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I have a 1997 SC with a Japan swapped GE motor (original motor broke).
The CEL has been on since the swap and it's always been P0401 insufficient flow.
The EGR modulator was bad and has been replaced with a good one.
The EGR valve itself tests ok when vacuum is applied to the top port. The car stumbles and almost stalls, although a little slowly.
I have a spare EGR valve but I know the current one opens and closes.
I've cleared the code via OBD tool and it comes on in about 100 miles or a week or so.
I know the VSV UNDER THE MANIFOLD could be related to this but I'm not looking forward to messing with that.
Is there a chance that the Japan GE block doesn't have an open EGR flow port? I don't know what to do.
I've been asking for someone to take a picture of the vacuum lines by the EGR valve in another thread but nobody has chimed in. I know what the hood diagram looks like, that's not what I need.
Japanese motors never had EGR. Only export engines had it. I think what is happening is that you have everything connected correctly, but since the whole EGR system is blocked on the back of the head, you're not getting any flow at all.
Try reading up on the EGR delete. I think all you will need is a resistor in the EGR thermoprobe harness and the stock ecu will be fooled into thinking the EGR system is working.
I deleted the EGR on my 97 5spd with the blockoff plates and the resistor and I have never got any codes.
I have purchased the10K 1/2W resistor and soldered it in to an extra temp sensor harness and verified the resistance on the plug connector with an ohmmeter.
I cleared the code using a scantool and I guess I'll have to wait another 100 miles to see what happens.
I've read this might not work on OBD2, but you might be a case of it working, so I don't know.