95 gt, known to run but now doesnt run so well

[thelastofthem23004]

I've got a 95 GT that was running very well and then suddenly didnt want to run well at all. This is how it went down, and I do put this BEFORE I tell mods for a reason. Please read until the end, Thanks in advance for your time reading.
Car was down for about 2 years due to a transmission issue (AKA I'm a dumbass and shifted into first when I meant third).
New trans in with new clutch as of mid May, drove home no problem.
Got new front tires on (so I could run my welds) and off we were.
Plenty of high RPM shenanigans, and all that. Things were going quite swell.
I went for a drive the other day, and it fired right up, we went for an easy run (nothing past 3/4 throttle) and it ran well. I got to the part of the drive where I wanted to really go and it wouldnt go above half throttle. I fueled it up (because I thought it had gotten ahold of some bad fuel) got two more blocks and I had to walk. Read up on it because I thought I might be suffering from vapor lock (high humidity and heat in my area) and sources pointed me to the fuel filter. I accepted this because of the rarity that vapor lock is on fuel injected vehicles. I was unable to start the car after I had to walk home to grab my tow vehicle. I decided to change the fuel filter.
Fuel filter is now changed! I'm getting the fuel pressure I've always gotten at the fuel rails. The car starts and runs very well dir ectly after starting. The longer it runs, well the worse it gets.
I know that engine mods are a factor on every build, however, I am trying to do a troubleshoot on a car that ran fine before this, and now does not. Yes mods can be a factor, but mods are (in most cases) direct replacements for stock parts. If there is a thread related to this I would appreciate the fuck out of a link to that thread. Otherwise your best thoughts on the matter would be greatly appreciated

 

[Silver95bird]

I could be wrong, but i wonder if the TFI is going. I know theres a tfi checklist, hopefully someone has a link.

 

[evilcw311]

Still need to know mods. Here’s a great example why.

Let say you did a complete msd ignition system. We could then say it’s a great chance it’s the msd coil cause they are notorious for problems like this. But we don’t know so we can’t help.

This is like going to the doc and saying my chest didn’t hurt yesterday but it’s hurting today and that’s all the info you need. Now tell me what’s wrong.

Help us help you. Obviously the fuel pump is fine so it’s more than likely an ignition problem. Or is it?? How did you Check fuel pressure and what did it read?


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[ttocs]

sounds like you kept the old gas in the tank? How much was there? I recently chased similar gremlins all around the fuel system till I realized the tank was dirty and making the fuel bad. After all the time I had in it I just swapped out the tank but I would recommend starting by draining the tank, replacing the filter again and then cross your fingers and hope you didn't dick up the injectors bad enough to be a problem. Try a fuel system cleaner additive when you put the new gas in.

 

[thelastofthem23004]

Ok, so finally I got a new MAF installed. I figured I would start there because when the old MAF was unplugged the car would start. It wouldnt run well, but it would do more than it would with the old MAF. Now that the new MAF is in the car starts and idles great! Its the best it has ever idled. Unfortunately...... I cant go above half throttle before it begins to cut out and miss. It doesnt die or fail to idle once i've let off of the throttle, but everything over half is just no, It wont do it. So since I've routed out fuel and the MAF, i suspect the TPS. The TFI is not something I'm familiar with and if I have the stock one on I will update as needed. Could my coil be failing? Ive got a MSD blaster on it, but its easily as old as the old MAF. When this is cured I will tell exactly what went wrong. Thanks for your input

 

[thelastofthem23004]

Oh and as a side note, Since I was able to get my old MAF identified through its serial number I now know that I am running 24lb injectors. So new 24lb MAF and what was on when I bought it 24lb injectors

 

[thelastofthem23004]

I went and looked and was more than suprised to see what is in the pictures i uploaded. Fully rusted rotor shaft and then my TFI module which looks to be stock, but isnt quite in the right spot? Ill look into a new TFI asap, and before I fix that I'll clean up some stuff on my distributor.

 

[ttocs]

I see no tfi. On the fox bodies it was mounted to the dist, on sn's its mounted to a heat sink on the passenger fender. I would start by testing the tps as its easy to do. With the key on IIRC you probe the two wires and then slowly move the throttle blade and make sure it shows a smooth voltage sweep with no dead spots. Or slap a new one in and see what happens

 

[evilcw311]

That dizzy looks like it’s had some serious moisture inside.

If your coil can’t keep up then it will struggle in the uppers Rpms. Throw a ford motorcraft cool back on it. Msd has a huge reputation for failure.


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[thelastofthem23004]

Update on the issue: I threw on a new coil and TFI and the car starts much easier, but still cannot get above half throttle. I'll post a video tomorrow of what startup is like and I'll try to rev it. For now, I'm going to unplug the battery overnight and see if a fresh reset to the computer will do anything.

 

[sn95rcs]

2 years outside? Stock air intake hose? Rat/squirrel nest at the air filter? Simple, but can't hurt to look.

 

[Chip66]

The 1/2 - 3/4 throttle problem sounds just like when my ignition pickup went bad on my '89 GT. From the looks of the inside of the distributor, I'd say that's a good bet.

I don't know a good way to test it. I simply bought an ignition module and pickup. The module changed nothing, but the pickup fixed the problem. I promptly returned the module.

Make sure you have silicon dielectric grease behind the module, it needs it for sinking heat off.

 

[ttocs]

I had a similar problem with the throttle position sensor which is why I suggested checking it. Testing it is easy and replacement also.

Also when you replaced the TFI did you clean off the old heat transfer cream and put a fresh layer down?