Engine No power after idle

Hey guys and gals! My name is Justin and I need help. To give a little background on myself. I have been a diesel mechanic for the last 20 years and I built Foxbodys on the side for around the same amount of time. I’ve ran into almost every problem you could think of but this one. I have a 90 mustang GT that’s been sitting in a barn for the last 24 years. The car has original 40,000 miles. I had to change the fuel pump and fuel tank, obviously changed all of the fuel lines, the fuel injectors, and the fuel rail because they were full of crud. I have replaced the whole ignition system with all original Motorcraft from spark plugs ,distributor ,distributor cap ,spark plug wires, and ignition coil. I replaced the TPS sensor because it was really out of range and did the base idle reset. I had a problem with number eight injector where the signal wire was opened. I got that fixed and got the injector working. I pulled the EEC out and replaced all three capacitors because they were messed up, it has an A9L EEC. I also went through the EEC and tested the other components just to verify everything is good. I have tested every sensor on the engine tested sensor function with everything giving the proper values. I am having the correct fuel pressure at idle and WOT. Here is the issue at idle. It runs good. It is running a little rich but running good regardless I have ran my timing from 10° to 12° to 14° with all the same outcome I decided to stay at 10 since the car is non-molested. When you start to takeoff in the car, it completely falls on its face and shuts off and will not start back until it cools off unless I hold the pedal to the floor to tell the computer that the engines flooded and then it will fire. I went back and checked my TPS sensor just to verify correct operation and I’m at .98 with a smooth transition to 5 V. I have completely unhooked every single vacuum line and smoke tested the engine with zero vacuum leaks. I checked the ignition coil and swapped it out just in case I was missing something with the same outcome so I put the new one back on. I swapped the maf sensor even though it tested good just a double check. Sorry also no CEL. I have checked all of the grounds and they all seem good. At this point, I’m absolutely stuck and passed the frustration part. Does anyone have any ideas to give me before this car turns into a carburetor car lol (jk)

38ish idle and 44ish at wot

Sorry, and it stay steady

JustinTilley86 said:

Sorry, and it stay steady

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I have checked the codes on this car more times than I’d like to admit at this point. Nothing but the tps the whole time but thats fixed now.

89ripper said:

Hey Justin. I am Justin too, nice to meet you. These kind of problems can drive you nuts. Kind of hard to diagnose without being there. So it always cuts out when you put it under load? I was a little confused because you mentioned fuel pressure under WOT

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So when the car sits, I can get it to tack up to about 3500 before it starts cutting out. Sorry I should’ve been more specific. The car is running extremely rich for some reason. When I put the car under a load is when the car will shut off and will not start back kind of like I flooded the engine, but I will pull the plugs and they will be just as dry. At this point, I’m starting to wonder if I have two different bad distributors.

89ripper said:

Yes...I was beginning to think ignition at first but had to understand what you were talking about with regards to fuel. So you took the original distributor out, and replaced it with another?

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Yeah, it’s a brand new Motorcraft distributor. And it was still the exact same thing which is why I had originally purchased this one because I thought that distributor wasn’t giving it the correct timing. I’m about to start pulling the bottom half of the dash out just to see if possibly a rat got in there and chewed on the wires, but I haven’t saw anything as of right now

General karthief said:

I think you need to go through this checklist:

Help me create the "Surging Idle Checklist"

Updated 05 July 2022 to add rough idle when cold and smooth idle when up to normal operating temperature. See the EGR tech information, section #15 for more help. Many of you are familiar with the "Cranks OK, but No Start Checklist for Fuel Injected Mustangs" checklist and the No Crank...

www.stangnet.com

before you start pulling wires under the dash.

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I’m gonna print that out when I get to work I can tell you I’ve probably went through at least 95% of that. I’ve went to the extreme of pinning out every single wire that goes to every sensor switch other harness connection. But either way, I will run through this whole entire list again just to make sure I didn’t forget anything so thank you for the list that was pretty detailed.

89ripper said:

Also I wouldnt have replaced stock distributor mine is still good has like 186000 miles on it.

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Normally, I would not do that, but this thing is killing me

AeroCoupe said:

Yeah pulling codes can get old and 100% agree on running through the checklist and checking for vacuum leaks.

Are the injectors the originals? If so I would recommend having them cleaned. If the rest of the fuel system was crudded up then I would almost bet they have some issues. If they cannot atomize/spray the fuel correctly it will cause all kinds of issues. Being a diesel mechanic you know about injectors and hopefully have access to or know a shop that can do the work.

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As far as the fuel system goes, everything is brand new and I’m talking about everything from fuel lines to the fuel rail. I mean, I changed everything. As far as vacuum leaks goes I unhooked every single vacuum line, even the fuel pressure regulator and smoke tested it. I’m gonna run through that complete checklist again tomorrow hopefully I just miss something.