Kevin Cederquist

I'm having some trouble with my car. It was running fine this winter, but lately has started rough idling pretty bad, and surging and stalling at higher RPMs. I still have a lot of things to check and try, but I did take the Injectors out and took them to a local injector place to have them serviced. He just got back to me and said the Injectors are aftermarket, and they are high impedance, whereas the 944 used low impedance Injectors. Based on the car history that I know, I suspect when the car was 'resurrected' a few years ago, that these new injectors were put in.
So, my question is, could these new high impedance injectors be causing, or contributing to my problem? And if so, how do I go about fixing it? Can I just add resistors onto the injector wires from the ECU to match impedance, or is there a new chip I should get?
I should add I'm planning to replace the AFM with a MAF from Lindsay Racing, and change the chip anyway, will this chip come ready to support high impedance injectors? I admit, injector circuits are not my strong suit. Any help would be greatly appreciated.

Glenn R

As I recently learned, there is a difference in FI impedance depending on the year. I had the wrong injectors for the DME and it wouldn't even start. If your car ran fine earlier, you are likely looking in the wrong place. I would check the speed and reference sensors and the air flow meter, to start with. A coil going bad can show up at high RPMs. So you might want to check that too.

Basically, step through ruling out the most likely components. The injectors are probably pretty far down that list. If you are not familiar with Clark's Garage, there are some great troubleshooting guides there. Give them a look.