Parking brake choking a throttle at 14-16 rpms

Hi guys,
I have a 99 volvo with a 12.7 s60 pre-egr. 2 years ago did the rebuild. To make a long story short, the mechanic screwed up big time. After the rebuild, the truck never worked right, and 6 months later started smoking (kinda blueish) on cold starts, which would go away after the engine warms up. Also a serious blowby. So after 2 sets of failed injectors, I discovered one problem – the mechanic put a wrong (undersized) cam and smaller injectors in, why don’t know. Like an physical 78mm cam, which wasn't supposed to be there (book says 80.3mm for my serial), but he mechanically tuned it for 80mm or something. And whatever damages that “tune-up” did I can only guess. Cylinder walls glazed yes, rings not tight anymore, etc. So I changed the cam (got one for 81mm) and put higher flow injectors in. Also changed fuel lines and installed FASS. Engine runs OK now, when it runs, but a blowby and cold start smoking remained.

And a new problem crept up. Here it goes: after the truck parked for a while I can start it fine. Idles no problem. I hit the throttle pedal – rmps go up smoothly, no issues. But as soon as I release the tractor (yellow) parking brake, then hit the throttle it chokes the throttle at about 13-16 rpm. I also see lot of blue smoke coming out of exhaust when this happens. After a little bit this throttle’s choking goes away, and the truck runs fine otherwise. Then I stop and park say 1 hour for unloading, crank it and this throttle choke happens again (only with yellow parking brake released). Also this happens when I begin driving after parking and shifting in low gears as rpms go up to 14-16 mark. Then after a bit of driving this throttle choking goes away and engines runs fine. Until the next stop and park, that is. And this problem seems to be getting worse now as weather gets colder. Not using much oil, does not seem to be losing coolant either.

So what can it be? What does parking brake have to do with choking a throttle at 14-16 rpms? Please give me some clues what to look at. I know I will need another inframe, but not ready just yet. Thanks in advance.

 

Well, it's not about 14-16 rpm actually. Gets colder outside now, and the problem seems to be getting worse. Might have something to do with a Detroit cold start in ecm?

Fired up the truck this morning. Started fine, although coughed a lot of blueish smoke until warming up, but that has been happening since the failed rebuild. So rmps at around 11 on a cold start. Couple of minutes idling, parking brake engaged, hit the throttle - no problem at all. Released yellow parking knob and slightly hit the throttle again - choked immediately even at 11-12 rpm and also tons of blueish smoke out of exhaust. Engaged the parking - no problem throttling. Released the parking - same choking. And only stopped after a few minutes of idling when idle rmps dropped to about 8.

So what in the world can this be? If was a leaking injector/seal, then it would choke throttle with a parking brake engaged also, but it doesn't. Only when released. Replaced the oil temp sensor recently, no luck. Could it be some electric switch on the parking brake? Something to do with a cruise control/fast idle?

Please give me some ideas, for I am at a total loss. So are local mechanics...