Stumble on acceleration during open loop
Thread Starter
Intermediate
Joined: Mar 2011
Posts: 33
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Stumble on acceleration during open loop
I have a 1987 coupe that runs very well except for an acceleration stumble during open loop operation. It is much worse during cold weather (under 40 degrees) when initially driving after a cold start. Clears up when in closed loop. Could it be related to the EGR Time Delay Switch? (It's the only sensor that hasn't been replaced) No problem with starting cold or hot. Any ideas?
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
I think maybe you mean EGR solenoid. It's mounted on the thermostat housing. It takes ported vacuum from the throttle body and feeds it to the EGR valve.
The EGR is only used during closed loop and only when cruising at a steady speed (not accelerating).
My car has a bad stumble when cold right off idle. It goes away in closed loop mode. I can fix it temporarily by resetting the ECM. The ECM then relearns its bad habits and the stumble comes back.
Try resetting the ECM to see what effect that has. Disconnect this connector for a second or so:
The EGR is only used during closed loop and only when cruising at a steady speed (not accelerating).
My car has a bad stumble when cold right off idle. It goes away in closed loop mode. I can fix it temporarily by resetting the ECM. The ECM then relearns its bad habits and the stumble comes back.
Try resetting the ECM to see what effect that has. Disconnect this connector for a second or so:
Thread Starter
Intermediate
Joined: Mar 2011
Posts: 33
Likes: 0
I think maybe you mean EGR solenoid. It's mounted on the thermostat housing. It takes ported vacuum from the throttle body and feeds it to the EGR valve.
The EGR is only used during closed loop and only when cruising at a steady speed (not accelerating).
My car has a bad stumble when cold right off idle. It goes away in closed loop mode. I can fix it temporarily by resetting the ECM. The ECM then relearns its bad habits and the stumble comes back.
Try resetting the ECM to see what effect that has. Disconnect this connector for a second or so:
The EGR is only used during closed loop and only when cruising at a steady speed (not accelerating).
My car has a bad stumble when cold right off idle. It goes away in closed loop mode. I can fix it temporarily by resetting the ECM. The ECM then relearns its bad habits and the stumble comes back.
Try resetting the ECM to see what effect that has. Disconnect this connector for a second or so:
BTW, if the EGR only functions when in closed loop, do you know the function of the EGR Time Delay Switch (Autozone part# EDS4) and its relationship with the cold start valve?
