Okay
This is a little perplexing
P0401
EGR Insufficient flow detected (when by itself, a SIMPLE fix.)
P0402
EGR Excessive flow detected.
Are you absolutely sure that you read the codes/were told codes correctly?
I would think it posible to inverse a two numbers, perhaps an 0420? (Catalyst below efficiency.. caused by major vacuum leaks, which can also cause an 0401. (insifficient because there is a vacuum leak on the EGR.
Actually, I just received that combination of codes (0401/0420) a week ago...
Either way.. IF it is a 0401, 0420, then the things we will check for are:
vacuum leaks (tubes broken, etc)
faulty EGR valve
faulty DPFE (differential pressure feedback for the EGR)
(all DIY if you want to...)
Look in the engine bay and find the EGR valve. (It looks like a little silver UFO disk with a green vacuum tube connected to the top via a small rubber elbow.
Firstly: make sure that green tube isn't cracked, broken, or missing (warning: It will be very brittle, at this age of car, and you could break it if you aren't gentle when removing it from the top nipple of the EGR)
If the tube looks to be in good condition, and the length of tube (running to the back and in to a bundle of red/green tubes) looks great throughout, then do the following:
Remove the green vacuum tube from the top of the EGR. With the car running, apply a vacuum to the EGR nipple itself. (suck on the nipple.. yayaya I know it's the only time I can say suck and nipple on CEG without being rude...)
Does the car stumble and choke/die? (If so, then the EGR itself works great...) (Replace the tube on top of the EGR)
Next we need to check for TINY cracks in the vacuum tubes (so small you can't see them...)
All you do is start the car, and spray carbeurator starter spray in different areas of "vacuum tubes".. if the car stumbles, then the spray made its way in to a small crack in whichever area you sprayed.
If all of this fails, then the more common failure would be the DPFE.. if all those tests fail, then we'll walk you through the way to replace the DPFE.
If the codes are, in fact, 0401, and 0402.. then I can't think of ANYTHING to cause BOTH!!!
Ray
