Let me say I'm sorry I didnt listen to everyone who said its a vaccume leak. Alright guys, after many, many hours under my hood I think I have found my problem. It seems the intake manifold is not sealing. I belive it might be warped.

I found that if i plug the oil filler hole with my hand the Idle speed raises about 75rpms and the engine sounds as smooth as silk. So I need to replace my intake manifold right?

Well here is my problem and I hope yall can help. I'm having trouble finding one. The v6 manifolds I find are for a 2 barrel carb, and not fuel injection.

Does anyone know where I can find a new one. I'm on a very limited budget right now so I can't afford to spend alot. Should I take my chances with one out of a wreck yard. Is there anything I can do with one out of a junk yard to make sure it will seal. Is there any type of intake setup that will make it run and preform better.

Thanks in advance

 

i have a stock one out in the shed *hint*. PM me for details. I, hopefully, will have my new performance design done soon... it'll take a little more time though.

 

That is very strange. I don't know why it might do that, but I can't imagine how it could be related to the intake manifold. IF your manifold is warped a good automotive machine shop might be able to resurface it.

Too bad I just threw away a perfectly good manifold that I didn't need.

 

After all those years (since 1986), intake manifold do not "start to leak" or "Become warped" like some humans I know!
IF it was never disturbed or prior owner removed, I doubt you found the problem in your manifold.
Keep checking, I'll bet you'll find the true vacuum leak source.
One other simple way is to spray lubricant spray on the gaps/surfaces. Seeing bubbles will confirm the leak source.
An engine management system from 1986 is bound to have more than one leak source, too.

 

You say if you plug your oil filler hole with your hand the idle smoothes out. It sounds like the problem is a leaking oil filler plug.

I don't know much about the 2.8, but engines using MAF can run lean with an oil cap leak. The engine will draw air through the PCV system that should be drawn from the breather connected to the intake. This way the PCV air is drawn through the MAF. If the oil cap is missing air can get in that bypasses the MAF.

I've seen a MAF Toyota that ran like crap without the oil cap, but as soon as it was put back, it ran great.

 

Or yank the pvc hose out of the rubber intake hose and plug off the hole.


Mine is un done and plugged. I run a filter on the end of the PVC hose n run it as a fresh air system.

 

U can see it here.

Along with orange hitemp gasket goop everywhere.

 

Gumby, Did you rerout your vaccum tree. My PVC filter is on the back side of the driver side valve cover gasket. Also what did you plug the PVC hole with?

 

You don't want that crapy PCV air going throuh the maf.
It shouldn't draw that much air through the PCV. Just enough to throw it off.
The air can eather go through the air filter and maf or through the leaking cap the breather and then the to the intake.
It will take the path of least resistance.
Make sure your the valve cover is tight, when you put your hand over the hole and you are pushing down on the valve cover you could be resealing the gasket.
One valve cover on my Z28 all the nuts weren't even finger tight, oil was just poring out.
It sounds weard but it could hapen.