Strange bogging under light throttle and won't start hot
01-26-16, 11:40 AM
#51
Check the voltage at the ECU for the water thermosensor. W/key to on and the engine cold it should read 2 to 3 volts. When warm the reading should be close to .5 volts. If the reading is high w/the engine warm then the ECU thinks the car is cold which uses more fuel and might result in the flooding issue. Also, is the engine and all the wiring JDM or is part of it USDM?
01-26-16, 12:18 PM
#52
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Some ideas to stew on:
-Repair every electrical ground you can get your hands on. Dash, ECU, Engine harness.
-The boost gauge pegging means it is sending the same signal to the stock ecu and is triggering the over-boost fuel cut. This is the fall-on-face, backfire behavior. Possibly the wrong boost sensor.
-The fan running without the key and the boost gauge pegging indicates bad wiring and/or mismatched components.
-The thermosensor on the water pump housing affects the mixture, but shouldn't prevent it from running. Rich hot starts are an issue with the stock ecu.
-The N340 ecu is somewhat unknown, kind of like the N374 japan turbo ecu. On the N374, the USDM mileage switch signal matches up to the jdm speed limiter and cuts fuel to the rear rotor. Look into the other suggestions before tackling this one. https://www.rx7club.com/2nd-generati...rsion-1056618/
-Repair every electrical ground you can get your hands on. Dash, ECU, Engine harness.
-The boost gauge pegging means it is sending the same signal to the stock ecu and is triggering the over-boost fuel cut. This is the fall-on-face, backfire behavior. Possibly the wrong boost sensor.
-The fan running without the key and the boost gauge pegging indicates bad wiring and/or mismatched components.
-The thermosensor on the water pump housing affects the mixture, but shouldn't prevent it from running. Rich hot starts are an issue with the stock ecu.
-The N340 ecu is somewhat unknown, kind of like the N374 japan turbo ecu. On the N374, the USDM mileage switch signal matches up to the jdm speed limiter and cuts fuel to the rear rotor. Look into the other suggestions before tackling this one. https://www.rx7club.com/2nd-generati...rsion-1056618/
-The boost gauge is working properly now that I hav the correct N318 pressure sensor installed. The car no longer bogs/hits fuel cut. Only the flooding/AC fan running with key out issues remain.
-Which one is the thermosensor? I have 2 sensors on the back of my Tstat housing. One looks like a fuel injector connector with the metal clip. The other (broken) one looks like the one on the bottom of the radiator.
-Thanks for the link.
Last edited by 0pistons; 01-26-16 at 12:27 PM.
01-26-16, 12:26 PM
#53
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Check the voltage at the ECU for the water thermosensor. W/key to on and the engine cold it should read 2 to 3 volts. When warm the reading should be close to .5 volts. If the reading is high w/the engine warm then the ECU thinks the car is cold which uses more fuel and might result in the flooding issue. Also, is the engine and all the wiring JDM or is part of it USDM?
01-26-16, 03:53 PM
#54
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I don't remember if I missed it if you did already but getting compression numbers might be a good idea if you're having problems hot starting. Weak compression and hot start flooding go hand in hand.
Also a weak starter can make hot start flooding more prevalent if the compressions weak. A nice fast spinning starter will fire up a weaker compression engine easier and be less likely to flood instead.
Also a weak starter can make hot start flooding more prevalent if the compressions weak. A nice fast spinning starter will fire up a weaker compression engine easier and be less likely to flood instead.
01-26-16, 05:22 PM
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I don't remember if I missed it if you did already but getting compression numbers might be a good idea if you're having problems hot starting. Weak compression and hot start flooding go hand in hand.
Also a weak starter can make hot start flooding more prevalent if the compressions weak. A nice fast spinning starter will fire up a weaker compression engine easier and be less likely to flood instead.
Also a weak starter can make hot start flooding more prevalent if the compressions weak. A nice fast spinning starter will fire up a weaker compression engine easier and be less likely to flood instead.
I am stuck in a hotel in the city for work for the next few days, and probably won't have time to mess with it again until Friday or Saturday night. Keep those suggestions coming, it has to be SOMETHING......thanks again guys.....
01-26-16, 05:32 PM
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Yeah get the actual numbers. Make sure you perform the test properly as it's not the same as the piston engines.
Fingers over the holes isn't accurate 3 even puffs might be 3 good or 3 weak. Always good to know even if it's not your issue which hopefully it's not.
Fingers over the holes isn't accurate 3 even puffs might be 3 good or 3 weak. Always good to know even if it's not your issue which hopefully it's not.
01-26-16, 05:50 PM
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I paid over $4k to have this motor built 74 (seventy-four) km ago, new s5 rotors and housings, all brand new seals, so there better not be a compression issue, but not going to hurt to check; you're right.
01-27-16, 08:27 AM
#58
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Lol, when I read "74km ago" I thought to myself "What? Bernie Sanders isn't president yet" but then I noticed you are in Canada. 
I would highly doubt a compression issue considering the mileage, but still worth checking.
My car can be a bit weird when I crank it hot but it's because my coolant temp sensor is off. It'll start fine but will idle a little rough for a few seconds until the motor clears out the excess fuel the ECU dumped in during start. Runs great and is a strong motor. Idles spot on at 750rpm even with the charging system loaded up, the idle never budges. I've actually been thinking of making a youtube video titled "ever seen an rx7 idle perfect under any circumstances?".
I would highly doubt a compression issue considering the mileage, but still worth checking.
My car can be a bit weird when I crank it hot but it's because my coolant temp sensor is off. It'll start fine but will idle a little rough for a few seconds until the motor clears out the excess fuel the ECU dumped in during start. Runs great and is a strong motor. Idles spot on at 750rpm even with the charging system loaded up, the idle never budges. I've actually been thinking of making a youtube video titled "ever seen an rx7 idle perfect under any circumstances?".
01-27-16, 10:47 AM
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I guess I missed or forgot the part where it's a recent rebuild. Its not that uncommon for rebuilds to be a pain to start until they have worn in and compression has come up. But still probably worth checking.
02-02-16, 06:28 PM
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I installed a switch in line with the 12V signal to the fuel pump, and can get the car to fire right up every time this way. At least this way I can start breaking in this engine.
For some reason I can hear the fuel pump running all the time while cranking the car. If I remember correctly, it is supposed to prime when the ignition is turned to on, then stop until fuel pressure drops, usually when the car starts. Mine is ALWAYS running as long as I am trying to start the car and I think that is what is making it flood.
Also, the round relay closest to the center of the car is clicking as soon as the battery is connected. I am pretty sure this relay controls the electric fan, and not sure why it would always have power if the battery is connected. For now, I just unplugged the electric fan.
For some reason I can hear the fuel pump running all the time while cranking the car. If I remember correctly, it is supposed to prime when the ignition is turned to on, then stop until fuel pressure drops, usually when the car starts. Mine is ALWAYS running as long as I am trying to start the car and I think that is what is making it flood.
Also, the round relay closest to the center of the car is clicking as soon as the battery is connected. I am pretty sure this relay controls the electric fan, and not sure why it would always have power if the battery is connected. For now, I just unplugged the electric fan.
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