hey i did a search and yes understand what the code 34 is and how to diagnose it, but before i go out there and unplug and plug trial and error the sensor could this code have been caused by one of those plastic vaccume tubes comming off of the Air system. or w/e that crazy 3 way vaccume hose thing is under the maf???

reason i ask is. i was driving my 85 to the local Corvette specific shop (marcel's Corvette Mechanicville NY) and before i got there i had the SES light come on. i pulled over immediately and checked under the hood without shutting off.. to my suprise i found one of those hard plastic lines to the Air system 3way valve thing that sits under the MAF had popped out of the L connector the the AIR system valve, plugged it in SES light went off shortly later but then came back on before i got home. 30min of total run time before i got it home and pulled the code. i had no change in the way the car was running. just a loud air leak sound when i first popped the hood and found the hose off.

thanks for looking and any info is greatly appreciated.

 

and i would have had it checked out @ the corvette shop but they were closed :hammer:

i read through my haynes manual that was only helpful in telling me what my SES code was, the reason i ask about the AIR system vaccume line is because the repair manual does say to check for air /vac leaks in the intake system.

 

disconnect your battery for 30 seconds, if the code clears and doesn't come back....you've answered your own ?

 

How did you get a code 34 and still have the engine run "normal". A code 34 (MAF air flow low) will cause the ECM to drop into "limp-in" mode and the MAF readings from that point on will be ignored- the thing (in My experience) will run really poorly. Cycling the ignition (shut off and restart) will reset that and it'll run OK again, at least until the next "occurance" of the code 34 set.

The code itself Will remain stored until you clear it - the "no power to the ECM for 10 sec" thing. BTW - you don't have to disconnect the Battery to do that - either pull the ECM fuse or disconnect the harness power lead (single in-line connector in the harness sort of next to the battery..).

Anything that causes a large enough vacuum leak will cause the code 34. All it means is that air is being drawn into the motor Without passing thru (and being measured by) the MAF. Hence the low MAF reading and the code. A leak from an "open" small hard plastic vacuum line Might do it - but that ends up as a pretty small leak...

Seems to me that if that One single small vacuum leak causes the code to appear, and Stopping that leak cures the code setting, that you may well have Other vacuum leak(s) someplace that don't quite let enough air bypass the MAF to cause that code. I'd be having a really good look at that possibility

BTW - a code 34 will Normally appear (if it's going to happen at all) right at or immediatly after startup - as the car is settling down to idle. That's where the throttle plates are closed, the IAC valve is wound down to it's most closed setting and the MAF is looking at the lowest normal airflow. Doesn't take much air bypassing the MAF (under those conditions) to let the Measured airflow fall below the code 34 threshold value.

Also - the code 34 diagnostic is one of the things that can be turned Off in the PROM program - you can disable it.

 

SES definately didn't come on till i was about 30min away. and i'm sure it was that vaccume leak that caused it. unfortunately i don't put much milage on my vette so tomarrow will be my first day that i'll be able to take it out and run it. i'll clear the code first. i'm sure other vaccume leaks are definately a nother possibility and prolly a reality in my case, i've already replaced about 5 feet of vaccume hose that was badly cracked or leaking :P comes with the territory tho having a 24 year old car