I have couple of problems that I cannot figure out if they’re related. I’m working on my 97 GMC 1500 2 Wheel dirve 5.7L engine. I have a low idle problem below about 750 rpms. It will cycle down until it stalls. If I unplug the MAF sensor it will run smooth around 800 rpm and up. I have an OBII diagnostic scanner. I have no other codes.
1. MAF sensor P0120 code. With the engine off and the key on, unplugged from the sensor the plug has 11.9v at ignition pin to battery ground. I have.5v at the MAF sensor signal on the plug pin. Both are in spec value. I did a continuity test between the ground pin on plug and battery ground and it is good.
I’ve taken my whole air intake units off my other 97 & 98 GMC Yukon 5.7 engines that I drive with no problem, but come up with the same issues. So, I don’t believe it is the sensors. I replaced the Idle Air Controller on the carb and cleaned the port.
2. My scanner shows me that the #6 cylinder is missing. I clip my timing light on the wire and watch it flicker. It appears to me it is flashing at a steady rhythm. I pulled the wire off plug and grounded it. It was firing showing the same. I ended up replacing all the plugs wires, rotor, and cap. It still shows 6 as misfiring.
have the same problem?
Tuesday, April 12th, 2016 AT 12:12 PM