engine when revved hangs up in the rpm - ideas?

[Mike]

Ok, so I am looking for some ideas of things to check on my turbodelta 116 Alfetta GTV.  When free revved, the engine is slow to return to the idle revs.  This is also the case when accelerating in any gear, when I back off the accelerator, the revs don't drop, and instead I have to press the brakes to slow the thing down.  To further clarify, the car is new to me as of a couple of days ago, and according to the previous owner, it did not do this when he had it...very odd.

Anyway,  I have checked the throttle linkage to ensure it is not hanging up on anything, it does not seem to be.  I ensured the enrichment and accelrator pedal adjuster are disengauged, they were.  I have had a very basic look for air leaks between the carbie and the head and can find none, but have not resorted to soapy water in a spray bottle (I'll get to this if nothing obvious rears its head).

Whether it is relevant or not, the engine boost increases unusually slowly from engines I am used to, the turbo is not stock, and is a small garrett of some description.

I'm leaning toward it being something really simple, as the previous owner said this is a new issue.

Any advise would be greatly appreciated.

[jimnielsen]

Mike, I think you need to be careful if you drive the car like this - if you have to put your foot on the brake rather than just throttle off to back off the speed a little, this could be quite dangerous. On 116 type Giulietta's I have seen the later ones had a small electronic controller on the carby linkage to control the decel rate (as an anti pollution measure).  I have always removed them on racecars. It may help to remove all the inlet manifold paraphernalia to that you can see the butterflys and the linkages to see what is really happening.  If the turbo is a small garrett of some description, its probably a T3 variant. They spool up very quickly if setup properly for the application - and you dont have any leaks.....

but I'd fix the revvs problem before I worried to much about boost. As you have the problem when the engine is free revved (when there is no boost) the two problems may be unrelated.

jim ~

[Mike]

Hi Jim, there is no way that I plan to drive the car with this issue, as you say, too dangerous.  I think the two issues are unrelated as you say.  I will remove the inlet gear and as you say, suss out the butterfly positions etc.  It may be that the carby balance srew needs to be altered.

Anyt other thoughts?  Anyone had this issue?  I have had it on my mazda with a 48ida before and from memory this ended up being too high fuel bowl pressure leading to dripping jets, but pretty sure it just meant the revs hung high all the time, mine returns eventually to a rough idle, which is odd.