Erratic idle after coming off gas

[Dan Sarandrea (Phila)]

I didn’t realize there was an O ring on the idle screw, I don’t recall seeing one when I removed it. Good to know! I’ll have to find one.

I'm pretty sure that there is no o-ring on the X---it is not listed in the exploded parts diagram and my car also did not have one. Other contemporary cars with Bosch L-Jet did use an o-ring here, such as Alfa Romeo. IIRC the FI Spiders did, too.

 

[FRUNKenstein]

Good info. Thanks for all the info. I did order a new fuel filter, as well. No telling how old the current one is.

 

[kmead]

I'm pretty sure that there is no o-ring on the X---it is not listed in the exploded parts diagram and my car also did not have one. Other contemporary cars with Bosch L-Jet did use an o-ring here, such as Alfa Romeo. IIRC the FI Spiders did, too.

Indeed you are correct, the last Fiat FI car I fiddled with was a 124 Spider which has such an O ring. My apologies, I work on a number of other people’s cars and one does tend to have them run together occasionally.

My apologies.

 

[Mxgrds]

In the past I had exactly the same problem. Almost stalling when stopping. The cause was a air leak in the big rubber hose attached to the plennum. Very difficult to find. It was the zoom where the two rubber half are glued together. At idle there is no leak. When driving the zoom opens due to the underpressure and air is sucked in that is not measured by the afm. This is causing a lean mixture. As long as you drive, you don’t notice it. But when you release the throttle, the mixture is still to lean for the first seconds of idle, causing it to almost stall the engine. But now the zoom is closed again and the mixture is corrected and so is the idle. I found the leak to presurise the system from the hose connected to the fuel regulator and close the afm inlet.