Hot Start Problem

[Air Force Rascal]

I don't know if anyone has had this problem or not..I have a 93 SC400 starts right up evrytime cold and runs just great..

Then when I stop and turn off the engine for aprox an hour or so and come back to start it,,it will start up..the rpm will go up then fall all the way down past the idle speed..and sit there at about 100 or 200 rpm and then eventually just die..if I try to give it gas it hesitates and doesn't want to take it.

To get it going I have to turn the engine off several times until it finally just on it's own will start and run just fine...weird..?

Anyone have any Ideas..? Thanks for any help..

[lexus082]

How is the idle when the engine is warm while stopped at a traffic light? I had a similar problems due to a bad mass air flow sensor.

[Air Force Rascal]

How is the idle when the engine is warm while stopped at a traffic light? I had a similar problems due to a bad mass air flow sensor.

Once I get it started and it's hot..it's idles just fine until I shut it off again...I'm leaning towards the EGR Valve..I'm going to get a Mityvac and do the test on the EGR Valve to see if it's working or not. I cleaned out the throttle body and maybe I got some crud in the EGR Valve clogging it up..don't know yet.

Thanks for your reply...

[Air Force Rascal]

How is the idle when the engine is warm while stopped at a traffic light? I had a similar problems due to a bad mass air flow sensor.

Once I get it started and it's hot..it's idles just fine until I shut it off again...I'm leaning towards the EGR Valve..I'm going to get a Mityvac and do the test on the EGR Valve to see if it's working or not. I cleaned out the throttle body and maybe I got some crud in the EGR Valve clogging it up..don't know yet.

Thanks for your reply...

Well...I gave the EGR Valve a check and it's working fine...guess I will just have to get a diagnostic test to find out...

[SKperformance]

Sea foam

[Air Force Rascal]

Sea foam

I tried Seafoam in the gasoline to no avail...also, I cleaned out the throttle body with throttle body cleaner..and I think that is what caused the whole problem...either that or some sensor is getting hot..and sending wrong information to the ecm...thanks SK

Sea foam

I tried Seafoam in the gasoline to no avail...also, I cleaned out the throttle body with throttle body cleaner..and I think that is what caused the whole problem...either that or some sensor is getting hot..and sending wrong information to the ecm...thanks SK

PS.. I also tried to do a Code Reader test with an obd I todya and all the check engine light would do is..just kept blinking and never stopped..so now I'm really confused on this one!!!!

[Air Force Rascal]

Sea foam

I tried Seafoam in the gasoline to no avail...also, I cleaned out the throttle body with throttle body cleaner..and I think that is what caused the whole problem...either that or some sensor is getting hot..and sending wrong information to the ecm...thanks SK

Sea foam

I tried Seafoam in the gasoline to no avail...also, I cleaned out the throttle body with throttle body cleaner..and I think that is what caused the whole problem...either that or some sensor is getting hot..and sending wrong information to the ecm...thanks SK

PS.. I also tried to do a Code Reader test with an obd I todya and all the check engine light would do is..just kept blinking and never stopped..so now I'm really confused on this one!!!!

OK, here is the results of my problem..found it to be the Throttle Positioning Sensor..was opening up or closing the Butterfly on the throttle body too much or not enough after it got hot...

By the way SK..I did the full Seafoam treatment and now the car is running really smooth and seems to have even more PEP...I even used the Seafoam "DEEP CREEP" in the throttle body...took the car out for a drive after the treatment and it left a BLUE Smoke trail for about 8 miles then it cleared and and ran like a stuck hog..city driving really takes a toll on these cars as far as carbon build-up is concerned..espacially if you drive it around town with the O/D on.finding out it's better to run the car with the O/D off in the city..keep the RPM's up and carbon buildup down..some people say I will use more gas this way..but I've been told actually I will probably not use as much..because it's not trying to shift back and forth every few seconds while driving in the city traffic..not to mention the wear and tare on the transmission..over a long period of time...

Thanks again for your help SK...