How to kill, repair and not kill again an A9L in an 88 and possibly others.

Topic: How to kill, repair and not kill again an A9L in an 88 and possibly others. (Read 3652 times) previous topic - next topic

How to kill, repair and not kill again an A9L in an 88 and possibly others.

October 02, 2018, 09:34:21 PM

Years ago when I swapped my car to GT40 I used a speed density EEC from an auto Mustang. The car ran great, I made the jump to MAF with an A9L and the car has never run as good as it did with speed density. Years of troubleshooting, trying different parts and failing to get codes from the DLC but I never fully resolved the issue. I took the EEC apart and repaired the all to common SigRtn circuit but it never repaired the problem. In rebuilding my car I started some new research and stumbled upon all things pin 30.

Pin 30 in regards to a stock 88 EEC works as a neutral indicator by grounding the pin to chassis ground through the starter solenoid of all places. This wire runs through the Neutral switch on the transmission, this is how the computer knows the car is in gear. Reference to ground on pin 30 through this circuit tells the computer the car is in park, no reference to ground = car is in gear. When the car is started power is applied to the starter solenoid starting the car. During this there is 12v applied to this wire, the solenoid has a diode to force the 12v through the coil engaging the solenoid. Our stock computers can handle this 12v during cranking by its own diode protection. The speed density HO computers use this configuration as well as the A9P, all are safe to install and no change is required to this circuit.

The A9L uses reference to SigRtn through both the neutral switch on the clutch pedal and the one on the transmission, these switches are in parallel so that either will provide reference to SigRtn with either the clutch pedal pressed or the transmission in neutral. The Mustang guys find a problem through the O2 sensor harness. I am not certain what the problem actually is but I am pretty sure that there is no problem with our O2 sensor harness, the Mustang one looks like it runs the NGS through its O2 harness and ours does not.

Now to some pictures.

Page 44 of the 88 EVTM shows the start pin of the ignition switch connected to the starter solenoid through the neutral safety switch. You can see the red with light blue stripe wire goes to the transmission and back to the starter solenoid changing to a white with pink stripe wire at the transmission. This is the how your car actually starts. Notice the brown with white stripe wire coming off to the left and where it shows to follow it to. You can also see the diode in the starter solenoid that allows reference to ground but forces 12v through the coil.

Page 61 (not 58 as it says, thats a 3.

shows the brown/white wire on its way to pin 30, the only connection is C143 and that is one of the connectors by your brake booster. So it leaves the starter switch and goes through the firewall to C143 by the booster, this is one of the engine to body harness connectors. From there it goes strait to the EEC. With both of these we can see how the car applies 12v to pin 30 while cranking and reference to ground when running. Neither thing an A9L Wants.

This is a picture of my starter switch, you can clearly see the brown/white red/light blue crimped together at the switch just like page 44 shows. As a safe start to an A9L conversion the brown/white needs clipped from this location. There are many different plans of attack from this point forward from all over the internet. Some say leave it open however you cannot pull KOER codes. Others say to connect it strait to pin 46 (SigRtn), however others complain of idle issues. Wiring like factory is ideal, parallel the clutch switch and the Neutral safety switch on the transmission. Myself I have an Sn95 t5 so I have no neutral switch on the transmission so I will use only the clutch switch. So the brown wire can go to one side of the clutch switch and a wire run from SigRtn to the other. This means a wire across the back of the dash to the EEC as there is no SigRtn on the driver side. Ideally you would run the red/light blue wire through the other switch on the clutch pedal so the car wont start unless the pedal is down.

I'm sure this is not new information to some of you and I may find that all of this info is already on this forum but I only found bits and pieces in different threads but I also didn't look to hard. I needed to have a mind dump so I figured you all wouldn't mind.:hick:

How to kill, repair and not kill again an A9L in an 88 and possibly others.

Reply #1 – October 05, 2018, 04:54:14 PM

I have been curious about what pin 30 does in the past. I made a spread sheet of how it is shown in the 84-88 T-Bird/Cougar EVTMs.
On the 2.3L they show two separate pin 30's. One for Auto and one for Manual transmissions.

5.0L
84-87 pin 30 not used.
88 Pin 30>NSS>Starter Relay Coil>Ground

3.8L
84-87 Pin 30>Diode>NSS>Starter Relay Coil>Ground
88 Pin 30>NSS>Starter Relay Coil>Ground

2.3L
84-86 Auto Pin 30>Diode>NSS>Starter Relay Coil>Ground-- Manual Pin 30>Ground
87 Auto Pin 30>NSS>Starter Relay Coil>Ground-- Manual Pin 30>EEC Pin 46 (signal return)
88 Auto Pin 30>NSS>Starter Relay Coil>Ground-- Manual Extra Pin 30 shows no connection

The Diodes are shown blocking cranking current from flowing toward Pin 30.

Unclear to me what the EEC does with this Pin 30 info

How to kill, repair and not kill again an A9L in an 88 and possibly others.

Reply #2 – October 05, 2018, 06:56:51 PM

From what I have read the EEC uses the pin 30 info to maintain idle quality and idle speed while in gear in an auto car. In a standard car it allows KOER codes to be pulled, I’m not certain if it works that way for safety or if it is part of the test. I’m also not certain if it’s idle quality as well.

funny that an LA2 car is different than an LA3 car.

How to kill, repair and not kill again an A9L in an 88 and possibly others.

Reply #3 – October 09, 2018, 09:56:07 AM

Not sure how or why this thread was locked?

Posting this link for future reference, disregard for now. I am going to acspoogeulate all the pin 30, nss and A9L conversion stuff I can find and dump it here.

This link I am referencing because it mentions a jumpered connector that I want to find in my removed dash on my 88 xr7. It is possible it can be used for a t5 conversion but at first look I see a red/blue wire which is used for the starter solenoid, it could be used for the multi function clutch switch.

http://www.foxtbirdcougarforums.com/showthread.php?38430-A9L-T5-and-NSS-wiring

This link I have here because it talks about the O2 sensor harness and using one from a mustang. My first order of business is going to be verifying or debunking this information. I am pretty sure that our harness only has the O2 wires and nothing else. Paul says his had 6 wires. That would be three for each o2 which is correct. Looking at a mustang O2 harness it does not look like they ground the sensors behind the heads like our cars do, there is also an extra unknown plug. Most of the O2 sensor stuff I read is always referring to 89+ newer mustangs. Across the board it looks like ford changes things in 89.

http://www.foxtbirdcougarforums.com/showthread.php?38796-O2-sensor-harness

Very useful thread on VSS info and fuel pump relay sense.

http://www.foxtbirdcougarforums.com/showthread.php?38096-Mass-air-conversion-question/page2

Here is a thread with the exact same issue and talking about the exact issue on pin 30. On his thread 88CougarGT even says he compared the O2 harnesses and found the cougar to be different than the Mustang. His thread talks about repairing the A9L but what to do with pin 30 is a bit open to interpretation. There is a bit of incorrect information in this thread with grounding pin 30 through a clutch switch. It should use sigrtn instead of chassis ground.

http://www.foxtbirdcougarforums.com/showthread.php?31025-Fix-for-poor-idle-rich-mixture-and-poor-performance-after-HO-T-5-mass-air-swap

Thread with bad info but saving for later. Also talks about the lack of O2 harness issue.

http://www.foxtbirdcougarforums.com/showthread.php?30551-Mustang-vs-5-0-Thunderbird-computer!

O2 harness for t5

Reply #4 – October 09, 2018, 08:49:54 PM

Alright, I have spent some time on the O2 harness issue today. From what I can tell installing either auto or standard mustang O2 harness would accomplish nothing good and in fact cause your car to run in open loop only and throw codes. Can any of you using the mustang harness tell me for a fact your car is not throwing hego codes? Unless anyone can disprove what I have found you need to switch back to a thundercougarfalconbird harness.

Let the diagrams speak for themselves.

First a mustang hego diagram I pulled from the web. It shows both auto and manual harness locations and the differences.

Now here is a diagram I made using the mustang harness for direct comparison. I verified this from jcassity's link to the 88 evtm and comparing that to my 88 harness that is on my engine out of the car on a stand. As you can see it is very different. So again, unless proven otherwise I say never use the mustang O2 harness.

How to kill, repair and not kill again an A9L in an 88 and possibly others.

Reply #5 – October 10, 2018, 12:49:01 AM

FWIW, everything I ever read about using Stang O2 harnesses with CatBird cars ended poorly. Most common: fried EECs...

Never had an issue with my Sport (HO transplant), but I used all the Sport's factory engine wiring, including the existing O2 shiznit..

How to kill, repair and not kill again an A9L in an 88 and possibly others.

Reply #6 – October 10, 2018, 10:47:31 AM

I can say I've not had a problem with the MAF conversion in my car, but I run an A9P. It has the stock wiring with 4 wires added for the MAF and the two Thermactor wires moved.

I believe you can run an A9P/any auto EEC-IV with a manual transmission no problem. Well except some stall issues at times.

The way it looks is something has to be figured out for pin 30 on our cars if you want to run an A9L.

I'd still like to know Ford's logic for these wiring changes between a manual and auto car. Seems like using the same harness would have been easier.

How to kill, repair and not kill again an A9L in an 88 and possibly others.

Reply #7 – October 10, 2018, 11:23:31 AM

Quote from: thunderjet302;467509

I can say I've not had a problem with the MAF conversion in my car, but I run an A9P. It has the stock wiring with 4 wires added for the MAF and the two Thermactor wires moved.

I believe you can run an A9P/any auto EEC-IV with a manual transmission no problem. Well except some stall issues at times.

The way it looks is something has to be figured out for pin 30 on our cars if you want to run an A9L.

I'd still like to know Ford's logic for these wiring changes between a manual and auto car. Seems like using the same harness would have been easier.

An A9P is completely safe in our cars as the pin 30 circuit is basically the same as it is in a mustang. You are completely fine with an A9P and a standard especially if having the car tuned, they can basically tune out any idle flair.

Beyond clipping the brown/white from the ignition switch an A9L is not a good choice for our cars. There is no provisions for clutch pedal switches or having a sigrtn under the driver side of the dash to use in conjunction with the clipped brown/white for a clutch switch for pin 30. Use an A9P and tell your tuner it is in a T5 car. However used A9P’s are nearing the $400 mark on eBay.

Adding to the sigrtn under the driver side, it looks like even the TC did not have this. Looks like an 89+ mustang thing too. The TC only ran the red/blue wire through the clutch switch and pin 30 was ran strait to sigrtn.

How to kill, repair and not kill again an A9L in an 88 and possibly others.

Reply #8 – October 10, 2018, 02:33:22 PM

How are the 86-88 Mustang speed density cars set up? Are they like our cars? I don't have an EVTM pin out for them to compare.

How to kill, repair and not kill again an A9L in an 88 and possibly others.

Reply #9 – October 10, 2018, 04:13:43 PM

Briefly looking I cannot find an 87 specific diagram. The 88 appears to be the same as the 89+ from the diagrams I can find online. The only 86 diagram I can find shows that there is no difference between auto and manual and the white/pink wire goes to pin 30 on both styles of computer. However it is one of Diagrams on line that someone made. It would be nice to see a factory diagram for all of these, perhaps Carmen can help us out with this.

How to kill, repair and not kill again an A9L in an 88 and possibly others.

Reply #10 – October 10, 2018, 06:38:15 PM

From the 93&94 Mustang EVTMs
The 93 Mustang 5.0L with the manual trans. The O2s and pin 30 do share connector C101.

The 94 Mustang has several changes. They went to the AODE transmission and 4-wire O2's.
There are 5 different resistances between pin 30 and signal return depending on where the gear selector is.

How to kill, repair and not kill again an A9L in an 88 and possibly others.

Reply #11 – October 11, 2018, 12:06:14 PM

In 94 and 95 the EEC controlled the automatic transmission so it would want to know what gear the transmission was in (AODE). The 89-93 MAF computers could care less what transmission was behind the engine. All they needed to know was whether or not the transmission was in gear.

How to kill, repair and not kill again an A9L in an 88 and possibly others.

Reply #12 – October 11, 2018, 12:11:47 PM

Quote from: softtouch;467518

From the 93&94 Mustang EVTMs
The 93 Mustang 5.0L with the manual trans. The O2s and pin 30 do share connector C101.

The 94 Mustang has several changes. They went to the AODE transmission and 4-wire O2's.
There are 5 different resistances between pin 30 and signal return depending on where the gear selector is.

So we agree that the mustang o2 harness is significantly different than our cars and should never be used? It is even longer and the harness plugs in by the evap canister while our cars is behind the intake manifold.

interesting to learn how an MLPS actually works.

Do you have an evtm for an 87 mustang?

How to kill, repair and not kill again an A9L in an 88 and possibly others.

Reply #13 – October 11, 2018, 12:32:30 PM

Looking at the 86 evtm it looks like it shows a pin 30 connection to the start circuit but perhaps it is incomplete? It shows the pin ending at c499 but I don’t see what this connects too. It does show an external diode. I cannot read Scott’s 87 evtm, it is too fuzzy.

The nifty thing about the 86 evtm it shows a jumper through c288 and references a neutral switch for a manual transmission. It is possible that the 86 v8 cars have the jumped out connector for the clutch pedals for the starter safety switch. Anyone have an 86 v8 car they want to look under the dash for a connector?

How to kill, repair and not kill again an A9L in an 88 and possibly others.

Reply #14 – October 11, 2018, 04:50:31 PM

I may be oversimplifying the hell out of this but since it does not appear any of the wiring for PIN 30 runs through the O2 harness on our cars that you can clip the wire on PIN 30 and just add the same wiring that is in a Mustang for the clutch/transmission switch.

But I could be wrong. I'm not an electrical expert.