93 lx 5.0 conversion

[FoxF350]

Hi everyone,

I’m from Florida with a 93 fox. It used to be a 4 cylinder teal car, I bought it as a black 5.0. I love the car, but so far it hasn’t loved me haha. I’ve had my fair share of issues, so I’m hoping to get a little more involved in this community. I also really need to take some better pictures, but so far the focus has been fixing her up.

 

[broncojunkie]

Welcome! I'll be down in FL here in a couple weeks for work. I can't remember the last time I was there on vacation. We have family in Tampa and Daytona, though.

And yes they all have their share of issues by this point! Poor quality of most aftermarket parts doesn't help much!

 

[Erkenbrand]

Welcome! Issues come up. Any big ones you're tackling?

 

[FoxF350]

Welcome! I'll be down in FL here in a couple weeks for work. I can't remember the last time I was there on vacation. We have family in Tampa and Daytona, though.

And yes they all have their share of issues by this point! Poor quality of most aftermarket parts doesn't help much!

Well hopefully the airports aren’t flooded still when you arrive haha if you’re flying that is.

 

[FoxF350]

Welcome! Issues come up. Any big ones you're tackling?

Thanks! And yes… my ecu went bad, I think… I took it to get repaired, and it was “repaired”. Now it starts but immediately dies.

Longer version is, I finally fixed some coolant leaks and put new tires on it, noticed the car seemed a little low on power, and it was running very rich. Didn’t think too much of it, and drove about an hour away, and it started running terribly. Kinda like it’s misfiring but worse. It felt like the car was just cutting out and turning off almost and it made some awful noises, it kept dying on me, and the temperature gauge was fluctuating like crazy, along with the tach sometimes. I raised the idle RPM and it kept it from dying on me, and luckily I made it home. It wasn’t terrible at highway speed around 70, but any acceleration and it would run awful, and have no power.

I tried to start the car the next day and it wouldn’t start, it would however start and run a little off of starter fluid, but not on its own. I then listened for the pump and noticed the pump would not stop priming (with the key on) tried swapping relays with the ac WOT relay but when I did that it didn’t prime at all, my AC has never worked so I assume that relay may be bad. After some research I saw the computer could be the issue, and I could see some darkening around the capacitors so that’s what made me believe it was the problem. The guy I brought it to said he replaced a bunch of things. But after putting the computer in now it will start, then immediately die. If I give it throttle nothing different happens, it doesn’t rev up or last longer or anything. I haven’t had a moment to do more diagnosing, I saw a post somewhere that said to disconnect the computer and turn the key and see if it continually primed or not, and if it does it’s not a computer problem, if it stops or doesn’t prime then it could still be the computer is my understanding.
I also need to see if it stays running until I let go of the key or not, some were saying that could be the problem.

I know that was a lot and I should probably make a post elsewhere but I wanted to do some more tests first to see if I could figure anything out.

 

[Blueknights75]

FoxResto in Locust, NC are true experts when it comes to ECU rebuilds. Definitely a great company and very knowledgeable people there. Highly suggest using only OEM parts for any electrical issues…trust me on this one as I dealt with many electrical gremlins and started replacing everything I could with Ford OEM parts.

 

[Erkenbrand]

+1 on sticking with OEM and a place that knows what they're doing. I swapped the drive line from a 91 GT into a 1992 Ford Explorer (that was a fun project), but it just wouldn't run right with similar problems you're reporting. I finally narrowed it down to the ECU. Pulled one from the junk yard, no luck. Sent it out to have rebuilt, and when it came back everything worked great. I don't remember who worked on it. That was 20 years ago or so.

 

[FoxF350]

Any tips on how to confirm if it’s still the ecu?

 

[broncojunkie]

Any tips on how to confirm if it’s still the ecu?

I'm really not sure on that one. I know that the most common problem is that the caps will leak and disintegrate the legs that connect them to the board. In the past, if I suspected the ecu, I would just pull it and inspect for this problem.

Judging by your description of a pump that doesn't stop priming, although I haven't personally experienced it, I've heard about that being a common symptom of a bad ecu.

The other symptom you are referring to (dies immediately after it starts), I have experienced that one myself. After being stumped for months, having replaced and tested everything I could think of, I finally realized I could leave slight thumb pressure against the key as I started it. In other words, don't let the key spring back to the run position on its own. The original ignition switch had completely fallen apart after sitting for 15 yrs or so. I replaced it with a parts store aftermarket cheap one. It worked fine, as long as you did it this way. I chalked it up as a theft deterrent. If you haven't already, I would suggest checking the ignition switch.

 

[FoxF350]

I'm really not sure on that one. I know that the most common problem is that the caps will leak and disintegrate the legs that connect them to the board. In the past, if I suspected the ecu, I would just pull it and inspect for this problem.

Judging by your description of a pump that doesn't stop priming, although I haven't personally experienced it, I've heard about that being a common symptom of a bad ecu.

The other symptom you are referring to (dies immediately after it starts), I have experienced that one myself. After being stumped for months, having replaced and tested everything I could think of, I finally realized I could leave slight thumb pressure against the key as I started it. In other words, don't let the key spring back to the run position on its own. The original ignition switch had completely fallen apart after sitting for 15 yrs or so. I replaced it with a parts store aftermarket cheap one. It worked fine, as long as you did it this way. I chalked it up as a theft deterrent. If you haven't already, I would suggest checking the ignition switch.

She runs! Turns out it was the TPS sensor, got to looking at it and realized someone before me had used butt connectors to crimp it but had left wire exposed and the wires were touching. Wiggled them free and she started and ran! Now it does feel like it’s missing at constant throttle but seems to be good at full throttle. In a video I watched the TPS sensor caused that problem too so I’m likely gonna order a new one. Maybe I’ll gain enough effort to actually test the sensor first haha. Here’s a video of it at constant throttle in case anyone has other thoughts. Also think it may still be lacking in some power… but never driven another one to know for sure.

 

[Erkenbrand]

Yay for easy fixes!! That's fantastic.

 

[broncojunkie]

Ah.. the ol tps! Gotta hate those lol! Keep that on your radar. They like to go out and cause problems! Glad to hear you got her going!

 

[FoxF350]

She’s going but even after adjusting the voltage to around .92/.93 it’s not running quite right. Putters during constant throttle and sometimes on acceleration it cuts out and even though I’m not moving the pedal it’s sounds like I’m repeatedly pressing and unpressing the pedal quickly. Does that sound like the tps is bad? I tried to check with the car on and I didn’t see it bouncing voltage but I couldn’t check while driving.

 

[broncojunkie]

There are two tests you can do. One is for voltage and the other is to see if you get a smooth transition throughout the sweep. Does it only act up at part throttle? How's the idle and full throttle?

 

[FoxF350]

There are two tests you can do. One is for voltage and the other is to see if you get a smooth transition throughout the sweep. Does it only act up at part throttle? How's the idle and full throttle?

Idle seems pretty normal, however it does kinda sound like it has a cam and I don’t think it does. At full throttle sometimes it’s fine, other times it cuts out bad and the revs jump like crazy and it’s pretty violent.

I didn’t see if it’s smooth through the sweep I can try that.