Mysterious engine miss

oldsmobile
cylinder

#1

My 1994 V6 engine has an obvious but sometimes intermittent miss. I have identified the cylinder with the use of a laser temperature gun which shows one cylinder at it’s exhaust manifold branch, much cooler than all the others. I have checked for spark and it is there. I have listened with a long screwdriver touching the base of the fuel injector and have determined there is no characteristic clacking sound coming from that same cylinder

indicating to me a bad fuel injector. I have checked the terminals of the plug going to the injector and it reads nominally 13 volts.

I have replaced the injector and still have the same miss and using the same sound conducting procedure it appears the new injector is also not pulsing. With the engine running I read .6 volts across the other injector terminals and nothing across the terminals of the suspect cylinder. Is this an issue of my engine control computer or is it something else. I’m out of ideas at this point. Thanks. TOBYC6


#2

There could be a problem with the ECU as you say. Check to see if the same 13 volts is on the injector wire where it ties to the pin on the ECU. If you see that same voltage there then that means the wire connection is good and the trouble is inside the ECU. If it is you might try opening it up and see if there is a simple bad connection to that pin. If you don’t see the same voltage at the ECU pin connection then there is a problem with the wire connection to that injector.


#3

When the plugs are removed from the injectors, I get the same 13volts readings across the two pins on the plug whether it goes to a working injector or not. I will try following the color code of the suspect wire at the other end of the harness and see if there’s something obvious at the computer, but as for voltage - it is there. The only electrical difference I can come up with is reading the voltage through sharp probe pins of the voltmeter while the plug is connected to the various injectors. Then, I see about .6 volts on most injectors and virtually nothing on the suspect injector. I dont see how this can be a wiring break since I see 13 volts on the same connector when removed from the injector. Hope this makes sense.