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Technical (156)
 Alfa Romeo forum : Technical (156)
Subject Topic: Unstable idle and driveability not smooth Post ReplyPost New Topic
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Junior Alfisti
Junior Alfisti

Joined: 02 November 2017
Location: Portugal
Online Status: Offline
Posts: 1
Posted: 02 November 2017 at 19:54 | IP Logged Quote tgferreira


I have bought an Alfa 156 around a month ago. Overall I am really happy with it but now I have found a problem that, until now, I cannot solve.

When I bought it, the previous owner alerted me to the fact that the idle, when cold starting it, was not very smooth. He was right: the car went up and down in the RPM range (when stopped, going bellow the ~1000rpm but not much above) but as soon as I started driving, maybe 1 or 2 minutes after, the problem was gone. I ignored it without any problems.

Around one or two weeks later, the problem got worse: I could not maneuver out of my parking spot without the car stalling 2 or 3 times. So, I removed the MAF and cleaned it with contact-cleaner. I also cleaned the throttle plate, in place, with a rag and some WD-40. I think (I am not sure) that the problem got mostly solved after this. In the meanwhile the car also had a stuck open thermostat that I replaced.

And that brings me to now: in the past week or so, the car has a really high idle. When I start it, it goes to around 1500rpm. Sometimes it stops around 1000rpm but as soon as I press the gas it goes up (as it should) but then it gets stuck at an high value (1500~2000rpm). For example, when I stop at a stoplight, the car stays around 2000rpm. That bothers me quite a lot, to be honest.

Also, when coasting, a bit after releasing the throttle, the car "shakes". I can feel that shaking on the gear lever as if the gearbox is somewhat loose. Note that before this problem of high idle I could also feel it shaking a bit when coasting but not as much!

Yesterday I replaced the knock sensor (goddamn location, my arm still hurts) because someone on another forum told me that part could be at fault. It isn't because the car behavior is exactly the same. After that failed, I removed the whole throttle body (is it the cable one), cleaned and "lubricated" it with wd-40. The problem is still there. I have also hunted for vacuum leaks several times with starting spray and gas for lighters and nothing came of it. Also, I have disconnected the MAF with the car still running and in another chance I drove the car without it connected at all and the problem is still there. I really don't know what else to look at or do. I am willing to retry the same things again but I'm feeling a bit stuck. Could you please help me?

Thank you very, very much!

Info about the car:
Year: 2000/01
Engine: 1.6TS
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CJ Romeo
Don Corleone
Don Corleone
Random Awards 2010, 05, 07, 2nd ,06

Joined: 15 January 2004
Location: Scotland
Online Status: Offline
Posts: 17863
Posted: 04 November 2017 at 09:49 | IP Logged Quote CJ Romeo

Try the throttle reset

Assuming your car has a cable throttle with an electric actuator and its not the full fly by wire type.

The Bosch throttle actuators are very sensitive and can be damaged by manipulation though, so someone migh have damaged it.

2008 Alfa Romeo 159 Ti RIP

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