ok, here is my problem. my 91 z (305 tpi) just had the intake resealed. there had been coolant in the oil and vise versa. i am 99.999% sure that this was b/c of the intake, bc the car was fine before. now since i got it back, it wont hold an idle when you first start it, unless you rev it a little. once you drive it for a few seconds it holds it idle fine (about a couple hundred feet of driving), but still idles a little funny-but barely noticeable.

also, the oil press. gauge reads about 45 psi at cold startup, then as the car warms up, it drops to about 30 while you are driving, and when you come to a stop, and the car is idling in D, the
pressure gauge drops to zero

any help would be greatly appreciated, thanks

 

I'm no expert, but it definitely sounds like something is causing inadequate flow through the intake, but I am at a loss as to what...

45psi oil pressure at start up sounds about right. When oil warms up, it changes viscosity and falls to about 30-35psi...

BUT 0psi is NOT normal. Does your car die when this happens? Does the idle worsen?

I am sure this all has to do with the intake... sorry I can't really be of much help.

-ONE2FLY

 

the car doesn't die when it is warmed up and reading 0 on the oil pressure gauge.
when the shop did it, they had to replace the coolant temp. sensor., and the guy told me when i picked it up, to drive it kind of hard for a few days, so it could relearn its idle, and running conditions.
but, the only engine ive ever heard of that has to relearn the idle is the 2.8/3.1 flat-plenum mpfi v-6's.

any help or sugg. are greatly appreciated-i gotta figure this out soon

 

I don't know about the Idle problem, but the fluctuating oil problem could be due to a bad oil pressure sending unit. The one on my 87 iroc 305 tpi is next to the distributor behind the driver side head. It looks like a bell and is about 2 and a 1/2 inches long. I had a similar problem with the fluctuating oil guage and when i changed the sending unit that fixed it. but be CAREFUL, the little metal tab broke on the new sending unit( that the wire connects to ) so I decided to replace the broken sending unit and I guess i put the wrench on the wrong part of the sending unit and i broke the threaded portion of the bronze piece that screws into the block off (it's separate from the sending unit itself) and it was stuck in the block or the head whatever it screws into it' s hard to see, but anyway this created a huge oil leak and i spent hours trying to fix, couldn' t extract the broken piece with an extractor, ended up breaking that to. finally i tapped some threads and used a screw( yes a screw, only thing i could find to fit the threads i tapped into it) oh and had to use some teflon tape because the screw didn't make a perfect seal. I know it sounds really dumb just don't want anyone to go through what i did. Teflon tape is great i would personally like to thank the creator of that stuff. Hope that helps some.

 

does anyone know how much the oil pressure sending unit costs? i might replace it just to be sure. the cold start and highway readings seem fine, but its when i come to a stop and the car is warm, that it reads 0. the engine doesn't knock or stall out
please help