I am building a ground up car and now i find my computer will not hold codes or wont repeat them now the car will barely run i unpluged my ecm and the car will still try to run does the computer not have to function to work the fuel injectors ??/ or is there some primary system at work and the ECM just regulates everything ????

 

A little more info on the car, engine, and year would help

 

Big bad 434 under 10 to 1 200 Cfm AFR heads tpi after
Market intake tubes 58 mil throttle 36 lb injectors etc etc the computer seems toasted but it still runs if I prime it to start and hold the throttle about 1/8 open it will run for a few miniutes so the injectors are working the ECM runs that rite ? I am going to put on my ostrage 2 and emulator and see what happenes now ever time I. Plug the ECM or the memcal or anything with the computer do I have to in hook the battery ?

 

From what I've been able to piece together from your multiple threads on what seems to be the same topic, it sounds like you're trying to run large (36 lb?) injectors without any tuning. If this is the case, it won't run very well in this configuration and will be very rich.

In order to help you, we need to understand what you really have in the present tune. Is it a 100% stock binary, or a custom tune?

First, you can check the eprom label (if it is still present under the blue cover) to identify the original broadcast code (bcc). Otherwise, you can try and read out and save your existing bin file with a programmer to try and identify it via the prom id, or with comparison to known bins. You could also check the prom id with an appropriate scan tool.

Once you have an idea what you really have, first step would be adapting the tune for the injector size assuming that the hardware is all functioning properly.

 

No man I have all the gear 700 bucks worth of the best stuff I am trying to get a start on this, The car should idle run so I can see what it needs. I have the right gear a data logger a ostrage 2 all the adapters a MTX air fuel ratio gauge etc etc. My thing is it Doesn't do me any good if nothing else is working it is bezzar odd I can run the car but barely, I have to prime it to start it and every sensor shows voltage but it never seems to very (change ) at all I think the ECM is toast but my question was if it was toast could the car run at all wouldn't the fuel injectors not work at all ?? I am going to run a different bin it is from someone else's car they have 33 lb injectors and I think it is stroked a bit 383 . My problem is I am not well versed in fuel injection programs I have built many old school engines so I have no trouble with the mechanics But the language ,, I'm learning but slowly so Patience is soo appreciated.

 

That's my problem the hardware I know something is wrong but every checklist I run down I end up with an option the list Doesent have or the list ends without telling me what to do next . I'll figure it out but it is sometime a bit frustrating like 2 min ago I closed the pass door leaving a screw driver in between the corner of the windshield and door busted my windshield badly

 

Any one know that question Does a Car with NO ECM Run will the injection system function and if so what else could go wrong with the wiring to make a car run but every other function TPS stuck at 5 volts mas stuck at .5 volts the cold start doesent seem to work any time i try to set up anything i cannot the codes they wont work constant engine light. I checked the grounds all good if i remove the ECM i get no engine light . this also says the wiring is probably good . The wire that can turn the ECM off by the distributor it is beige rite does it attach to the dist like the tach or beside it I haven't found it yet if it was not attached or riped off some how what would the symptoms be ?
Again don't mean to be a pain in the rear but these can be frustrating .

 

The computer will go into limp mode if there are major problems with the sensors. Interestingly, I have never seen a list of the things that will put it into limp mode.

All those wacko voltages point to bad grounds. Check the ground connections on the side of the block above the oil filter. Depending on the year (which you didn't specify) you might have some ground connections on one of the bell housing bolts.

The cold start injector thermo switch only works while the engine is cranking (it's connected to the starter). It has a timeout built in and will turn off after 8 seconds and/or when the coolant temperature is greater than 95°.

How are you trying to read the codes? Did you connect pins A & B together on the ALDL connector? The ECM controls the SES light, so disconnecting the ECM will keep it from lighting. There is a section in the FSM on how to troubleshoot problems with the SES light.

The tan wire with the black stripe disconnects the timing advance from the ECM. The base timing of the distributor will still be in effect. The connector is next to the windshield wiper motor.

 

I'll look at the grounds the car is an 87 but it seems to have more 88 in it I bought it not running and now regretting that move saved some money but could end up costing my sanity . Yes I grounded out the A B on the obd1 terminal and I traced back the ground and the wire to the ECM both wear fine so I keep comeing back to there must be a glitch in the ECM no one seems to know if the injectors will pulse without the ECM working ? I am going to look for a computer in the morning and I'll see if that helps thanks for the info

 

The ECM controls the injectors. There is an injector driver transistor (basically an electronic switch) inside the ECM that turns them on.

There are two ways the injectors are pulsed. One is by the calculations and lookups from the fueling tables that the microcontroller does. The other one is "limp mode", which is controlled by the FMD (Fuel Modeling Device) chip and the resistor networks in the MEMCAL.

 

It should definitely not run if the ECM is unplugged but there is a backup network in the ECM that can get the engine running in the case the ECM is plugged in but there is some significant failure with the main computer.

Since you talked about an ostrich it is also possible you have a bent pin on the EPROM cable, corrupt BIN or some other issue. Fried computer is also possible, just relatively rare.

If you can get your hands on a known good stock ECM just swap it in. If that doesn't work then at least you know to start looking at wiring.

 

Thanks soo much I took the ECM to my home lab I fix Led LCD and Plasma TVs the flat screens any how the technolagy is simple compared I checked all the parts I could there is a few small silo transistors and Optocoupler or two that I couldent test but the components seem fine the circuits are intact I don't think it's the issue anymore I am going to try to do a data log the car will barely run I have to hold the throttle about 1/8 to 1/4 open to allow it to idle and that's at a good 1200 My question will a data log tell me what the ECM is doing or will it work at all because I think the data port may not be working correctly I also will relocate the ground wires they wear bolted to the block but there may be clear coat or paint possable it is causeing the issues should I attach the grounds to the aluminum heads ? Sorry guys it's nice to have a sounding board on this when I fail and come in defeated it gives me some new hope as to figureing this out . The old me would have taken this to an expert alwready but in this case I want to do this all myself I want to know this car like the back of my hand and besides the expert is a 7 hour trailer ride away and charges 200 an hour lol

 

Start with the basics. Check for good power and ground (try measuring with a volt meter right at the ECM connector) and then get it into diagnostic mode with the ALDL pin. If you can't get the CEL to blink stuff I would get a new ECM before going any further. If you really want to entirely eliminate wiring issues, see if you can find a set of ECM connecters at a wrecker and then try firing it up on your bench. I don't have the same computer as you but grab a wiring diagram (you do have a FSM, right?) and have a look. I expect that even with nothing connected except power, ground and the CEL you should be able to get it to flash codes.

Once you are confident the ECM is sane then start looking at codes to see what else it thinks might be wrong. You can also use datalogging to see if that tells you anything.

The two big things a PCM has to get right to run are fuel and spark. Your symptoms don't sound like they are related to spark but stuff like MAF, MAT, and TPS can mess up the fuel, as can fuel pump and regulator. See if you can pin down the problem to one or more of those. Sometimes disconnecting a sensor altogether (MAF is a good example -- just make sure you do it with the ignition off) can help determine whether it is the cause of the issue. In some cases the car runs better with no data than with bad data.

Keep your determination, there is no reason you can solve this yourself. Good luck!

 

Thanks that's an exelent beginning to this also say my Mem Cal is toast will the ECM flash with emulation

 

Also this started out as a timeing question as I was playing with my tunner pro and the ECM and it has gone off subject a bit hope it is ok to keep it going for me it is an invaluable tool

 

You won't get your normal codes if the memcal is bad but you will probably get something else flashing to indicate there is a problem.

 

I should find a obd1 port pinout so I can see what each wire is suposed to be doing and can make sure they are . I also am seriously looking at upgrading to Map its not nessasary yet although I would love to turbo this in a few years and I wouldent have to tear the car apart again then but it would be nice to start with a good running system first . Another issue I noticed someone has changed the Mas air flow unit plug was cut and different plug with different color wireing was spliced in could this be wired in wrong could this be incompatable with mine I need to run its number . If I unplug that I may get my answer . Thanks again

 

Hmmm... well, a different connetor isn't an issue, but do check to make sure they are electrically equivalent and wired appropriately. Unplugging is also an easy thing to try.

 

I was not worried about it when I first saw it I assumed this was the correct unit it looks like and fits perfect in the vette but the plug I thought maybe it had broken and was falling off and they replaced it but now I think I should double check what all uses mass air flow old Camaros TAs did they use the TPI in anything else ?
Apretiated Budd I'm going to go try some of these things

 

I'm guessing anything with a TPI used a MAF, not sure what all that was but Camaros for sure. I you can find a part number on the MAF google might tell you what that should work with.