Hello,
This is sort of a continuation of an earlier thread (Need advice on stubborn engine codes)
That thread was getting so convoluted I wanted to start a fresh one.
Here I'll present what the current situation is, and what has been done so far. I want to keep it as simple as possible:

Original situation: I was seeing a variety of engine codes, mostly related to fuel trim, o2 sensor, map sensor, etc.

What I did:

• Replaced all 21 feet of vacuum hose
• Found broken tee, replaced
• Replaced both ABV solenoids after ABV code started showing up.
• Traced all 21 feet of vacuum hose to ensure no mistakes. No mistakes.
• Replaced spark plugs
• Ohm'd fuel injectors.

After all that, this is what I am still getting. I've driven 700 miles to be sure all the codes are logged:
P0173 Fuel Trim System (LH) Malfunction
P1540 ABV Malfunction
P1170 HO2S FRH - no inversion
P1173 HO2S FLH - no inversion

Now, when I replaced the hose and found the broken tee, I thought for sure that was the solution - but instead, I got rid of some of the other errors (aside from what's above) and added a new one (P1540). So obviously something ELSE is wrong.

I'm looking for advice on what the possible problems could be, and what I should try first.

I'm almost ready to give up and sell the car but I'm finding it hard to throw in the towel.

Thanks!
Paul

 

Does this thing burn oil? Both front O2 sensors are themselves an issue, that is probably giving you the fuel trim code.

 

i may be having a similar problem. i just did all the hoses and the valve cover gaskets. now i get egr(0404) and abv(1540). idle is rough, and it goes limp home. look at this pic:

1370A - EMISSION CONTROL SYSTEM (2300CC). Fits: 1999 Mazda Millenia | Jim Ellis Mazda

under the 4 solenoids that control abv, there are 3 that control egr valve(vacuum and vent) and purge. the part number for the set is the very first part on the list next to the diagram. i think the vacuum lines from egr vacuum is tied to abv, and that may be causing my 1540. i am hoping that the vent solenoid is sticking, holding egr valve open, thus the rough idle. these are only sold in a set, so perhaps mazda knows something. the solenoids will be here tomorrow, i will post if they solve the problem.
the 1170/73 are your pre cat o2 sensors, perhaps they are dying. dunno how many miles your car has on it, but for both to die at the same time is unusual. 0173 generally is a vacuum leak, but again, since both intake plenums are kinda tied together by the vacuum lines, i would think it would throw both 0173 and 0170. perhaps one orfrice on the front bank is leaking? just a guess. if you notice, some of the vacuum lines are pressurized. these will have the little spring clamps on them. the ones that just pull vacuum dont have clamps. also, the green/white one way valves, one may be on backward. i dont know what will happen if one is, but you might check them. also, there are a couple of the larger breather hoses that connect the hard metal lines, i know that at least 2 of them have one-way valves INSIDE, and you can see arrows marking the direction of flow on the outside of them. these suckers are expensive, too.

 

Hi, Kevinkpk,
Yes, I do have an oil leak on the front bank. What effect do you think this might be having?
Because the error is for both O2 sensors, my suspicion was that something else is the cause, because it would be rare to see both go at the same time.

 

That will have an affect on the sensor.

 

Hi, keninn,
You mentioned the larger hoses that have arrows on them, and that have one-way valves inside - I wonder if it's possible that I put them back on pointing the wrong way? If so, how do I tell which way the arrows should point?
Secondly, did replacing the EGR solenoids fix your problem?
Thanks.

 

Do you think if I changed the valve cover gasket it will fix the O2 sensor errors? If so, how big of a job is this, especially if I only change the front bank (the rear is not leaking)? Do I have to remove the whole damn air intake again? Fourth time's a charm!

 

valve cover gasket is a big job, and the intake has to come off, all the way to the heads. you can leave the injectors on, that will save you some time and gaskets, but you have to pull the hose that connects both rails. also, you need an allen(i think 6mm) that is really long to get to the bolts that hold the intake to the head. and i dont think the valve cover gasket has anything to do with the sensor codes. and the front bank is like 10 times easier than the rear bank

 

ok, i went out and looked. on the abv, there are 3 small vacuum hose connections, and 2 very large ones. the large ones are right next to each other, on the cabin side of the abv. one is a bit closer to the driver side of the car, and there is no clamp on it. the other sits a bit lower and to the rear of that hose, and this is the one with the arrows on it. it has clamps on both ends, because this hose sees pressure. the arrows should point to the abv. the other one way hose is the same size, it comes up alongside the ignitor, on the front bank cyl head. the arrows point to the ignitor

replacing the solenoids did not fix the problem. i know the egr is bad, i have one coming. i think the other problem(1540) is from some of the vacuum lines that have hardened and no longer fit tightly on the solenoids and tees. i changed them, and when i get the egr, i hope it fixes the problem. i am sure it is a simple solution, after all, i was doing so much work on the car, i may have not connected a line correctly.