: 93 Northstar stalling

I need tech help
01-14-07, 10:47 PM
I just bought a 93 Eldorado with the 4.6 Northstar motor in it.After about 20-40 mins.of running it hesatates,and stalls.It useally restarts but runs ruff and stalls again right away.It has codes P071,P105,and IO52.I replaced the ign.control module,coils and plug wires(no help)Can anyone help me?I hear that the Northstar is known to have problems with the crankshaft pos.sensors?Does this sound like it might be the problem?Thanks,Bruce

Cad tech
01-15-07, 11:28 AM
Mat sensor problem or you have cracked plenum or major vaccum leak in plenum area. It will be vacuum related though, with the 71 (MAT sensor prob) and 105 brake booster vacuum problem...which leads to manifold leak not creating enough vacuum.....

I need tech help
01-15-07, 11:54 AM
I checked the vaccum to the brake booster and MAP sensor,it was good.I thought because it was stalling maybe it set those codes as it stalled and lost vaccum?Did the 93 northstars have problems with the crankshaft position sensors or was that a problem on the newer northstars?

Cad tech
01-15-07, 12:12 PM
so you took off top cover of plenum to access the MAT sensor???Did you measured the kpa reading PD02 on the onboard compute using a vaccum pump? yes they had problems with the CKPs but with your descripion of problems and codes it leads me away to check other things, those codes just dont come up to throw you off the trail..it wont give give you codes for low vacuum unless the engine has a serious problem in that area, it would give you a near stall code maybe...Also check fuel pressure..

I need tech help
01-15-07, 08:32 PM
I think your right about a vaccum leak Cad Tech,Its funning when the car has set for along time when first started it runs fine for 20-30 mins.the engine temp was 223 and it was still running fine,then it started fluxuating up and down.I checked the PD02 and it was going from 10-35 at 1000 rpm and 10-55 at 2000 rpm.as the engine fluxuated.So it sounds like I'm going to pull the plenum cover,I don't have a vaccum pump to check the MAP,is there another way to check it?Also were would I look for a cracked plenum(sides,top,can't really see the bottom)Thanks for the help so far,I feel I'm getting closer to the problem!

Cad tech
01-15-07, 09:27 PM
good job keep plugging away and we will be here to help.....see if you can borrow one on just go down to local parts house and rent or buy a vaccuum pump they are pretty cheap now almost obsulete lol....

I need tech help
01-17-07, 09:27 AM
Thanks for your help Cad tech! I took the intake off and it was a cracked plenum,got one from the salvage yard from a 94 Eldo.and had to change everything over(wiring was different for injectors)Now its running fine.What alot of power it has!

Cad tech
01-17-07, 09:37 PM
Right on very happy we could help!!!!

01-18-07, 01:42 PM
Wow! Give that man some props! Nice to know there are people like Cad Tech, and Ranger able to come to the rescue! Nice job!:thumbsup: