Stumble/lack of power between idle and 4200 rpm on 1.6L DOHC
Posted: March 1st, 2010, 6:02 pm
But here's the catch: only once the engine has warmed up does this occur.
Symptoms: I can depress the gas pedal ~25% before the engine bogs down between idle and ~4200 rpm. This only happens once the engine is heating up/at operating temperature, however. Once above 4200 rpm, the car responds normally. Also, once warm, the car is incredibly hard to start; requires much cranking, and sometimes an application of starting fluid (which I don't know whether or not is harmful to the electronic components in the intake).
So far, I've replaced the MAS (~4.8 ohm on the intake air temp sensor vs. ~2.4 ohm), and am going to replace the O2 sensor tomorrow (reading 8.6 ohms vs. 6 ohms spec @ 68F).
I've also checked out the throttle position sensor per the FSM, as well as the EGR valve. These are within operating spec. I have checked the resistances of my plug wires (16Kohm per meter, iirc) and they spec OK. Plugs themselves are fairly new (<5,000 miles), as is the dizzy cap. Fuel and air filters are brand new. I have inspected the air inlet lines, and can find to cracks or holes.
Things I haven't done, but am thinking about: jumpering GND and TEN connectors on the test port while @ operating temp, testing the fuel rail inlet line pressure, testing resistances of the fuel injectors.
Nothing I've done has alleviated my problem. Does anyone know which sensor the ECU takes a reading from between those RPM ranges (or thereabouts) and at operating temperature? That, or the ECU itself, is the likely culprit, IMO.
Any help would be greatly appreciated.
edit: Also, there is no check engine light illuminated during any of these conditions. I have verified that the CEL does work, so it's not a burnt out bulb.
Symptoms: I can depress the gas pedal ~25% before the engine bogs down between idle and ~4200 rpm. This only happens once the engine is heating up/at operating temperature, however. Once above 4200 rpm, the car responds normally. Also, once warm, the car is incredibly hard to start; requires much cranking, and sometimes an application of starting fluid (which I don't know whether or not is harmful to the electronic components in the intake).
So far, I've replaced the MAS (~4.8 ohm on the intake air temp sensor vs. ~2.4 ohm), and am going to replace the O2 sensor tomorrow (reading 8.6 ohms vs. 6 ohms spec @ 68F).
I've also checked out the throttle position sensor per the FSM, as well as the EGR valve. These are within operating spec. I have checked the resistances of my plug wires (16Kohm per meter, iirc) and they spec OK. Plugs themselves are fairly new (<5,000 miles), as is the dizzy cap. Fuel and air filters are brand new. I have inspected the air inlet lines, and can find to cracks or holes.
Things I haven't done, but am thinking about: jumpering GND and TEN connectors on the test port while @ operating temp, testing the fuel rail inlet line pressure, testing resistances of the fuel injectors.
Nothing I've done has alleviated my problem. Does anyone know which sensor the ECU takes a reading from between those RPM ranges (or thereabouts) and at operating temperature? That, or the ECU itself, is the likely culprit, IMO.
Any help would be greatly appreciated.
edit: Also, there is no check engine light illuminated during any of these conditions. I have verified that the CEL does work, so it's not a burnt out bulb.