BDR1973

Anyone run into this code in there car, P1400. Place had car for over a week looking at it from time to time. They said I was showing high voltage to MAF, O2 sensor upstream. This all started last Friday when I started my car. It struggled real bad to stay running. But once you have it some gas, it ran smooth.

RJ_RS_SS_350

Not much on that one here. I found this on google.
http://http://ricksfreeautorepairadv...400-chevrolet/

Oldblue

Properly clean the throttle body and the MAF sensor

https://www.chevyhhr.net/forums/gene...le-body-20839/


https://www.chevyhhr.net/forums/prob...roblems-41743/

donbrew

Mitchell doesn't have a lot of info, but here is the diagnostic procedure.

BDR1973

Oldblue, they cleaned the throttle body and has a new mad. They reset the codes and they came right back on. Plus it has the code p0171 which no one can find the problem. Trying two more places and if no problem found. Will most likely out car up for sale. Only about 125,000 miles on it.

Oldblue

I'm thinking if your tb was cleaned correctly and the MAF is new then the P0171, check for cracked hose from the valve cover to the elbow just before the to, check to ensure the MAF is installed in the correct direction and it is in tight and sealed , then there is the possibility that your flex pipe has a crack in it and is throwing the O2 sensor off!

http://www.obd-codes.com/p0171

donbrew

Did you consider that they are related? Like including that in the OP? Anything else you left out?

Note the idle speed, engine airflow involvement in the p1400 code.

I know you have "checked everything" but it sure sounds like a vacuum leak. Or a cracked flex pipe.

The top attachment is P1400, the bottom one is for P0171.

BDR1973

UPDATE: Its been at second shop for about a week now. Still getting the P0171 & P1400. He has cleaned the fuel injectors, did smoke test and found no leaks. Each day he drove it, acted some what good and one day it gave acted bad on startup. But once you gave it gas, it was fine. Having him check the FLEX PIPE for crack and just waiting to hear back.

donbrew

What both codes mean is that unexpected air is being introduced to the combustion chambers somewhere between the MAF sensor and the #1 O2 sensor.

Possibilities include:
breather tube
EVAP canister purge valve/tube
manifold gaskets
the air tube between the MAF sensor and the throttle body
throttle body to manifold
flex pipe
etc.

My favorites are:
the breather pipe and
the purge pipe or valve especially because "Each day he drove it, acted some what good and one day it gave acted bad on startup"
"Slow to start" is a frequent symptom of a bad purge valve.

Seems from reports I've heard that smoke tests are not worth doing. Eyes and fingers can do it.

BDR1973

UPDATE: well car still in shop. tried to see if new flex pipe w/cats on and still got the same problem codes coming up. I'm in no hurry right now since back up car is still running. hopefully hear something back soon. just waiting for him to get caught up on other cars before he gets back to mine. its bugging him to the point that he wants to figure it out. just glad he is not giving up on it.