retro engine for 1988 corvette?
Race Director
Joined: Apr 2002
Posts: 10,036
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From: Anaheim CA
Finally got it fixed! Had a good old school mechanic check it all over and everything was good...grounds fuel spark, etc. but no injector pulses. Called Jim's performance in Maryland, and he talked to my mechanic for almost an hour helping him double check everything...MAF you name it still no pulses! At first Jim was pretty adamant it wasn't the VATS because the starter would turn over but no injector pulses. He said VATS would not allow the starter to crank. After going through everything with my mechanics he agreed that the VATS was the only possible problem. We sent him the chip and he eliminated the Vats from the computer program now it starts every time. Funny thing is now my power antenna will not go down. I hear the motor running but it won't return the antenna to the down position. This experience was a very costly one for me but hopefully it will help others out there that run into the same problem. i highly recommend Jim he is an outstanding individual, talking to me for 20 minutes and my mechanic for nearly an hour and would not accept any reimbursement when i offered it!
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Wow I am amazed at the smug know it all posts of a few people on this board! I already posted that everything checked out ok......including the codes that he did run, (3 times), the last time with Jim's Performance. Never once did a code 46 show up! This was a very unique problem and proves out that things are not always as straight forward and "matter of fact" when dealing with these computer systems. Jim is supposed to be very knowledgeable and even he was stymied! He concluded it had to be the vats even though there was no error code 46 and the injectors still would not pulse even though all other checks proved out ok.
Melting Slicks
Joined: Jun 1999
Posts: 2,931
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From: Ashland Alabama
Umm actually it can be vats and do what he's saying it did.
If the logic in the vats reads the correct pellet resistance in the key its happy. At that point it goes into the all ok mode.
If the dark green wire from the vats works the starter works.
If the purple wire from the vats works the ecu gets its signal which will then cause the injectors to get pulsed, fuel etc.
If the dark green wire works but the purple doesn't the motor spins over but no injector signal.
The above can be caused by a bad wire, bad connector or even a bad vats if it has internal issues.
If the logic in the vats reads the correct pellet resistance in the key its happy. At that point it goes into the all ok mode.
If the dark green wire from the vats works the starter works.
If the purple wire from the vats works the ecu gets its signal which will then cause the injectors to get pulsed, fuel etc.
If the dark green wire works but the purple doesn't the motor spins over but no injector signal.
The above can be caused by a bad wire, bad connector or even a bad vats if it has internal issues.
Melting Slicks
Joined: Jun 1999
Posts: 2,931
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From: Ashland Alabama
One thing I didn't mention in the above is that yes it will crank and not fire the injectors in the above scenario BUT it should still set a code in the ecm for a vats problem. Not sure if for some reason his isn't or he didn't check the codes. Wasn't there so cant guess more than that.
Le Mans Master
Joined: Oct 2008
Posts: 9,758
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From: Houston Texas
Believe me, I am keeping an open mind and I'm not doubting the experience of Jim or his abilities, I've got an 88 with a similar intermittent no cranking issue, so I'm trying to learn as much as I can.
I don't think you understood my question.
As far as I know (anybody please feel free to correct me if I wrong) VATS cuts the power to both the starter and the injectors, not one or the other, but both at the same time.
So if it was genuinely a VATS issue, first and foremost you shouldn't have been able to crank the engine over at all.
I don't think you understood my question.
As far as I know (anybody please feel free to correct me if I wrong) VATS cuts the power to both the starter and the injectors, not one or the other, but both at the same time.
So if it was genuinely a VATS issue, first and foremost you shouldn't have been able to crank the engine over at all.
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Le Mans Master
Joined: Oct 2008
Posts: 9,758
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From: Houston Texas
I don't know how and why all I know is that even though there was no error 46 code that eliminating the vats from the prom chip corrected a problem that had us all pulling our hair out over. ! am having fun driving it now and am very thankful to have a great dependable American sports car!
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Oil Producer
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[QUOTE=Bandit1977;1588731852]Believe me, I am keeping an open mind and I'm not doubting the experience of Jim or his abilities, I've got an 88 with a similar intermittent no cranking issue, so I'm trying to learn as much as I can.
I don't think you understood my question.
As far as I know (anybody please feel free to correct me if I wrong) VATS cuts the power to both the starter and the injectors, not one or the other, but both at the same time.
So if it was genuinely a VATS issue, first and foremost you shouldn't have been able to crank the engine over at all.[/QUOT
in this case would the wire/defective vats need to be replaced or would just programming the vats out of the equation allow both crank spark and fuel to happen?
my understanding is that the poster had his vats removed from the software? in other words creating an ok condition, but if there was a physical gap in the signal getting through, unless the ecu can send the signal down another path it still should not start?
i think these are some of the greatest and toughest gremlins to track down!! thanks to the op for coming back and reporting his findings.
I don't think you understood my question.
As far as I know (anybody please feel free to correct me if I wrong) VATS cuts the power to both the starter and the injectors, not one or the other, but both at the same time.
So if it was genuinely a VATS issue, first and foremost you shouldn't have been able to crank the engine over at all.[/QUOT
in this case would the wire/defective vats need to be replaced or would just programming the vats out of the equation allow both crank spark and fuel to happen?
my understanding is that the poster had his vats removed from the software? in other words creating an ok condition, but if there was a physical gap in the signal getting through, unless the ecu can send the signal down another path it still should not start?
i think these are some of the greatest and toughest gremlins to track down!! thanks to the op for coming back and reporting his findings.
Melting Slicks
Joined: Jun 1999
Posts: 2,931
Likes: 127
From: Ashland Alabama
Even with the vats removed from the software its still needed to work the starter. Software alone isn't going to make it allow the starter to work.
But if the vats is functioning enough to allow the starter to work then an ecm update will get the car running.
But if the vats is functioning enough to allow the starter to work then an ecm update will get the car running.
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
Wow I am amazed at the smug know it all posts of a few people on this board! I already posted that everything checked out ok......including the codes that he did run, (3 times), the last time with Jim's Performance. Never once did a code 46 show up! This was a very unique problem and proves out that things are not always as straight forward and "matter of fact" when dealing with these computer systems. Jim is supposed to be very knowledgeable and even he was stymied! He concluded it had to be the vats even though there was no error code 46 and the injectors still would not pulse even though all other checks proved out ok.
Also note that you can bypass the VATS starter enable relay (which is done fairly often) and the engine will crank even if there is a VATS problem:
Last edited by Cliff Harris; Jan 17, 2015 at 03:20 AM.
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Sorry. I guess I missed it where you told us you checked the error codes and found none. Which post was that in? You told us in several posts that you couldn't check error codes because you didn't have a scan tool. That's why I suggested the "paperclip" method, which doesn't require a scan tool.
Also note that you can bypass the VATS starter enable relay (which is done fairly often) and the engine will crank even if there is a VATS problem:
C4 Corvette Cutaway VATS other Relays - YouTube
Also note that you can bypass the VATS starter enable relay (which is done fairly often) and the engine will crank even if there is a VATS problem:
C4 Corvette Cutaway VATS other Relays - YouTube