03-02-2021, 05:09 AM
1996 X90, 16v G16b. Stock engine, full rebuild. 2 years ago. Thorley Exhaust Manifold.
Here’s the rundown as it stands:
For the first 6 months after rebuild engine ran well, no obvious complications, summer in midwest so average temperatures. P0400 showing, been hunting for the cause with no luck since beginning. Winter cold sets in and I begin to experience an idle surge. Random, occasional progressively got worse until flatlining as constant with the following conditions.
At this point I’m running my OBD2 scanner pretty much at all times in hopes that it will give me an alert upon some circumstance which will point to the issue, but so far no luck. Occasionally I’ll get an “Idle Air Control System” code. Very rare, this has been happening for almost a year now and I’ve only gotten that code twice. Still consistently getting the P0400 EGR code, no luck deciphering its root.
cold start idle holds at anywhere between 2500-3000 for 30 seconds to a minute, then drops and begins to surge
1800-2300rpm. Once fully warm the surges increase in sequence slightly, and drop slightly 1500-2100rpm.
Replaced the ISC; No change
Replaced the entire throttle body out of suspicion that the thermal IAC was defective; No change.
Disconnect ISC; no change,
Disconnect (electrically) any (and even all at same time) piece of the EGR system; No change.
Pinch test every possible line in and out of vacuum/EGR system; No change
Physically open EGR Valve; slight decrease in top and bottom of RPM surge.
Any thoughts would be REALLY appreciated. Its excessively annoying as much as it is concerning, and has an unsafe effect on driving when the throttle surges and pulls even in gear if not on the gas pedal.
Thank you!!!!
Here’s the rundown as it stands:
For the first 6 months after rebuild engine ran well, no obvious complications, summer in midwest so average temperatures. P0400 showing, been hunting for the cause with no luck since beginning. Winter cold sets in and I begin to experience an idle surge. Random, occasional progressively got worse until flatlining as constant with the following conditions.
At this point I’m running my OBD2 scanner pretty much at all times in hopes that it will give me an alert upon some circumstance which will point to the issue, but so far no luck. Occasionally I’ll get an “Idle Air Control System” code. Very rare, this has been happening for almost a year now and I’ve only gotten that code twice. Still consistently getting the P0400 EGR code, no luck deciphering its root.
cold start idle holds at anywhere between 2500-3000 for 30 seconds to a minute, then drops and begins to surge
1800-2300rpm. Once fully warm the surges increase in sequence slightly, and drop slightly 1500-2100rpm.
Replaced the ISC; No change
Replaced the entire throttle body out of suspicion that the thermal IAC was defective; No change.
Disconnect ISC; no change,
Disconnect (electrically) any (and even all at same time) piece of the EGR system; No change.
Pinch test every possible line in and out of vacuum/EGR system; No change
Physically open EGR Valve; slight decrease in top and bottom of RPM surge.
Any thoughts would be REALLY appreciated. Its excessively annoying as much as it is concerning, and has an unsafe effect on driving when the throttle surges and pulls even in gear if not on the gas pedal.
Thank you!!!!