I'm lost and I'm reaching out for some direction... for starts, here's the background...

I bought this car over a month ago from a tow yard for 700 bucks. The car wouldn't start with the key but would crank when jumped from the starter. After a new ignition cylinder, key[(with the dreaded VATS pellet) because I originally suspected a VATs problem], starter, battery and much needed cleaning, I got the car to fire but with a surging idle. So after looking at thread after thread on here, I solved the surging idle problem with a tbi rebuild kit from Oreilly's. Worked like a charm!!!! That is until I came up with the nifty idea to change the IAC valve because I thought the idle was too high. Not knowing that I needed to allow the ecm to readjust to the new iac valve, I failed that step in the procedure. The next day, I went out to start it and noticed the fuel pump didn't prime and I had no spray from the injectors so I changed the fuel pump.

Now I have a new fuel pump, nice strong prime and fuel at the throttle body but no spray from the two injectors. So I get two new injectors, a new throttle body, ecm for the heck of it and still no change. Frustrated and ready to torch it, I have it towed to the Chevy dealership for their service department to diagnose its ailment.. one look, minus a few choice words about its condition and we're back at VATS!!! I was told that I would "probably" need a new vats module, ignition, and keys ($500) and about 7 hours of labor just to pull the dash although the system says 2.5 hrs. Wtf!!! AND THAT DOESN'T EVEN GUARANTEE THAT THE ISSUE IS REALLY WITH VATS OR NOT!!

that's my story... here is a list of things I've changed...
MAP sensor
IAC Valve
OPSU
THROTTLE BODY
INJECTORS
CTS/TPS
FUEL PUMP/FILTER
ECM
FUEL PUMP RELAY
IGNITION CYLINDER

Anyone, please help me!!! I ordered one of those fancy vats bypass modules. If this doesn't work, I don't know what else Ill need to do to get her running again..

someone, in all your wisdom, help me please ...

 

you dont need a fancy bypass module. to shut the dealership up go to radio shack and buy the big pack of assorted resistors, its like 5 bucks or something, take a DVOM and measure the pellet on your key in ohms, do a search on here, you dont have to be dead on but i believe its like within 200 ohms that you can get away with, pretty much take the resistors you bought, add up some numbers ( the closer the better) then solder them together in series ----R----R----R---- like that, find the appropriate wire for the vats module, cut it, and place your new resistor setup in between the two ends, i soldered mine in place and heat shrunk it.

5 bucks and a bit of time is better than a bypass module plus shipping, and worlds better than 700+ labor

 

Thank you. I'll be trying that in the morning.. I have a number 6 key which I believe is 1.47 ohms but I have no idea how to go about making a resistor to match that. Maybe the radioshack people can help.
In the meantime, if the bypass doesn't work, what could be another reason I have no spark when turning the key?

Just out of curiosity, since mine measures 1.470 ohms can I just get one 1.5k ohms resistor instead of connecting a bunch of smaller ones to get the resistance?

 

Resistor only gives the correct signal INTO the VATS module so it operates.

Does nothing for the required fuel enable signal OUT from the module to ECM
if the VATS module itself is faulty.
The bypass module generates this fuel enable signal so VATS is removed completely

 

If the vats module is bad, is there any way I can replace that myself without going to the dealership?? If so, where might I find this part? Or is it specifically GM specific?

 

ahh damn vettoz youre right lol i didnt even think about that, my key went out on me so that was my fix, so i guess the second cheapest option is gonna be a module

to the OP yeah 1.5 should be within range but vettoz made a valid point that the problem is on the output side, not the input

 

Is within the required range
See
https://www.thirdgen.org/vats_passkey_system

 

It is just a plug in unit; doesn't require a mechanic to do it
the diagram in the link above shows where it is under the dash

Is going to be a GM OEM part only
Finding a new one could be a problem ( and cost $$ ) so the bypass is probably the cheapest cost effective option
You could get a junkyard module but would have to try all 15 resistor values until you found the one that is programmed in to module.
Units can not be reprogrammed to different values

 

Ok. So the bypass module will delete VATS like I don't have it? Or is it a more temporary fix until I get a new VATs module itself? I ask because the bypass module only ran me about $20 bucks and if it does ever go bad, then i probably should order about 10 of them. lol.

thanks for the insight. ill definitely post the results. besides vats, is there any other reason I get nothing when turning the key?

 

Look back at the diagram in post #4. The module not only disables the injectors, but the starter as well.

 

So if the module is bad can it still read a bypass?

 

For all practical purposes the bypass is the key.
If the module fails to read the key it won't output the enable signal to ECM.
I have a VATS module on my '88. I don't have a pellet in my key, but my starter still works. I have to disable the VATS in the EPROM to enable the injectors. So either there is a key bypass, or the starter enable relay has also been bypassed.

 

Thank you for your help. So essentially there's a two step process in the bypass... bypassing the key, then bypassing the starter enable relay? It may sound stupid but what is a prom/eprom?

 

An EPROM is a memory chip for the ECM.
In your case I believe the key bypass should get you going.

 

Ok. Great. Ill try it this morning. Will I have to ground out the black/yellow wire from the starter enable relay?? Where exactly is it located? The diagram is a little confusing to understand.

 

As long as the key bypass works you won't need to do a starter bypass.

 

Ok. I'll post my results as soon as its done.

 

No luck with the resistor... hopefully the bypass module will do the trick. If not, I'm converting from tbi to a carberator.

 

Ok.. so after some tweaking, I got it to start but I have the surging idle issue again. I see how it surges but I'm not sure why. The injectors are spraying but its not constant. It's just a slow pulse/spray which causes the motor to surge... any ideas?? Plus, it won't fire up without me pouring a little gas on the throttle body. Does anyone know why? Could that be the vats module telling the ecm not to fire the injectors properly?? Or is there a way to adjust the rate of speed the fuel comes out of the injectors? Otherwise, I found a 3 bolt adapter thatll fit on the intake in order for me to convert it from a tbi to carberator..