Tim Murphy

I'm curious what you did to rebuild the injectors.

Could be a bad chip. I had Hacker put one of the same chips in his car and it started right up and ran as far as I know. His is not the same file as on your chip but that should not matter. He burned it so I will have to check with him to see what he has.

Tampa 928s

I had the same company rebuild IE clean and test all the injectors includes a data sheet. One injector was blocked one was leaking. This company did both my BMW and 85 Euro and no problems!
It comes down to the LH chip the only thing I do see is the Maf voltage is 2.65Volt at idle way too high; is this because of the Maf restrictor?
I have my data log files if your interested!

dprantl

2.65v MAF @ idle doesn't sound high to me, sounds just about right.

Dan
'91 928GT S/C 475hp/460lb.ft

Tampa 928s

OK, I read some where it should be around 1.6V.
Must be the chip since the car is running although not very good!

Tim Murphy

In your first post about rebuilding the injectors it appeared to me that you did the rebuilding vs having them rebuilt.
I'm glad you had them rebuilt as we discussed because they had been sitting around for a long time even before I got them.

~1.7v ign on - eng off. I forget exactly what it is with the eng at idle but 2.65v sounds about right.

Just talked to Hacker and he has the same chip and virtually the same file as yours and his car runs perfect with the LH chip. This doesn't mean I didn't mess something up when I burned your chip but it would seem unlikely.

hacker-pschorr

It's a long shot, but make sure all the pins are in place on the new chip.

Last year I installed a chip in my LH, one of the pins bent inwards and did not go in the slot. The car ran, but not 100%.

Tampa 928s

I went ahead and double check by reinstalling the stage-3 chip as soon as I started the car it was the same issue cars stalls!
It was shipped with out a anti-static bag that would account for it going bad, not uncommon.

Tony

I assume you did messing with the LH..but Did you unhook the battery for a few minutes?

Tampa 928s

Tim,

I know that there is a difference of quality of the chips they make, you would have no way of knowing that when you buy them. Over the years we have had chips burned for us for Telephone systems and a failure rate of 10% is not unheard of.
I am assuming some of the cells did not take or were corrupted, since the car did run. One time in the past that a whole run of chips were bad; "we found out later from our supplier". We did not find out until we placed them in service this caused a Hugh headache since they were installed over a six month period.

I am curious were these eprom or proms?

Tampa 928s

Yes always; but the 86 does not have memory retention like the later cars.

Tim Murphy

eprom
AM27C32-150DC

I'll burn another one with the exact same file and make Hacker try it in his car.

His car is a Euro setup but should run on the same chip, I think. He has 42lb injectors and the MAF restrictor device.

This would be the first time that I had a problem with a chip, that I can remember anyway.

Tampa 928s

Should I be looking for anything else?

I made sure it was not a vacuum leak I smoked it. I checked the MaF connection Temp-2 and all other connections that were disturbed.
The install was pretty easy so changing the chip is not a big deal.

Tampa 928s

On a useless quest to find why Eproms go bad this is what I came up with.

I used a ground strap "recommended' when removing or installing any chips. Most likely some type of static discharge damaged this chip; "not uncommon", Most of the time nothing happens but sometimes it does so by using a little caution when handling and installing theses chips it might help someone in the future.
The other reasons for failures are listed below and is tedious reading but for some entertaining!

Mitsubishi AM27c32-150dc eprom cmos

CAUTION!

To avoid failures and faulty functions in the product caused by static electricity everybody who handles the product must take proper precautions. To be certain that the used protection devices indeed function in the expected way, they must be checked on a regular basis. The protection device recommended is a wrist wrap. Wrist wrap is a device where are at least following parts; a wrist "bracelet", a wire and a connector. It´s purpose is to connect the person handling the electrical devices and the electrical device itself in the same electrical potential, so that ESD phenomena´s can be avoided.

What is ESD?

The phenomena of Electro Static Discharge (ESD) has been around since time began. We occasionally feel the effects of such a discharge when we receive a slight shock after touching the metallic doorknob or the metallic handle of an automobile. We first learn about electrostatics in basic physics back in high school or earlier, and we observe ESD on a gigantic scale when lightning strikes occur during thunderstorms. About 5-10 years ago, the major cause of IC (integrated circuit) failures was Electrical Over Stress (EOS), which results in gross damage to the internal metallic structure of the integrated circuit´s.

If electrical devices are not handled properly, you might damage them by giving it small "lightning" eventhough you do not notice anything or can see any physical damage. Therefore it is recommended that use professional person in order to upgrade your chip. If you want to do it by yourself, follow the instructions so you do not them harm the PCB.

Improper packaging of ESD sensitive (ESDS) components,
assemblies and equipment resulting in hard and soft
failures has cost both manufacturers and users millions of
dollars, maybe even billions. This is because most suppliers
and customers do not understand how (ESDS) items can fail.

Every time a component or assembly is placed-in or removed
from a package, whether slid into a static shielding bag, placed
in a plastic clamshell or a corrugated container it can become
charged. If already charged, it also can become discharged.

Charge residing on
the styrofoam tray was induced into the EPROM. Damage
occurred when one of the EPROM pins touched grounded.
Even if the operator wore a wrist strap, the problem would not
have been solved.
As a result of the visit to this facility, operators were
instructed to dispose of all styrofoam from the work areas.
Unfortunately, even now styrofoam is still sometimes used
allegedly to protect an integrated circuit or transistor pins from
mechanical damage. In addition, you often see a styrofoam
coffee cup in a work area where it does not belong. A
styrofoam cup, even full of coffee, can be a significant charge
generator because the charge that is on the outside of the cup
stays, regardless of whether the person holding the cup is
grounded or how much coffee was left.

What is an EPROM?

EPROM(Erasable Programmable Read Only Memory) can be programmed and erased enabling them to be re-used. Erasure is accomplished using an UV (Ultra Violet) light source that shines through a quartz erasing window in the EPROM package.

Note that all UV erasable devices will erase with light
sources having wavelengths shorter than 4000 Ċ, such
as fluorescent light and sunlight. Although the erasure
process happens over a much longer time period, exposure
to any light source should be prevented for
maximum system reliability. Simply cover the package
window with an opaque label or substance.

OK, So tell me, just how does an EPROM work?
EPROM memory cells use floating gate technology. A floating gate is a gate with a special capacitor for its only electrical connection. This special capacitor takes on an electrical charge in a quantum physics effect called tunneling. The presence of a charge determines the value (1 or 0) of the memory cell. In our example below, a room with a very narrow door represents the memory cell. People in the room represent electrons with their associated charge. These people can only enter or exit through a much too narrow door with much pushing or shoving to represent the tunneling effect.

Think of a room with about 30 people acting as the electron charge. A full room of people represents a '1'; when empty a zero. When an EPROM is erased, all 30 people are pushed into the room and provide the charge that we call '1'. When we program an EPROM bit, we shove these people until they pop back out by applying a pulse of high voltage to the memory cell. This pulse drives the people out of the room changing the bit from a '1' to a '0'.

When programming a bit we can only change a 1 to a 0 because changing a 0 to a 1 requires erasing. To erase an EPROM, we apply an UV (Ultra-Violet) light (that shines directly on the chip) to drive our imaginary people back into the room. Erasure works on the whole EPROM not individual bits.

An EPROM cell is really an analog device. If it were digital, we would only have an empty room or a room with one person in it. Instead, a cell sensor circuitry compares how many people are in the room to a reference to determine if the cell represents a 1 or 0. With more than 15 people in the room, the cell is considered a 1.

When programming an EPROM you have to apply the specified programming voltage for the specified time. Too short a time or too low a voltage and not all the people get shoved out of the room. When you don't program an EPROM properly and you still have 5 people in the room, it will slow down the cell sensor circuitry, which slows down the read access time of the EPROM or might even corrupt the data. A similar thing can happen if you don't erase the EPROM long enough.

On the other hand, if you apply too high of a program voltage or over erase the EPROM, it is equivalent to blowing the doorframe right out of the wall! Our imaginary people now enter and exit the room, milling around on their own whims and we no longer have information storage! The long and short of it is you need to double check Vpp programming voltages and follow the recommended time for erasing (don't store unused chips in the eraser!).
[edit] A typical EPROM Pin Out

An EPROM requires a specific frequency of UV 253.7 nanometers (2537 angstroms). In fact the high frequency UV light used will not pass through plastic or most glass. To pass this light, the window in the EPROM is made of quartz crystal. The correct frequency of a light source alone won't guarantee proper EPROM erasure. The intensity of the light source combined with the distance from the light source determines the intensity of the exposure. Light intensity varies inversely with the distances from the source. (The longer the distance the lower the intensity of the light.) You will find that the closer the chip is to the light source, the faster the EPROM will erase. Chip manufacture tell us, "the EPROM should be 1" from the light source with an intensity of 12mW/Cm2". The manufactures state a 1" distance to ensure that the light intensity is even over the entire EPROM, defused, with no shadows over any part of the EPROM silicon. (Yet, I have successfully used a 1/2" distance to speed my prototype work.)

Besides bulb to chip distance, bulb age also effects exposure time. Be aware of the age of the EPROM technology you are erasing. Older 1.3 micron technology takes longer to erase than .7 micron technology. With all these variables, the best way to determine exposure time is to run an empirical exposure test. First, expose the EPROMs for 1 minute and test for erasure. If they are not erased, expose them again for another minute. Keeping track of the total exposure time, repeat this process until they are erased. Now take the total time and multiply by 1.5. For example, if it takes 3 minutes we should use a 4.5 minutes exposure time to ensure good erasure without over erasing. Remember if you leave an EPROM in the eraser too long, it can remain erased forever and will no longer program.

Every time an EPROM is programmed and erased it wears out a little. Erasing cycles will slow down access times, but this is usually of no consequence unless you erase them an extreme number of cycles or for an excessive exposure time. An EPROM with slow access time, may still program and work fine on an EPROM programmer, but beware that the EPROM programmer does not require or test for a fast access time. A worn out EPROM may program correctly yet fail to work in the equipment that requires a fast access time.

Some people have problems when programming CMOS EPROMs on older programmers because of the differences in programming voltages (CMOS has a 12.5V Vpp). CMOS EPROMs also require a supply voltage (Vcc) of exactly 6 Volts. CMOS parts are easier to erase but prone to die if over exposed to UV light.