Can bad EGR cause trnsmission problems?

Guess the advice about the vacuum modulator did not make an impression. :)

UPDATE!! EGR was replaced this afternoon. Codes cleared. Test drive resulted in "Service Engine Soon" light coming on 2 miles from the shop. Still not shifting into OD. Returned to shop and code scan resulted again with bad EGR. Engine runs fine with plenty of power. Will be later this week before I can get it back into the shop. Updates to follow:

Thanks again for all the responses.

allbrandauto wrote:
I fully understand how the system works the leak at idle I'm talking about is when the pintal sticks open at idle caused by carbon build up or carbon in the seat causing the valve not to close anyway the op is trying to find out why the trans. wont go into high gear

OK, I understand that but that particular failure mode isn't the only way it can fail. More often, the diapragm gets a hole in it.
One way could effect it at idle and the other wont.

Can an EGR issue cause shifting issues.... Complex answer

It can cause a general loss of power in the engine the result is you open the throttle more and on a Gasoline engine this lowers manifold vacuum. On some transmissions this vacuum helps to control or operate the clutches.

As for your specific Engine and Transmission. I do not know

But I'd get the EGR fixed as it can affect MPG

I fully understand how the system works the leak at idle I'm talking about is when the pintal sticks open at idle caused by carbon build up or carbon in the seat causing the valve not to close anyway the op is trying to find out why the trans. wont go into high gear

double post

You can read codes yourself.
How to read code
Doubt if it is EGR!

This 1994 P30 should be OBD1. How were the codes pulled and what were they? This Listing
shows several EGR codes. Hopefully replacing EGR will clear any/all of them.

Notice there is a Vehicle Speed Sensor (VSS) and it too can throw a code.

I mention VSS because some automatic transmissions of this vintage would shift 1-2-3 but not into OD/4 if VSS had failed.

Deleted - entered in error.

I'm sorry but my experience indicates you are wrong. You also don't entirely understand how the EGR system works.
There IS NO EGR present at idle - no vac is applied at the EGR valve, therefore a leak will not make it idle rough. It will not run rough going down the road either because of the raised RPM's. You can verify this by disconnecting any small vacuum line and driving - the eng will run smooth enough at higher RPM's (than idle) that you wont suspect anything is wrong.
I've had experience with several failing EGR's and none made it run rough.
If the valve itself is sticking, it will result in power loss but that is rare.

allbrandauto wrote:

ScottG wrote:

allbrandauto wrote:
A egr valve that has a vacuum leak will give you rough idle when you go down the road the egr valve opens up letting exhust into the intake to get rid of a gas called nox don't think this is your problem again cat. converter can cause this but you would also have no power is it not going into high gear or is the torque converter not locking up if its the torque converter not locking up could be brake light switch

It wont always give a rough idle.
Vacuum is only applied under certain throttle conditions (not at idle) and with the throttle closed, the engine will idle perfectly unless the EGR valve is stuck open - that is the only time it will cause a rough idle and that failure mode is rare. The usual failure mode of an EGR is that the vacuum diaghram gets ruptured. Then the vavle doesn't respond properly. Then at intermediate throttle positions, you will have a vacuum leak because the ECM is trying to apply vacuum to it and it's leaking.