I recently upgraded the engine in my Mustang to the specs that are in my signature, but the car is still off after making sure other components such as the timing were exact. I knew I would have to get a custom chip burnt for the car, but I didn't know where to begin...I assume this is something that will require me to take my car to a speed shop, I just can't call someone with my specs and have them burn me a chip, correct? I also didn't know if anyone knew what to expect for a price to have something like this done...I'm expecting at least $450?

Any help would be greatly appreciated!

 

I can tell you that you have something else going on there and a chip isn't what you need. On a Fox car I have done a lot more modifications than you have listed and never used a chip. The A9L computer is more than capable in handling what you have. I can tell you that without the Supercharger installed your 70mm TB is too big...but it will be find with the S/C...however your injectors are too small for a supercharger. Have you checked or set your TPS sensor?

I am telling you from years of experience though that a chip is a waste of money on a Fox as long as you are within the parameters of what the stock processor can do....and you haven't even come close to maxing that out.


1989 Mustang GT
BBK CAI & BBK 70MM Throttle Body
Vortech 73MM MAF
Ford Racing Cobra Upper & Lower Intake
Accel 24 lb. injectors
Mac Ceramic Coated Equal Length Headers
Pypes Stainless Steel from X-Pipe back
Maximum Motorsports rear upper & lower control arms
Ford Racing 4:10 rear gears
Paxton SN93 Supercharger (awaiting install)

 

Thanks for the quick reply Paul...I haven't touched the TPS sensor at all. When I got the throttle body from BBK, a brand new TPS was already installed on the throttle body. What I don't understand is that the car fires right up with no problem and idles perfectly. However, when I hit the accelerator I am not getting the kind of throttle response I would expect, not anything like before. It seems as though the car is running rich because it seems to bog when I hit the accelerator even a little bit when driving.

I know the car is timed perfectly because I used a timing gun and it wouldn't even run when it was barely out of time when I had timed it without a gun...I am just dumbfounded.

I don't have any intentions of putting the supercharger on the car until the car performs correctly...I already have one problem and dont want to make another

I know this is going to sound dumb, but I have never done anything to do with the TPS, how would I go about setting it? is it all about the position it is screwed in?

 

The TPS voltage reading must be taken with a digital volt/ohm meter (DVOM) with the Key On/Engine Off and with the Key On/Engine Running. A cheap one works fine and you should have one in your toolbox if you are going to be working on cars anyway.

The TPS is located directly on top of the throttle body and is adjusted by loosening the two phillips mounting screws and positioning the sensor until you get the highest reading. It may be necessary to elongate the holes with a small file to achieve the desired reading...some sensors have oval holes and some do not.

The spec range for Key On is from .88 to 1.0 volt; shoot for .97 to .99 volt. With the engine running the voltage should be no higher than 1.05 volts.

Incorrect Throttle Position Sensor (TPS) voltage will result in reduced performance and poor throttle response. The best way to take a voltage reading is by using two safety pins peirced through the wire insulation on the wires coming out of the sensor. The positive lead is attached to the green wire, while the negative goes to the black wire. Always ground the meter through the sensor's black wire.

 

Thanks for the help Paul. I am going to see if I can adjust it right now at my dads shop and see if I can get this thing to run right!

 

well, i adjusted my tps with a voltmeter, and it now runs a little better, but the car still sounds choppy when i hit the accelerator. I have no idea what it could be...I guess I will have to get it looked at.

 

Just check all the basics....plugs, wires, cap, rotor, fuel pressure etc. Make sure you MAF is calibrated for the 24lb injectors....although that is too much fuel for your current setup which could be parte of the problem too. It would probably do you good to just get some dyno time and see where your A/F ratio is and adjust fuel pressure and timing accordingly on the dyno.

 

Thats whats got me wondering what could be wrong with this...I have replaced the plugs, wires, cap, rotor and coil within the last month and a half...the fuel pump is stock, it is working fine, but could the small pump be a problem in regards to the size of my injectors? I tried advancing the timing with no luck either...

 

All the more reason to get on a dyno. Your stock pump is 88LPH, the 93 Cobra came with 24lb injectors and had a 110lph pump stock.....it also had a better intake, and different cam profile. The 24lb injectors are too much for your current setup but aside from that you have to have the right fuel pressure. A dyno will tell you where your air fuel ratio is and you can adjust from there. You can just throw a mixture of parts on the car and expect them to always work properly. If you put the 19lb injectors and a 65mm throttle body on your car it would probably make more power but work with what you have and get it on a dyno and see where you stand....then you will have some information that will tell you where to go from there. Guessing will get you nowhere.....

 

you are right, I will contact my local speed shop and see when I can put it on a dyno...just to get a general idea, how much would something like that normally cost? Price won't curb me from doing it because I obviously have no choice, but I have never really paid for a service such as a dyno run so I don't know what I should be expecting to pay...

 

Dyno's usually have an hourly rate or a basic 3 pulls for $60 or around that.

 

i am not a real mechanic but i did stay at a holiday inn express last night!

it sounds like it is fuel related and i absolutely agree there is no need for a chip, mine is running on the a9l with no problems, other than a really choppy idle..lol... really what jumps out is your maf is not matched to the injectors. and that is a rather large tb you got there.

it has been several days since you have responded to this thread, did you figure it out yet?

 

I am going to have the car put on a dyno, hopefully this week, it has just been a hectic past couple of weeks with college, work and I play semi-professional football for a team up here in New England so I just have to find time in between that stuff...

I had ordered the MAF after getting the injectors, and the MAF is made specifically for 24lb. injectors, so thats why this is throwin' me off...I thought I had to get a bigger MAF since I got a significantly larger throttle body and different injectors...?

The main reason I stepped up to the bigger injectors was because when I took the stock ones off they were horrible, and I figured I might as well get the 24 lb. ones anyway. Maybe I shouldn't have...

I am running a stock fuel pump, and am going to buy at least a 110 lph because I think that is part of the problem- I am not getting enough fuel at a fast enough rate.

Either way, I need to see what the numbers are after putting it on a dyno..

 

you are going about this backwards, you need to build to support your sc. ask paul as he is more informed than i but i believe the injectors are too small for the blower and i would put a 255 pump in the tank. right now i know he said and i agree with the tb is too big but i think the problem is exactly what you stated, maf not matched to the injectors and fuel pressure. i personally think the dyno is not needed but i am not an expert, this can be all diagnosed on the ground. but the dyno will give you a good baseline and do not get your feelings hurt on the numbers, when you throw the blower on there it will be a good push.

trust me, map this out before you you buy unwanted parts and double labor.... been there and done that. the first car i modded, i bought all of the fancy stuff and realized afterwards that they were not a good combo. with these cars everything has been done before... at least once. good luck and keep us informed.

 

i ordered a 73mm mas air meter for my 92 when i had it. They sent me the sampling tube for 30lb injectors not the 24lbs I had asked for. And it ran exactly like you stated, no power, no throttle response because the sampling tube was causing the car to run rich. I had to crank the fuel pressure way up because it was dumping so much fuel in it, it looked like the car was not getting enough fuel the pressure went from 40 lbs to 25 lbs. I called and had them send me a new tube for the right injectors, adjusted the fuel pressure back to 40 and the car ran fine.

 

I know for a fact the MAF tube they sent me is for 24 pound injectors, all the mfg. numbers on the packaging, etc. confirms that, I called Vortech directly and I confirmed it online. the reason i purchase both the TB and MAF is because I tried using the stock ones and the car woulnd't run at all. The only reason I got 24's instead of 19's is because when I bought additional tubing to go with the Supercharger I have in my possession (but have not yet installed) I called the company who supplies the parts for the Supercharger. Not to ramble, but a company by the name of Paradise Wheels, Inc. out of California bought the rights to Paxton's line of SN93 Superchargers (which Paxton no longer makes, was replaced by a newer series)...Paradise Wheels now owns all rights to that line, and additionally install the units. When I called the owner of the company to purchase the parts I needed to install, I also asked him what size injectors I would need. He told me to ideally have 24 pound injectors. That is the reason I bought that size....I thought I would be killing two birds with one stone by only buying one set of injectors now, as opposed to buying 19's now and 24's in the near future...I am now beginning to believe hindsight says otherwise.

I am not saying I am right, but I am just saying why I got those size injectors ...I take the advice of the the people on this forum seriously because there are people on here who are professionals in the automotive field who fortunately take the time to reply to my posts, and probably should have asked these same people for their input before purchasing the TB and MAF. I thought when I made the purchase I made the right decision, but I guess not.

Nevertheless, I need to have someone with the know-how to look at this car at this point as opposed to going with my limited knowledge, I just have to find time to get the car there.

On another note, I want to thank everyone who has patiently read and given advice to my car problems, I really appreciate the continuous support of this forum.

 

Well, I have to say the guy you spoke with that recommended 24lb injectors steered you wrong and didn't know what he was talking about. The SMALLEST blower installed on a Fox would require at least a 30lb injector. Keep in mind that Paxton sold the rights to that blower likely because of lack of sales.....and the people bought it because they thought they could do something with it but they likely don't have near the knowledge needed to support it....and the name of the business being a wheel business really would leave me with an uncomfortable level of belief in their knowledge about superchargers.

Either way though.....don't waste your money on a 110lph fuel pump...you are throwing it away. The system is a return style fuel system which means that any unused fuel not used gets returned to the fuel tank....so buy a 255lph pump and be done with it...it will not cause you to use more fuel and any unnecessary fuel will return to the tank......AND you will have the fuel you need when you need it.

 

255 it is! I will order up one of those, and I will have to get the injectors when I install the S/C during the winter...

 

Ok I finally have something to contribute to this thread: Walbro GSS340

 

Just called my local speed shop and they said thats one of three models they carry, and the guy actually recommended it as well....so it looks like thats what I will go with...I will attempt to make a trip there today.

Thanks for the advice guys!

I will try to install it tonight and see where it takes me.