Quirks with cold engine and transmission

[JBlakeman]

Hello all. This is my second post as I've not had my truck for very long but I've been experiencing two issues and just wondering if these are normal or if it requires a trip to the dealer.



First, when cold (below 30 degrees) the engine surges in RPM between 750-850 at idle for about 5-10 minutes. It even does this on high idle between 1000-1100 RPM. This issue even comes up with the block heater plugged in. It disappears when hot and assumes normal idle and has only sprouted up in my first winter with the truck? The only thing I can trace it to is when the manifold heaters are cycling. Is it a problem or normal, someone let me know.



Second, my trans has a tendency after being warmed up a bit and coming off of extended O. D. operation (above 50 or so) and then coming to a turn or slow down (coasting) then re-applying the throttle after the turn or off-ramp (around 15-20 MPH) to shift annoyingly into O. D. at 35 MPH! This only happens when the truck is still in 3rd gear and on moderate acceleraton (like 1750 RPM shiftpoints). It will retain O. D. bogging the engine until the 4th gear shift (which really bumps the engine RPM) at 45 then correctly goes into O. D. at normal 50-55 MPH. Again, has anyone else had this issue, is it a normal thing on these 48RE's or does it need service?

Thanks,

 

[cerberusiam]

Surging for 5 to 10 minutes after start doesn't sound right. Can you see the bounce in rpm's or does the ngine tone just change and sound like surging. Mine doesn't surge at all at any temps and the grid heaters only cycle for a minute or 2 on cold startup.

 It will retain O. D. bogging the engine until the 4th gear shift (which really bumps the engine RPM) at 45 then correctly goes into O. D. at normal 50-55 MPH.

Not quite what your are describing here. OD is the 4th gear shift. Is it just not downshifting to drive until you accelerate a bit? Maybe your are just feeling the TC lockup without enough throttle? Roll some more throttle into it when accelerating and it should down shift. It will tend to hold the gears longer until you get some boost into the engine.

 

[JBlakeman]

The surging is noticeable even from the tach inside the truck. Like I said, it's only when cold that it seems to happen. It get's less noticeable as the engine warms up. So for the first few minutes it's worse, then closer to the 10 minute mark it's barely noticeable but still can be heard.



I may be describing the T. C. which is normally engaged at 50 MPH in these trucks. I'm getting lockup at 35 sometimes which I think is not normal. Also instead of staying at least locked, it disengages for the 4th gear shift then re-engages at 50. Hope this helps clarify. This doesn't always happen though. Every complete stop it doesn't. Only if you keep going from a slowdown like taking turns, etc.

Thanks for the thoughts.

 

[cerberusiam]

How many miles on it and how often do you really work the engine? Do you use an additive all the time? If you don't run the snot out of the engine periodically it will tend to carbon the injector tips and could cause some problems. Are you hearing any injector knock or chnage sin the engine sound.



As far as the trans, lockup at 35 in drive sounds about right. Yes, they do unlock and relock on OD shift. Since yours is the earlier 48RE am not sure about the programming but it sounds right. Heck, mine will even lock the TC in second gear. The one thing I like about it is the lockup action. Don't like the tendency to drop gears under a load and high throttle but I can usually work around that.

 

[Rams-n-Hogs]

TSB's 14-003-05 and 14-004-05 cover the surging idle issue. Mine does this, too. As far as the trans, mine acted similar, before I upgraded it.



Jim

 

[JBlakeman]

Thanks for the posts, based on what I'm hearing the trans is normal, so I won't bother with it until I can afford to upgrade it at a later date. I can always use the "OD-OFF" option when tooling around town to avoid both T. C. and 4th gear shift.



I do run the truck agressively occasionally by letting it get to the 3100 RPM redline just to clean things out but it seems the trans hates this however, it shifts very abruptly and confused in this state; so normally I keep my accelleraton moderated to achieve a 2000-2200 RPM shift on most runs, especially on the highway.



The ony additive I've been using (as I've read by other threads on TDR) is Standyne Performance Formula and I use it per instructions on every fill-up. The truck has 45K on it now and I really haven't towed much as of yet. One car trailer so far, nothing real heavy. I don't hear any real "injector knock". In other words it doesn't sound like a Ford.



The engine still concerns me so I think I will run it in to a dealer and see if they can pull up the TSB's on it. I'll probably leave it with them overnight so they can diagnose it cold.

Thanks again.