Cold Engine Surging when put in gear, posting for a friend

[AH64ID]

I have a friend with a 2006 QCSB w/ 48RE. The trans is a built Gorend unit, and he is running II 60hp injectors and a GT3782R, fuel is supplied by FASS. He is running a Smarty Jr w/UDC but the issue occurs with UDC, SJR, and Stock tuning so we don't feel its a tuning issue.

This is his summary.

When I start the truck in the mornings during cold weather and I put it in
reverse to back out of the garage the idle drops maybe 500 rpm and then
comes back up to about 700/750 in a constant and regular up/down until the
engine warms up or I take off driving and after about 2 miles and come to a
stop light it is smooth again and it does not do it anymore.

It is an intermittent issue he has had for about the last 2-3 months, and can sometimes go weeks without occuring.

Any thoughts?

 

[JJPage]

Grid heaters cycling?

 

[AH64ID]

They do, but it's not that.

 

[cerberusiam]

FCA sticking is about the only thing that can cause that kind of rpm bounce, but, with those II injectors in there it is hard to tell. Different injectors will cause all manner of differnet reactions in idle and throttle reaction.

 

[AH64ID]

The injectors, nozzles actually, had been installed for about 12 months when issues started. It doesn't mean it's not related to them, but they had a few miles on them and no issues last winter.

FCA would fit the bill, he doesn't monitor rail pressure unfortunately. I should probably send him my SGII for diagnosis.

 

[cerberusiam]

A heavy dosing with Power Service and\or favorite lube may make some difference. Easy and cheap to try. Not usre the rail pressure would show a difference on that small a bump in rpms, I think the ECU does too much smoothing of that signal to catch it but a monitor whne it happens would show for sure.

 

[DocDetonancour]

Sounds just like my 04. Normal??

 

[AH64ID]

He isn't driving it much right now, but dosed it up and will be doing a road trip soon.

This is not normal.

 

[leaky gasket]

That cold loping reminds me of an old Detroit that I had,it did the same thing. And it would always do it when the weather got cold or I ended up going to someplace where it was cold. I know his truck is not a over the road tractor but my best guess would be that the grid heaters are not working 100%. Or somehow he's just getting a little bit too much fuel on start up.