So the swap went real well. Heres what I dealt with.
Its an 88 mustang gt convertible. I changed the SD ecu with an 89 A9P.
I swapped the ecu harness with one that I was told was from an 89 car.
The car runs great when it runs. Recently I have an interminent issue with the fuel pump. It has cut out while running before. Mostly the relay won't kick on key on. I've heard stories with 90+ mass air harnesses wrecking havoc on FP relays due to those cars with air bags. Did this guy who sold me the harness lie about the year it came out of? Or is this a seperate issue? In the case of incompatible year harnesses shouldn't the FP relay just not work at all, not intermentantly? Or should I just replace the relay and this is freak coincidence? Any advice or links would be greatly appreciated, spring is near and I wanna park the big diesel. I'm not sure where to proceed next. Thanks in advance fellas.
I should have added, with enough key on key off cycles, I can get the relay to finally kick. I'm stumped
Ignition switch ever been replaced..?
I don't think so. I couldn't tell ya what the last owner did though.
Since you had the problem before the swap, I wouldn't think the harness would cause it. An Ignition switch can play havoc on a few problems. The other option is to test to see if you get juice to the relay repeatably.
No, no problems before the swap. Immediately after the swap the car ran fine. Its intermittent. Ran all day yesterday, today I got to my destination and it cut out, after a million key cycles I couldn't get the relay to pick, so I towed it home. Now the car runs fine again. until next time.
Why did you swap the harness instead of just adding the MAF wires to the 88 harness? It is really easy to just add the MAF wires.
Have you tried replacing the relay and checkin grounds to the relay??
I thought there was a wire that had to be run to the back the fuel pump relay when a
car was swapped over to mass air
where on a mustang is the relay? on the harness you changed or under the seat i'm asking to see if the fuel pump monitor wire the mass air computer wants is hooked up or not. i'm in the middle of a mass air conversion (stupid speed densidy harness) during an carb to Efi upgrade (84 fila tbird)351w 5 speed from carb aod and i'm having lots of fun with wiring right now also.
I changed the harness altogether to try and solve another issue that I had, which seemsto have worked. I did not run the FPM2 wire, the relay is under the drivers seat, I already changed it.
You do not need to run the wire for the fuel pump monitor. You'll get a code 95 for the fuel pump monitor but it won't affect the operation of the EEC. I didn't run that wire when I did the MAF swap and it runs fine. Did you run the wire for the speed sensor? If you didn't you should or you'll have some stalling issues on deceleration.
I did not run the VSS, Haven't looked to see if I even have that sensor yet, its a non-cruise equipped car. Everything sounds like that the culprit, but when that reported stalling issue takes effect, why the hell wont the fuel pump relay pick again. I can put my hand on it and nothing happens with it, which is why I changed it itself first. The car renders itself useless for a while and I'm stuck borrowing a tow truck. Then hours later after its home, it'll work again. If I get time tonight I'll run the VSS to try. My next suspect was going to be the ignition switch. For $11 its a cheap thing to change. The key and cylinder doesn't seem perfect, it works fine to the rest of the car but for some reason my mustang ignition key, is a one-sided tooth key. Never seen a ford like that in all my life. During pulling codes on a fresh batt hookup I obviously got no continuous codes, just the ones that I should for thermactor and egr since that stuffs has long been removed from the car. Not once have I gotten a FPM2 or VSS code yet. Yesterday the pump relay ped out for a second so I unhooked and rehooked the batt and it seemed to have got it working again. So far thats the roadside persuasive fix but this shiznit has gotta stop. Any other thoughts or ideas welcome, next step I'm gonna run VSS I think.
Keep at it, you'll get it! Make sure you post up the fix to help us that haven't done the conversion yet.
Still didn't investigate further yet but the car has been getting me around all day.
3 days it went with a new batt/eec reset. Failed today at work in the parking lot. Took about 75miles I'd say. So I'm running FPM2 right now, pin 19 is empty in the harness. When I get to VSS, there is a green wire in pin 6 at the eec. Pin 3 is empty. What the hell is pin 6 doing there and why is it green? Any ideas?
Check your grounds, and the Power relay by the ECU. It sounds like your computer may not be turning on at all. Make sure you have the ground lug that attaches right at the ECU is good and sung, and it wouldn't hurt to run a resistance check from the neg battery post to the ground lug.
If thats all nice an snug, see if the computer is supplying 12v on the fuel pump line at the ecu connector when you first turn on the car.
When I did my swap. I "tested" to see if the computer was working by popping up the distributor out of the block (so it would clear the cam but still touched the block-IMPORTANT). Then I rotated the cam button and listened for the (injector fire, then plug fire) of each cylinder. I would check your grounds first. Mine works fine without the FPM line.
-Z
Check that last post of mine. I was looking at the eec connecter backwards, all needed wires are present. Its an 89 harness from, god knows what. into my 88 convertible. Should I tap into these wires or is it already plug and play. Which explains why I haven't pulled a code 96 yet. Least not on a fresh koeo or koer.
Also as well, Failed to mention... duh. Theres no EGR in this car. Valve is blocked off and gone. Thermactor and smog is idios too. The harness are just hanging. Should I least leave the egr sensor hanging? Least it'll pick it up as WOT the whole time. It was my previous understanding that if the sensor is gone and there is circuit failure of EGR, that the mass air ecu doesn't put it into calculation. Or is it still trying too? I really need a ecu guru, someone whos tuned these things before. Cus a tweecer I think is next before the blower goes in.
The FPM nor the speed sensor have diddly to do with the FP relay kicking in... You need to do some real troubleshooting with a test light at pin 22 of the EEC to see if there is a signal being fed to the relay...
Also you can ground the tan/green wire in the EEC test plug, if wiring, relay and pump are OK, pump will run even with the EEC tossed out into the street...
Well... I'm wondering where the chassis' FP/FPM2/VSS wires hook up into the EEC harness. I'm gonna start tracing and see what the deal is. I can't find my friggin multimeter anywhere now that I need it. I did find a black/Orange wire on the chassis harness near the eec test port where the two mate together. This black/orange wire ran into my SD harness on the eec test port, atm its just chillin there loose. Not sure what this guy does or if its related. Also my EGR question still goes unanswered, the sensor is in a box in the garage, should I hook it up and let it hang at least or leave it with an egr circuit failure code. Not sure if the A9P calculates this or not when its not present. Due to this being intermittant I'm starting to wonder if I bought a bad eec.
EGR has nothing to do with the FP relay operation either...
rofl so as I'm hitting my head wondering wtf is wrong with this car. I'm following all sorts of wires with the key on. And then it happens! BEHOLD! I touch the eec power feed wire at the solenoid, and the whole car just reboots. touch it again, restarts again. just the slightest motion triggered it. So I cut the wire back, recrimped and hooked it back up. Haven't had a problem since. Also checked every ground and adjusted everything else. So far its still running. The wire previously had what appeared to be a nicely done shrink tubed crimp. but evidently I was wrong. I'll keep everyone posted if the car dies out again. I do experience some stalling to a stop issues. I suspect thats vss playing its part. Its a non-cruise car so I don't think I even have the sensor. We'll see as time goes on.
Gotta love the electrical gremlins..... Congrats on the fix.
I was close. Good work.
I may soon have one for sale
I had this problem on my V8. I had cleaned and oiled and disassembled my IAC about 4 times. The car would run great but would have idle fluctuations and whenever I came to a stop, it would almost stall, sometimes it would. I reset my base idle about a dozen times.
I finally broke down and replaced the IAC with a brand new one. It runs like a sewing machine now. I guess the old IAC was still sticking.
-Z
Agreed the iac should be checked 1st.
Hooking up the vss wires would be a good idea. It might help correct a stall on decel and if you ever log with a tweecer you will be able to see your speed which is helpful.
Glad you found the main wiring issue!
Is the IAC on a 2.3 the same as the 5.0