93 - 940 turbo How to fix EGR Fault 4-1-3? Why?

[morganb]

Hello guys -

So i just purchased a 1993 940 turbo with 125k miles. I paid $1900 in California and i'm happy with the car so far. Fuel pump was leaking, and i just replaced it. Lambada (check engine) light has been on since i got the car last week. It's throwing OBD fault 4-1-3 from port 6. There was a vaccum line from the manifold that was connected to nothing - and sucking at idle. The EGR vaccum booster was going to a T which connected to another manifold vac port (sucking as well) and then over to some little device near turbo booster on passenger side.

So, i got rid of the T and replaced all the vac lines. Connecting the EGR vac boost to the manifold port that was connected to nothing before.

The car seems to run great, there is a very slight RPM fluctuation at idle, and it bothers me that the light is still on. I cleared the codes and the light goes off, but comes back on with same 4-1-3 fault after 20 minutes of driving. So here are my questions:

1. What does the EGR do? Is it necessary and what are the symptoms of one failing?
2. Are there some tests i can do to see if it is the EGR valve or the EGR vac booster that is failing?
3. Are there other issues that can cause a 4-1-3 OBD Code from port 6?

Thank you for your time! It is very much appreciated

[morganb]

For what it's worth - the guy i bought it from said that he cleared the codes and took it to the emissions shop and it passed......even though the EGR must have been faulty then too. I'm not sure i believe him. Any thoughts on passing emissions even with a temporarily cleared EGR fault?

[zippinbye]

The reset you describe could easily lead to an emissions pass. The seller is basically telling you what he did. It may be too late, but he's fessing up to a cover up. Perhaps an inadvertent one since he's talking about it. As long was your EGR behaves from the reset until the smog check, it should pass. Unlike an OBD II there's no trace of the event or drive cycle reset process/readiness check for your 1993. In some states, I don't think it would matter to have the check engine light on in a pre-OBD II car, as long as it burns clean enough into the exhaust probe.

[morganb]

Thanks for that, but i sure wish someone would respond to my original questions.....anyone? please

1. What does the EGR do? Is it necessary and what are the symptoms of one failing?
2. Are there some tests i can do to see if it is the EGR valve or the EGR vac booster that is failing?
3. Are there other issues that can cause a 4-1-3 OBD Code from port 6?

[jmscdgn]

very long shot, but i am facing an identical issue. Did you have any luck solving?

Thanks