Brad Huff

I apologize in advance because this is going to be long but I need advice from some of you that have already been down this road. I am now working on a 93 Monster 5.0 that I purchased a year ago. I have almost all paperwork related back to the birth of the car. It was converted to the engine it has now back in 2002. A 94 5.0 Cobra engine with a Cobra intake, a E303 cam, Edelbrock Performer heads, 24 lb injectors, a 65mm throttle body, and a 75mm MAF. There are issues with the smoothness and drivabiltiy that I am working out now. This is my first experience with an EEC-IV EFI engine. The plumbing between the EGR valve and the header has been removed, however the rest of the assembly appears to be there. The paperwork describes a Tweecer that was installed shortly after the conversion. I didn't worry too much about the EGR because I figured it had been deleted with the "tune". Shortly after acquiring the car I found a Tweecer, and cabling but no 5 position "tune select" switch in the trunk. Initially I didn't think much about it as the car has passed through a couple of other owners since the conversion and has been very roadworthy, at least according to the previous owners. When I read through the accompanying paperwork I discovered that a replacement computer had been installed back in 2015 due to ignition and other issues so when I found the Tweecer I just figured that one of the previous owners had it retuned with a more modern chip. A week ago I pulled up the passenger side carpet and removed the shield. What I found was a F4ZF-12A650-EA unmolested computer. The knockout covering J3 still in place. It's now obvious that I have a stock computer the one good thing is that the reconnection of the VSS sensor and bolting the rear transmission mount to the floor pan might help with the low speed bucking. My question is this--- How much can the stock computer correct? Is it possible that the changes made still fall within the window that the computer can handle without a "tune". Can I hurt anything if I plug the Tweecer into the J3 port? Will the Tweecer even work without the 5 position "tune select" switch box? What about the EGR system. I should probably be getting CES light but I'm not. I do know that there is a working bulb there because it did light briefly once. How much hp and torque am I leaving on the table by not having it tuned? I mentioned earlier that I am dealing with some drivability issues so I want to go through some basic adjustments and smoke test for vacuum leaks first. Other than that I have been very impressed with the quality of the build. It is a very clean, rust free car that was converted properly. My issue is with the people that worked on it since. I don't believe that either one of the 2 people that owned it since the first sale were that mechanically inclined instead leaving the work to be done to local auto shops in their areas. As always, thank you in advance for your help.-Brad

engineer

Hi Brad,

The stock computer can correct to a degree, however its pretty limited and even factory standard cars benefit greatly in horsepower, drivability and economy post a custom tune. So to answer your question. Yes get a custom tune, the car will be as best as it can be after it.

As for EGR, you can leave it as is as far as performance goes. It is for pollution reduction purposes only. Your state may require it hooked up and working for smog tests. But the car runs better without it.

I cant comment on the tweecar 5 position switch question, as I have not personally used it (I use SCT tuner). But plugging it into the J3 port should not cause any issues, the electronics in the factory ECUs is pretty robust.

cheers