1990 Lumina 3.1 issue
 

I have a 90 model lumina euro with the 3.1, a while back I had an issue with the car acting up & and running bad & dying when putting it in gear, check engine light came on, being odb 1 i jumpered the diag port to get the code... gave me a code 34, Map sensor low voltage i do believe, I replaced the map sensor with a new one, acted same way & gives me same code, however if i leave the pigtail unplugged from the map sensor, the car runs great, but of course the check engine light is on all the time....

what could the issue be?????

vaccum leak or a bad pig tail maybe ????

please help

Doubtful, however with it running spray starting fluid on intake mounting locations, vacuum hoses ect. If nothing, it might have to have a relearn. I know MAF sensors have a relearn, and the same with them unplugged runs better. I don't have obd1 codes in front of me, but low voltage? Is that reference, or return, or supply?

exact code meaning
 

yes all i get is a code 34 which means

34- manifold absolute pressure (map) sensor signal voltage low

that is the odb 1 meaning for the code on this car

also with the pigtail unplugged the car runs GREAT... NO issues what so ever

but the minute i plug it in when I start the car and give it gas it will die then
the car it will run and drive up to only 25 mph and then start bucking, like a fuel issue. the code is why i replaced the MAP sensor, like i said the new one acts & the does the exact same, and gives the same code, but with it unplugged it's like nothing is wrong, so thats why i am trying to figure out WTF it is...

Sounds to me like a connector or wire issue. Can you check continuity from the map to ecm, pcm or whatever?