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Topic: 87 T-bird W/92 5.0 Swap High Idle (Read 1466 times) previous topic - next topic

87 T-bird W/92 5.0 Swap High Idle

Bought a 1987 Thunderbird for my brother. The car was originally a 5.0 non-HO. The previous owner swapped in a 5.0 HO out of a 1992 fox body and a AOD trans. He also swapped in the A9P eec without doing any harness changes. The previous owner never did the MAF conversion to the 87 harness and could not get the car to run right.

 So when I picked up the car, instead of wiring in the MAF, I decided to pick up a 1987 auto mustang EEC (DC model) in hopes it would match the speed density harness the car already has. The car started fine but has a high idle of 1200 rpm. If I disconnect the IAC the idle drops back to normal (750 rpm). So I replaced the IAC twice now with the same issue. I replaced the MAP, same issue. Ive adjusted the TPS. Did an idle reset procedure, when I kicked all the accessories on (head lights, radio, A/C) the car idled rough and quickly stalled out.

 The car does not spit out any codes. Ive done the old school way with the test light and jumper wire and get nothing at all. With the key off I get a steady 1 light every few seconds. key on gives me nothing. With a snap-on scanner hooked up, its does not communicate with the car. Fiddling around in the engine bay I found some loose grounds. I tightened them and added an extra ground from the battery to the a/c bracket. Thinking the DC EEC is bad since it would not communicate with scanner or jumper wire, I had a local ECU remanufacturer test it out and it has tested GOOD.  Is the "DC" eec the right computer for the job?

 Im lost at where I need to probe next. I need to get this car running asap.

 Am I missing something in the harness. Is the EEC harness different from a 1987 tbird to a 1987 mustang? Do I need to change some pins around?

 Please help. sorry for long post. Thanks in advanced

87 T-bird W/92 5.0 Swap High Idle

Reply #1
I've got some info here that may help...
http://www.coolcats.net/modifying/ho_conversion.html

Assuming the firing order is switched around to HO, correct?

Have you set the timing with the SPOUT connector off?

Just trying to establish a baseline here.

I have run across instances, and have had others tell me, where sometimes a car will just not give codes. In other words, the EEC cannot be properly scanned. Obviously that's not right and something is going on somewhere, and grounds are good places to start. It can drive you nuts just trying to figure out why it won't behave properly. Does this car happen to have the full electronic instrument cluster, by any chance?

87 T-bird W/92 5.0 Swap High Idle

Reply #2
I'm assuming the firing order is correct as the car was driveable with the A9P eec. And I'm also assuming the timing was good as the car did a good burn out with the A9P eec. It would just stall coming to stops. Thus I swapped in the DC eec. And now I'm running into stated issues.

The car does have the full electronic/digital dash.

87 T-bird W/92 5.0 Swap High Idle

Reply #3
Also. I have done a bit of digging on the coolcats site. Giving me the idea that DC EEC may be incorrect. As this is not a conversion motor but a full motor swap from a 92 mustang gt with essentially a deleted MAF.

87 T-bird W/92 5.0 Swap High Idle

Reply #4
Quote from: hjbjzj;462917
Also. I have done a bit of digging on the coolcats site. Giving me the idea that DC EEC may be incorrect. As this is not a conversion motor but a full motor swap from a 92 mustang gt with essentially a deleted MAF.
Whether it's orig HO or converted, assuming cam, injectors heads etc are swapped computer requirements are same...

According to this website DC is a correct code for a '87-'88 AOD Stang...

http://www.fuelinjectedford.com/page17.html

There are only seven(oops make that nine for '87) wires to add/change when converting to mass air... Four are added for MAF meter, two for TAB & TAD solenoids are moved, one added for fuel pump monitor, two added for speed sensor(these were added to '88 models)... Only other change is remove the vacuum from MAP sensor so it can function as a BAP sensor... The Ford Racing kit only added the MAF, neglecting other changes, those ran OK but were not smog compliant... I've had a '87 T-Bird SD harness in my '88 Turbo Coupe with the MAF mods since '99 always worked fine...

If present computer won't give codes you may not have any... A double blink is code 11 which means system, clear no codes to report... The computers I've seen that won't give codes(no blinks), idles rich, runs lean and has a fixed high idle speed have been FUBAR... I have seen a couple that won't communicate with the scanner but run fine...

If you are going to keep this car and don't have a real scanner, I reccomend one of the cheap Innova 3145

https://www.amazon.com/INNOVA-3145-Ford-Digital-Reader/dp/B000EW0KHW

87 T-bird W/92 5.0 Swap High Idle

Reply #5
Well I'm trying to stay speed density. I do not want to go to maf.

I want to make the DC EEC work.

Something is sending a signal telling the iac to open up and there is something preventing the scanner from communicating to the EEC

Im hoping the gentleman chimes in on if the digital dash can cause these issues

87 T-bird W/92 5.0 Swap High Idle

Reply #6
It just seems like most of the people with the EEC testing issues happen to have the full digital dash. I don't know if that's coincidence or not. Just an observation.

87 T-bird W/92 5.0 Swap High Idle

Reply #7
I did order the cheap scanner off of Amazon. The simple digital read out one for 23$. Should be here Wednesday. I know the check engine light works. So there's that.

I can't seem to figure what would tell the IAC to open up the way it is to give the car the high idle. And then when the accessories turn on the car dies.

The ecu remanufacturer tested the DC EEC and it tested good. No issues found.

87 T-bird W/92 5.0 Swap High Idle

Reply #8
Iac will raise idle a ton more then 1200rpm if all the way open.

Usually this means that the idle set screw is too high or you have vacuum leaks. You can also try running an engine ballance test. This will tell you if the computer and iac are communicating properly.

The code reader just basically flashes or beeps, same thing as the check engine light really.

To do a engine ballance test, run codes. Within about 30 seconds of the codes flashing stops, floor the car. If it works, the idle will raise significantly and randomly turn off injectors to measure rpm drop. Thjs may help point to a bad cylinder or head gasket.

If you unplug the iac while the car runs, you should be able to back the idle down with the throttle screw until it barely runs. If not, the iac is either stuck open or you have excessive vacuum leaks which will give the same effect. The computer does not measure air coming in.
Quote from: jcassity
I honestly dont think you could exceed the cost of a new car buy installing new *stock* parts everywhere in your coug our tbird. Its just plain impossible. You could revamp the entire drivetrain/engine/suspenstion and still come out ahead.
Hooligans! 
1988 Crown Vic wagon. 120K California car. Wifes grocery getter. (junked)
1987 Ford Thunderbird LX. 5.0. s.o., sn-95 t-5 and an f-150 clutch. Driven daily and going strong.
1986 cougar.
lilsammywasapunkrocker@yahoo.com

87 T-bird W/92 5.0 Swap High Idle

Reply #9
the MAP is connected back to manifold vacuum, correct? the mustang the engine came out of would've just been atmosphere. that'd be a simple mistake that'd cause funny things.
1988 Thunderbird sport
2004 Ford F150 Lariat
2008  Chevrolet Cobalt Sport
2007 Suzuki DR-Z400S dual sport/Supermoto
1988 Thunderbird LX - sold
1988 Mercury Cougar XR-7 with GST kit - gone

87 T-bird W/92 5.0 Swap High Idle

Reply #10
I did go out and buy a new map as the original one was disconnected. The new one is connected but not correctly. I currently have it running to the vacuum tree on the firewall. I found the diagram for vacuum lines last night. I will reroute vacuum lines accordingly and test it out.

Also going to locate some vacuum gauges and see what I come up with. Also still need to test the computer ground wires.

I will have a full weekend ahead of me.

87 T-bird W/92 5.0 Swap High Idle

Reply #11
Quote from: hjbjzj;462925
I did go out and buy a new map as the original one was disconnected. The new one is connected but not correctly. I currently have it running to the vacuum tree on the firewall. I found the diagram for vacuum lines last night. I will reroute vacuum lines accordingly and test it out.

Also going to locate some vacuum gauges and see what I come up with. Also still need to test the computer ground wires.

I will have a full weekend ahead of me.
As long as vac source  connects directly back to manifold and isn't leaking, it ain't gonna make any difference... 18" of vac is 18" of vac...

87 T-bird W/92 5.0 Swap High Idle

Reply #12
1. Turn the key on without starting. the fuel pump should run for 1 or 2 seconds and shut off. If the pump runs continuously it means the EEC software is not working and you are running in limp home mode. Or a previous owner has hay-wired the pump circuit to keep it running.

2. When you pull codes, try jumpering the pigtail wire to ground instead of to the signal return in the main connector. If you now get codes, it means the signal return circuit is blown out. Probably a blown land pattern in the EEC. (This can be fixable).

87 T-bird W/92 5.0 Swap High Idle

Reply #13
EEC ground:

87 T-bird W/92 5.0 Swap High Idle

Reply #14
Quote from: EricCoolCats;462921
It just seems like most of the people with the EEC testing issues happen to have the full digital dash. I don't know if that's coincidence or not. Just an observation.

I have the full digital dash and a MAF conversion with an A9P. EEC puts out codes fine either with a paper clip or scan tool.

It's possible people aren't very fastidious about wiring, which accounts for the issue.
88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, bunch of other stuff.