P0505, new ISC, next step?

[Josh Kinzey]

First off, I'm brand new to import cars, so be easy on me, . Done my fair share of fuel injected domestic stuff, some dinking with Turbo Buick Regals, but nothing on an import before. Recently, a customer stopped by with a 97 turbo eclipse and asked me to look at a problem he is having:

Car was idling at 1500 RPM and CEL was on. I read the code and it was P0505. I replaced the ISC motor with no change in symptoms, CEL is still on.

I disconnected the battery hoping to clear the CEL. While this did clear the CEL, it seems to have created another problem. The idle now oscillates or surges from 1500 to 1000. This did not occur before the battery disconnect, but I'm not 100% convinced that unhooking the battery is responsible for this new symptom.

I read on here that the base idle screw should have an O-ring in the bore. On this car, there is no O-ring, but I'm not 100% that the post I read about the BISS was pertaining to this year of car. Regardless, the BISS screw doesn't seem to affect the oscillating idle issue.

I've unhooked the ISC motor with the car running, and the idle continues to surge. That, combined with the fact that swapping in another ISC motor made no difference in symptoms makes me think the ISC is not the problem.

I've pinched closed all the vacuum lines with no change in symptoms, so I don't think it's a vacuum leak. After lunch, I was planning to put some compressed air into the system with the car off and watch the boost gauge. If it drops from ~15 PSI rapidly, that would indicate a vacuum leak somewhere that I have yet to find.

I suspect that the EGR valve is bad and allowing un-metered air into the motor, but I'm not sure how to test it. Does anyone know the correct procedure for testing the EGR valve?

I've read on here that cleaning the throttle body is a common fix for similar issues, so I plan to do as well.

Any thoughts, advice, criticisms, or direction would be greatly appreciated.

Thanks,

Josh

 

[MuffinMan7580]

Get an o-ring on your biss and try again.

 

[delta448]

It sounds like you have a good idea of where to start. There is only two other things I can think of that you may not have considered. First, swapping the ECU. Did the owner mention anything about accidentally grounding out the battery, -possibly from not having a proper tie-down in place? This wouldn't be the first DSM that suffered an ECU injury from a battery issue. The other thing I'm thinking is in relation to the fuel system. Possibly a failing pump, bad FPR or the Evap solenoid.

 

[motomattxxx]

First off, I'm brand new to import cars, so be easy on me, . Done my fair share of fuel injected domestic stuff, some dinking with Turbo Buick Regals, but nothing on an import before. Recently, a customer stopped by with a 97 turbo eclipse and asked me to look at a problem he is having:

Car was idling at 1500 RPM and CEL was on. I read the code and it was P0505. I replaced the ISC motor with no change in symptoms, CEL is still on.

I disconnected the battery hoping to clear the CEL. While this did clear the CEL, it seems to have created another problem. The idle now oscillates or surges from 1500 to 1000. This did not occur before the battery disconnect, but I'm not 100% convinced that unhooking the battery is responsible for this new symptom.

I read on here that the base idle screw should have an O-ring in the bore. On this car, there is no O-ring, but I'm not 100% that the post I read about the BISS was pertaining to this year of car. Regardless, the BISS screw doesn't seem to affect the oscillating idle issue.

I've unhooked the ISC motor with the car running, and the idle continues to surge. That, combined with the fact that swapping in another ISC motor made no difference in symptoms makes me think the ISC is not the problem.

I've pinched closed all the vacuum lines with no change in symptoms, so I don't think it's a vacuum leak. After lunch, I was planning to put some compressed air into the system with the car off and watch the boost gauge. If it drops from ~15 PSI rapidly, that would indicate a vacuum leak somewhere that I have yet to find.

I suspect that the EGR valve is bad and allowing un-metered air into the motor, but I'm not sure how to test it. Does anyone know the correct procedure for testing the EGR valve?

I've read on here that cleaning the throttle body is a common fix for similar issues, so I plan to do as well.

Any thoughts, advice, criticisms, or direction would be greatly appreciated.

Thanks,
Josh

The egr does not allow air into the engine at all, it only allows burnt exhaust gasses back into the combustion chamber as a way to cool the combustion chamber and reduce knock. You could make a block off out of a piece of thin metal to temporarily test your egr for leakage, though the egr on these units are generally stout and dont usually stick open.

 

[U2_slow]

It sounds like you have a good idea of where to start. There is only two other things I can think of that you may not have considered. First, swapping the ECU. Did the owner mention anything about accidentally grounding out the battery, -possibly from not having a proper tie-down in place? This wouldn't be the first DSM that suffered an ECU injury from a battery issue. The other thing I'm thinking is in relation to the fuel system. Possibly a failing pump, bad FPR or the Evap solenoid.

He is not getting a CODE: P0505 because of a failing fuel pump...

I have the same code, and my fuel systems fine.

 

[U2_slow]

He is not getting a CODE: P0505 because of a failing fuel pump...

I have the same code, and my fuel systems fine.

I posted the exact same topic and did exactly what you did and I am still waiting on a useful response, , check it out

http://www.dsmtuners.com/forums/problem-diagnosis/317796-check-engine-light.html

 

[delta448]

Right, it is a long shot that the fuel pump could be causing the issue. Maybe I'm way off base here, but if everything else checks out okay, the pump just might intermittently not be getting a good voltage supply or something little like that. The most likely solutions to the problem were already addressed in his first post, I was just throwing out some far-fetched scenarios on a whim. More than likely there is either a vacuum leak as he mentioned, a filthy throttle body seriously in need of cleaning or a little electrical glitch is affecting the ECU.