Thread: Argh! Still using tons of gas!

So I did the following: (91 NX) w/ Exhaust and Cone filter only)

Disconnected Battery (for about three days)
Removed EGR/BPT/AIV systems.
Made sure no vac leaks
Regrounded MAF/Tried two mafs...one known good.
Changed Front 02
Changed temp sensor
cleaned TB
cleaned aac/new gasket
new plugs
new nissan wires
new nissan cap
new rotor
checked timing (@17)

Initially, car ran nicely, pulled really hard, and got almost 29MPG after I did all this.
T H E N
Idle started getting goofy.
Car runs on 3cyl. upon cold start, then after about 45 sec. is fine, unless you blip the throttle then it drops to three cyl again and pops back up after 5 sec. Doesn't do this once its warmed up.
Idle takes forever to drop when car comes to rest.
GETTING 9 MPG!!!!!!!!!!!!
Car seems kinda lazy in the throttle response area and overall acceleration.
I am sick of chasing this.

Anyone have a definitive answer to what the hell is wrong? How the heck could it be fine initially after the work and then go to shit again?
My guesses:
TPS? (Causes bad MPG?)
Injectors?
AACV? (That wouldn't cause the bad MPG?)
Alternator?
Coil?

There is no CEL.

Well, with no cel, then from your options it could be the injectors. One or more could be bad, or the O-rings. You can test the injectors easily with a DVM. I don't remember the specs, but near 10-14ohms. Don't quote me though, check FSM. Also unbolt, and pop out the dizzy(mark your timing first), and fuel rail, then turn ignition on to prime the pump. Spin the dizzy slowly to see if each one sprays fuel consistently. Put a rag down to catch fuel before you do that too. At the point you prime the pump, you should notice if any of the O-rings are leaking/seeping. Coil and TPS cause CEL, but none or the others except the alt. maybe make the battery light come on. I really don't think any other stuff you listed making you get 9mpg, besides your fuel system in general. I'd also check the fill and vent hoses for leaks since they are common problem areas. May as well do a general inspection of all fuel hoses for leaks while you're at it.

Edit: Also do you get a woosh of fumes when you open the fuel filler cap? You should get something since its a sealed system. If you don't then that's an easy way to tell you have a leak.

x2 on checking the injectors.
With mpg that bad, guessing bad o-ring(s) and/or bad injector (very low or zero resistance).
10-14 ohms resistance is correct. Check with DVM, engine off.
After 21x,000 miles, I had 3 injectors go bad within about 3 months.
IIRC one read around 40-50, one was like 80ish ohms, and one was infinite resistance.
If the resistance readings are within range, then you need to pull them and replace the o-rings if any are leaking. It should be fairly obvious if the o-ring is torn.
If you pull the fuel rail, and/or replace the o-rings, lube up the surfaces in the intake where the o-rings seat, and also the o-ring, before installation.

having an EGR hooked up and functional can increase your mpg...

It was hooked up and functional when this started occurring.

X2 on checking injectors. Sounds like you have a leaky injector(s). I didn't see where you stated what the tps voltage was? Did you check the TPS before listing it as a possible concern?

Does the car hunt for idle at all?

Have you checked the Fuel Pressure Regulator? Check your fuel pressure to see if it's bang on. If you get more pressure than what your ECU is programmed for then the FPR is your culprit.

I tried to check the tps for an accurate reading with no success. The car's idle is all over the place! Don't know if that would cause bad mpg tho

Bad idle can give tell tale signs of issues.

You need to check the TPS with the vehicle off but in the acc/on position. With the throttle body closed should see around .46VDC, and WOT throttle body should show 4.1VDC IIRC.

If your idle bounces or constantly hunts, then your IACV/AAV could be the culprit. I would look there as well.

yeah its hunting all over the place. I replaced the gasket and cleaned out the part that is on the end of the manifold...I think that's the iacv? Or is it the aac...dammit... The other things UNDER the manifold, right...the part with the bimetal strip in it.
This is the part I cleaned/changed the gasket on:


I didn't mess with this: