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check engine light questions

Maxwell

Maxwell

Active Member
my check engine light comes every now and again when im driving (quicker if im babying it) and goes off obviously when i shut the car off and turn it back on. before the light comes on its extremely peppy and will sweep through the RPM range with ease, however when the light illuminates the throttle response and WOT characteristics change as if its being restricted of fuel. Anybody have some ideas? Not sure if maybe its an O2 sensor issue (because it takes longer to come on if im getting on it a decent amount) or maybe a intake type sensor issue. ie. MAF sensor. any input will help thanks ahead of time.
 
MustangDan351

MustangDan351

Guest
Only way to know for sure is to check for codes, I think there is a way to do it by cycling the key but I could be wrong. The other way is to use a code reader plugged into the diagnostic plug behind the drivers side shock tower.
 
FoxBodyMustangs

FoxBodyMustangs

Administrator
Staff member
Maxwell said:
my check engine light comes every now and again when im driving (quicker if im babying it) and goes off obviously when i shut the car off and turn it back on. before the light comes on its extremely peppy and will sweep through the RPM range with ease, however when the light illuminates the throttle response and WOT characteristics change as if its being restricted of fuel. Anybody have some ideas? Not sure if maybe its an O2 sensor issue (because it takes longer to come on if im getting on it a decent amount) or maybe a intake type sensor issue. ie. MAF sensor. any input will help thanks ahead of time.
Click to expand...

or just go to any Auto supply store and get you a EEC-IV code reader they are like 39.00 dollars. Post up the codes and we can help you troubleshoot.
mN5Dxw8_NnTY7yTz5PqJamQ.jpg
 
Maxwell

Maxwell

Active Member
So here are the codes KOEO 11, 33, 41, 91, 92 and KOER 21, 33, 41, 91.

11 is system pass

21 is Engine Coolant Temperature (ECT) Sensor Out Of Self Test Range. 0.3 to 3.7 volts

33 is EGR valve opening not detected

41 is System Indicates Lean -passenger side(R), No o2 Sensor Switching Detected. always lean -passenger side

91 is o2 Sensor Circuit Indicates Lean -driver side(R), No o2 Sensor Switching Detected. always lean -driver side(CM), Shift Solenoid 1 Circuit Failure (O)

92 is o2 Sensor Circuit Indicates Rich -driver side(R), No o2 Sensor Switching Detected. always rich -driver side(CM), Shift Solenoid 2 Circuit Failure (O)

What's y'all's input kinda weird to have a always rich and always lean on the same bank
 
Blown347

Blown347

Moderator
Staff member
The rich/lean codes are because of the o2 sensors. My 95 GT did the same thing when they were bad. A bad ECT can cause problems as well. I'm not sure on the EGR code, but you definitely need to change both o2s and the ECT. The ECT is screwed into the lower manifold, I think they're like 25 or 30 bucks. And o2s are about 45 a piece.
 
FoxBodyMustangs

FoxBodyMustangs

Administrator
Staff member
Maxwell said:
So here are the codes KOEO 11, 33, 41, 91, 92 and KOER 21, 33, 41, 91.

11 is system pass

21 is Engine Coolant Temperature (ECT) Sensor Out Of Self Test Range. 0.3 to 3.7 volts

33 is EGR valve opening not detected

41 is System Indicates Lean -passenger side(R), No o2 Sensor Switching Detected. always lean -passenger side

91 is o2 Sensor Circuit Indicates Lean -driver side(R), No o2 Sensor Switching Detected. always lean -driver side(CM), Shift Solenoid 1 Circuit Failure (O)

92 is o2 Sensor Circuit Indicates Rich -driver side(R), No o2 Sensor Switching Detected. always rich -driver side(CM), Shift Solenoid 2 Circuit Failure (O)

What's y'all's input kinda weird to have a always rich and always lean on the same bank
Click to expand...

Easy fix..

For Code 33 you need to replace your EVR that fixed my code 33
EVR_View.jpg

For my Code 41 / 91 I did the below... Turnout to be my 19 wire not in the right position..
41 - System Indicates Lean -passenger side(R), No O2 Sensor Switching Detected. always lean -passenger side(CM)
91 - System Indicates Lean -driver side(R), No O2 Sensor Switching Detected. always lean -driver side(CM)

For Code 41 and 91 do a continuity test from pin 49 at the ECM connector, ECM disconnected, to a good ground source, the resistance reading should be equal/less than 5 ohms

SDC10091.JPG

Codes 41/91 (Lean Condition) specific tests:
For codes 41/91 (lean condition), it is always recommended to check the condition of the HEGO GND circuit (pin 49 at ECM connector), a bad/open ground circuit will cause lean readings from the O2 sensors. The HEGO GND is an Orange wire, with a ring connector, that goes bolted to the back of the driver side cylinder head. Identified as item #19 in the following harness diagram.

'86-'93 O2 sensors are 3-wire setups, eventhough the following chart shows a 4-wire setup, the tests can be performed as specified. 3-wire sensors DO NOT use a SIG RTN circuit....
mustangharness_Injectors-to-carb.GIF

Once you fix the one's I have identified the rest will go away..
 
Maxwell

Maxwell

Active Member
FoxBodyMustangs said:
Easy fix..

For Code 33 you need to replace your EVR that fixed my code 33
View attachment 752

For my Code 41 / 91 I did the below... Turnout to be my 19 wire not in the right position..
41 - System Indicates Lean -passenger side(R), No O2 Sensor Switching Detected. always lean -passenger side(CM)
91 - System Indicates Lean -driver side(R), No O2 Sensor Switching Detected. always lean -driver side(CM)

For Code 41 and 91 do a continuity test from pin 49 at the ECM connector, ECM disconnected, to a good ground source, the resistance reading should be equal/less than 5 ohms

View attachment 753

Codes 41/91 (Lean Condition) specific tests:
For codes 41/91 (lean condition), it is always recommended to check the condition of the HEGO GND circuit (pin 49 at ECM connector), a bad/open ground circuit will cause lean readings from the O2 sensors. The HEGO GND is an Orange wire, with a ring connector, that goes bolted to the back of the driver side cylinder head. Identified as item #19 in the following harness diagram.

'86-'93 O2 sensors are 3-wire setups, eventhough the following chart shows a 4-wire setup, the tests can be performed as specified. 3-wire sensors DO NOT use a SIG RTN circuit....
View attachment 754

Once you fix the one's I have identified the rest will go away..
Click to expand...
well some good news fellas i found the HEGO ground not even connected i put new ends on both the HEGO ground and the ground from the body to engine and after getting it nice and warmed up and a little road test everything is running great. Ive noticed a very minimal drop in power when i get on it but all and all its running a lot smoother and no check engine light so i can live with that. hopefully gonna take it on a cruise this weekend to be completely sure but the odds are looking good. thanks for all the help and i will be keeping you guys posted on how it turns out afterwards if i don't break it first :p
 
MustangDan351

MustangDan351

Guest
Even though the cel is not on now you should test for codes again just to make sure there are no problems.

Sent from my SPH-M820-BST using Tapatalk 2
 
Maxwell

Maxwell

Active Member
well drove Jolene a decent ways today and no CEL and no codes so hopefully that ground fixed it. still noticing its not as peppy as it was but i can deal with that. also just got done putting on my new k-member brace next will be fixing my CAI so i can fit my new strut tower brace, some little things to tinker with on the weekend until i can afford that procharger ;)
 
FoxBodyMustangs

FoxBodyMustangs

Administrator
Staff member
Maxwell said:
well drove Jolene a decent ways today and no CEL and no codes so hopefully that ground fixed it. still noticing its not as peppy as it was but i can deal with that. also just got done putting on my new k-member brace next will be fixing my CAI so i can fit my new strut tower brace, some little things to tinker with on the weekend until i can afford that procharger ;)
Click to expand...
There other stuff to check to make it peppy..:) Check your TPS voltage
 
John2002

John2002

Guest
One more ghost to chase if you haven't allready...the hard to get PVC filter screen. WTF was Ford thinking where they put that thing. Mine looked like the bottom of a grease trap. Made a big difference....I replaced the trio (groment/pvc/screen)...don't drop it....LOL
 
MustangDan351

MustangDan351

Guest
Tell me about it John. I changed the upper intake in the 93 I had years ago, must not have gotten the pcv back in right, didn't get the upper tightened properly, the grommet blew out of the intake. Oil was blowing out, had to have a friend fix in his shop for a six pack, lol. I was only 18 then.

Sent from my SPH-M820-BST using Tapatalk 2
 
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