switching to CARB...

Why is a carb simpler? Is it because it doesn't have a computer and wires? How much time and effort have you put into learning what EFI is and how it works? How many book and papers have you read?

Some of the motivation of my negative comments about carb to EFI has to do with the quality of electrical workmanship. A lot of the wiring “repairs” that I have seen on the road and in the junkyard looks like road kill. The other part of my negative view stems from people who can’t grasp the operation and tuning of EFI. Carbs have their own set of requirements and some learning is required to get the best performance. Every car is different and each installation needs to be tuned to get the best performance. Putting an “out of the box carb” or one from someone else’s car isn’t the way to success. There is no auto compensation for small variations in carbs like there is for EFI. Just throwing a carb on a car because you won’t bother to learn how EFI works is a poor excuse.

Good troubleshooting takes time. Everyone seems to be looking for the magic tip that says replace this $13 part and your problems are cured. You don't have to think, dig or diagnose, just buy the part and install it. Unfortunately, it doesn’t work that way 99% of the time.
Thinking is hard work and educated thinking requires much more effort than simple parts swapping. The complexity and age of these 5.0 Mustangs works against that, as well as the number of hands that have “modified” the original design. Sometimes that modification is well done with good workmanship and other times it is mechanical road kill. It is very easy to become the victim of the previous owner’s efforts.

I spend a great deal of time trying to communicate the methodology of structured troubleshooting principles. For those who haven’t been beaten with this stick before, here they are again:

1.) Understand the system. That involves reading some books to get an overall picture of how it works. For 5.0 Mustangs, that list starts with the Chilton shop manual and the Probst book, Ford Fuel Injection & Electronic Engine Control 1988-1993 by Charles
Probst :ISBN 0-8376-0301-3. It's about $30-$40 from Borders.com, see
Amazon.com: Online Shopping for Electronics, Apparel, Computers, Books, DVDs & more. Select books and then select search. Use the ISBN number (without dashes or spaces) to do a search. Use the ISBN number and your local library can get you a loaner copy for free for 2 weeks or so.
For free automotive electrical training, see Automotive Training and Resource Site . I have personally reviewed the material and it is very good.
Another resource is the following website by Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring: Mustang FAQ - Wiring & Engine Info. Study the diagrams and tech articles. There is an amazing amount of good stuff in one place for FREE.

2.) Isolate the problem. You need to be able to break the system down into functional blocks or subsystems. Once you know what subsystem has failed, it is much easier to troubleshoot. Group problem symptoms according to what system controls them. Don’t
look for a fix for ignition problems by adjusting the fuel pressure. Have an organized, step by step, approach to work your way through a subsystem before you quit and go off wildly chasing rabbits. You have three tools to use in your efforts:[ : measure, observe and think!. Use these three tools to narrow down the list of possible failure points into a small, easily managed list of items.

3.) Install the fix. Now that you have a short list of suspected villains, plan your repair efforts so that you do the easy things first. If an item from the easy list didn’t fix your problem, then look at the high failure rate items. Spend some time here on Stangnet and you’ll get an idea of what the most commonly replaced parts are, things like TFI modules, ignition switches and fuel pumps.

If you make a change and it doesn’t relieve the problem symptoms, put it back the way it was. I have a stack of parts from where I swapped a part and it didn’t fix the problem. I put the old part back on the car and the new part went on the shelf. Someday I will either
use them or trade them for something else.

Ill trade you my carb stuff for your efi stuff then

jonbacon said:

I have tired to get it right and still cant seem to get there. Im use to cabrs.. i have done idle reset and tps, still isnt right. will crank and idle a after 2 or 3 tries then idle at 700, but when i go tot drive it will lose power and cut out around 10,mph. i let off the gas and it idles at 700...im just not sure what I am missing. tps is a t 1,1..... new IAC<TPS<MAF...still no fix?? im just lost in the stang

Click to expand...

You give up too easily. No one ever said life or fixing 5.0 Mustangs was easy. The people that that succeed are the ones who don't give up when the going gets tough. They dig in, get the understanding and information needed to fix the problem and then go at it.

All the documentation need to find and successfully fix the problem is available. See http://www.stangnet.com/mustang-forums/825424-adjusting-your-tps-0-98v-not-necessary.html for TPS troubleshooting help.

Ditch the cone filter and go back to the stock airbox. It is one of the trouble items in the "Surging Idle Checklist

Had a tfi module do that once.

Is it throwing any codes?

If you disconnect the MAF does it run any better? Actually sounds like ignition to me. These cars are simple for the most part.

Since 14 of the 16 threads you've started here have all dealt with this same issue and in all of them you've been told to reset the computer and pull codes, and you're still asking the same things over and over, I have to assume that you are unable to work on this car. MY recommendation is, rather than blistering your fingers by constantly f-ing with the TPS, why don't you pay a reputable shop a couple of hundred bucks to fix the damned thing and be done with it? For the amount of parts you've thrown at this thing, you could have had it fixed and on the road twice. Otherwise, read the sticky, follow the steps and quit trying to shortcut the whole process.



This is how you're suppose to do it.

Idle issues are a bitch but the multiple threads on the same topic are going to keep people from taking you seriously. Go through the surging idle checklist one item at a time. I promise you will have a completely functional car by the time you are done.