Thought its was a vacuum leak at first but...

[Imprezaman201]

Ok so a few weeks back my 2001 rs developed a hesitation at around 2800rpm, at all throttle positions. Figured it was a vacuum leak, and went through my hoses and cleaned the IAC. It didn't make a difference. Monday morning it stalled out while I was warming it up before work. I started it and had to stay on the throttle to keep it going or it would die. Was bogging out anywhere under 3000 rpm unless over 60 or 70% throttle. Tuesday morning it started fine but the idle is stuck at 2000 rpm. ( I unplugged the IAC harness with no difference to idle and unplugged the vacuum line to from it and it made no difference, not sure if this means anything) As for driving, I can cruise at anything under 10% or so throttle or over 70% or so. Anything in between it falls on its face and starts to flood out it seems, the intake will pop occasionally, and you can smell it running rich as hell. Gas mileage is that of a V8 now as well... TPS? Plugged Cats? Sensor? If anyone can point me in the right direction, it' be greatly appreciated!

 

[Nigel Prodrive]

plug wire. check resistance on each, bet you find one where it's sky-high

 

[Matt]

It's the upstream o2 sensor. Betting money

 

[Imprezaman201]

Matt, No cel and my ignition has cycled well over a dozen times since the problem has started...

Nigel, cylinder #3 wire reads 6.2k ohms as well as #4, #2 reads at 7.3ish k ohms, and #1 at 8.7k ohms. What should they be at? and How close of gouping should be tolerable?

 

[Nigel Prodrive]

Resistance range is specced at 5k to about 12k so seems like plug wires aint the issue.

 

[jaKe]

A/F sensor my guess if it happened suddenly

 

[Matt]

My rs did this very thing a few months back and didn't throw a code for nearly 2 weeks. Finally went after an hour long drive up 95.

 

[Imprezaman201]

odd thing is I haven't gotten any misfire codes yet, id imagine I would

 

[Matt]

I never did either. Just the code specifically for the a/f sensor.

 

[Imprezaman201]

Yea it happened two years ago too, I changed the fuel filter, plugs and wires and didn't do anything, Ended up letting it sit for a week and it came out of it when I started it

only codes im getting are p500 and p1540 which is just my broken speed sensor. It has been broken for over a month now though, so I cant imagine its related

 

[Tyler]

PCV? Not really sure, but it's cheap enough to give it a shot if it hasn't been done in the past.

 

[boostproduct]

this may sound messed up but my old subi did the same thing.. unplug your maf an get some maf sensor(mass air flow) cleaner an clean the heck out of it. an then try it. by the sound of what your cars doing is , it was the same problem. could be an easy 8 doller fix

 

[wrangler25]

I get a hesitation at 2800 under certain throttle positions but hasnt bothered me enough to look into it . No codes .