So last month I bought this beautiful blue iroc z. New parts all around, couldn't find a problem until we took it for a test drive. Wouldn't idle right, and bucked a bit almost like a misfire when at 1-2k rpm. After about a week of replacing everything we could I called the guy I bought it from back and described the problem. He owns a racing shop where he does nothing but work on these TPI cars and offered to fix any problems I found for free as he sold it turnkey for 4500.

Anyways, turns out the problem is that the computer in there is from a 350. It's a 305 in the car. Obviously too much gas.. He still has the original computer but cannot use that since he swapped the anti theft system because the old one took a crap. Apparently swapped with one from another year car. I don't understand much about the anti theft system, but I do know I need the key with the resistor to start the car.

Now my question is as such: I really do not care too much for the anti theft system. The car has been sitting a month now because he cant find a 305 computer to work with the anti theft system. (I don't know the details about the system as I didnt have the car long enough to look.) At this point I'm wondering if it's just possible to gut out the anti theft system completely without buying replacement parts ? It might be faster....

Is it a pain? When I suggested that idea to them they seem to have brushed it off which made me wonder how much work is involved.

Edit: I'd also like to try to gut this out without any crazy codes firing all the time, or issues occurring.

Thanks,
Bez

 

here check this out
https://www.thirdgen.org/vats
https://www.thirdgen.org/vats_passkey_system

 

Well you see they way it works is the vats system would send a 30 hz or 50 hz signal to the ECM to enable the fuel injector pulses. Now the reson they cant get a computer for a 350 that dosnt have vats is because you TPI set up im assumeing dosnt have the cold start injector and the only computers designed to work without the cold start injector also had a VATS installed. So without VATS the ECM wont get the signal to enable the fuel injector pulse and the car will not run. No if you get into custom programming of the EPROM i hear theres ways to eliminate the vats system or if you created a electronic modual that would put out a 30 hz or a 50 hz signal again you could eliminate the VATS system but in the end its their problem to fix its and its kind that they will make no mistake but they should be able to get it squared away.

 

Hrm. Here's hoping he can get it fixed soon. Been a month now and I want to drive that baby. :P

 

I am having the same problem, but i was wondering what the vats actually does.
when i bought my 89 TA the guy had starter switch mounted on the dash. he told
me the vats disables the starter,and the i heard it disables the ignition, but the
car was running,altho it was missing plus it had aa bad cylinder.

 

how do i know if the vats module in my TA is bad,i was told that the vats
in my TA was bad and that is why the dude that sold me the car,put a
starter switch on the dash. but i heard somewhere else that it will disable
the ignition as well.

 

Well its my understanding that theres 2 parts to the VATS system on our third gens. 1 is it dissables the starter and 2 it dissables the injector pulse. Now the switch in the dash probably just activates the relay that would have been controlled by the vats modual. All it is is another switch in series with things like the nutral saftey switch. However in addition to that it also dissables the injector pulse so someone cannot attempt to bypass the VATS starter relay and start the car anyways.

 

Update:

Spoke to original owner of car. VATS took a dump so he replaced the computer with a motor from an 87 5 speed TPI 350 w/o VATS.

Which explains why it starts like crap on a cold start because it doesnt have a cold start injector but the comp is trying to use it. It explains a ton.

Now the question is.... can I just swap the PROM on there with the correct one? Or do I need to replace the whole ECU/ECM w/PROM. I obviously need one for a 5 speed 89 (no cold start inj) 305 TPI, with no vats....

 

Well thats the whole problem. Although im pretty sure the computer itself is the same and you can swap chips around for different motors ect the catch is this they got rid of the cold start injector in i believe like 89 which also happened to be the year they started installing VATS. So unfortunetly to my knoledge there is no PROM from the factory that does not use the the cold start injector that also does not use VATS.

 

Does he have the original VATS key? If so, your in luck.

Either.....
1. Figure out which resistor value chip is in the key & buy the correct value resistor from Radio Shack.
2. Or just use the actual key...


Now...Pull the wires that go up to the key cylinder, that connect to the key slot, that read the keys chip. And solder those 2 wire ends to the key chip or the resistor you bought from Radio Shack.

Wrap it up to protect it from shorting out anywhere.

Done.


And now, the original ECM can be put back in & always think that the correct key has been inserted. I bet that you are even still using the original key, right?

 

That could be terrible.

 

I have the original key (or so I believe, it has the resistor in it and starts the car heh), but I'm curious. Soldering in the resistor tricks the car into thinking the key is always there (well at least the resistor is always there), but the guy I bought it from believes the VATS module itself took a dump. While it's entirely possible it's just failing at looking for the resistor, I wonder if it really did take a dump. If that's the case, I do not believe the resistor would help correct?

 

Correct. If your VATS box took a dump, that won't help. New VATS box(with matching chip), if nothing else?

 

I did find some solder in vats bypass box that emulates the signals of the VATS on ebay worst comes to worst.

At this point I'm not sure what to believe from the guy who sold it to me. Cool guy but at the same time certain things just don't add up. Told me to find a comp from an 89 z28... yeah.. I'll get right on it when they exist. I'm not even sure if he really HAS the original computer. i'm hoping he does, because if he does I will just take that, slap it back in, and try the resistor/order the bypass module. Worst comes to really worst, I saw a place selling a small board that goes between the PROM and ECM that lets you program custom things in and you tell it on order whether you want to enable VATS etc. Either way, this is looking to be a pain. 4500 for the car (Near mint condition otherwise), bit steep but hard to find one not butchered TERRIBLY out here in NYC, and I've not been able to drive it for a month now.

I'd hate to buy a new computer because he lost the old one, slap it in, bypass vats, and then find out that it didnt fix the issue. He says that he took one from an 88 auto and tested it fine it just ran with the shift light on non stop....

Sigh.

Thanks gents, I'll find out if he has the stock ECM/Prom, grab the car from him and play with it myself in my backyard. I feel I'm getting the run around.

Oddly I work in computers... and you think I'd enjoy a computer in my car.. nope. :P

 

The ECM wasn't from an auto car, if the Shift Light was on.

But if that was the only problem? Pull the Shift Light bulb out...Problem solved & your golden!

And you said this guy is some sort of TPI mechanic? Apparently not!

 

Hrm. Interesting. As for the shift light problem... Yeah I agree nothing terrible but it was from a customers car anyway (he just borrowed it to test mine heh.)

He owns a racing shop out here that deals with nothing but third gens and TPI only. What's odd is the fact things just don't seem to be adding up. I know for a fact he has cars that run great, but mine ran like ***.

Here's hoping he still has the original computer, and that all it is is a resistor. Just hope he didn't remove the entire damn VATS completely heh. Doubt he did however.

 

Yea your telling me ive earned my degree in electronics engineering and youde think that ide have an appreciation for all this electronic stuff. Nope just added complexity. Some stuff is nice but for the most part give me a non computer controlled motor anyday. Now the way i see it i would just instal the right computer and repair the vats system or bypass it with the resistor trick or the modual that emulates the everythings ok signal. You could also swap to the TPI manifold that uses the cold start injector but that i think would be more of a pain than anything else. Although i take it if hes telling you to get the comp he dosnt have the original or he does and its broken. Idk for a TPI expert this all seems like things you wouldnt overlook.

 

He swapped the injectors too, so who the hell knows if it DOES have a cold start injector. I doubt it though as it starts like crap and requires pumping of the gas pedal to get it started.

Hrm... I may just try to get my money back and sign the title back over to him, but I doubt that'll work. Either way at this point I almost wonder if I should just take it back from his shop (Which is far away) and keep it in my backyard and work on it there.