I have a 1990 corvette, auto trans, 108,000 miles. when i start the car it cranks and runs like it were new, however after 10-15 minutes of running the idle begins to surge and any input from the gas pedal will cause it to stall out. i have checked the fuel pressure it is at 38 lbs, i have also checked engine vacuum, it is at 18 at idle then falls to 15-16 when the car it up to temp. the spark looks good on the cylinders i checked. the fuel filter is new and i just did an oil change. also i have replaced the ignition control module, coil, magnetic pickup, and the rotor button. please help me fix this car!!
I have the exact same problem, please let me know what the fix is. thanks
If you have a scan tool you should monitor the throttle position sensor with the engine off and key on.Slowly depress the throttle to the floor and back while monitoring the voltage readings on the scan tool.If at anytime the readings fall to zero then replace the sensor.Check the wiring to the sensor and make sure it is good.Hope this helps.Good luck.
Take some carb.or brake cleaner and check the intake gasket to see if they are leaking.When the engine starts to act up then spray around the intake and if it has a bad spot you will hear the engine idle change when you find a leak.If you have a scan tool try checking for codes.If no codes monitor the tps,map,o2,and coolant sensors.Also check and make sure the egr is not opening when you step on the accelerator in park.The egr solenoid could be defective and putting vacuum to the egr on accel.in park.this will cause stalling.The only other thing is to do an injector balance test to make sure the injectors are working properly.But this takes special tools.Let me know what you find.
Do you have a scan tool to monitor the sensors or to check for codes?Have you checked the idle air control valve?
When you get a scan tool make sure and check the throttle position sensor (TPS) with the key on engine off.Just depress the gas pedal slowly and watch the voltage on the scan tool.If at anytime if falters or goes to zero then replace the TPS sensor.As far as the idle air control valve you can watch the counts.The ECM reads the iac in counts.The higher the counts the more air the lower the counts the less air is going into the engine.What seems to be happening is while the computer is still in open loop.The engine is running fine.Open loop is when the is cold and the computer is substituting fixed readings into the engine til it warms up.Then it goes into closed loop operation which is the computer is now using the various sensors to keep it running to maintain certain emissions. t his is when the engine is up to operating temperatures.
You can check this with the scan tool also.It should read the temperature that it is outside give or take a few degrees when you turn the key on at first start up.So if it is 60 degrees outside it should read very close to this.A scewed sensor would read very low or hi.Low would give it more gas and hi would give it less gas.
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38 lbs is not enough fuel pressure. replace the fuel pump
HAS THE FUEL PRESSURE REGULATOR BEEN REPLACED?
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ok, i replaced the fuel pump and changed the spark plugs, all to no avail. i still have the same problem. while on a batt charger, i unplugged the alt from the harness and the idle improved, but the car still has a rough idle and shuts off after a peroid of time. so now, i have changed; coil, ign module, rotor button, fuel filter, fuel pump, spark plugs, magentic pick-up ring. please somebody has to know whats going on here, please i beg help me with this.
so far everything has come back within tollerences. the only thing on the fuel system i havent changed is the reuglator. i am at a loss as to the problem. i am to the point of trailering the car somewhere to be looked at. the down side is lack of cash flow to do this.
i have a scan tool, and i plan to put it on it this, week proablly tomorrow. how would you check the iac for proper function?
ok, zero dtc's. the tps is reading correctly with no anomalies. i didn't have a chance to check out the iac due to the rain. i hope tomorrow evening will be better weather for the iac test and to check for intake leaks. am i wrong in thinking that since the vacuum readings(15-18@ idle) i got were good that it most likely does not have a vac leak?
i was told today it could be a faulty water temp sensor forcing the ecu to adjust the fuel map based on a false reading, could this be a possiblity?
today i replaced the front temp sensor, and still no change. i guess tomorrow i will replace the one in the intake itself and hope for the best. any ideas as to what this problem is?????
the regulator has not been replaced yet. money has pinched down a bit due to rent. i guess it should be next on the list.
after breaking down and taking the car to a shop the problem was found to be injectors. as soon as the car comes back with a new set of 8 we will see if that is the correct answer.
the problem was the fuel injectors. after replacing them all, the car runs like a champ. thank you to evrybody for the help.
justin
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