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I have a 2002 civic with manual transmission. when car is cold it starts and runs ok, but after its been warmed up if you turn it off it will not restart.

The starter will crank the motor, but it won't start. If when this happens, I let the car roll I can bump start it with out any trouble!!

Any idea why it can be bump started but not started by the starter? If I let it sit for 10-15 minutes it will usually then start with the starter, as long as I haven't run down the battery trying before hand.

 
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Any codes? Could be a variety of problems... clogged air filter, bad sensors.

 
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Has new air filter. Cold air intake.

The cat got blocked when it got driven with a misfire, so my son opened it up and took out the guts of it. The sensors are still in place, and after its been running for a while it will throw the 420 code. But the no start condition can happen after I've driven it to the gas station, about 1km away, long before that code would come up.

If it was a sensor from there, I would think it wouldn't start at all, but it will bump start.

 
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Not the A/F & O2 sensors -- the ECT (coolant temp) or IAT (intake air temp) sensors. My guess is ECT, due to exposure to a lot more heat.

If there's no core in the cat, the downstream sensor will know it. Disconnect the downstream sensor and see if the start problems persist (should see code). If it resolves, need a cat (or a workaround). If it doesn't, look into the sensors above.

 
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OK, got a chance to have another look at this over the weekend.

I disconnected the sensor downstream from the CAT. The problem still occurred.
I reconnected it, and then disconnected the ECT, still the same. Reconnected that and then disconnected the IAT, still the same.

Should I be just disconnecting the ECT and IAT, or should I be replacing? I assume if they were a problem that they give some invalid value causing the car to either flood or have no gas?

But if that were the case, then would it still start on the bump??

Thanks

 
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Hmm... just remembered that this problem occurred earlier with another poster. Look at ezone's replies and see if you can find it -- bump-start, but no crank-start.