Hi Everyone,

I have a problem. It all started after a long idle, the check engine light came on.
Plugged in my computer (HT300) and got P0171 and PO170 I think. I cleared these and kept on getting fuel too rich.
As I drove the vehicle around to trouble shoot, I noticed that short term field trim (STFT) was around 30-40% at idle and deceleration.
When I get on the highway or constantly accelerate, both the STFT and LTFT get back to normal or close to it (0-10%).

Went to an autozone, and someone told me my throttle body (TB) was not communicating and I should replace that.
Seeing this as odd, I cleaned the TB and reset it by disconnecting it and the battery.
After puting it back on the car, I get new codes—P0223 and P0123. I have cleared these several times, and keep getting the same codes.

My issue is, besides the low idle feel (~600rpm), the car seems to function pretty well. I have good acceleration, decent gas mileage for a car with 200,000 miles.
My question is what are some thing I can troubleshoot? What more can I do the narrow it down?

After warming it up and driving it around, the idle live data is the following CalcLoad (18%), ECT (187°F), STFT (30-40%),LTFT (5-8%), MAP (29inHG), engine RPM (614), Speed (0mph), SparkAdv (9.0-10°), IAT (113°F), MAF (.21-33 lb/min), TPS (12.5%), O2SLoc (O2S11&O2S123), O2SB1S2 (.350 V), STFT B1 S2 (-1.6-.8%), OBDSup (ODB II), skip a few, Command EVAP (0%), skip a few, EVAP_VP (-.3 InH2O), LAMBDA B1S1 (.991), O2S BI S1 (-.03-0 mA), CAT Te 11 (542°F), ECU Volts (13.850 V), LOAD Value (15-17.3%), EQ Ratio (.985), Rel TPS (.8%), TPS B (29.8%), ACC Pedl D(20%), ACC Pedel E (9.4%), Command TAC (.8-2.7%).

Some of these values are a range, but I did my best to get them close to what they show. I really don't think it is the pedal assembly. There is something causing the rich idle that I just can't figure out.

Thanks in advance,
Big C

 

As an update, I cleaned the PCV valve and got a little improvement.
Still got high STFT.

Thanks,
C

 

So I SOLVED the problem. The evap was close, but it was the PCV hose under the manifold that was the problem.

Bought a dowstream O2 sensor, and that did not solve the problem. So I rented a smoke tester. Sure enough, tons of smoke coming from below the manifold. A mechanic shop quoted me at $1000 to replace the hose, which is shameful.



The hose is $50 at a parts store (https://www.oreillyauto.com/detail/c...pcv+valve+hose) and the job took me an hour and a half. The manifold is easy to remove if you can find the bolts ([MEDIA=youtube]CyPhXt4N3FM[/MEDIA]).



The lessons I learned is...if your short term fuel trim is bad, but all the other values look ok, you likely have some evap leek upfront. I HIGHLY recommend renting a smoke machine if you can, and start at the front of the car looking for a vacuum or hose leek, rubber hoses and plastic parts are more vulnerable. Don't throw parts at it.



Thanks!