M103 EGR Valve
 

I'm at my wits end with Gertrude. I've replaced the OVP, Oxygen sensor, fuel filter and governor. It still stalls like it's losing vacuum. I tested the EGR valve this morning. It doesn't hold any kind of vacuum.

I think I know of one in a junkyard I can get if it's good.
Should I just plug mine in the meantime? I've searched on here and that's the assumption that I get.

I would assume the EGR losing vaccum and malfunctioning would cause the car to stall on full throttle. If this solves it you'll hear a big "HURRAY" from Dallas to Houston.

Thanks for any ideas!!!

First test the EGR valve itself. Fit a metal plate between the EGR valve and the exhaust manifold. This will prevent any exhaust gas leakage from upsetting the engine vacuum.

The fact that the EGR valve vacuum actuator won't hold vacuum is not of any consequence at idle since the EGR circuit shouldn't be active at idle. With no vacuum signal the the EGR valve, it should stay closed.

I'd like to understand why some M103s have an EGR valve and some don't. I've never heard of a CA spec vs 49 state spec M103. Is there such a distinction?

Sixto
91 300SE
87 300SDL

The car idles incredibly smooth. It's just under full throttle when the car is warm does it stall out. When I used my trusty MightyVac to pull vacuum to the EGR it wouldn't hold any. I tried an old 2.6 engine at my mechanic's shop yesterday and the vacuum held fine. I'm going to plug the line and see if it runs any better.
It feels like a major loss of vacuum as the transmission shifts harsh/late and the engine stalling.

Thanks for input!

I thought you had trouble idling. My bad.

Before you go through the trouble of replacing the EGR valve, plug the end of the red vacuum line and see if the car runs any better.

Sixto
91 300SE
87 300SDL

I plugged the line and poof. No difference. I didn't describe another symptom it's having. When I let off the gas around 40MPH (about 2000RPM) the engine will drop to 1000, then surge back up to 2000 a couple of times before settling down. The car sort of "lurches" forward slightly.

When I've stopped the car the last few times, I've smelled a pretty strong exhaust smell and odor from the converter. It has only really been doing this since the 02 sensor was replaced. The car doesn't have any problem revving or at high highway speeds which makes me think it is NOT the converter. I could be wrong on this like I have been on everything else with this problem. Would the converter cause a problem with low speed and not high speed? When it gets warm it IS more sluggish both at low and high speeds but still doesn't have any problem going once the revs build. The car passed the emissions inspection with flying colors just 500 miles ago.

Since I'm keeping this car, I'd REALLY like to discover the problem...especially before I get hit in traffic from it stalling. I appreciate any and all ideas.

Whats the lambda duty cycle when good and hot? Should be around 50%.

I also just had one with a bad battery that would overload a already undersized charging system and freak out the idle control circuit.

Joe