Ok... So I read that cleaning your IACV is a good thing to do even if its runing OK. Took it apart, found that the screen was almost fully clogged, cleaned it, put it back together, started car, idle was bouncy to hell when engine was cold. Thought it was vacuum leak but could never figure it out. I ran it like that for about a month or 2 but also had noticed that my gas milage had gone up like a mother for the first time I've owned this car.

So before I cleaned anything I was getting about 21-22 MPG.. and after cleaning the IACV and o2 sensor My milage jumped to 32.7 MPG and was happy and freaked out about it and made a post here about it. But I was seriously fed up with the embarrasing jumping idle with cold engine and everyone looking at me (I have a loud exhaust)

I read about cleaning the FITV and decided to try it. It was somewhat dirty but had the screw thingy all the way out as much as it could. I cleaned it, screwed it in all the way, put it back together, Idle is almost perfect but just a lil bit low at operating temp.

Of course now that everything is back to normal (no bouncy idle, cleaned components), my mileage went back down again to 21 as before I dont know why. My assumption is that because the IACV was dirty and clogged, AND also being that the FITV was open all the way caused a balance between the 2 messed up components causing the engine to run fine (no bad idle) but with crappy mileage before all this. After cleaning the IACV causing MORE air flow into the engine running the car less rich. I learned that my car loved the extra air coming in, and didn't run rich like it has all its life. I believe there was too much air coming in though causing the bouncy idle. Is my theory right or wrong?

I cant think of what could be wrong. I'm about to go and unscew out the FITV out a lil to help with the low vibrating idle since the idle screw isnt doing crap and see if it helps. Can the IACV and FITV cause ANY changes in gas mileage and A/F ratios? Should I try screwing the FITV thingy in half way. Heres my current condition if this also helps. Cold engine idle = 700 rpms.. Warm engine idle = 500 or less. Obviously I have to adjust the FITV some. Could these stupid lil changes be causing my mileage?

I want my gas mileage back

Thanks in advance!


Modified by sageuvagony at 9:52 AM 6/21/2007

 

 

bump

 

Please help a friend

 

 

Well, dirty, clean, mis-adjusted either of those valves can cause poor fuel mileage yes.

What is the year, make, model, motor, mileage???

 

the engine itself is swapped D16Y7 with 80,000 miles on it (but EVERYTHING else was kept, only the bare engine was swapped.) Everything else has about 149,000 miles on it. My car of course came with a D15B7 (since it's a 92) but that thing died. When I switched to this new engine I was hoping my gas milage would improve, which it didn't. I kept EVERYTHING the same except for the bare engine itself. So I now know for a fact that it's in the intake area somewhere causing this. Could a bad TPS do this?


This is a very old pic but just showing how only the engine was swapped.



Everything that came with the engine that I didn't use.

 

Pull the ECU fuse ever time you change the environment your engine will be running in.

My .02