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Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
Hello everyone. I've gotten a lot of great information here, but have never posted anything. I'm having issues with my 1986 Iroc z. I bought it 8 years ago. It has a 305tpi with a 6spd t56 in it. The issue that I have is sometimes when I stop at a light it revs to 2krpms and other times it stalls. The only code I get besides 12 is 24. It has shorty headers but not a heated O2 sensor. Could that be the issue?
The worst that would happen with the non heated O2 is kicks back to open loop fueling at idle, which wouldn't necessarily cause stalling issues.
Code 24 is for the vehicle speed sensor. If the problem is occurring right after you come to stop, this could be a problem. Without the VSS operating properly the ECM can't work the deceleration elean fuel subroutine properly. Could be running into a fuel starvation issue. Then when the rpms drop precipitously, the anti-stall kicks in and the engine rpm jumps up.
I would get the VSS sorted out before going any further.
Did you not hook the VSS back up after the transmission swap?
I bought the car with the swap already done. It's always had the hi idle issues but just started stalling out after the headers and exhaust were done. I'll look into the vss. Thanks.
So I finally had a chance to look into the vss. There is a Dakota digital sgi-5c under where the ash tray is. How do I know if it is connected properly or working? Plus is it the right one?
Somebody club me like a seal if I don't know what I'm talking about...is your speedometer functional?
What would be good to know if you're using a manual or auto PROM?
Not sure how the previous owner set it up. The stock trans probably had drive/driven gears that turned a cable that's up on the backside of the speedometer. Back side of the speedometer also has a optical sensor that sends signal to the ECM. This all needs to be functional to prevent stalling when coming to a stop.
The T56 if it's a '93, had a 11 tooth tone/reluctor wheel and all other years 17 that puts out magnetic pulses so it doesn't have a cable drive.
The SGI and abbott is what bridges the gap of not having the cable drive. I'm not familiar with either and not sure what the PO did. Since the speedo's optical can talk to the ECM, all you would need is the Abbott to spin the speedo. I'm thinking the Abbott needs the SGI to convert the 17 p/r but not sure. Keep in mind in this scenario, either failure points of the SGI or/and the Abbott would cause driveability issues.
Not sure about your SGI model but if your SGI has multiple outputs, it could be used to feed the ECM directly and use a second output to feed the Abbott. If you set it up in this manner, the Abbott could fail to spin the speedometer but since the SGI is feeding the ECM, it wouldn't present any driveability issues.
Last edited by stew'86MCSS396; 11-12-2022 at 09:26 PM.
09-09-2022, 08:56 AM
Dakota digital sgi-100bt if you don’t have it 
