*Intermittent no start, can't chase it down*

[m00k_]

were you able to verify your trouble codes? AutoZone will check them for free.

The car is not road legal yet so I cannot take it anywhere just yet. But I know from prior experience that all three of my local parts stores (O'Reilly, Napa, and Autozone) will not try to check codes on an OBD-1 system. They've told me before they will only do OBD-2

 

[35th]

I doubt autozone will check trouble codes on OBD I

 

[m00k_]

were you able to verify your trouble codes? AutoZone will check them for free.

I got a hold of a code reader capable or connecting to the EECIV connector and no luck. The code reader kept saying no connection to vehicle when it would try to pull the codes. There is some disconnect somewhere between the plug and the ecu. Is it possible the pins fell out of the plastic plug and got put back into the wrong holes? My old Mustang had that problem then self test connector was so wore out the pins didn't like to stay in the plastic. They didn't seem loose on this thunderbird though.

 

[DOUG H]

I know its a silly question, but you did have the key turned to run or it was running?

 

[m00k_]

I know its a silly question, but you did have the key turned to run or it was running?

Yup. And I kind of suspected something was amiss because when I first started this thread I tried to pull the codes by using the jumper wire method. Did it plenty of times on my Mustang, and nothing at all would happen with this thunderbird.

 

[m00k_]

I know its a silly question, but you did have the key turned to run or it was running?

I was finally able to pull codes today. Got codes 511, 341. Then code 512 was stored in memory. Also while pulling the ecm out inorder to do some dvom testing at the computer connector I found something very strange. A circuit board coming out of the bottom of the pcm case (picture attached), covered with tape to protect it I suppose. Obviously the tape is not normal but is the circuit board supposed to stick out the bottom and maybe it's just missing the factory cover? Or is this some sort of "performance" chip installed by someone? I've never seen an eecIV look like this. Lol

 

[SuperChicken89]

I was finally able to pull codes today. Got codes 511, 341. Then code 512 was stored in memory. Also while pulling the ecm out inorder to do some dvom testing at the computer connector I found something very strange. A circuit board coming out of the bottom of the pcm case (picture attached), covered with tape to protect it I suppose. Obviously the tape is not normal but is the circuit board supposed to stick out the bottom and maybe it's just missing the factory cover? Or is this some sort of "performance" chip installed by someone? I've never seen an eecIV look like this. Lol

That appears to be a aftermarket chip. One of the codes should indicate a chip has been installed but don't remember offhand which code. Someone has done some tuning on that car. I don't recall you stating the year of your SC but the 89/90 EEC-IV computers have a chronic problem with the electrolytic capacitors leaking on the circuit board causing all kinds of problems. I've had the two EEC-IV computers go bad in my 89 SC due to the leaking capacitors. I've been successful replacing and repairing three 89 EEC-IV computers so far.

 

[DOUG H]

511 is READ ONLY MEMORY TEST FAILURE, usually get this when any type of chip is installed
512 is PCM POWER INTERUPT IN KAM-(Keep Alive Memory), ECM lost power unexpectly with key on-disconnected battery or bad connection in battery supply to the ECM
341 is CAM SENSOR RETURN CIRCUIT OUT OF SPEC.

 

[m00k_]

That appears to be a aftermarket chip. One of the codes should indicate a chip has been installed but don't remember offhand which code. Someone has done some tuning on that car. I don't recall you stating the year of your SC but the 89/90 EEC-IV computers have a chronic problem with the electrolytic capacitors leaking on the circuit board causing all kinds of problems. I've had the two EEC-IV computers go bad in my 89 SC due to the leaking capacitors. I've been successful replacing and repairing three 89 EEC-IV computers so far.

The car is a 93. I did open the case and checked the capacitors as I had read about them leaking sometimes and as far as I can tell there is no leakage from any of the caps and no burnt or broken traces on the circuit board. Had to repair a burtn trace on a Mustang ecm before so I was sort of familiar with what to look for in that regard.

 

[m00k_]

511 is READ ONLY MEMORY TEST FAILURE, usually get this when any type of chip is installed
512 is PCM POWER INTERUPT IN KAM-(Keep Alive Memory), ECM lost power unexpectly with key on-disconnected battery or bad connection in battery supply to the ECM
341 is CAM SENSOR RETURN CIRCUIT OUT OF SPEC.

Code 512 would make sense because I believe I forgot I had the key on once when I disconnected the negative terminal in order to start poking around and testing things. Found out when I hooked it back up and the fuel pump kicked on lol. Is there a way to test the cam sensor?

 

[DOUG H]

Keep in mind, 341 is for Cam sensor circuit which means it could be a problem anywhere between the sensor & ECM.
Could be the sensor, DIS module & any harness in between, even the connection at ECM.

 

[drtybird]

I was wanting to start with the basics and do the KOEO and KOER tests to pull codes before posting here, but aside from the mysterious no start that comes and goes, the self tests wont even start. When I use the jumper wire and turn the key to start the test I a loud constant tone and the CEL and and a yellow light with a black arrow point up illuminate constant. I have a little bit of experience with the EEC IV self testing system as I used to own a fox mustang. Never seen this behavior before.

A little back story on this car, I bought it out of state and drove it about 6 hours home. and noticed two issues right away. Both times I stopped for gas the car wouldn't start back up again. Ultimately the car just decided to start again after sitting a few minutes. Once the car is running it stayed running no problem. The second issues i noticed was when under 2000 rpm the throttle pedal basically does nothing. The car will not accelerate and stumbles a lot. Once above 2000 rpm the car accelerates just fine, which was fortunate for me because 99% of my drive home was highway, so I just made sure to keep it just above 2000 rpm when cruising.

On the intermittent no start problem, I do not believe its fuel related as starting fluid did not help, and after a few cranks you can smell fuel pretty good. So I figured ok, its a no spark issue then. So I grabbed an inline test light and hooked it up between the coil and the number 1 spark plug, to confirm no spark. Had a friend helping me and he started cranking before I could get the test light fully seated, and to my surprise, I got a pretty hefty shock from the coil. That perplexed me even more. It seemed to me this no start issues was related to engine temp. it may be just coincidence but it seemed like once the engine got to operating temp it wouldn't start once you turn it off until it had sat for a while. I tried starting the car again today (making sure the jumper wire was removed from self test connector) after trying and failing to run the KOEO test and it started right away but the CEL start flashing immediately.

It flashed I believe 8 or 9 times, with a pause then another 8 or 9 times. that's when I realized it was a pattern and paid closer attention. it then paused and flash 1 1 3 then a pause and began to flash 1 1 and then the car died as it was trying to flash the last digit, which I believe was going to be another 3. and now the car won't start again. I am going to wait a while and try and start the car again, this time I will record the CEL and post it below.

So now I'm here, asking for input from those who most assuredly have more experience than I do lol.

Things I've noticed that the previous owner had changed are that it seems to have an after market MAF sensor as the housing is made of black plastic instead of cast aluminum. The pigtail next to the MAF connector on that harness isn't plugged into anything and actually has one of the wires cut. Sorry for the long post, trying to provide as much info as I can that might be relevant.

I have had the same issue.

I believe the IAC motor causes this.
I changed the IAc and it fixed.

Mine would run fine even for long drives. Once I shut it off it would crank and crank. Without starting. Towed home then turn the key and perfect start.

 

[m00k_]

I have had the same issue.

I believe the IAC motor causes this.
I changed the IAc and it fixed.

Mine would run fine even for long drives. Once I shut it off it would crank and crank. Without starting. Towed home then turn the key and perfect start.

I'll keep that in mind for sure, right now I am waiting on some parts to hopefully sort out a low fuel pressure issue discovered in the process of trying to figure this out lol

 

[drtybird]

I'll keep that in mind for sure, right now I am waiting on some parts to hopefully sort out a low fuel pressure issue discovered in the process of trying to figure this out lol

That issue you have is so embarrassing I feel for you. Since I was changing sensors I did the cam sensor and the coolant temperature sensor.

 

[drtybird]

That issue you have is so embarrassing I feel for you. Since I was changing sensors I did the cam sensor and the coolant temperature sensor.

If you think you have fuel pressure issues. Fuel pressure regulator and the 255lph fuel pump is a good way to eliminate factors for low pressure

 

[m00k_]

If you think you have fuel pressure issues. Fuel pressure regulator and the 255lph fuel pump is a good way to eliminate factors for low pressure

Yeah waiting on a regulator now. And I thought about replacing the cam sensor, crank sensor, and ign module. Since I do not plan on keeping this engine in the car long term, I can't justify spending the 1100$ on the kit for those three items lol

 

[m00k_]

Sorry it took so long guys, I sure this thread is dead by now but the fuel pressure regulator just arrived a couple days ago. I bought the bullet adjustable unit from super coupe performance. I swapped it out and set the koeo fuel pressure to 40psi. Car started up but the fuel pressure never dropped it stays solid at 40 psi.

Yes the vacuum line is connected to the regulator, and I also connected a vacuum guage and the engine is pulling 12-13 in. Of vacuum at idle. And now it seems like it's backfiring out the mufflers fairly consistently. (1 or 2 times every five or ten seconds)

 

[m00k_]

Here is the worst of it.

 

[drtybird]

Sorry it took so long guys, I sure this thread is dead by now but the fuel pressure regulator just arrived a couple days ago. I bought the bullet adjustable unit from super coupe performance. I swapped it out and set the koeo fuel pressure to 40psi. Car started up but the fuel pressure never dropped it stays solid at 40 psi.

Yes the vacuum line is connected to the regulator, and I also connected a vacuum guage and the engine is pulling 12-13 in. Of vacuum at idle. And now it seems like it's backfiring out the mufflers fairly consistently. (1 or 2 times every five or ten seconds)

I have had all these issues. Cam sensor and IAC motor.

These tow sensors were the Bain of my existence for a long time. I've towed it home and then it work fine. IAC would cause the car to not start run funny back fire and sound like shit.

 

[drtybird]

I have had all these issues. Cam sensor and IAC motor.

These tow sensors were the Bain of my existence for a long time. I've towed it home and then it work fine. IAC would cause the car to not start run funny back fire and sound like shit.

These sensors are not break the bank I would swap them out asap