Service engine light issue

You haven't been putting any additives (like octane booster) in the gas have you? You may have a bad O2 sensor.

U.M.

Yea what said!!

A lean code would not be from a Iac issue, the reason why the car stalls and the idle goes up and down is because you have a lean code and the PCM is making adjustments to ST fuel trims to compensate for a issue. Check make sure you have no vacuum leaks or hoses that blew off.

Bank 1 is left bank 2 is right.than theirs downstream what was the po#

Lean = too much air, not enough fuel.

03stangvert said:

4. Like I've said before, I'm not a mechanic by any means....how many different O2 sensors are there? ( I have MILs on the exhaust)

Click to expand...

I believe there are 4 total when stock. By installing an O/R mid-pipe you eliminate the post-cat O2 sensors hence the need for the MIL's. The front O2's are still there and they are responsible for measuring whether your engine is running lean or rich.

U.M.

That would be a yes.the po# is where problem starts.on my 03 if i pull any vaccum hose or electric plug my cel lites and when checked with code reader was 100% on

Ok, here is the problem. You have a code p0174 then for lean conditon bank 2. You can always tell which bank is which by which head sits further forward. When you stand in front of your car it will be the right side. (drivers side) A vacuum leak will normally throw both p0174 and p0171, both banks lean. Do you have any exhaust leaks before or around the o2 sensors upstream? I would check for vacuum leaks anyway. Its possable that the p0171 is pending, meaning it won't come up on a cheap scanner but on the IDS it will show pending. This means it hasn't set yet but will soon. It all depends on whether the drive cycle has completed yet. The idle seems to act like a vacuum leak though. The IAC will try to keep idle at target. Even when there are other problems causeing a low or high idle. When you get a lean code the lt fuel trims have reached there end and can't adjust anymore, ussually around 20-30%. In my experience a lean code is almost always a vacuum leak. Theres been rare times when the maf was contaminated or exhaust leak near o2. Check your baro reading too. If this is off it can cause all kinds of problems. Hope this helps. Good luck.

Clean the heck out of the MAF, check your TB blade for build up.

If you replaced the IAC you should have replaced all the hoses too
I hope. I had a similar problem and replacing the IAC / related parts did it.
I also replaced the oil fill cap, they tend to crap out.

Sounds like a vacuum leak.