89 Vert engine bucks and hesitates for the first 10 min.
 

I have an 89 vert auto. The car has been hesitating during the first 10 min after start up. I just checked the fuel pressure. Here is what I got,

Max pressure from pump, 70 psi.

Pump hold pressure 62 psi.

System hold pressure when gauge is connected to the fuel rail after 5 min 32 psi, when pump is running 40 psi.

Then sometimes when I shut the pump off the pressure doesn't hold it drops below 18 psi, and quickly, but it only does this sometimes. This is when the gauge is connected between the filter and fuel rail. Like above.

I checked the pressure regulator and it seems to be working within factory specs. Could the regulator have an intermittent problem like this or could it be something else.

Thanks,
Mike

It sounds to me like an iffy Throttle Position Sensor. Sometimes they don't like to work right until they're warmed up. RX-7 fuel systems are pretty beefy - I don't worry about 'em too much.

Brandon

Definatley a problem with the cold start system. Check TPS and thermowax.

A faulty coolant thermosensor would certainly cause these symptoms. If it’s not working the ECU ignores it and defaults to an 80ºC setting. This means as the engine warms up it won’t be getting enough fuel to run smoothly, just like running an old carby engine without using the choke! Check it’s resistance when the engine’s cold, than take a few more readings as it warms up. There’s info in the FSM on what readings you should get.

Thanks for the input, I will check out those sensors. Another thing the computer is giving me error code 17, which means the oxygen sensor is reading 0.55 volts or higher for extending periods of time, could this have something to do with the problem.

No, probably not :) The ECU only reads from the sensor under cruising conditions, and only when it's hot. But it'd be a good idea to replace it anyway - it'll improve your gas mileage if nothing else...

Brandon

whats an old carb'd motor mean? Are you refering to the first gens? :)

Any old motor with a carb that had a manual choke. You might be a bit young to remember... :D