Check engine light, rough idle, and P0171 code

I have a 2000 ZX2 with a 5 speed stick and 140k miles. My engine light came on and the code scanner read 171, engine running lean. Car idles rough and will stall once in a while when stopping or depressing the clutch, almost all the time if the AC is on. Acceleration is fine, car runs with the AC on if I’m going down the road with my foot on the gas.

I tried cleaning the MAF with electronics cleaner: no change.

I disconnected the MAF to see if the computer would go into a default mode and run better: no change.

I tried using gas from a different gas station with Sea Foam fuel system cleaner: no change.

I sprayed throttle body cleaner on the all hoses while it was idling to listen for an increase in idle: no change

Visually inspected hoses including PCV (but I haven’t pulled it out to look at it).

Replaced the fuel filter (it was due :wink: ): no change.

Can anyone suggest what I should do next? Did disconnecting the MAF prove that it was not the cause? Or should i have cleared the code before pulling it’s plug?

Thanks in advance,

I don’t know about all that, but a look at the Fuel Rail Pressure Sensor value on a scanner compared to actual pressure would help give this troubleshoot some direction.

Well, I finally got around to changing my PCV valve. It needed it. Engine runs a little better but still exhibits the rough idle and stalling if I switch the AC on while in idle. I cleared the code to see if it will come back. I still don’t know if disconnecting the MAF sensor proved that is not the culprit, anyone know? Assuming the MAF is good since I unplugged it and it ran no different (rough idle), I am now down to the O2 sensor and the IAC. Any suggestions would be appreciated.


I’d try a different maf if unplugging it made no difference. A zx2 idles rough with ac on at idle, it’s just a fact so I wouldn’t worry too much on that part. If the o2’s were faulty you’d get a code specifically for them. the iac is an expensive part that i wouldn’t replace unless i was certain that it was the cause

ya might try replacing the hose that runs from the pcv valve to the firewall. THis is a common problem with the zx2.

Also, don’t forget to replace and or clean (depending on condition) your breather filter. I took mine off, tried to blow through it and was amazed at how restricted it was after 150,000 miles. Who knew? Hehehehehehehehe. Anyways, I cleaned it out with brake cleaner to avoid melting it and blew it out with gentle bursts of compressed air until I could freely blow through it. It definitely made a difference in the way the car ran and the valve cover gasket stopped leaking too . . . . . . bonus! Then I disconnected my PCM for a bit to re-zero the adaptive memory and drove the shit out of it to re-establish the baro. learned value.