Engine Strange drivability issues and can only pull koeo codes

Foxy420 · Aug 7, 2019

Ok guys I’m at my wits end with my 1990 GT. Mods in my sig. Car was carbed when I got it so I found all the correct 90 specific wiring harnesses and explorer intake and put it back to efi and it’s never ran quite right since. It does this thing where every time I start it hot or cold it runs terrible for a few minutes. It won’t take more than 1/4-1/2 throttle without bucking and popping out the intake, cold start is worse tho and it don’t want to idle cold and takes a good 5 minutes to warm up enough to drive. Then once it comes out of it, it runs pretty decent up to 3/4 throttle, if you go full throttle you can feel it loose like 25-50 HP. The car is literally faster at 3/4 than full throttle?? Another thing that could be related is I can’t get it to flash Koer codes just the koeo ones witch are all emission related as it’s all been deleted. My thoughts are possible Vacuum leak at lower intake although it has really good vacuum for the cam I’m running. Bad ecm, but I just had it apart and replaced the e-caps and checked the trace for pin 46 everything looks good in there. All tune up items are new along with O2 sensors and tps and clean iac. So I guess my question is what would cause it to not spit koer codes only koeo? When it finishes koeo and goes to do koer it revs a few hundred rpm for a brief second then the cel just stays on??? And what would cause it to run like crap every time I shut it off and restart it? And make less power at full throttle than 3/4?? I know someone has had to of had these symptoms before

Mustang5L5 · Aug 7, 2019

My guess is that something in the wiring is not correct.

Start with this check

Electrical - Unable To Pull Cel Codes

Hello everybody, I recently purchased a 1989 Mustang GT, and it has a check engine light. I don't have any history on the car, so I'm really starting at step one. I followed jrichker's post here on the process for checking the CEL codes but unfortunately the CEL light never flashes. It just...

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Also, have you verified the o2 sensor jumper position is correct for your car?

Foxy420 · Aug 7, 2019

Yes O2 jumper is correct. I’m going to dig deeper into the wiring when I get time. I just realized that a lot of my wires change colors at the s&p shaker connectors. Is this normal or did someone repin my harness wrong at some point or sell me a non mustang harness?? For example the blk/white wire to pin 46 changes to a grey/red wire at the s&p connector? Is that normal?? I figured if that was the problem it wouldn’t give me koeo codes???

Foxy420 · Aug 7, 2019

Also I forgot to add to the list of symptoms this thing gets terrible gas milage. And seems to run pig rich

Mustang5L5 · Aug 8, 2019

Foxy420 said:
Yes O2 jumper is correct. I’m going to dig deeper into the wiring when I get time. I just realized that a lot of my wires change colors at the s&p shaker connectors. Is this normal or did someone repin my harness wrong at some point or sell me a non mustang harness?? For example the blk/white wire to pin 46 changes to a grey/red wire at the s&p connector? Is that normal?? I figured if that was the problem it wouldn’t give me koeo codes???

According to my wiring diagrams, it shouldn't change color.

Are you sure the injector harness is for a Mustang? Other 5.0 engine equipped fords got injector harnesses with some slight differences. Does yours have the provision for the oil pressure switch?

jrichker · Aug 8, 2019

87GTForSale said:
Stupid question, in step one what screw am I jumping to the part woth the battery wire on it?

Foxy420 said:
Yes O2 jumper is correct. I’m going to dig deeper into the wiring when I get time. I just realized that a lot of my wires change colors at the s&p shaker connectors. Is this normal or did someone repin my harness wrong at some point or sell me a non mustang harness?? For example the blk/white wire to pin 46 changes to a grey/red wire at the s&p connector? Is that normal?? I figured if that was the problem it wouldn’t give me koeo codes???

Foxy420 said:
Also I forgot to add to the list of symptoms this thing gets terrible gas milage. And seems to run pig rich

The different wire colors are a result of Ford's changes from 90 wiring colors to 91wiring colors and later . You may have a mixture of years or Ford cut over the last of the 90 production models to use the some of 91 wiring where the wires went to the same circuit with no changes in pinout. The engine wiring for the fuel injector harness is the same for 87- 90 and 91-93. The 91and later body wiring harness uses a different fuel pump wiring circuit plan and may not work with a 90 body.

Dump codes sticky

Look at the top of the 5.0 Tech forum where the sticky threads are posted. One of them is how to dump the computer codes. Codes may be present even if the CEL (Check Engine Light) isn’t on. You don’t need a code reader or scanner – all you need is a paper clip, or if your lady friend has a hair pin, that will do the job.
I highly suggest that you read it and follow the instructions to dump the codes. http://www.stangnet.com/mustang-forums/threads/how-to-pull-codes-from-eec4.889006/

Foxy420 · Aug 8, 2019

Mustang5L5 said:
According to my wiring diagrams, it shouldn't change color.

Are you sure the injector harness is for a Mustang? Other 5.0 engine equipped fords got injector harnesses with some slight differences. Does yours have the provision for the oil pressure switch?

Yes I’m pretty sure it’s for a mustang. I bought it off a pretty good guy on the corral who had semi trailers full of mustang parts and knew what he was talking about. By oil pressure switch provision you mean the single push on connector for the gauge correct? If so yea I have that. Any other way to verify it is a mustang harness?

Foxy420 · Aug 9, 2019

Also something that has me kind of stumped on the wire harness, the eec power ground pig tail that is supposed to be a black round 1 pin connector by the battery with a black/green stripe wire. Well my wire harness has a 2 pin connector there. It has the black with green stripe and also a black with yellow stripe?? Should them both go to ground or is 1 power and 1 ground?

Foxy420 · Aug 9, 2019

jrichker said:
The different wire colors are a result of Ford's changes from 90 wiring colors to 91wiring colors and later . You may have a mixture of years or Ford cut over the last of the 90 production models to use the some of 91 wiring where the wires went to the same circuit with no changes in pinout. The engine wiring for the fuel injector harness is the same for 87- 90 and 91-93. The 91and later body wiring harness uses a different fuel pump wiring circuit plan and may not work with a 90 body.

Dump codes sticky

Look at the top of the 5.0 Tech forum where the sticky threads are posted. One of them is how to dump the computer codes. Codes may be present even if the CEL (Check Engine Light) isn’t on. You don’t need a code reader or scanner – all you need is a paper clip, or if your lady friend has a hair pin, that will do the job.
I highly suggest that you read it and follow the instructions to dump the codes. http://www.stangnet.com/mustang-forums/threads/how-to-pull-codes-from-eec4.889006/

I have the fuel pump relay under the driver side seat, where it is supposed to be for a 90. And I’ve read the dump codes sticky a million times. I can dump koeo but it will not dump the koer codes. After it completes the koeo self test it just revs up slightly and then. The cel stays illuminated it won’t flash koer codes

jrichker · Aug 9, 2019

Foxy420 said:
I have the fuel pump relay under the driver side seat, where it is supposed to be for a 90. And I’ve read the dump codes sticky a million times. I can dump koeo but it will not dump the koer codes. After it completes the koeo self test it just revs up slightly and then. The cel stays illuminated it won’t flash koer codes

Please post all the codes you get. I have 5.0 Foxbody code definitions and fixes that can help you find and fix the problems.
Does the code dump give you a code 67? That will prevent you from getting the engine running codes.

Foxy420 · Aug 9, 2019

jrichker said:
Please post all the codes you get. I have 5.0 Foxbody code definitions and fixes that can help you find and fix the problems.
Does the code dump give you a code 67? That will prevent you from getting the engine running codes.

No code 67 well I had it at first but I’ve read literally probably everything you’ve ever posted lol. So I jumpered pin 30 to ground and it went away but what do ya know, it still won’t dump the koer codes???? Even though no more code 67????? The only other codes I got were for emissions stuff as it’s all been deleted they were koeo 31,82,84,85. I plan on replacing all the emissions stuff after I get everything else sorted out

Foxy420 · Aug 9, 2019

jrichker said:
Please post all the codes you get. I have 5.0 Foxbody code definitions and fixes that can help you find and fix the problems.
Does the code dump give you a code 67? That will prevent you from getting the engine running codes.

Did you read my post above about the 2 wire connector where I thought would be a single wire connector for the eec power ground?? Ever seen that??

jrichker · Aug 9, 2019

The picture shows the common ground point for the battery , computer, & extra 3G alternator ground wire as described above in paragraph 2. A screwdriver points to the bolt that is the common ground point.

The battery common ground is a 10 gauge pigtail with the computer ground attached to it.
Picture courtesy timewarped1972

Correct negative battery ground cable.

The computer's main power ground (the one that comes from the battery ground wire) uses pins 40 & 60 for all the things it controls internally: it comes off the ground pigtail on the battery ground wire. Due to its proximity to the battery, it may become corroded by acid fumes from the battery.
In 86-90 model cars, it is a black cylinder about 2 1/2" long by 1" diameter with a black/lt green wire.
In 91-95 model cars it is a black cylinder about 2 1/2" long by 1" diameter with a black/white wire.
You'll find it up next to the starter solenoid where the wire goes into the wiring harness.

Foxy420 · Aug 9, 2019

jrichker said:
The picture shows the common ground point for the battery , computer, & extra 3G alternator ground wire as described above in paragraph 2. A screwdriver points to the bolt that is the common ground point.

The battery common ground is a 10 gauge pigtail with the computer ground attached to it.
Picture courtesy timewarped1972

Correct negative battery ground cable.

The computer's main power ground (the one that comes from the battery ground wire) uses pins 40 & 60 for all the things it controls internally: it comes off the ground pigtail on the battery ground wire. Due to its proximity to the battery, it may become corroded by acid fumes from the battery.
In 86-90 model cars, it is a black cylinder about 2 1/2" long by 1" diameter with a black/lt green wire.
In 91-95 model cars it is a black cylinder about 2 1/2" long by 1" diameter with a black/white wire.
You'll find it up next to the starter solenoid where the wire goes into the wiring harness.

Yea that’s what I’m saying I don’t have that, instead my harness has a round black cylindrical 2 wire connector in its place with 1 black/green and1 black/ yellow wire in it. So I spliced into the black/green wire and grounded it but what does the black/yellow wire go to?

jrichker · Aug 9, 2019

Foxy420 said:
Yea that’s what I’m saying I don’t have that, instead my harness has a round black cylindrical 2 wire connector in its place with 1 black/green and1 black/ yellow wire in it. So I spliced into the black/green wire and grounded it but what does the black/yellow wire go to?

Check computer pins 40 & 60 to see if the wire is there...

Computer wiring harness connector, wire side

Computer wiring harness connector, computer side

Foxy420 · Aug 9, 2019

jrichker said:
Check computer pins 40 & 60 to see if the wire is there...

Computer wiring harness connector, wire side

Computer wiring harness connector, computer side

Yes both pins 40&60 have the black/green wires going to it. The black/yellow wire I’m not sure were it goes. It goes through the firewall along with the other wires to the eec. It practically runs right along side the black/green wire but I loose it on the inside of the fire wall. Like maybe it goes to a relay way up under the dash that I’m not seeing??? Has anyone even seen a 2 pin connector for the eec power ground by the battery? All the info I’ve seen says it’s a 1pin connector there. Wandering if I should just guess and try to hook the black/yellow to ground or power??

Foxy420 · Aug 9, 2019

Foxy420 said:
Yes both pins 40&60 have the black/green wires going to it. The black/yellow wire I’m not sure were it goes. It goes through the firewall along with the other wires to the eec. It practically runs right along side the black/green wire but I loose it on the inside of the fire wall. Like maybe it goes to a relay way up under the dash that I’m not seeing??? Has anyone even seen a 2 pin connector for the eec power ground by the battery? All the info I’ve seen says it’s a 1pin connector there. Wandering if I should just guess and try to hook the black/yellow to ground or power??

Foxy420 · Aug 9, 2019

UPDATE!!!! I was finally able to pull koer codes!!! I pulled my eec back apart and one of the e-caps I replaced I must have got the board too hot with the soldering iron and burnt a trace off the board that connects the e-cap to I think the processor.i could see a open spot in the trace and verified with my fluke meter it was open. So I soldered A wire in its place. Now I wonder if I messed up more than just that because on some of the e-caps 1 leg only has one trace going to it while the 2nd leg will have up to 4 traces going to it (checked by shining a flashlight from underneath to look through the board)??? The one I fixed though allowed me to finally dump koer codes although I don’t think they mean anything in my case as I believe they are all related to my missing emissions equipment. So here are my codes koeo= 31,81,82,85,84 CM= 31 koer= 94,44,31 and passed cyl bal test with a 9 four times. So my conclusion is I did more harm than good replacing the e-caps or they leaked so bad they messed up the board. Since none of my codes point to any bad sensors or anything that would cause my drivability problems. Does everyone agree? Have any input? What’s the cheapest/best route to get a new or refurbished A9L?
So would anyone else agree since

General karthief · Aug 9, 2019

All grounds in place?
good fuel pressure? That question requires a gauge to verify, too often we get the 'I pushed on the schrader valve in the fuel line and fuel squirted out'

jrichker · Aug 9, 2019

Foxy420 said:
UPDATE!!!! I was finally able to pull koer codes!!! I pulled my eec back apart and one of the e-caps I replaced I must have got the board too hot with the soldering iron and burnt a trace off the board that connects the e-cap to I think the processor.i could see a open spot in the trace and verified with my fluke meter it was open. So I soldered A wire in its place. Now I wonder if I messed up more than just that because on some of the e-caps 1 leg only has one trace going to it while the 2nd leg will have up to 4 traces going to it (checked by shining a flashlight from underneath to look through the board)??? The one I fixed though allowed me to finally dump koer codes although I don’t think they mean anything in my case as I believe they are all related to my missing emissions equipment. So here are my codes koeo= 31,81,82,85,84 CM= 31 koer= 94,44,31 and passed cyl bal test with a 9 four times. So my conclusion is I did more harm than good replacing the e-caps or they leaked so bad they messed up the board. Since none of my codes point to any bad sensors or anything that would cause my drivability problems. Does everyone agree? Have any input? What’s the cheapest/best route to get a new or refurbished A9L?
So would anyone else agree since

One side of the electrolytic cap is ground (negative or - sign). The other side goes to the circuit it serves.

Engine Strange drivability issues and can only pull koeo codes

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