yellow dragon

im throwing a code 33, EGR valve, can someone tell me what this is, where it is, and how difficult it is to replace, my local shop told me they would have to pull off the intake manifold, i'd rather not until my miniram shows up

its a '91 TPI

65Z01

code 32 is the EGR system
-valve located under the center of the plenum
-solenoid under the left front of the plenum

code 33 is the MAP sensor
-located on the right rear of the plenum

yellow dragon

do i have to remove the intake manifold to replace the EGR, or can i just remove the upper center portion of it?

rick lambert

You need to remove the plenum

yellow dragon

doesnt sound too bad, shop wanted 3 hours labor to do it, y'all just saved me some cash, thanx

mark

CFI-EFI

Why would you spend time messing with the EGR valve when your code came from the MAP?

More importantly, why would you spend the equivalent of 3 hours of shop labor (which will take you more than three hours) to replace an untested, and not inexpensive, EGR valve? Don't shoot the messenger!

RACE ON!!!

yellow dragon

thanks CFI, i rescanned it and found it to be a code 32, the mechanic told me it was a 33 EGR, he was wrong about the code number but right about the EGR. just goes to show that GM Goodwrench isnt always a better shop than a local "Jim's automotive". although they do have a bigger wallet to back up there mistakes,

thanks for the advise.

mark

CFI-EFI

I figured maybe that was the case after 65Z01's post and you kept talking about the EGR valve. What about my second paragraph?

Don't shoot the messenger!

RACE ON!!!

yellow dragon

if i threw a code for the EGR valve, what else could it be, the solenoid? is there any way to test these items? or would taking it in to the shop be the smart thing to do?

mark

CFI-EFI

If you will check your factory service manual, it will tell what readings (the conditions) the ECM has to see in order for the ECM to set the code. Just because the reading came from the EGR circuit doesn't necessarily mean that the EGR is bad. A sensor can either be faulty, or it can correctly cause a code to be set because of out of parameter conditions, with a cause other than the sensor. There could be a loose, disconnected or shorted out wire. The FSM has trouble shooting charts that you can follow to track down and TEST the suspected cause of the problem, before you "throw money" at it by replacing good parts. If the EGR valve is in fact not the cause, you would have spent the time and the money to replace it, and then you'd be right back here, in a day or so, with the same problem. Don't shoot the messenger!

RACE ON!!!

yellow dragon

you were right CFI-EFI, the EGR valve wasnt the problem, i pulled the one from my dad's '90 and used it, only an hour to swap, still threw the code, i ran the snap-on scanner and noticed that my exhaust oxygen curve was all over the place, not a smooth line, bouncing from bottom limit to top limit, rich to lean... which leads me to believe that i have a faulty 02 sensor, the car is running rich, i can even smell it in the exhaust at idle,

could a bad o2 sensor be causing the car to run rich therefor causing the computer to believe the egr valve is malfunctioning? im not too familiar with OBD1, i know that with OBD2 cars the o2 sensors help set the air/fuel ratio.

conv90

The O2 sensor voltage is right like this when you are in closed loop.
" not a smooth line, bouncing from bottom limit to top limit, rich to lean... " = perfect.
-Beppe-

yellow dragon

i took the plenum off again. the solenoid, and valve both work, and there are no vacuum leaks in the system. is there an EGR temp sensor or does the system use the temp sensor on the engine block? im looking for anything else that could cause this problem.

thanks

AGENT 86

On my 86 the EGR temp sensor is in the back of the intake where the EGR tube from exhaust manifold ties in. Heres some info from my 86 manual. It still may be helpful to your year.....................

http://members.shaw.ca/corvette86/Code%2032.pdf

blown87

look for plugged passageways in the intake, that is what causes that code about half the time. as far as your O2 sensor, it is not supossed ot be a even voltage, it should rapidly go between about .300V to .900V it is when it does not do this is when you have a problem with the O2 ( we are talking about the pre cat one here) Greg

CFI-EFI

I really wasn't "right" because I wasn't saying that the EGR valve was good. I merely wanted for YOU to assure yourself that it really need replacing before you started throwing money at the problem, in vane.


A bad O2 could be causing the engine to run rich, but if it were, you should get an O2 code. A rich mixture will not cause a code 32.


You are bouncing around from pillar to post, with no clue as to what you are looking for or testing. I seems as though you don't have a FSM. Get a hold of one and follow the trouble shooting chart. The book will explain how the system functions, for your year, and lead you through a course of trouble shooting steps, in a logical, organized sequence, to best isolate the cause of the problem.

RACE ON!!!

65Z01

There is an EGR test method on my site; just ignore the part about testing the EGR Temp SW, as your '91 does not have this item. Your '91 ECM uses input from the MAP sensor along with other input to calculate feedback status on the EGR system.

BTW, when is the code 32 set? That is, does the ECM throw the code at startup or after cruzin at steady speed for a short while??

yellow dragon

after cruizing at steady speed, usually while on the highway