1993 RX-7 Idle Quick Rev Engine Rough

jamesg302 · 12-22-2010, 12:48 PM

Hello. I'm looking for some advice from the great people here at RCC. We have a 1993 RX-7 that is stock except for removing the pre-cat and installing a down pipe.

Brief history. About a year ago the car was being driven home from work at night and experienced a sudden over-heating followed immediately by massive coolant overflow on the passenger side of the engine. The car had to be trucked home as it would not run and could not be driven. Prior to starting any work error codes were checked and there were no error codes. After some investigation it appeared that the thermostat was stuck closed and was therefore replaced. We also discovered that the L2 spark plug wire was arcing immediately at the connection to the coil as the end of the wire was corroded through and basically fallen off in the coil plug. The leading coil was tested and found to be outside of specification (low resistance) and was replaced along with the spark plug wires. At the same time as this work the opportunity was taken to replace the vacuum hoses.

After putting everything back together and testing the car there is a problem. Starting the car cold and warm yields a fairly smooth idle at 700-950 rpm. However, if you quickly hit the gas and let off the rpm will drop to approx. 400-700 and the car will begin to run very rough along with a knock or pinging sound. Depressing the throttle to raise the rpm to 800 does not smooth out the engine. If the engine is turned off and back on the car will idle fairly smooth again at 700-950 rpm. When road driven the engine will attempt to quit when stopping at lights unless more gas is given by the pedal. The only error code is #38 Accelerated Warm Up. We have not troubleshooted the error but given that this solenoid is only activated to quickly warm up the car by keeping the rpm high on start it seemed unlikely the a faulty solenoid would create the problem we are experiencing. Other symptoms/observations. Vacuum seems good and is 20 to 12 on idle. Boost seems good; goes to approx. 12 on acceleration. Oil pressure varies greatly. Is this normal? Oil pressure on acceleration goes almost to top of gauge (100+-) and on idle or deceleration goes down to bottom 15%.

Any advice or suggestions for troubleshooting would be greatly appreciated. Thanks in advance.

- James

12-22-2010, 12:48 PM	#1
jamesg302 The Newbie Join Date: Aug 2010 Posts: 7 Rep Power: 0	1993 RX-7 Idle Quick Rev Engine Rough Hello. I'm looking for some advice from the great people here at RCC. We have a 1993 RX-7 that is stock except for removing the pre-cat and installing a down pipe. Brief history. About a year ago the car was being driven home from work at night and experienced a sudden over-heating followed immediately by massive coolant overflow on the passenger side of the engine. The car had to be trucked home as it would not run and could not be driven. Prior to starting any work error codes were checked and there were no error codes. After some investigation it appeared that the thermostat was stuck closed and was therefore replaced. We also discovered that the L2 spark plug wire was arcing immediately at the connection to the coil as the end of the wire was corroded through and basically fallen off in the coil plug. The leading coil was tested and found to be outside of specification (low resistance) and was replaced along with the spark plug wires. At the same time as this work the opportunity was taken to replace the vacuum hoses. After putting everything back together and testing the car there is a problem. Starting the car cold and warm yields a fairly smooth idle at 700-950 rpm. However, if you quickly hit the gas and let off the rpm will drop to approx. 400-700 and the car will begin to run very rough along with a knock or pinging sound. Depressing the throttle to raise the rpm to 800 does not smooth out the engine. If the engine is turned off and back on the car will idle fairly smooth again at 700-950 rpm. When road driven the engine will attempt to quit when stopping at lights unless more gas is given by the pedal. The only error code is #38 Accelerated Warm Up. We have not troubleshooted the error but given that this solenoid is only activated to quickly warm up the car by keeping the rpm high on start it seemed unlikely the a faulty solenoid would create the problem we are experiencing. Other symptoms/observations. Vacuum seems good and is 20 to 12 on idle. Boost seems good; goes to approx. 12 on acceleration. Oil pressure varies greatly. Is this normal? Oil pressure on acceleration goes almost to top of gauge (100+-) and on idle or deceleration goes down to bottom 15%. Any advice or suggestions for troubleshooting would be greatly appreciated. Thanks in advance. - James