help!!! idle all over the place, now its dying after running great... AAAAHHHHHH!!!!!

[Gaiwaine]

hey everybody. I have a 90 cutlass supreme, that has been doing a very rough idle overthe past few days. it fluctuates from between 500rpms up to about 1200. and it will change idle speed very quickly. Also, when cruising around highway speed (65-70) the idle willgo from a steady 2500rpms and will fluctuate by itself up and down, until more throttle is given. Then last night the damn car died. just went dead . there was still power to everything, it would crank, just not catch. we let it sit for about 10 min. then it fired right back up. I checked again this morning and again, it fired right up, but died after about two min.

I checked the fuses, relays, and fusible links, and they were all fine. the battery is fine, and there is spark in all wires to plugs, any ideas??? I am at a loss. please help me.


Thanks alot,

The know-nothing cutlass guy

[jstonemo]

The problem is most likely your crankshaft position sensor. If it goes bad, you can have all or some of the problems that you are having. I have done the repair myself on my 97 Grand Prix which has a 3.8 liter V-6. I would consider the repair a job for an experienced do-it-yourselfer. Otherwise, take it to a shop you know. Hope this helps.

[melman]

check the valve on the feul manifold it looks like a place to air up a tire with the key on push the stem in if no gas sprays out its the fuel pump whitch is located in the gas tank i replaced mine in 2 hours after the same thing happened

[drewzer]

Hi I have a 91 with a 3.1 and last year my car did the sme thing, the car would just die after i took my foot off the gas. after replacing all 6 fuel injectors and throttle pos sens. and crank pos sens, and 1600.00 later they added 2 grounding strapps from the frame to the motor and the car has never ran better. hope this helps.

[Slade901]

Originally Posted by Gaiwaine

hey everybody. I have a 90 cutlass supreme, that has been doing a very rough idle overthe past few days. it fluctuates from between 500rpms up to about 1200. and it will change idle speed very quickly. Also, when cruising around highway speed (65-70) the idle willgo from a steady 2500rpms and will fluctuate by itself up and down, until more throttle is given. Then last night the damn car died. just went dead . there was still power to everything, it would crank, just not catch. we let it sit for about 10 min. then it fired right back up. I checked again this morning and again, it fired right up, but died after about two min.

I checked the fuses, relays, and fusible links, and they were all fine. the battery is fine, and there is spark in all wires to plugs, any ideas??? I am at a loss. please help me.


Thanks alot,

The know-nothing cutlass guy

My money is on the TPS (Throttle Position Sensor). It is located near the throttle body. You can't clean it but just replace it $19. The IAC controls the IDLE and if that IAC (Idle Air Control solenoid) gunks up or failing then it will give you IDLE problems. Try removing the IAC near the TPS and try cleaning it first with a throttle body cleaner and test it and if not then just replace the IAC.

However, two other posibility causing this problem is the CTS (Coolant Temperature Sensor) and Fuel Pressure Regulator diaphragm ruptured.

Check your CTS (Coolant Temperature Sensor). If the CTS is bad, either it gives out a too cold signal or too hot signal to the computer.
If it is stuck in too hot, it signals the computer and in turn it will immediately close the fuel injectors and not stay long enough.
If it is stuck in too cold, it signals the computer and in turn it will immediately open the fuel injectors for a long time and probably flood the engine.
During initial startup (cold engine), the Normal CTS sends a cold signal to the computer to open the fuel injectors longer and then gradually returns the fuel injectors to normal operation as the temperature rises.

The Fuel Pressure Regulator has a diaphragm inside and if that diaphragm ruptures, excess fuel is sucked into the Fuel Pressure Regulator vacuum hose and into the intake. Check the Fuel Pressure Regulator vacuum hose for any sign of fuel inside the vacuum hose (do it after the engine has been started for a while).