'91 420 SEL with 199,899 miles is sputtering and stalling
 

Hello again all,
Here is the scenario please let me know what you think;
While idling in either park or drive the car maintains a fairly steady 500-600 rpms but every once in a while the idle drops to almost 0 and the check engine light comes on. Sometimes the motor will stall but usually it will go to 1000 rpms before returning to 500-600. The problem is now occurring with more frequency and also happens when I decelerate or as I come to a stop.

I just removed and opened the fuel pump relay but it looked fine and all solder joints are solid. Coud it be the OVP or is it something more sinister?

In the spirit of throwing parts at a problem I replaced the orig. OVP today but the problem persists. Any ideas?

Try checking the following....
 

1. Hall effect sensor. It is a little magnet gizmo found inside the dashboard, behind the instrument panel assembly. Sometimes the HES is responsible for causing the stalling that you described.

2. Check the fuel pump relay. It can also cause the condition that you describe.

Let me know how it goes.

fred
 

does it do it on acceleration from a stop, or just randomly . Does it do it when driving at speed or only from idling.
m

It only happens when idling or when comming to a stop. It's fine at speed and when accelerating.

I have now cleaned the idle control valve with no change. I do notice there is what sounds like a spring loaded click coming from the passenger side of the engine compartment that seems to trigger the lower idle.

fred
 

In the footwell of the passenger side is the idle control brain. I have not openend one up but there are some tests you can do on it in the cd's that test for it. That could cause idle problems although, I am not sure what you are getting is a direct effect of that. Idle on these is a beast to diagnose. I assume you have checked all your plug wires and connectors and the rotor and cap.

The other thing to check is the throttle switch and the potentiometer on the air mass flow. do a quick search on those. I have a stall on accelerationand am pretty sure it is my potentiometer.

Spend the time and test test test, you can through money at these and still not fix it.

good luck.
m