Need help with our Supercoupe

rwferguson

Registered User
1994 SC has been upgraded with a built bottom end. The car is very familiar on this page. My Dad recently toke the car to the shop to get some things fixed and checked. The shop replaced the sending unit in the gas tank among other things. The car ran great prior to dropping it off to the shop. When the shop tried to use the obd1/2 port they stated they weren’t getting a connection to figure out why the CEL is now on.
So here’s our problem!

The car acts like it’s a miss fire, horrible hesitation, won’t idle, and have to use starting fluid to get it to start.

when it’s running it dies if u don’t back the gas off slowly. We just changed the plugs and still no change. I noticed a vacuum line that broke and fixed it but still no change. The car doesn’t have an egr valve and is spitting out black liquid which smells like raw fuel. We also replaced the MAF thinking maybe that was an issue because when we unplugged the old MAF nothing changed. Something is horribly wrong with the poor girl and I’m visiting my dad hoping to get her up and running again. Now the plugs were coated it black build up! What I think is happening is the car has default to full rich dumping too much fuel into the engine and blowing spark out. I’ve did some poking around on the forums and may have narrowed it down to the following:

Fuel pressure regulator
O2 Sensor
ECU lost the tune
Bad ECU
Vacuum leak
Clogged IAC

so any help would be much appreciated!! We have been members for 10+ years maybe even longer tbh. I’ll post a video on YouTube so y’all can also see what’s going on. I’m hoping somebody can help pin point this problem. Thanks in advanced for any help and anything right now is much appreciated because we are completely stumped. The shop can’t even figure it out as well
 

MadMikeyL

SCCoA Member
If the car was running good before being dropped off, then the shop screwed something up. Let us know everything the shop did and that will give us some clues as to where to look.
 

rwferguson

Registered User
If the car was running good before being dropped off, then the shop screwed something up. Let us know everything the shop did and that will give us some clues as to where to look.
So according to Dad they replaced the sending unit in the gas tank and fuel filter. According to the shop they were clueless on why it was running like crap. But before they dropped the tank the car ran perfect! So we are baffled on what it could be. The car is running full rich and is literally blowing fuel out the back exhaust tips. Checked fuel pressure and it within spec, changed spark plugs which were fouled out with new motor craft double platinum, replaced the MAF and nothing. We have checked and replaced everything that may cause the car to run so rich with no improvement. Now here’s the odd part. The CEL is on but when I try to read the codes I can’t get a connection to the ECU, even did the jumper trick to force the CEL to flash the codes out but didn’t do anything at all. Almost like the ECU is disconnected or in limp mode. Are there any connection near the transmission or gas tank that we need to be looking at?
 

MadMikeyL

SCCoA Member
My first thought was that maybe they pinched off the return line when putting the tank back, but if the fuel pressure is in spec, that rules that out. There is nothing near the fuel tank or trans that would affect the fueling. Were all the plugs fouled, or just certain ones? Try unplugging the O2 sensors to see if it gets any better.
 

rwferguson

Registered User
My first thought was that maybe they pinched off the return line when putting the tank back, but if the fuel pressure is in spec, that rules that out. There is nothing near the fuel tank or trans that would affect the fueling. Were all the plugs fouled, or just certain ones? Try unplugging the O2 sensors to see if it gets any better.
Yes every plug was coated it black. We are thinking at this point the ECU lost its tune or the ECU is bad.
 

rwferguson

Registered User
Update:
Sorry everyone we have finally confirmed the Moates Chip lost battery power and we are assuming we lost the tune. I disconnected the chip from the ECU and reinstalled the ECU. The Supercoupe is now up and running! Night and day difference. The CEL is off rn but we know it’ll come back on. We are trying to get ahold of Moates to see if they will let us upgrade the chip with one that has a replaceable battery. We have reached out to Dave from Super Coupe Unlimited for assistance as well. Wish us luck! We are super thrilled rn. We have done some research and there’s a possibility even though the chip has a dead battery the tune is still in the memory. Trying to talk Dad in letting me replace the BR2330A battery with the CR2032 battery. If by chance anyone knows how we can replace it please let us know also if you know about if we lost the tune or not. Again!! Thank you all for everything you have no idea how much this means to my dad rn. He is going through a very hard time in life rn and this car is something he loves. Again i can’t thank y’all enough for all the support, ideas, comments, and even people who read the thread but didn’t know thank you. This is an amazing community and I’m so grateful for all of you!! Hope you and your family’s stay safe.
 

MadMikeyL

SCCoA Member
I didn’t realize the car had a quarter horse on it. A dead battery in that would definitely cause issues.

Yes, the tune will still be stored on the quarter horse even with the dead battery. The newer ones have a socket for a CR2032 instead of the battery soldered directly to it. If you are good at soldering, you can do that yourself, or I think you can send it back to moates and they will do it for you, for a fee. Either way, you should also get a J3 chip and burn the the tune onto that for daily driving. The chip has no need for a battery, and will eliminate the possibility of it failing again.
 

rwferguson

Registered User
I didn’t realize the car had a quarter horse on it. A dead battery in that would definitely cause issues.

Yes, the tune will still be stored on the quarter horse even with the dead battery. The newer ones have a socket for a CR2032 instead of the battery soldered directly to it. If you are good at soldering, you can do that yourself, or I think you can send it back to moates and they will do it for you, for a fee. Either way, you should also get a J3 chip and burn the the tune onto that for daily driving. The chip has no need for a battery, and will eliminate the possibility of it failing again.
Yes sir! Dad looked the company up lastnight and they upgraded one with the removable battery is 100.00 but we were concerned how long it would take for them to send it back to us. Their site states they only work Tuesday, Wednesday, and Thursdays. May try calling another company that works with them per their website and see if they could possibly get something done faster. The car has been sitting for a couple years now which is why dad toke it to the mechanic up the road . Technically wasn’t their fault at all but we appreciate everything once again. We are super excited we found the issue with y’all’s help and can’t wait to take it around town. She pulls right around 18 lbs on the daily driver tune. Ig there is 2 other tunes but the octane needed for them is pretty hard to find. Like to try the race tune but have to find 101 octane in GA. She is a mean car lol. Scares me at moments but you have to be careful and on your toes when you wake her up lol
 
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