At idle MAP is reading 0.98 (Basically 1v).
I've put silicon tape on the fittings on the hose and have done carb cleaner tests at the points of connection and I believe there are no leaks.
I'll order a vacuum pump though, I tried to get one at the part store the other day but they didn't have one.
One question though, the map connects to a port on the back of the TB, not on the intake. Could that be a problem? Note this is how it was connected on the donor truck, which I assume was the stock way it was connected.
Also, I've read somewhere that the map needs to be mounted with the vacuum port pointing directly down but the stock bracket has it pointing up at an angle. Could this be making the map malfunction?

 

Here are some engine photos.

 

I’m speechless….

I mean the level of disappointment is simply inexplicable…………

There’s not nearly enough blaze orange on that engine!!!

I recommend verifying the MAP is receiving a 5 volt reference and has ground - it may be reading 0.98 at idle but if it’s receiving only 4.5 volts or less, the signal will be off.

As I stated before, the MAP and TPS share the same reference circuit, so compare the MAP to the TPS to verify the signal. They should match with no more than 0.1 volt difference. It should be there at key on and after starting.

The MAP orientation will not affect its signal as long as it’s a functional sensor and is receiving full manifold vacuum. You could mount it upside down on the firewall if you wanted. And really, why NOT?

If it’s receiving ported vacuum, it should be relocated.

Also, it occurred to me that you need to “reverse” the vacuum leak test. Plug all the vacuum ports again, only this time, attach the MAP sensor first. It’s possible (though unlikely) that the ECM didn’t respond to the vacuum leak until the MAP was hooked up. So by reversing the test, you’re verifying the problem with a different method.

P.S. I’m on vacation through the weekend so don’t be surprised if I don’t respond much.

 

Yeah, I know right?

Thank you for all of the info, I'll give all of this stuff a try... Have a great vacation!

 

How goes the battle?

 

I do BMX racing and nationals were Memorial Weekend and I haven't had a chance to get back to the truck. The alternator died on me yesterday (luckily under warranty), which caused me to realize it's missing a brace so I ordered that, so hopefully that will help the new alternator not die and stop the serpentine belt from chirping. The truck is running a lot better, I did get to adding a GPS speedometer sender for my digital dash and have been able estimate my MPH at 18.5 which isn't bad. The fluctuation is still there sometimes, but definitely way better. I really think there are more vacuum leaks around the intake manifold. I sealed one side but haven't been able to get to sealing the rest of the way around it. The mechanic who installed the intake manifold is going to redo it for free since there where tons of vacuum leaks after he did it. After he does that, if that doesn't fix the problem, I'll try the tests you mentioned again... Do I need to run a PVC valve, or can I just use a breather on both valve covers (trying to minimize spots where the TBI could have vacuum leaks now or in the future)?

 

You can just run breather filters but I wouldn’t use them permanently. They will eventually cause a consistent oil mist to coat the engine/engine bay.

But that’s just my preference.

If you want a different setup than stock, I’d recommend adding a PCV catch can. If you go that route, make sure the can is of adequate volume to allow proper separation of the oil mist.