going to look into trying to disassemble the TB and replacing any O-rings on the throttle blade shaft that could be leaking.

I will probably drop the tank this week when its not a full tank and take a look, 1) to make sure no lines are broken, but 2) i noticed today that my car used to suck in air when i would take the gas cap off after its been run, but the last 3 times now it has no longer done that. Which is kind of an odd thing to notice, but now im wondering where its getting it air from thats keeping it from doing that anymore.

was going to try the slipped gasket test but ran out of time, so im going to try that tomorrow before i go to work or when i get home and see if the cars trying to pull air from the lifter valley
 
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jrichker

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@jrichker

I have been trying to scour the forums and using google searches but for some reason i cannot find previous posts you made and was hoping you might be able to retrieve a little easier then me.

Disregard this part jrichker, i searched using the forums rather than google and found it quite quickly. (I remember reading a post about lower intake slipped gasket and something created by I believe you and Tmoss for trying to do a test for this without pulling the entire intake to check.)

I was also looking for a post on how to test the 02's to insure they are actually being "heated" to rule out that possibility of a bad fusible link. Or can i just probe both sides of the wire in the harness around the fusible link with the key forward and see if there is 12vdc? Thank you for all of your help!
The following are diagrams courtesy of Tmoss & Stang&2birds

Look at the diagram below; in the lower RH corner of the diagram is the power feed for the O2 Sensor heaters. It also includes information about the fuse link for the O2 sensor heaters. Look for 12 volts on that wire with the ignition switch in the Run position.
5.0 wiring diagram for Fuel Injectors, Sensors, and Actuators.

fuel-alt-links-ign-ac.gif


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/ Everyone should bookmark this site.


TFI module wiring for 94-95 Mustang GT
http://www.veryuseful.com/mustang/tech/engine/images/Mustang-94-95-IgnitionControlModule.gif

Complete computer, actuator & sensor wiring diagram for 94-95 Mustangs

Complete computer, actuator & sensor wiring diagram for 91-93 Mass Air Mustangs

Complete computer, actuator & sensor wiring diagram for 88-90 Mass Air Mustangs

5.0 wiring diagram for Fuel Injectors, Sensors, and Actuators

Ignition switch wiring

O2 sensor wiring harness

Vacuum diagram 89-93 Mustangs

HVAC vacuum diagram

TFI module differences & pin out

Fuse box layout

Mustang 5.0 Lights and Radio schematic, by TMoss:
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxLights-Radio_diag.gif

87-92 power window wiring

93 power window wiring

T5 Cutaway showing T5 internal parts

Visual comparison of the Ford Fuel Injectors, picture by TMoss:

Convertible top motor wiring http://www.veryuseful.com/mustang/tech/engine/images/mustang88VertTopMotorCkt.gif

Engine mounted fuel injector harness

Location of the TPS, IAB, and the 10-pin connectors on a 5.0, picture by TMoss:

Starter circuit

Alternator diagram for 94-95 Mustangs.
 
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79MercCapri93

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May 12, 2012
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drove the car home last night and no lights on, it was glorious!

Today i went to work earlier then normal, stopped to get food and left about 20 minutes later, and probably about 3 minutes into the drive my check engine light came on again. Im going to pull codes when i get home, really hoping its the code 33 and not 41/91 anymore.
 

79MercCapri93

Member
May 12, 2012
84
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drove the car home last night and no lights on, it was glorious!

Today i went to work earlier then normal, stopped to get food and left about 20 minutes later, and probably about 3 minutes into the drive my check engine light came on again. Im going to pull codes when i get home, really hoping its the code 33 and not 41/91 anymore.

Was able to jump out from work for a second to pull codes, came back with 33 (expected from the EGR delete), 41, 91, and 96 (which 96 may be from shutting off the car and just turning the key forward to right before on, while i coasted to the gate for work.
 
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79MercCapri93

Member
May 12, 2012
84
7
8
30
This is a long shot, actually two.
seems to me that the lean condition is happening during the cruise mode (?) And maybe you need to inspect the vacuum line from the purge solenoid to the fuel tank. This may involve dropping the tank. Also on another stang I worked on had a problem with the air idle control valve hanging open, but this effected the idle on that car too.
I will also mention that a deteriorating lower intake gasket was a problem on my car, I have had my intake off soooo many times in the past that I could do it in my sleep, and likely the reason I call it the exxon valdez because the last time I didn't get the back rail sealed up good and it leaks from there.
Yeah, I was asleep on that one.

im going to take a look at the fuel lines either tomorrow morning or this sunday after i get back from the car show out here in Ocean City. If i end up having to pull the intake im just going to put the explorer intake in that i have. No reason to pull the intake to put the same thing back in when i have another sitting here that ive been wanting to put in but have not had a chance to.
 

Window

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any happy ending here? genuinely curious because i chased the same issue for a while lol.
 

79MercCapri93

Member
May 12, 2012
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any happy ending here? genuinely curious because i chased the same issue for a while lol.
Still troubleshooting! Just got back from Ocean City on Sunday and did not have time to mess with the car. I bought a new O2 harness that im going to put on, but am also going to drop the tank and check the fuel lines as well as taking a look at the IAC. Just been waiting to not have a full tank of gas in the car so I dont make a mess haha

I am also thinking of trying my stock MAF, or swap meters from my stock mass air and put the meter on my 94-95 and see if that corrects the issue as well
 

Window

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Feb 13, 2017
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Do the harness 1st and dont forget to pin the extra plug that comes with it, it's different for each year or something like that. Careful cause u can damage the ecu if u forget it. My money is on the harness fixing it cause that's what worked for me. I had the same 41/91 only hitting the cel after like 10 mins of operation.
 

79MercCapri93

Member
May 12, 2012
84
7
8
30
Do the harness 1st and dont forget to pin the extra plug that comes with it, it's different for each year or something like that. Careful cause u can damage the ecu if u forget it. My money is on the harness fixing it cause that's what worked for me. I had the same 41/91 only hitting the cel after like 10 mins of operation.
I am hoping it fixes it, I reached out to LMR because the harness i purchased says its for 91-93 but it came with a plastic piece inside one of the pins on the main harness connection going to one of the 02's?
 
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