Engine dies
Thread Starter
3rd Gear
Joined: Feb 2023
Posts: 3
Likes: 0
Engine dies
I have a 1985 C4 4+3 and the engine dies when I down shift. It idles at about 850 to 900 RPM and runs fine going through the gears,but when I down shift and depress the clutch, the engine dies !! Any suggestions ??
Burning Brakes
Joined: Aug 2008
Posts: 823
Likes: 216
From: Tampa, FL
Could be any number of things, from a fuel issue (possibly from a failing TPS).
The factory service manual has a pretty good section under fuel injection that talks about the various "stages" of the ECM, from idle, to run, to accelerate, to deceleration... and in those sections, it talks about which sensors are specifically driving the inputs ... which can help you determine where the issue likely is.
Melting Slicks
Joined: Nov 2016
Posts: 2,219
Likes: 3,046
From: So Cal
2023 C4 of the Year Finalist - Unmodified
Does the speedometer work?
Have you checked the ECM for the presence of Code 24? (No VSS signal present.) (In an Atari Dash car, the VSS is processed by the dash cluster and sent to the ECM.)
If there is not a VSS signal, the ECM does not know that the car is moving, and off-idle. As you motor along, the ECM will completely close the IAC in an attempt to get the idle speed down to to the desired RPM because it thinks it is supposed to be idling. With the IAC completely closed, when you push in the clutch the ECM can not open the IAC quickly enough to prevent the stall.
Have you checked the ECM for the presence of Code 24? (No VSS signal present.) (In an Atari Dash car, the VSS is processed by the dash cluster and sent to the ECM.)
If there is not a VSS signal, the ECM does not know that the car is moving, and off-idle. As you motor along, the ECM will completely close the IAC in an attempt to get the idle speed down to to the desired RPM because it thinks it is supposed to be idling. With the IAC completely closed, when you push in the clutch the ECM can not open the IAC quickly enough to prevent the stall.
