Maverick H1L

iTrader: (8)

Why is it that when I take a vacuum reading, from the "T" in the back of my upper plenum, and get 16" Hg of vacuum, take another from the center port on the throttle body (small dia solid hose) and get 13" Hg, and from the other small port on the throttle body, I get around 2-3" Hg of engine vacuum? I took apart the throttle body to see if any of the vacuum ports were clogged, and they weren't, except for the outer small port (the one on the driver's side of the engine), which seems not to have a port into the plenum chamber, but a very small slot. How is it that I can get such a large vacuum drop between the ends of the upper plenum? According to my emissions sticker, I am supposed to be using both the small port on the plenum "T" (the one NOT connected to the brake booster hose) for the cruise control, the orb of power, and the HVAC control head. The center TB port is supposed to be reserved for the FPR only, and the other small TB port is supposed to be used for the EGR and charcoal canister. However, I now have the WHOLE SYSTEM hooked up to the middle TB port, and I am quite sure this is affecting something somehow, and not in a good way.

Can anyone explain the vacuum drop?

Nixon1

Go by your first reading, you want to measure vacuum as close to the manifold as possible. Try to keep the original vac line routing and locations as much as possible.... For example, less vaccum than normal applied to the fuel pressure regulator will increase fuel pressure at idle and lower rpms/cruising and cause a rich condition. There are other things that can be affected as well.

Maverick H1L

iTrader: (8)

I don't seem to have a problem with the FPR at the moment. I have checked the fuel pressure and it is about 41-43 (been a while since I checked it... maybe I'll recheck it) PSI with the engine running. However, I run LEAN due to a bad MAF sensor, but that is not my question. Does having a lower than normal vacuum pressure (not quite sure what to call it) at, say, the charcoal can do anything? What about the EGR valve? I am supposed to run the EGR and EEC off of the port that has the extremely bad clog in it, and the FPR off of the port that has about 10-13" Hg at all times.

Ovrclck350

You need to re-route the vaccum lines the way the diagram says.

2_point8_boy

One of the ports on the TB is a manifold vacuum source, meaning it's behind the TB, and the other is a ported vacuum source, meaning that it is in front of the TB and only has vacuum applied to it when you open the throttle. the manifold source is for the FPR and the ported source is for the EGR/EVAP systems.

Re-route the lines and don't stress out too much about the difference in readings. The only one that you should care about as far as engine health is the one that is closest to the intake manifold. I always use the tee on the back of the upper plennum although the best place would be the connections at the base where the PCV hose goes on.

Maverick H1L

iTrader: (8)

NOW finally someone tells me what to do with the three ports...

I've been fighting this for over a year (since the shop put the 3.1 in) and now I have a reason to replace all of the lines (again) along with the broken EEC solenoid (been leaking, finally broke on me and I just have been too lazy to replace it, having bypassed it instead). I'll have to deal with this when I replace the MAF.

2_point8_boy

I suggest replacing the lines and getting them routed right BEFORE you replace the MAF. If the lines are incorrectly routed, then you'll get a car that runs bad because of certain things having vacuum when they don't need it, and you might actually get a MAF code.

Maverick H1L

iTrader: (8)

Ummm, I've been having problems with a code 34. A couple of days ago, I got a code 33. I cleaned the connector for the MAF and the code seems to have gone away. However, I would have thought that having the EEC canister running the WHOLE time would make the engine run rich, not LEAN, as I have been experiencing. I don't see how having the EGR solenoid have engine vacuum the whole time the engine is running would have anything to do with how much exhaust enters the intake air charge, when the solenoid only opens the flow of vacuum to the valve when the ECM tells it to.

Oh, and BTW, I managed to scrape up enough scrap vacuum hose to reroute the vacuum lines properly. We'll see how things go.