Corvette Forum : DigitalCorvettes.com Corvette Forums banner

1 - 8 of 8 Posts

·
Registered
Joined
·
2,480 Posts
Discussion Starter #1
i took my 90 l98 apart to redo the intake gaskets. but it seems like the car has ate the wire to the map sensor on the intake plenum. i have pulled the distributor back out looking for it and i dont see where it is anywhere. so i need some help finding where it should be running from. i am positive it came from the distributor area when i took it apart but i sure dont see it anywhere in the engine compartment let alone where i thought it to be. also on the distributor install i put the red wire to battery positive and brown to tach. pretty sure that right but tach not working now
thanks
shane
 

·
Premium Member
Joined
·
7,092 Posts
Not sure about the map sensor wire, but as for the tach wire....on my '86 their's 2 beige wires with brown connectors near the distributor. One is for the tach, and the other we could never figure out what it was for. I was told that it may be for diagnostic purposes that the normal person would never need. See if you have both identical wires. If you find another just like the one you have for the tach, plug that one in. My tach did not work when I bought the car, but once I found the "other" wire and plug it in it worked.

(click on pic for bigger)
 

·
Registered
Joined
·
2,480 Posts
Discussion Starter #3
map sensor local


this where i am looking....well all over but.....


est...or electric spark timing. undone when setting timing
 

·
Registered
Joined
·
724 Posts
The arrow in the picture is actually pointing to your MAT sensor.(manifold absolute temp.) The wiring for it is in one of the harnesses that are behind the plenum, around the distributor. You are looking in the right place. May need to take the loom off to find them because if they are cut, they may have slid into the loom. When I get home from work, I can see if I can get a picture of mine for you. But you really should take the MAT sensor out of the plenum anyway, and you will gain a couple HP. Unscrew it from the bottom of the plenum, And plug the hole with a screw in plug with sealant on it so it doesn't leak vacuum. Then drill a hole in your plastic air cleaner housing, and screw the sensor in there. Then once you locate the wires to it, extend them out to the sensor. Just make sure you locate it where the hood won't hit the sensor when it's closed. When that sensor gets real hot from engine heat, it can lean your motor out too much. The cooler air coming through the air cleaner housing will prevent that and will actually gain a few hp when the engine is hot.
 

·
Registered
Joined
·
914 Posts
I agree.....that's your MAT. The wires on my MAT run from the MAT to a 2 wire plug located above trans bell housing left side. Close to but slightly below the oil pressure and oil temp sending units. I tried to show this plug in a picture but it's very hard to show with everything else in the way. Check out my pics to see the plug.:thumbsup:
 

·
Registered
Joined
·
724 Posts
Brown connector on distributor is tach wire. White connector with red or pink looking wire is B+ when key is on, and energizes your coil. Most stock caps have this imprinted on them right above the connectors. The three wire connector behind those, two wires connect the coil to the control module in the distributor, and one is a ground.
 

·
Registered
Joined
·
2,480 Posts
Discussion Starter #7
thanks guys i got it figured out. my wire was brown from the oil staining it. the tach wasn't working because it was so far out of time that i guess it wasn't reading it. i got it close enough and it is working. i guess car was timed properly when i got it as distributor won't turn far enough to get it to 6 btdc. so i got to pull it out and move the cap to get it right. as for map sensor wire i have to thank mr hanes manual for miss informing me. it is the mat sensor. previouse owner had grinded the mat sensor wire clip down so i had it install in the wrong spot...ie the third pic. when i took it all apart in desperation i noticed that i had be ground on and that the parts missing would make it the wire i was looking for. good news car running...bad news i broke trow out bearing 5 minutes after that......here we go
 

·
Premium Member
Joined
·
7,092 Posts
Glad you got it figured out, but sucks about the clutch. She'll be back on the road in no time. :thumbsup:
 
1 - 8 of 8 Posts
Top