Injector Duty dropping to 0%
 

Hello All,

Picked up a different FD recently. It had been running flawless for a couple of months. Until now...

The FC Commander is showing injector duty dropping to 0% and then ramping back up over and over. This happens starting at 1/4 to full throttle with the transmission out of gear or under load. My feeling is a fuel delivery issue (not enough fuel, not enough pressure, etc.)

Has anyone run in to this issue before?

https://youtu.be/9oOwpc9A4I4



DigitalTEN
93' FD Touring

Sounds like it's just a loping idle...like what you would have with a vacuum leak? Injector duty goes to zero during the decel part, which would be normal. Doesn't sound like a fuel issue.

Thank you for the reply Sgtblue

I've traced the vacuum lines and they all appear good. Most of the them are newish. The loping does not happen during idle, only under engine rev in neutral or in gear / load.

I've searched the forums and haven't found a match to other members having this issue. I see the loping idle, but idle is fine and hovering around 900 rpm.

There are times I start the car and this problem doesn't show up. I then come back to it hours later and the problem is there again.

Aside from throwing parts at it, I am at a loss. I put an inline ignition spark tester and I don't see it missing. Next thing I thought it might be is fuel. If there was a fuel rail test port, I would monitor the pressure. Seems like an inline pressure gauge would need to be installed to get this data point.

if you haven't depinned the 4 wires at the ECU for a USDM car with a PFC then usually you will get the lopey idle as fuel cut engages to lower the RPMs.