start with fsm charts, "cranks but no run,' A-3 in my book, that verifies strong spark, and injectors working. will also direct you to other symptoms. your initial problem was run 3-4 secs.

the fundamental diagnosis starts with the simple pick up coil test. your engine fires, but I would not overlook anything, esp since it costs nothing but time and effort. does pu coil match coil polarity? chart c-4, item 4.
faulty grounds cause wandering run issues. only the poster knows what has been altered.

lots of contradictions here. the engine ran fine with new icm, then didn't, ran with tps unplugged AND one inj bank out. from there, only the OP knows what happened or what changed.

now runs with maf unplugged. all other components in circuit? BR said that connectors are always suspect.
the TPS can be verifed with a meter. also, with both tps and maf unplugged, ecm is supposed to set a default value. not sure if my info is correct on that.

my experience, most problems are not resolved by "thinking" unless that involves a process, thus the fsm. but, from your first comments, it points to TPS, as the "now" problem.

 

Spark is ruled out, the car runs without MAF...no way unplugging the MAF could correct a defective spark issue...

Fuel follows the same suit......


Has to be a sensor shutting things down, this is where I run into issues as I do not have a MAF circuit diagram. FSM says if you unplug the MAF and a code 33 sets, its the MAF. (Now I can't find the post with the diagram)

 

I have all the code charts on my webpage.

http://members.shaw.ca/corvette86/

 

not debating, just commenting. I would rule out spark and fuel, too, if not for the history of issues you have mentioned. weak spark is not sufficient to run.

anyway, my fsm does not say code 33 equals maf. it DOES say that a failed maf uses the TPS to control fuel delivery. from your first symptoms, there was no code 33.

the problem "has to be" any number of things. keep plugging.

saludos, joe

 

http://members.shaw.ca/corvette86/Code%2033.pdf

Went through the entire process....points to bad MAF.....

That being said its setting of a 33 because its running with it unplugged.


I am going to clean all of the terminals, reset TPS and lets see what happens.


Thanks Agent86 for posting...big big help

I also can't help but notice that oil pressure sensor is in the same loop
but Joe you seem 110% certain that would not be it

 

not that certain of anything, gaff. your 87 uses oil switch and fuel pump relay for power to maf, mine has MAP.
I am almost certain that if FP relay is working, oil switch is backup, so says fsm.

if fp relay is working, oil switch voltage is immaterial. also, did you verify that the switch was indeed out of the circuit? the engine is running, so it is a moot point.
I reckon that if the maf had no power, unplugging it would not make a difference.

 

Just for the heck of it,
Swap your MAF sensor power relay & MAF burnoff relay around.

They are identical in the 1987 Model year.

If your Corvette fires up..........you found the problem.
MAF sensor was not turning on...........BAD MAF POWER RELAY.

I have had both MAF power & burnoff relays fail on my 87 vert last year.

Replace them both with the latest GM update relays.

 

Both replaced yesterday...no luck

 

Is the 2 wire oil switch the one that cuts power?

 

Going to try another MAF

 

Swapped the MAF and still nothing......I jumpered the ALDL term G with 12 volts after having no luck...this was on a whim that if I did this I might rule out the oil switch...or maybe I created an excess voltage condition.


I did receive a sign....as I got in the car with the new MAF Sensor there was a paper clip on the ground....maybe someone is trying to tell me to backprobe the TPS.....not an easy task with the rams horn on the callaway. I also need to look through the FSM for testing, code 21 I think is done with car running.

More to come...thoughts are welcome

 

What I use. Engine off, key on. Procedure is in fsm.

 

Lee I've got a Maf low output code on two cars recently.Both cars ran 3 or 4 seconds and died. Both cars ended up with bad ECMs. I was told the bad ECMs would not allow fuel enable. I still do'nt know why I got a MAF code.

 

Not sure why people get all up in arms..Looks like someone deleted their post

I suggested the TPS first...everyone said its the injectors or or injector harness...

followed the FSM and tested the fuel injectors
I tested the MAF per the FSM code 33
I replaced the relays...which was suggestion too

I checked fuel pressure, per the FSM

Am I an expert on electrical issues, no.

But I think what I have done is far from being fixated on the oil pressure switch. I tried backprobing the TPS, not an easy task with the rams horn in place it bolts throught the TB. I was not confident my readings were accurate. I am not sure if having the TB uneven could through off the setting or not....I guess it would not as it measures the switch position....

pic of TPS butting up against the rams horn:

 

I see the problem, but, the TPS should be verified, and set to spec if needed. maybe you could trace the wires back and test them using the pins?

not being sarcastic, but what did you learn about the oil switch? you mentioned jumpering G in aldl but didn't say what the result was. for my view, that repeated lack of information, or sparse info in your one liner posts was not enough to work with.
"which oil switch cuts power?"
no one replied probably because they had no idea what you were talking about. power to what?

after all the thrashing and parts changing, I still am confused about how long the engine runs before you kill it or it dies, because you never explained that. has it been 3-4 all along?

we are not experts, either, and we're not clairvoyant.

anyway, appears that you have to remove some of the components to check the tps, or maybe someone knows a solution.

joe

 

The car starts up, catching fast like a normal start and then just dies. 3-4 seconds tops.

The question about which oil pressure switch cuts power is referring to the fact that there are two switches at the back of the motor; 1 that feeds the gauge cluster and one that shuts off the motor to protect it from low oil pressure. The parts store refers to it as light and gauge, the switch with two prongs is the one that is a satefy net for the motor.

http://www.autozone.com/autozone/par...23513_0_0_5835

After the 2nd MAF did not make a difference, I decided to use the 12V supply w/fuse to terminal G; that is used to test the wires to the MAF for a short to ground.... to see if I supplied power to the MAF sensor if it would run. My thought was if there is something shutting down the MAF if I kept it supplied with voltage then I would bypass any sensor cutting off power; oil pressure, etc.....again that was a guess but it took 5 minutes to try.

I will try to figure out a way to test the TPS, which was my first thought, the pressure from the rams horn seems like alot and 20 years of it I thought might cause some issues.

So that is my next focus, I did get a copy of the 87 FSM from a member and will test for an issue with grounded circuit on the TPS.

I am getting a code 12, so ECM is on my mind but not the next to test, although if you followed the FSM I had a code 33 with every indication I had a bad MAF Sensor. At this point, I will stop with the updates and just let everyone know when I get the issue solved.

Joe I was not referring to you, there was someone who posted that people would help if I would follow the FSM.....they then deleted the post. Clearly if I am making fusible link jumper wires to the ALDL G connector I am following the FSM, as this is not something I know how to do off the top of my head....

 

You can check the TPS voltage at the ECM (pin C13) by using a straight pin. Just ground your DVM to the ECM case. It's fairly difficult to get the pin down into the back of the connector. I got a hat pin (about 3" long) from somewhere. That's what I use.

The car should run with the TPS disconnected. The ECM uses a default value.

Error 33 indicates a bad MAF or open connection to the MAF. Try opening the ECM reset connector (Figure 4 on page 6E-6 of the FSM) for a few seconds to reset the error codes and see if the error is still there afterward.

 

Can't comment on your Callaway, but the oil pressure switch is just a back up power supply to fuel pump, in case fuel pump relay or circuit is damaged.

Using a scanner or laptop with software, is going to be your easiest way to see what TPS voltage, the ECM is seeing.
Anyone in you area have either ?

 

Thanks for the info Agent 86.....no one in my area that I know of....I would be willing to buy the software, etc.....but not sure what all I need....obviously an ALDL cable, but what else?

 

Datamaster is free for 20 sessions. You would also need a cable interface.

Does it still run with one bank unplugged ?