ok, i just swapped an engine into my 92 gmc K1500... my rings went bad ... the engine is an 86 350 with 35,000 miles on it. i swapped my tbi over to it and all the sensors and all. brand new alternator and a new temp sensor.

Problem:
with the engine at idle, voltage is at 14 volts. when i turn on my headlights the voltage drops down to 9 volts, the engine speeds up, i get a check engine light (obd1, checking the code 2morrow), and the radio flickers on and off. when i turn the headlights off, the voltage stays low. after i turn the engine off, i can turn it right back on and all is fine. at higher rpms the voltage is fine untill i turn the headlights on.

does anyone have an idea on what would cause this? could it be a ground strap? i don't think that i hooked up the ground strap from the frame to the body, its the only ground strap that i have. i have a ground that goes to the engine, and one that goes to the body in at the fender wall.

thanks in advance for the help

 

Have the alternator tested. Just because it is new..... doesn't necessarily imply that it is good.

 

alternator is testing good on my little tester, battery load test is good... i checked my ground straps, neither of them were connected, so i connected them and it seems to have fixed the power issue... i checked the trouble code, its a code 33... Mass Airflow Sensor... i'm using the same sensor and all from the old engine cause it was all working. only things different are that there are 2 spacers under the TBI and i had to move the coil to the other side of the intake manifold, so now its closer to the wiring harness. is this code really a big deal? if so, i can relocate the coil, all i would have to do is extend the wiring on it, but i can't remove the tbi spacers.... i went from a vortech motor to a non-vortech motor, and the tbi intake manifold wouldn't bolt up to the head. i used the carbed style intake manifold from the new motor, and i put a tbi adapter on it to mount up the tbi, and then i had to add a spacer so that the tbi would clear the egr valve.

 

tbi doesnt have mass airflow sensor. did you use the computer from your 92?

 

ok, the code comes up as MAP or MAF sensor... everything got swapped over from the 92 to the new engine

 

map then. hmm did you try clearing the computer of codes and try again? check vacuum and time the engine

 

woo-hoo... got it... i took the old vacuum gauge to it, no vacuum at the sensor... the vacuum lines on my truck are stupid. a main line goes to the egr solenoid, then on the back side of the solenoid there are 2 lines coming off... 1 goes to the egr valve, and the other goes to the map sensor. the line going to the map sensor is a bypass valve, but the solenoid has to open the bypass... so i hooked the main line right up to the map sensor, and it works like a charm. went and drove around town like that for a bit and it drives really nicely now and doesn't stall when i stop. only thing that boggles me now is that the egr valve had no way of getting vacuum to open up, and i never got a CEL for the egr system... lol... well now i gotta go take the multimeter to the solenoid connector to make sure its getting power, and if it is then i gotta go get a new solenoid. thanks for the help

 

wow, i feel stupid now... all i had to do is look at the pics from my engine swap to figure this one out... lol... i had the vacuum line going from the map sensor hooked up wrong, go figure... its supposed to go to the back of the tbi unit, not to the egr solenoid... i don't see why they have to put 2 ports on the back of the solenoid to mess with people like me... lol