scr0tum

I assume that this is probably a voltage divider circuit as this is what we commonly use at work for temp sensors. I verified as I left work last night that the sensor was plugged in, I will try and get a reading when I get home to see what the resistance of the sensor says then check the voltage output. I would like to note that the procedure listed on Shoebox's site is very thorough and is exactly how I would have tested it.

A side note, I found an extra set of fuel rails I had laying around for a sequential fuel injection LT1 (two cross bars on opposite ends) with a FPR connected to it. The whole thing is rather dirty, and I plan to clean it with some gas and a toothbrush after letting it soak in gas overnight before i stick it in my car. It is a shame you can't take it apart to clean it better. I'm crossing my fingers that the fuel pressure problem is solved with an FPR rebuild kit. (Crosses fingers)

Injuneer

You do realize that the 94-97 rails will not fit on a 93 intake manifold..... correct?

scr0tum

That I do, which is why it was laying around . It did have the fuel pressure regulator that I plan to switch out attached to it. I figured after I cleaned the FPR I would hook it up to the fuel system before attaching it to the rail and turn the key to prime the system to see what kind of volume flows out, as well as cleaning out anything I couldn't get to with a toothbrush.

I saw the fuel pressure test on Shoebox's site and was wondering if anyone has tried pinching off their lines. My car is a 93 and I am worried about pinching the lines to hard and breaking them. Anyone try this?

Injuneer

Isn't the 94+ FPR "opposite hand" with respect to the location of the tab that bolts it to the rails?

scr0tum

That is a very good point. I will have to locate the stock unit I suppose.

After I got home today I attempted to test the temp sensor. I couldn't get the probe leads to make contact with the sensor, so I can't verify that it is working properly. I did measure 5.02V coming to the sensor though, which is good. The pigtail going to the sensor was covered in some crud though and i'm guessing it was preventing contact. I may have to go back and clean it again later as much as i don't want to. The elbow going to my TB has all kinds of cracks at the mouth.

Is seafoam the best product to clean the intake manifold? I am pretty sure it is all gummed up with fuel deposits.

Injuneer

Why would there be fuel deposits in the intake manifold? Its "dry".... only flows air.

You may have oil deposits in the intake, from the vent line that connects the throttle body to the passenger side valve cover.

scr0tum

You'll have to forgive me, most of my experience is with carbureted cars. The TB blades are black, I opened them to look inside and everything was black. I wiped my finger in there and it was kind of gummy and black and smelled of fuel. Later, when i turned the car off and opened the TB again there was smoke coming out, i assumed this was the last of the fuel that was vaporized and coming out as it smelled of fuel too. I think this may have been what coated the inside of the intake manifold.

An interesting note is that the LT4 intake manifold I have has provisions for the extra crossbar of the fuel rail in the 94+, but the fuel rail still will not fit properly.

Guest47904

The crud you see is from the EGR. Fuel doesn't leave that type of deposit. Any doubt and take off the EGR valve.

Injuneer

That's odd.... I have my 94 LT1 rails on my LT4 intake, no problems.

The vent line from the passenger side valve cover is supposed to pull air from a port in the throttle body, in front of the blades. That air flows through the valve cover, into the crankcase, and up through the lifter valley, picking up blowby gasses, and vents through the PCV valve on the driver's side of the intake manifold.

If your PCV valve is clogged, or you have excessive blowby, or your engine spends a lot of time at WOT ( ), when there is no real vacuum at the PCV valve to make the system work, the crankcase pressure starts to build, and it vents backward out the passenger side valve cover, through the hose to the side of the throttle body, and into a chamber under the cover plate on top of the TB. In the chamber is a port that leads down to a point in front of the throttle blades. If you have high flow backwards through the vent line, it entrains oil droplets, the oil puddles on top of the TB, and eventually flows into the throttle body ports, coating the blads, and the intake manifold.

Take the throttle body cover plate off, and see if there is oil puddling in the top chamber. Pull the vent hose and see if there is oil in it. If you have appreciable oil, check your PCV valve.

scr0tum

That is a lot of information, thanks. The only problem is that I have aftermarket valve covers. The guy that I had tune it said that I should leave caps on both valve covers, i.e. there is no venting possible through the valve covers. This was done because it increased my vacuum at idle making the tuning easier (According to the mechanic that tuned it). I did get frustrated with my caps popping off and keep a breather installed during the summer months. I think i've been through about 6 oil caps in the past 4 years.

I don't think that my car has much in the way of blow but I can't be for sure because I lose a fair amount of oil via leaks (about 1qt per month). The car has had synthetic oil since its 2nd or 3rd oil change. I would have cleaned the engine to find and fix the leaks, but I am too worried about messing up my opti which was replaced about 5 or 6 years ago.

While under the hood yesterday i noticed a valve between two hoses connecting the air system and the egr system (against the firewall). There was what looked like a vacuum port on the system but it was not connected to anything, is this normal?