1993 Plymouth Colt idle surge

1993 PLYMOUTH COLT
70,000 MILES • 4 CYL • FWD • MANUAL
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CHESTERBIRD
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idle surges after warm up. has repaired computer,new ISC,temp sensor,02,fuel pressure regulator, all sensors test with in spec.timing is good. new plugs, cap & rotor,fuel filter all vacuum hoses replaced. starts fine, when it reaches operating temp starts to surge, between 1100 rpm & 1900 rpm.If the ISC motor is disconnected it will continue to surge.NO CODES!! HELP!!!
Dec 26, 2009 at 6:04 PM
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RASMATAZ
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Hi chesterbird, Welcome to 2carpros and TY for the donation and selecting us as your auto repair site Feel free to ask questions at anytime and Merry Christmas and a Happy New Year 2010

Check the fuel pressure if its within specs if okay-check and test the throttle position sensor, Manifold absolute pressure sensor, airflow sensor and the PCV and EGR valves
Dec 26, 2009 at 6:33 PM
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CHESTERBIRD
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Thank you, all that you recommended has been done. My first thought was EGR or a vacuum leak, car dose not have EGR or MAP sensor. Do you have any other ideas????
Dec 27, 2009 at 12:23 PM
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RASMATAZ
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What engine liter do you have is it a 1.5L or 1.8L

Check again on the TPS and idle air control motor to include vacuum leaks
Dec 27, 2009 at 1:24 PM
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CHESTERBIRD
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1.8L tps is at spec. there are no vacuum leaks, and the ISC MOTOR is working, it is new
Dec 27, 2009 at 7:20 PM
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RASMATAZ
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Check the fuel pressure if its within specs and comeback with the readings
Dec 27, 2009 at 8:51 PM
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CHESTERBIRD
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OK, I'll be going through it all again,and will get back to you in a couple of days.
Dec 28, 2009 at 8:39 AM
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CHESTERBIRD
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Hi, the fuel pressure is 47.5psi w/ vacuum hose off and 38psi w/ hose on still trying to find a vacuum leak. If the fuel pump was going out, would fuel pressure be ok if you had more than half tank of fuel and not ok with less than half tank??? thanks bill
Jan 3, 2010 at 11:17 AM
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RASMATAZ
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The fuel pressure is within specs with and w/o vacuum.

Try running an injector cleaner thru the system and also check the coil resistances primary/secondary.
Jan 3, 2010 at 3:45 PM
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CHESTERBIRD
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Today I tried to adjust basic idle seed, and could not get any response form idle speed screw. I followed the factory procedure. Book said to replace throttle body, if you can't adjust. Coils are in spec. I've been through everything at lease twice.Today vacuum was 18 and steady.Serge only starts when engine reaches operating temp. I never believed ghost until now. Thanks,Bill
Jan 3, 2010 at 9:44 PM