94 Q45 Possible Fuel Pressure Drop?

[mattd1979]

If there was no change in idle while adjusting the valve then it sounds like you have a large vacuum leak. The y-hose connector on the back of the intake manifold that connects to the bottom of the IACV could have a split in it. When you turned the screw all the way in I believe it should have stalled because the bypass air would be closed off. That is why I say there must be a vacuum leak at the back of the intake or anywhere after the throttle body. Having low oil will not cause the symptoms your describing.

[94Q45Beast]

could bad a IAC gasket and a bad throttle body gasket cause this?, I will check all hoses and proceed as you recommended, but wouldn't an air leak cause the engine to idle higher?, the screw is not all the way in (little over a full turn) and this morning it idled at 450 rpm, and in gear it bounced between 200 rpm and 650 rpm, and it would have trouble picking up speed, like air is being starved and it would not go past 1st gear. but at times when picking up speed, it lunged forward powerfully and picked up speed fast (the way its suppose to because I had to go further down on the pedal to increase speed) for a little bit, then back to the air starvation feeling.

[mattd1979]

A leaking IACV gasket or throttlebody gasket will allow a vacuum leak. If I were you, I would get a vacuum gauge and see what the vacuum is at idle and then during acceleration. Search here and Google for the procedure on testing with a vacuum gauge. It sounds almost like you may have a partial blockage in the exhaust.

[94Q45Beast]

ok, will post back as soon as I put some temporary rtv around the IAC and throttle body. also my pcv hose was leaking air so I temprarily replaced it with the thick break booster line

[94Q45Beast]

the cats and entire exhaust system have only 50 some thousand miles on them, and were replaced by Infiniti in 2001, would infiniti cover this?

[mattd1979]

I don't know what type of warranty Infiniti places on replacement parts. It may have only had a 1 year warranty on the replacement.

[94Q45Beast]

the cats are blowing smoke normally, like they always do. this morning when I stared the car, I saw a constant flow of white fumes (from moisture), I'm first going to take care the gaskets to see if that fixes it

[94Q45Beast]

the cel light wasn't on but I still checked the ECU and the screw was turned to diagnostics already *weird* and it gave code 46, i'm getting like 3 mpg and I run only high quality premium fuel (shell v-power, Chevron, or Exxon Mobil), with white fumes coming out of the exhaust while driving and when I come to a complete stop or down shifting, it idles between 200 rpm and 800 rpm, but when it shifts into second gear and beyond, it runs fine. I believe that the secondary tps is restricting air flow while the primary tps is functioning properly and telling the ecu to add fuel, hince the fuel consumption and white smoke, could this mess up my cats and knock sensors?

i'm an teenage amateur that does everything on his own and doesn't trust mechanics other than T3 or the Dealership and that finds the FSM interesting, so let me know if my logic doesn't make sense.

[mattd1979]

If it is running rich like you said then it can cause damage to the cylinders with what they call "cylinder wash" which is when a lot of fuel gets around the piston rings and thins out the oil coating on the cylinder walls which will then lead to premature cylinder wear. it can damage the cats if driven that way for long periods by causing them to overheat. The knock sensors will not be affected from it running rich. They just listen for certain vibrations caused from spark knock and retard the timing to reduce the effect of the spark knock.

[94Q45Beast]

well when my busniess kicks off, I'm gonna build this car up from the chassy with brand new OEM parts with some mods, but in the mean time I'll just install a new TPS, when I looked under the hood the bottom screw that holds the Secondary TPS was bent. *EPIC WEIRD*

[94Q45Beast]

I can't thank you enough for everybody's collaboration on this issue

[94Q45Beast]

I can't thank everybody enough*