Siepel

If you're running lean I would also question the fuel pressure, but have you considered the injectors could be clogged as well? Have you had a chance to use an injection system cleaning agent?

Good luck and keep us posted!


Siepel

Cyclon36

Thanks. I've been meaning to put a cleaner in the fuel for a while. I usually fill with premium fuels though. I have been using a HESS station close to home though in the last five months. I figured they're good though.

R3DS2K

might be a long shot.. but recheck your valves? i know having them too tight or loose can cause lean and rich conditions..

Kirpich

Hey, try this, if you're mechanically inclined:

1. replace fuel filter. with mileage, it could be clogged up. cheap enough.

2. pull out and look through you catalyctic converter. The honeycomb might've fallen out and hit the secondary O2 sensor, thus causing damage under higher RPM (thus higher, faster airflow). The S2000 does lose the cat every once in a while.

If that's the case, then the exhaust will be restricted too.

Mark K.

Slows2k

It doesn't have a inline fuel filter, only the pickup sock on the pump.

Fuel pressure check is next, replacing multiple parts by guess rarely fixes things.

Cyclon36

Yup, as chris state, no fuel filter. Just a gym sock at the fuel pump

Cat was checked when I replaced the secondary o2 sensor.

jphish

Have you ever cleaned your IAC valve? If not, it's really easy and takes about 20 minutes. This caused my car to have similar conditions without the Check Engine light.

Slows2k

A faulty IAC isn't going to cause the P0171/172

jphish

It will cause studdering and intermittent dying of the car at idle though. There may be more than one thing wrong. The one may not necessarily have anything to do with the other. What does he lose by checking? 20 minutes.

Cyclon36

[QUOTE=jesusphish,Aug 2 2008, 10:26 AM] Have you ever cleaned your IAC valve?