My first stang 89 gt , help .

[tomcamaro97]

so as you could geuss by my name, im more of a GM guy.. but i like fords/lincolns too and normally have atleast one. I recently picked up my first stang an 89gt that needs some work.. ive been starting to dig into it and someone has definately played around with the electrical on the car. (example: removed the rediculous DVD player.. and dish lights started working). ive got two issues kinda related that im working on an hoping you pros can give me some guidance.. the car has a check engine light, and i think it needs to be timed (it got a hesitation on throttle ).. Im going to time it the old fashioned way with a liming light , after i remove the little cap thing by the distributor., whats agood reccommended tiiming for a 5.0?. assuming this works thatll take care of my first issue.. second is my check engine light.. as soon as i hook up a code reader to the car and turn it on, it dies. (thats with my snap on reader), if i do it with the car off it gets nothing., if i do it the old fashioned way with the jumper wire and a light/dash light, absolutely nothing happens. my good buddy is a fox body guy (supercharged 347) and he thinks its likely that when the code reader powers up its stealing juice from the ecu and thats why it dies.. any thoughts or places to look? where does the ecu get power from? i wonder if previouso owner teed into it somewhere. any help on both topics is great.

 

[Blown347]

Stock timing is 10* most people bump it to 12-14* and get more power. It varies from car to car so try 14 and if it pings just back it down a tad. Also need to check TPS voltage key on engine off should be less than 1v. That can cause a stumble as well.

In the tech section I have a sticky with every wiring diagram you'll ever need for a fox. I'm not sure off hand where the main power for the ecu is but those diagrams will help you trace it and see what's up with the diagnostic plug. (They're copies from a ford shop manual)

 

[tomcamaro97]

where are the stickies at? im used to the stickies being at the beginning of the forum section. these wiring diagrams will be amazing help im sure.. i was gonna have a friend pull it off alldata , but this will work even better.

Thanks for the tips on the timing/ tps... the 1 volt thats the signal wire coming off the sensor correct?

 

[Blown347]

The stickies are at the top. Here's the link:

http://www.foxbodymustangs.org/community/index.php?threads/Chassis-wiring-diagrams.462/

Yes the signal wire, it's green if I'm not mistaken. Just probe it and ground to the throttle body mounting bolt for the best reading. There are several write ups and videos on how to do it but basically you loosen the two little screws that hold it down and if the voltage is wrong you rotate the sensor to get the proper voltage. (Many people will tell you it needs to be .99v but that's not true, anything less then 1v and the computer will compensate) I shoot for .75-.99v

If the sensor doesn't rotate enough to get proper reading use a small drill bit or file to oval out the holes to get the adjustment you need. Hope this helps!

 

[Blown347]

One other thing that a lot of people forget, if you adjust the idle in the throttle body with the idle adjustment screw you MUST reset the TPS voltage.

 

[Blown347]

Something else, not sure how your doing it but you're saying that with Key ON engine off it gets no codes? It will only pull codes if the key is in run, not ACC or off.

 

[tomcamaro97]

so i tested the TPS last night.. ran neg 5 volts on the green wire.. adjustment didnt change it at all. .. i probed the orange wire as well and it gave me the exact same reading as the green wire. .. obviously i have something going on here does that sound like a bad TPS, or does it sound like there might be something more going on? (maybe related to my other potential wiring issues? )

you mentioned reset the voltage for the TPS? how does one do this?

Yeah I had key "on" engine off when doing my testing. but also had engine on as well, and thats when it would kill from turning my scan tool on.

 

[tomcamaro97]

ok so ive done some research... tps , from what ive read tps is supposed to have 5 volts key on (coming from the ref wire), but at idle this should be in the .8 volts range, going up as the throttle is opened. its still not working properly, but i think imgetting closer.. I replaced my idle air controll (as i had an extra one laying around, and the idle was a mess once it came off closed loop).. seemed to fix a bunch of my problems from a throttle response/ idle stand point..

then i moved on to my wiring mess (figue ill come back to TPS and code reading after i get these fixed).. looks like somone had a remote start system on it.. but removed the brain box and only re-hooked up the iginition wire.. so all the other wires that were cut/t'd into essentially went nowhere. (ive got about 4 wires left to fix but i have a feeling alot of my problems will be fixed once these are good. ) (wires are all yellow, yellow/blk, orange/black, and white) .. guess ill be spending some time with the wiring diagrams this weekend!!!

Also there is a brown box under the dash (right under the column) that was completely disconnected.. the connector with 6-8 wires was a few inches away so i plugged it in.. not sure what it does, but im sure its supposed to be plugged in. anyone know what this box does?

 

[Blown347]

Got a picture of the box that's unplugged? I can tell you what it is if I see it. I'm not sure from the description.

As for TPS, 5 volts is incorrect. The TPS has a 5 v range but key on engine off needs to be less then 1v. (This is what the idle is based off once it starts. When it idles the IAC valve will make the voltage jump slightly so you cannot properly set it with the engine on. If you set it at 5v key on engine off, you are sending a signal that the ECU will read as WOT. It will attempt to compensate but essentially will start extremely rich and start to go crazy with conflicting signals from the TPS vs the MAF and o2 sensors.

 

[tomcamaro97]

Looking at the wiring diagram, the box is the internal governer, still don't know what that does,? but its plugged in now... Still can't pull codes , check engine light is constant, reset battery and changed nothing check engine light was still constant, I've gone through all the wiring and am pretty confident nothing else is messed with, so at this point I'm thinking broken wires or maybe ecu or something ,Any thoughts?

 

[Blown347]

Sounds like a harness problem. But you're right it could be either or. I'd start by checking continuity between each of the test ports and the end of the harness that plugs into the ecu. Have you traced them to check for any damage or hack job wiring? That's strange I've never seen that problem.

 

[tomcamaro97]

Do you know what the internal governer actually controlls?(edit: it controlls the wipers) YeH I'm guessing whatever is going on , with not being able to pull codes is also my tps issue, and maybe others, ive chcked the ecu ground. And foun a write up on check the wires on the plug for co.tinuety. so i guess thats next, im leaning toward thinking an ecu, but the car runs and starts fine, so who knows , but yeah likely running in wot mode as tps is getting 5 volts no matter what. And thats with two tps sensors.. and who knows what else it wrog . But really wanna conirm things before I start throwing parts at it.

 

[tomcamaro97]

update, thoughts, help...

So the ground on my computer was burned up... which is why none of my items could be tuned, its also doing the whole runs to 170 degreees and then after you turn it off it wont restart till it cools down. .. i took it out the ecu and confirmed as such, theres defiantely a burned ground trace. the same one you would see every time you google it.. heres where it gets complicated. Ive got a 5.0 auto , and someone stuck an A9L in it ( manual trans ecu). from everything im reading you either need to do a harness swap or swap out some wires to run this computer sucessfully, does anyone know exactly what wires should be modified from stock, i dont wanna find/run a whole new harness. or should i just forget about this A9l, and pick up an A9P? thoughts/ help would be greatly apprecaited.

 

[Blown347]

I would say get the right ECU for simplicity's sake. Way less headache and you can pick one up for less then 100 bucks

 

[Hoonigan]

update, thoughts, help...

So the ground on my computer was burned up... which is why none of my items could be tuned, its also doing the whole runs to 170 degreees and then after you turn it off it wont restart till it cools down. .. i took it out the ecu and confirmed as such, theres defiantely a burned ground trace. the same one you would see every time you google it.. heres where it gets complicated. Ive got a 5.0 auto , and someone stuck an A9L in it ( manual trans ecu). from everything im reading you either need to do a harness swap or swap out some wires to run this computer sucessfully, does anyone know exactly what wires should be modified from stock, i dont wanna find/run a whole new harness. or should i just forget about this A9l, and pick up an A9P? thoughts/ help would be greatly apprecaited.

Get a stock ecu unless you can otherwise confirm that the wiring harness is from a cobra. Do you have stock injectors? Cobras were tuned with A9L ecus and had 24lb injectors stock. Get back to me when you find out. Stock motorcraft injectors are usually orange while stock cobra 24lb injectors are usually black or could have a fatter injector size(usually is silver) with an orange top.