Intermittent code 41 "injector circuit"

[NOSLO2PT0]

Quick history. Bought an 81k mile car non-running. Prev. owner says no compression, so I figure bent valves. I pull the head, no bent valves. Clean it up, slap it back on. No start. MPI fuse blown, ECU fried. Replace both, car fires up, sits and idles ok. Start driving it, car will intermittently start running on 3 cylinders. Do injector test with datalogger, everything points to cyl #3. Check resistance of #3 injector, specs out to 3.8ohms. Check voltage at the clip, cycles between 2.8V- 3.7V. Replace the 1G clip and solder in a 2G injector clip. Car does same thing.

I took a stethoscope and listened to all the injectors. #1, 2, and 4 injectors have a hollow "clicking" sound, which is normal. #3 has more of a solid tapping sound. Much deeper than the other three injectors. I don't know if this a coincidence or me just hearing things since I'm probably more focused on that particular injector. Not sure if an injector that has proper resistance and sounds like it's operating will set off this particular CEL.

I'm just trying to narrow down the reasons why I'm getting an intermittent code 41. The car can literally drive down the street fine for a few blocks, then start stutteringand the CEL comes on. 10 seconds later, the CEL turns off, and the car returns back to normal.

Any insight or suggestions?

 

[Only2G4Me]

Just a shot in the dark, but it might be a loose ground. Since you had the head off, maybe you forgot to tighten a ground wire? Or its got some corrosion on it and isn't making good contact. The reason I say this is because I had to replace the engine in my civic this weekend ( I know I know, different car but still the same idea) and I couldn't get the engine to start after I got everything back together. It would try to start but just backfire like the timing was off. I pulled the fuel rail out to see if the injectors were firing and they were but very erratic. I started checking all my connections and found a ground wire I forgot to tighten up. Fixed that and it fired right up. If not, swap that injector with another one and see if the logger data shows a misfire in the different cylinder. Then you'll know if it really is the injector or not. Hope this helps. Good luck either way.

 

[NOSLO2PT0]

On a 1G, there is only 1 ground wire, located on the back of the intake manifold. That one is connected. Also, 1G's don't give specific cylinder location when it comes to misfires and injectors. Hence why we have to physically turn each injector off and listen to the motor.

 

[pearl4gtsi]

U know whats funny, im havin that same problem with injector #1. Car was fine then headin back to work today it just startin missing like crazy. Check engine light gave me code 41. I swapped all injectors and still same problem. I think its electrical. Was looking at the wiring diagram a bit and there is a transister there. Think its the one bolted to the back of the head by the coil. Not sure. Gonna look into it more first thing in the morning. If i figure it out, ill let u know. Any help from anyone else is appreciated too.

 

[NOSLO2PT0]

*Update* Preliminary testing points to a bad injector resistor box. I swapped the old one out with a known good one and the code/misfiring went away. I've only driven the car a few miles on the new resistor box, but the car idles/runs perfect now.