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i know this has probably been asked a million times but i'm going to ask one more time. i have an 86 z28 with the tpi and as wondering what the best route is to delete this PITA? I've heard you can just unplug it and roll on and I've also heard you need the ecm out of an 88+ car because gm did away with the cold start injector. any help is appreciated
I also have an '86 TPI. The ECM is irrelevant. The PROM/CALPAK is what controls the service injectors through the ECM. There is a cold start enrichment routine in programming which can effectively replace the function of the cold start injector. If the programming is done the cold start injector can be removed and capped or abandoned in place.
Stepping back one or two paces, what is the problem with the stock cold start system?
I also have an 88 IROC that I want to delete the 9th injector. Is there anyone on here that will program my PROM for cheap? The problem with mine is the injector isnt turning off and fuel is getting into my vacuum lines wreaking havoc ! Any help appreciated as I am new to this. Thanks
I also have an '86 TPI. The ECM is irrelevant. The PROM/CALPAK is what controls the service injectors through the ECM. There is a cold start enrichment routine in programming which can effectively replace the function of the cold start injector. If the programming is done the cold start injector can be removed and capped or abandoned in place.
Stepping back one or two paces, what is the problem with the stock cold start system?
I think the stock injector is faulty which is dumping too much fuel on a cold start causing the car to idle weird with a strong smell of raw fuel
I also have an 88 IROC that I want to delete the 9th injector. Is there anyone on here that will program my PROM for cheap? The problem with mine is the injector isnt turning off and fuel is getting into my vacuum lines wreaking havoc ! Any help appreciated as I am new to this. Thanks
The cold start injector isn't even remotely associated with the ECM. Its circuit is completely separate from the ECM.
Originally Posted by kkirwan71
I think the stock injector is faulty which is dumping too much fuel on a cold start causing the car to idle weird with a strong smell of raw fuel
Unplug the cold start injector and see if the problem is still there.
This is how the cold start injector works:
The cold start injector gets its power (12v) from the ignition switch side of the starter solenoid.
The ground side of the cold start injector runs through its own coolant temperature switch that's located in the intake manifold below the thermostat. The temperature switch also contains a heating element that limits the time the injector is "on", inversely proportional to coolant temperature - it's on more when cold, on less when the coolant is kinda cold (within its operation range).
The cold start injector turns on only when the ignition switch is in the start position and the coolant is "cold"; the temperature switch is closed and grounded which completes the electrical circuit.
When the coolant is "hot", the coolant temperature switch is opened. In this case the electrical circuit is opened so the cold start injector will not turn on when the ignition switch is in the start position.
If you have a perceived problem with the cold start injector being "on" too much and you're a throw parts at it kind of person, you can start with a new coolant temperature switch. However, I strongly recommend getting out your FSM and following the diagnostic flow chart for the cold start valve because a new cold start temperature switch is around $200.
Correct me if I am wrong, but my understanding was that the ECM tells the injector the amount to spray depending on the signal it receives from the injector thermostat. I may be wrong. The reason for my question about reprogramming the PROM was if I delete the cold start injector, then it will be like the 89 and later IROC and couldn't i reprogram my PROM or replace it with one from an 89 with the same variants as my car 305 TPI and manual 5 speed?
Correct me if I am wrong, but my understanding was that the ECM tells the injector the amount to spray depending on the signal it receives from the injector thermostat. I may be wrong. The reason for my question about reprogramming the PROM was if I delete the cold start injector, then it will be like the 89 and later IROC and couldn't i reprogram my PROM or replace it with one from an 89 with the same variants as my car 305 TPI and manual 5 speed?
Again, the ECM does not control the cold start injector.
See the attachment. There is NO cold start injector connection to the ECM.
If you want to eliminate the cold start injector, I'd guess you will most likely have to re-program the remaining eight injectors to decrease their dwell time in order to richen the mixture just for cold starts. Alternatively, I believe you can unplug the coolant switch and plug in an EPROM from an '89 TPI, provided the cold start injector isn't mechanically fubar and leaking fuel.
Why you would want to go through all this instead of just fixing the cold start injector issue is puzzling.
Last edited by paulo57509; 06-20-2016 at 10:31 AM.
so the injector checks out okay. i feel like i've been struck with some sort of gremlin. the fuel pump likes to work when it wants to for the past couple days. when cold the car surges horribly almost likes it's getting ready to shut off. then when it straightens out, the check engine light comes on but no codes are stored. any ideas?
I don't think you'll find new connectors. Your most likely going to have to get them off a junked car. More importantly, you going to have to figure out why those connections got hot/fried in the first place.
Take more photos of the same things. This time, pan back a bit so we get some idea of where the connectors and wire looms are in the engine compartment.
Also, in the first photo, show the thing that's in your hand; show what the connector is plugged into.
I'm going to take a SWAG and say they're not for engine controls; no weather seals. Might be for HVAC?
Another question: Is there hacked wiring anywhere under the hood?
thats actually 2 different plugs. they're located on the driver side of the firewall. there are 3 of them that are exactly alike. 3 new connectors was $43 off rockauto.
those are your maf, burnoff, fuel pump relay connectors, I just replaced all mine they were starting to look like yours. You can pick them up off ebay, there is a seller that does them with the factory colors for the wires makes it really easy and professional looking
those are your maf, burnoff, fuel pump relay connectors, I just replaced all mine they were starting to look like yours. You can pick them up off ebay, there is a seller that does them with the factory colors for the wires makes it really easy and professional looking
sorry for the super late reply guys! my dad and i are tackling the project tomorrow. we have to re-pin one or two of the connectors since the big wires are in different spots but the connectors are easy to get apart so that'll make the job easier.
replaced the connectors and relays today. it seems to have solved the issue only time will tell. it hasn't been cold enough to replicate the first issue
06-19-2016, 08:48 AM
sorry for the super late reply guys! my dad and i are tackling the project tomorrow. we have to re-pin one or two of the connectors since the big wires are in different spots but the connectors are easy to get apart so that'll make the job easier. 
