engine running funny

[gimpy_28]

Ive got a 89 2.8 in an 86 blazer and everything went fine after the swap about a year ago but i just swaped the tranny out the other day and since then and i know it don't have much to do with the tranny but my motor is running a little funky... it idles fine but it has about 50 to 100 rpm drop and then it catches back up and i didn't really pay any attetion to it till today when it died on me in the drive way and after i stoped at a bottom of a hill.. and the oil pressure gage is wiggin out it jumps from top to bottom then stops then stays around 50 lbs the starts to jump back and forth then nothing... would anybody have a clue is to whats going on... i like the blazer but i dont' want the motor to die on me because its all i got.. and i made sure that the motor wasn't getting to hot it stayed about the same as normal and i checked the radiator and it was worm and the motor was fine so the water pump is working fine..

[jjcom]

I'm guessing the transmission you put in is controlled by engine vacuum. If one of the lines running to it is leaking, you have a vacuum leak. I'd go over all the vavuum lines and see if any are cracked/appear like they could be leaking. Get out some carb cleaner and spray at connections, if the idle goes up, you've found your problem.

[gimpy_28]

but what would make my oil pressure gage wig out so bad...

[jjcom]

As the idle is changing, so is your oil pressure. If it's doing that while your going down the road, thats not good. By "then nothing" do you mean it drops to 0psi, or does it go back to normal?

[gimpy_28]

the gage goes up and down really fast from top to bottom ... the stops .. then goes to 50 or so then drops then up and down really fast again... it changes from what ever to what ever...

[jjcom]

That seems strange, but is this at idle or while going down the road?

[gimpy_28]

both... its freaking me out because i have had nothing but bad luck this past year or so and thats just one more thing to go wrong...

[jjcom]

Does it changed at all with RPMs? That all does seem very strange...lost any coolant? Oil changing color? Milky? Black? Normal? At first it sounded like you had a vacuum leak...but now I don't know. Still could have a vacuum leak though, check for that. Maybe you hit something dealing with your oil pressure gauge when you put in a new transmission? Just random ideas crossing my mind. Good luck

[gimpy_28]

no all the oil is good and i didn't even take off the bell houseing..and it does it at all rpms.. the truck idles fine but it drops a lil bit then its fine again..