135sohc
02-10-2013, 12:57 AM
On my TBI daily slug the IAS has been acting up and tonight it was worse than usual. Motor was determined to idle at 3 grand, put the car in 4th and it would pull along @ 30mph like no problem.
This is absolutely related to the outside temperature and seems to come on once its below 50*f. Some days its just flaring between shifts a couple hundred rpms (5 speed car) and it calms down within a few seconds. Other times it flares up and hangs there. Coming to a stop it will sometimes flare and hang the idle and come down in 'steps'.
Its been awhile since reviewing the service manual to see the parameters that drive the motor but I am pretty well convinced the date stream that runs the IAS has become totally garbaged and it just doesnt know what to do. Couple weeks ago leaving work with the defroster running (so the a/c compressor was on) and accelerating from stop and clutch in to get 3rd, the idle speed screamed up to 4 grand and then fell just as fast to almost nothing. The engine felt it was stalling. Tried to recreate the scenario a few times since then and it wont.
No codes
speed sensor is the newer updated version with the better sealing connector, (no speedometer isses either)
IAS is a newer one. Passageway its mounted is not carboned up. I can plug in the scan tool and run the idle up/down all day long without a problem which is why I think the problem is totally within the SBEC and/or its inputs that ultimately provide a signal to the idle speed and where the computer think it should be.
This is absolutely related to the outside temperature and seems to come on once its below 50*f. Some days its just flaring between shifts a couple hundred rpms (5 speed car) and it calms down within a few seconds. Other times it flares up and hangs there. Coming to a stop it will sometimes flare and hang the idle and come down in 'steps'.
Its been awhile since reviewing the service manual to see the parameters that drive the motor but I am pretty well convinced the date stream that runs the IAS has become totally garbaged and it just doesnt know what to do. Couple weeks ago leaving work with the defroster running (so the a/c compressor was on) and accelerating from stop and clutch in to get 3rd, the idle speed screamed up to 4 grand and then fell just as fast to almost nothing. The engine felt it was stalling. Tried to recreate the scenario a few times since then and it wont.
No codes
speed sensor is the newer updated version with the better sealing connector, (no speedometer isses either)
IAS is a newer one. Passageway its mounted is not carboned up. I can plug in the scan tool and run the idle up/down all day long without a problem which is why I think the problem is totally within the SBEC and/or its inputs that ultimately provide a signal to the idle speed and where the computer think it should be.