Gazza82's 1998 Alfa Romeo 156 TSpark 2.0

Gazza82's 156 Idle Saga!

Latest news!
Mid-2002 and the idle speed on my car was around 1400rpm!!! No number of throttle or ecu resets would solve the problem. Even tried the throttle stop screw but that did nothing. The solution turned out to be a broken "oil separator" valve between the camshaft cover/crankcase and the inlet manifold. This is part of the recirculation system that burns off unwanted crankcase gases and doesn't just emit them to the atmosphere. (It's mentioned in the handbook).
separator_location1This connects just behind the throttle body, not the one in the intake pipe. The one behind is used when the car is idling, the one in front, and more obvious, is used when the car is running at higher speeds. (Look at the last picture on his page to see this clearly).
The new valve is to the right ... part number 71713715 ... cost £2.51!! (back in 2002!!) Pretty simple to fit apart from that damn pipe clamp that you can see in the previous picture.
The spring goes on the plunger (as shown) and this drops into the "hole" in the inlet manifold. (These are the bits that were missing from mine!)
Clean the "hole" with a rag or cotton-bud soaked in carb-cleaner first as they have been known to stick due to oil deposits.
The sealing ring goes on the central piece of the cover, and this pushes down onto the manifold to keep it all in place. It only goes on one way and has to be pushed fairly hard to get the clip to locate. Then reconnect the pipe.
>>>>>This solved the tickover problem after the ubiquitous throttle reset .... took about two minutes to drop from 1300 to this ....idle_speed
But it hasn't cured the "bouncing" revs at around 2500-3000rpm ... just the wrong place as this is the engine speed used for the MOT emissions test (fast idle).
I suspect the idle actuator ... throttle_body
... which is on the right hand side of the throttle body.
And just for good measure, this is what it looks like all in place .. this is a throttle-cable type (not the fly-by-wire you get on the Selespeed and V6 models). The ECU is on the top (two flip-off electrical connectors). You can also just see the second crankcase vent pipe here that is used at high throttle speed. throttle
Believe it or not, but I seem to have sorted it!!
But I'm not entirely sure how! I was running with a "loan" actuator courtesy of my local specialists, and had been for a couple of weeks. So I thought it was time to give this back and replace my own actuator. After all, neither were curing the bouncing idle and stalling. But then I started thinking that opening the throttle by hand to remove the throttle cable could be causing a problem or three. We have all read on the forums the problems fly-by-wire cars have had when their owners have cleaned the throttle body. Most needed a new actuator. So this time I took the throttle body off with the throttle cable still attached. That allowed me to turn the body through 90 degrees and remove the idle actuator without moving the butterfly .. in fact I held it shut with my finger.
I put my original actuator back and without moving the butterfly, bolted the throttle body back on. It is held on with three Torx screws. The hole in the operating gear locates on the pin on the end of the throttle butterfly splindle (see previous pictures). Turn it gently to line up the holes and refit the three screws. Just for good measure, I reset the Idle Actuator with my AlfaDiag software. After connecting all the intake pipes back up, I performed the "idle reset" trick, then started the engine with no throttle. It ran fast for a while, then dropped down to the 840-860 rpm mark and sat steadily. My problems were usually when the engine was warm, so I took it for a thrash up the M40 and back. At the first junction, I was expecting the engine to die .. and it didn't. Since then it's stalled once ... and that was driver error!! wink

Click here to read about the latest in the idle saga. July 2007 the revs started to wobble!