1989 Honda Civic Misses after reaching operating temp.

JB_FINE

MEMBER
1989 HONDA CIVIC

Engine Performance problem
1989 Honda Civic 4 cyl Two Wheel Drive Manual

Car starts and idles fine. Timing is on the money. Plugs are a light tan. Fire to each plug. I rebuilt the motor and it has roughly 40,000 give or take. The fuel filter, O2, pcv, and fuel pump have been replaced during or after rebuild. After the car reaches operating temp, not necessarily when the fans kick on just what the temp gauge normally reads, it acts like its missing. Its worse if trying to drive it. I replace the IACV with one from a junk yard with no luck. It will not show a fault code. I also Ohms checked the TPS and it seems to be working fine. I also replaced the igniter. It seems like a sensor is affecting it only in open loop. I'm not an idiot when it comes to vehicles but I'm at my ends wit trying to figure this one out.

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RASMATAZ

MECHANIC
75,992 POSTS

1989 Honda Civic Misses after reaching operating temp.

Engine Misfiring can be caused by worn or fouled spark plugs, a weak spark (weak coil, bad spark plug wire), loss of compression, vacuum leaks, anything that causes an unusually lean fuel mixture (lean misfire), an EGR valve that is stuck open, dirty fuel injectors, low fuel pressure, or even bad fuel

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Saturday, April 18th, 2009 AT 7:08 PM

F4I_GUY

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Try doing a cylinder balance test to isolate a cylinder. Do this by unplugging each injector one at a time.

If you cannot find a dead cylinder when the vehicle is mis-firing then you will have to run the checks that rasmataz has posted.

My first check would be for strong white/blue spark. Ignition coils are known to fail on those vehicles.

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Saturday, April 18th, 2009 AT 7:20 PM

JB_FINE

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This engine has a throttle body type injection. I have unplugged the injectors while the engine is running and it dies. The problem only occurs when the engine reaches a set temp. Or what I think is in an open loop condition. I did replace the thermostat with no luck. If the plugs or wires were a problem, it looks like it would have the problem on start up not just at a set temp. I did notice when I unplug the temp sensor that controls the ECU it is drivable. It still misses but not nearly as bad.

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Monday, April 20th, 2009 AT 8:44 AM

F4I_GUY

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You unplugged the ECT? Electronic coolant temperature sensor, and it stops mis-firing?

If so, that is most likely your issue right there. It is probably sending the wrong temperature to the ECU so the ECU is either over or under compensating on it's fuel.

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Monday, April 20th, 2009 AT 5:44 PM

JB_FINE

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Yes, I unplugged the ECT and it stopped missfiring; however, when I drove it it still would miss but not nearly as bad. This may be due to the ECT being totally unplugged. I am still wondering if this could be the cause since there is no fault code untill it is unplugged. I don't know if a sensor has to be totally or partially faulty before it throws a code.