4.8 Voretc hard start and then high idle
01-23-2019, 07:57 AM
#1
4.8 Voretc hard start and then high idle Hello:
I have this 4.8 on my home build engine test stand. The plan is putting it in my 72 Nova after some modifications and cam swap. As of now it is bone stock. The problem I have is to get it start it I have to play with throttle and give it some gas, like old carburetor cars, otherwise it just cranks. The second issue which is most likely related to the first one, when it starts it just revs up extremely high right from the beginning. I don't have a tach on my engine test stand but if I want to guess it is revving over 2500 RPM. It throws the code P0106 which is related to MAP sensor. I had a used MAP sensor from another engine transplant but that didn't change anything. I thought I have a vacuum leak, I have checked and checked and I ended up to change the intake gasket just to be sure but no luck. At t he end I changed the throttle body with another used one ,with all the sensors on it, from the other engine with no luck thinking it can be throttle position sensor although I don't see a code for it but again: hard cranking and then very high rev. Any ideas where to go from here?
Thanks,
I have this 4.8 on my home build engine test stand. The plan is putting it in my 72 Nova after some modifications and cam swap. As of now it is bone stock. The problem I have is to get it start it I have to play with throttle and give it some gas, like old carburetor cars, otherwise it just cranks. The second issue which is most likely related to the first one, when it starts it just revs up extremely high right from the beginning. I don't have a tach on my engine test stand but if I want to guess it is revving over 2500 RPM. It throws the code P0106 which is related to MAP sensor. I had a used MAP sensor from another engine transplant but that didn't change anything. I thought I have a vacuum leak, I have checked and checked and I ended up to change the intake gasket just to be sure but no luck. At t he end I changed the throttle body with another used one ,with all the sensors on it, from the other engine with no luck thinking it can be throttle position sensor although I don't see a code for it but again: hard cranking and then very high rev. Any ideas where to go from here?
Thanks,
01-27-2019, 09:29 PM
#6
I have changed the intake gasket and replace/inspected all the intake hoses.
I went through relearn process for ECU by disconnecting the TPS and ICA sensors and then the power the ECU. after connecting everything back again it was the same until I disconnected the TPS sensor. Engine starts and idle great when TPS is not connected but as soon as I connect it the engine revs very high again? Any ideas why? I have to say that when I modify the wires based on LT1swap instructions, I removed the TPS connectors out by accidents. When I realize that later I replace the wire back in to ECU pins. Is it possible if I have crossed the connections? Pins 46 blue and red 24?
I went through relearn process for ECU by disconnecting the TPS and ICA sensors and then the power the ECU. after connecting everything back again it was the same until I disconnected the TPS sensor. Engine starts and idle great when TPS is not connected but as soon as I connect it the engine revs very high again? Any ideas why? I have to say that when I modify the wires based on LT1swap instructions, I removed the TPS connectors out by accidents. When I realize that later I replace the wire back in to ECU pins. Is it possible if I have crossed the connections? Pins 46 blue and red 24?
