Chrushev

Ok, so I took off the IAVC and the throttle position sensor. Used Carb cleaner on the intake and the IAVC port (got in there with a shop towel to scrub the walls, was pretty black!) Throttle position sensor looked brand new even after 16 years, so I just sprayed it a sec and after drying put it back (those screws were a pain in the *** as there is no room for a normal screwdriver). The IAVC was filthier than Game of Thrones though (see pics https://imgur.com/a/6Rc4pEw). After giving it a good spray or five it was nice and clean.

After reassembling everything... I could immediately tell there was a huge difference. I didnt disconnect the battery during all this, so it retained it's learned settings and holy crap it was overcompensating. When I would get up to like 40Mph and let of off accelerator it was like cruise control, the car wouldnt slow down at all lol, would just keep coasting at 40. After about 10 minutes of doing that it started to decelerate but very slowly (was re-learning). I decided it would be better to juts reset it and let it learn from being zeroed out. So I disconnected the battery and left it off overnight. In the morning connected everything, and boom insta start, like it was the day I bought it. No stalling, no need to re-learn to idle (defaults were fine) and ofcourse deceleration was normal.

So Ive done about 10 starts so far, and each one has been instant like the day I bought the car when it had 0 miles on it. Amazing!

So in summary, replacing pump improved things, cleaning IAVC made the car start like new. Ill report back in a few weeks after I see more starts.

Edit: few more days and about 10 more starts and every time starts like a dream... im quite shocked actually. I have some brand new cars (less than a year old) and it starts just like those now, engine just turns over instantly and wroom its off to the races.

Ponce07

Edited Post: Just clarifying that there is a filter screen in the fuel pump assembly that can't be replaced by itself, you would have to replace the complete assembly. I don't believe that the filter screen can easily get clogged due to the strainer attached to the pump. You are able to replace the strainer and fuel pump by themselves

carlsson

Chrushev

If I am understanding you correctly, you are saying that the strainer is the filter? If so then thats not the filter. Filter is a separate part inside of that black cylinder in a glued in compartment. You can see it through at tube if you remove some pieces.

Just to be clear, there are 3 separate parts, pump, strainer, filter.

Chrushev

It got a lot better but not 100% fixed. The issue is non existent if the engine is cold... but if its hot its intermittent sometime takes a few cranks to start. Im thinking its either cam shaft issue (ive seen people report this), or issue with fuel injectors. I wish there was someone in my area so I could try their camshaft sensor, its like a 5 minute swap since its right there on top when you open the hood. If that fixed the hot engine issue then Id order the piece. I dont want to spend $80 jsut to find out its not the cam shaft sensor and is injectors or something else.

Ponce07

Now I understand what you were saying. Yeah, I saw the filter or mesh screen down one of the tubes, it's hard to take a decent pic of it. I wonder if it's for the fuel being fed out of the assembly or the fuel return line or both. My mistake, filter and strainer both function the same in my opinion, they prevent contaminants from passing through. I'll edit the filter part out.

Ponce07

That's good to hear, you're slowly pinpointing the issue. I would go with the cheaper parts first, I think the injectors are pretty expensive. Do you think there can be an issue with the ignition switch?

Chrushev

Yeah, the filter itself is more like a cigarette filter, very dense and doesnt let really tiny contaminants through, like smaller than grain of sand. While the strainer is for bigger pieces, like maybe rust pieces or a leaf that falls in during fueling or a tiny rock etc..

I look at it this way. Strainer is there to keep fuel pump from clogging, while filter is there to make sure your injectors/engine gets clean fuel.

Chrushev

Anything is a possibility. I dont know if ignition switch would behave differently on cold vs hot. Because like I said, if the car is cold its instant start every time. If its hot, almost guaranteed to crank for a few seconds.

I heard that on some cars if fuel injectors leak then when you turn off the car a drop will get through and evaporate. Now your fuel/air mixture is too rich and harder to ignite. But over time it escapes/evaporates, so by the time the car is cold the mixture is not too rich. I dont know if this is whats happening or even if its possible on Lancers (03 specifically). But thats one of many things it could be.

Others reported this kind of behavior with Camshaft sensor going bad (although I still dont understand why hot/cold would make a difference).

I dont want to just start buying parts if I dont know what the root cause is. I still consider this car pretty reliable with the issue present. It never failed to start (except due to the dead battery). Thats why I wish there was someone in the area that could throw a part in. If issue is gone then I can buy that part.

On the other hand an 03 Lancer with 100k miles is probably not worth more than $500. Thats how much (or maybe even more) it would cost to replace all 4 fuel injectors.