Persistent P0121 and P1238

[jruberto]

Symptoms:
- very rough idle most of the time. stalls at idle, especially on warm start.
- "throbbing" idle often when starting car. 400 to 1500 RPM about once per second.
- inconsistent throttle response. occasionaly, gas pedal is totally non-responsive when starting car. in general, feels really "soft".

Troubleshooting:
- checked for vacuum leaks, cursory visual inspection / spraying carb cleaner does not reveal leaks. no hissing.
- cleared codes, drove about a mile, P0121 and P1238 are immediately back

I have the IPD TCV -- wondering if P1238 is thrown because the aftermarket part simply operates out of spec?

Last time I was in the shop, got all software updates. Tech ran diagnostics on ETM, printed off chart showing good response. Throttle response got a lot worse after software update. Also, since software updates, cruise control is non-functional (pressing cruise button does not illuminate cruise indicator). I do recall reading somewhere once upon a time that if ETM has problems, cruise control will be disabled.

Disconnecting MAF sensor at idle provides inconsistent results -- usually causes a stall, but a couple times had no effect. I did clean the MAF sensor a couple thousand miles ago.

Do these symptoms add up to anything conclusive to anyone? Thank you thank you thank you! ~j

[jruberto]

Just a followup for posterity's sake.

Replaced MAF sensor. All these problems went away.