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I’ve posted a set of pictures of the car under “What Are You Working On.” I purchased the car knowing it had issues. It finally became clear I needed to replace (or rebuild) the engine. I choose to replace the engine with a rebuilt one. It’s now in. Most of the problems are gone now with that “new” engine. The car has the power and torque that it should have. It’s “almost” right. But it still seems to not be as smooth as it should be or as other 94 Mustangs that run properly are. No vacuum leaks, electrical is is really good shape. The replacement engine did not come with new throttle body (or new injectors). It still wants to throw an O2 sensor code so that will be tackled next. I’ve only driven it 7-10 miles since the install of the rebuilt engine. I would love input on designing a game plan to see if performance can be improved. I will not be kicking it hard until the engine breaks in more. I wanted a car that was an ongoing project, and I think I got that. I did have a cheap cold air intake on the old engine and now I’m back to stock. So, if you have ideas, I’m all ears! 🙂
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Thanks. I understand. But I know the when that engine was new (in other cars I have seen) it ran smoother. I’m really wondering right now if the throttle body is damaged from use of some cleaning agent that should not have been used some time in the past. It won’t throw a code, but something is still just not right. I may put in a used unit that I know works and see if that improves anything. Will still deal with the O2 sensor issue also. I feel sure the injectors are fine for now.
I’m going to throw a little more money on it and replace the 2 O2 sensors. Interesting that on the 94 GT there are only 2 – one on each side of the x-pipe (and not 4). The Cat seems fine. Looks pretty simple (that is always a bad sign).
If you are looking for a little more out of it try a BBK throttle body and some upgraded injectors, those small motors can be woke up a fair bit if you make them breathe.
Yep. I had not actually looked up under the car and just went by what I was reading on forums. It was amazing how many people kept saying there were 4 but 4 came later and like you said, it was to check cat performance. I’m learning a lot 🙂
Will be putting on new O2 sensors this Friday. Also got a deal on nice throttle body so will change that out when it comes – plus got a good new TPS sensor for that throttle body. I’m betting the O2s take care of most of the problem and the nice throttle body (60mm chromed Shelby type unit) with new TPS finishes the job.
O2 sensors are going to affect running performance because of rich/lean. Also if you reused injectors I am hoping with new o-rings you are going to want to run a fuel system cleaner through the car if it can some ford’s cannot run a fuel system cleaner. Once you have used it all up you then are going to want to change your fuel filter if you have one other then in the tank. That should give you a boost in performance. I would also check your pcv valve, air filter, and battery.
Thanks. I’ll check on the o-ring question – I had a pro shop do the rebuilt engine install and I know they reused the injectors. I’ll also keep your post and add those steps to the process. Thanks.
O2 sensors were replaced (seemed to be original equipment – as in, never replaced). Still threw a code even with new O2s. I’m going to put in new Air Temp sensor plus I’m changing out the old throttle body unit along with idle air control valve and TPS. I also plan to replace the injectors. I’m doing one at a time to see how the performance changes. With everything else that’s going on this time of year, that should keep me busy through Christmas. One thing I have discovered in all this, there are bargains out there on Motorcraft replacement parts if you do some real online shopping. I’m primarily getting stuff at RockAuto or Amazon, but sometimes even E-bay offers a real deal. I’m talking 90% off retail! Thereby keeping total expense down even with replacement of a number of 20 year old parts and sensors.
Throttle body ready to be installed. Already have new TPS and idle air control valve mounted on it. Got slowed down due to new gasket to attach throttle body to air plenum was wrong. For lack of a $1.47 part (the gasket), she would be up and running. Expect to have the correct gasket tomorrow.
I don’t consider myself an expert, but I did order my 94gt new from the factory back in the day. In the last 20 years I have performed about any kind of mod you can think of including a turbo.
A couple of things I’d like to comment on:
’94-’95 was the last year of the EEC-IV engine computer and the last year before the Mustang became OBD-2 compliant. Therefore the SN-95’s only had 2 oxygen sensors.
The reason Ford abandoned the original small block ford 5.0 was because of ever stricter emissions requirements. Because of this the EEC never responded well to a lot of modifications. A custom chip is a must especially if you change the cam.
The stock injectors are good to almost 300 hp. Don’t change them.
The throttle-body is well matched to the intake. They are optimized to maintain high flow velocity. This promotes good cylinder filling which enhances low rpm torque.
Everyone always talks about “better breathing”. Cold air intakes and freer flowing exhausts do very little to enhance engine breathing. Don’t fall for the hype. Ford spent a lot of money and time on R&D. They didn’t leave much hp on the table. Save your money. The way to better breathing is a bigger cam. (See above)
The next best thing is 1.72 roller rockers. Stock rockers are 1.6 ratio. 1.72’s will open the intake valve farther without changing timing events and causing EEC issues. Your mass air flow sensor will compensate for the extra air.
I would also consider installing numerically higher gears in the rear end. These cars came with 2.73 stock and 3.08 as a no cost option. Because the car is so heavy 3.73 or 4.10’s will really wake the car up. The shorter gears will help the engine get to its power band much faster with a negligible loss in mpg. 3.73’s were one of my first mods and i still got over 24 mpg on the highway.
As for the car running rough i have one thought and it may be a long shot but a common issue with ’94-’95’s.
Question: Is your harmonic balancer the stock one? If so, that may be your problem. The stock harmonic balancer is a two piece design with inner and an outer metal pieces with a rubber center. That rubber center degrades and the outer metal part slips causing the engine to run rough because it is no longer balanced.
Its worth taking a close look. It may be your problem.
Hope this helps
Nick K
Thanks. I really appreciate the ideas and advice. The car came with a cheap cold air on it and I retro-fitted an original intake. The throttle body I’m putting on is slightly used but in much better shape than what I had on the car and other than being chromed, it’s stock. I will check into the harmonic balancer issue soon. Now I need to read more about that (because other than what you have just told me, I know nothing). PS – I am really having fun learning all this.
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