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Discussion Starter · #1 ·
I recently upgraded my fuel injectors from 36# to 42#, removed the EGR valve, recalibrated the MAS and had my chip re-programmed. Now the car will not run for more than a minute or two without dying. When it is running, it is very rough; when I step on the gas, the car bogs down even more before revving up. I was able to keep it running long enough to verify that the timing is set at 10 degrees and that the fuel pressure is about 38 psi with vacuum off. I have tried lowering the FP some but it didn't make a difference. I have brand new spark plug wires and triple checked that they are secure. I have searched for vacuum leaks but haven't found any. I pulled a couple of the spark plugs and they were both completely black. Any suggestions would be greatly appreciated? I am running out of ideas.
 

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This is for the 95? Then, spend $200 and get an autoxray and do a scan, see your errors, and see your sensor data.
(BTW: Only the 94/95's support the extended DCL data that gives sensor and internal EEC data.)
 

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i would look again for a vacuum leak sounds just like the problem i had rite before my build up. good luck phil
 

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Discussion Starter · #4 ·
Would a vacuum leak alone cause it to run so rich the plugs are fouled? I also just noticed that when I turn the key on, (without starting the engine) when the fuel pump primes, the fuel pressure immediately drops down to around 12psi after the pump turns off, even if I turn the key on and off several times. If I remember correctly, it used to hold more pressure than that.
 

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Discussion Starter · #6 ·
How do you check for a stuck injector?
 

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First, double check for leaks, cracks, etc. in all fuel and vacuum lines, etc. Also check the electrical connections and wires.

Are you sure the injectors are working with the proper inpedence? Are they Ford injectors?

What all was done for the chip? Was it properly calibrated for the 42 # injectors? If you calibrated the chip AND "tricked' the MAF, then you will be way off. By "tricked" I mean, calibrated the MAF to work with a stock PCM so that the voltages sent are not stock values - they are adjusted to create the proper flow for 42# vs stock.

You need to make adjustments in one and leave the other alone, but not adjust both. The best solution is for the MAF to send actual voltage and the PCM be adjusted to the 42# injectors, but someone has to know what they are doing, and many chip burners cannot do this with 42#. You need to adjust the pulse width and every other factor where the fuel is adjusted. There are several parameters in the PCM that adjust fuel mix on a percentage basis and this creates a real problem with upgraded injectors, as their percentages need to be lowered. Most standard chip burning routines don't do this, they only adjust the standard pulse width parameters.

You are probably drowning in fuel because you just don't need a 42# injector until the blower is going full speed. This means you really have to know what your doing with the PCM/chip.
 

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Discussion Starter · #9 ·
I am using Ford injectors, so they should have the proper impedance.

I had the MAF calibrated for 42# injectors and a supercharger and JMS was aware of this before burning the chip so this should have been taken into account. I will try to run it without the chip to see if it is causing any problems. JMS actually suggested that I add the 42# injectors and have the MAF re-calibrated because I was running out of fuel on the top end with 36# injectors. Since it was their recommendation, I am assuming that they know how to create a chip for this combo.

I think I am drowning in fuel since the spark plugs were so dark and smelled like fuel.

I guess I’ll look for any type of leaks and try it without the chip.
 

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nonstock said:
First, double check for leaks, cracks, etc. in all fuel and vacuum lines, etc. Also check the electrical connections and wires.

Are you sure the injectors are working with the proper inpedence? Are they Ford injectors?

What all was done for the chip? Was it properly calibrated for the 42 # injectors? If you calibrated the chip AND "tricked' the MAF, then you will be way off. By "tricked" I mean, calibrated the MAF to work with a stock PCM so that the voltages sent are not stock values - they are adjusted to create the proper flow for 42# vs stock.

You need to make adjustments in one and leave the other alone, but not adjust both. The best solution is for the MAF to send actual voltage and the PCM be adjusted to the 42# injectors, but someone has to know what they are doing, and many chip burners cannot do this with 42#. You need to adjust the pulse width and every other factor where the fuel is adjusted. There are several parameters in the PCM that adjust fuel mix on a percentage basis and this creates a real problem with upgraded injectors, as their percentages need to be lowered. Most standard chip burning routines don't do this, they only adjust the standard pulse width parameters.

You are probably drowning in fuel because you just don't need a 42# injector until the blower is going full speed. This means you really have to know what your doing with the PCM/chip.

I'm confused. And I taught this type of stuff! :)

You're wrong on a number of points and semi-right in an idea.

First: The EEC and maf map MUST match. For a 94/95 it is **NOT** an option. The engine WILL GO BOOM!!!!!!!! :) For an 88-93 stang EEC, by DE-tuning the engine (timing), you *may* get by.

Mafs have a max air flow they can measure before they hit ~4.8v. Mafs maps/transfer-curves are chosen for max hp. A stock maf will max out ~300hp. Also, it's best to not go too close to the max air flow measurement of the maf.

To get an idea of how much HP an maf ADAPTION can handle see:
(BTW: Non-stock mafs are NOT calibrated for injectors. "Calibrated" is a BS marketing term.)
http://www.pro-flow.com/flow sheets/37ptflow.htm

BTW: There is no such thing as a single "correct value" per flow for a maf. Ford uses a number of maf curves. The curves are chosen for the max HP of the engine - it has *nothing* to do with the cyls or the injector size.
 

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If all the things are correct the other guys mention make sure you didn't pinch or mis-connect a fuel return line.
 

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Discussion Starter · #12 ·
I have not been able to find any vacuum leaks. By changing the sparkplugs I could get the engine to run ok (pretty rough but at least running). I turned the FP way down then ran the engine for about 30 seconds and checked the plugs again. All of them were completely black.

I don't think it's a stuck injector since all of the plugs are black. Would a mis-calibrated MAF cause the plugs to go black in less than a minute?
 

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dude i have the same problem... running pig rich u can see it coming out of the tailpipes... you first prime the fuel pump, fuel pressure goes to 40 then immediately drops to nothing, turn engine over to start... flooded. plugs fowled. if you sort this out, please let me know. Everyones telling me injectors also... i guess trash could keep the pintle from closing completely... and dumping fuel in all the time??
 
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