Sluggish acceleration when cold (1 Viewer)

[ATL Cruiser]

1992 HZJ77 automatic A440F
GTurbo
PDI Intercooler
OEM boost compensator

This is possibly (likely) a dumb question, but it's been a LONG time since I've daily driven a truck from the 90's.

My 77 automatic is super sluggish on cold mornings. The engine is producing power fine (EGTS go straight up like normal). It just feels like I'm pulling a trailer load of bricks uphill. Once it's warmed up, all is well, and it snaps right along.

It never smokes ever. Fires right up always.

My initial thought was transmission fluid. But it's fresh, clean, and full. Possibly sticking boost compensator? EGTs climb great though.

Or maybe this is normal on a 1992 transmission. Would love to hear some thoughts.

 

[Rigster]

This seems odd...

I suppose it would be nice to experience what you are seeing. When you say a 'cold morning', I am taking that with a grain of salt of course... how cold could it possibly be in Georgia? Cold for us here in Canada would start below freezing..... and probably start for @coldtaco in AK even colder.

When it comes to Diesels, they should never be put under load/worked hard until they have warmed up. Most wear on a diesel happens when it is cold. That said, it still should not make it 'sluggish' like you are describing. Especially Georgia cold.

If it was one of these newer vehicles with computers installed and such, then I could see the computer adjusting for warmup time and governing the fuel, but that would not be the case with a 1HZ.

Do you have a boost gauge? That would be the easiest to see if it is sticking until it is not, and you would be able to see what kind of boost values you are getting throughout the warmup process. If it is producing good boost, then I would agree, something is up with the tranny/torque converter... I have a 5 speed, so that is about as far as I can go with this, sorry!

 

[ATL Cruiser]

This seems odd...

I suppose it would be nice to experience what you are seeing. When you say a 'cold morning', I am taking that with a grain of salt of course... how cold could it possibly be in Georgia? Cold for us here in Canada would start below freezing..... and probably start for @coldtaco in AK even colder.

Agreed completely. They call it Hotlanta here for a reason. It only drops to 0C at the coldest in dead winter. Most mornings now, it's right around that and sluuuuuggish.

Yes, the boost gage ramps up great, just like normal straight to 5-10psi on the hills. EGT's climb like normal as well. It just feels like there is a sled of bricks dragging behind the truck.

I come from a VW TDI 5 speed. It has 260k miles on it and still drives great. The performance is the same cold and hot. Nothing noticeable like this truck.

In any case, thank you for the reply. I'm looking forward to getting this resolved.

 

[Behemoth60]

My theory is that It's the cold diesel fuel. The 1HZ has no fuel heater. Until the engine heat soaks the injection pump, which will have a side effect of pre-heating the fuel, the fuel will just absorb heat from the cylinder as it is injected (causing that sluggish feeling) before it finally ignites,

Many modern diesels have fuel heaters, I assume for this reason. There are some fancy aftermarket fuel filter systems that have integrated fuel heaters, again, I presume, for this or similar reasons.

I am assuming that in Georgia, you may not get something that we get in the Northern Climates that we affectionately call 'Winter Diesel'. The refineries change the blend in Northern markets to 'lighten' the diesel, to lower the gel temp, but also, I believe, making it a bit easier to ignite, with a side effect of reducing the energy content of the fuel, which some careful keepers of records may notice in a slight decrease in fuel economy during the winter months. I am assuming that this further exacerbates your sluggish feelings when it is cold.

Anyway, this is pure speculation on my part. You could have a crack in the head or a head gasket leak that seals itself up when the engine warms up. That was how the SR-71 blackbird worked. But I am going to speculate 'Cold Diesel Fuel', in your case.

 

[African]

@Behemoth60 not a bad call on the possible issue actually.
What if you tried some diesel anti gel additive run it long enough to have it well mixed in and through the lines and injectors, then check on a cold morning to see if it makes any difference…
Assuming the truck is stored outside

 

[lacalvette]

You sure it’s not just an heavy oil viscosity in diff and tranny? Mineral 80w90 is really thick on cold morning. Need to drive casual for a while…

 

[ATL Cruiser]

Thanks all for the suggestions. Good thoughts on the thick fluids and diesel fuel.

My other thought is that it is sticking in 2nd/3rd gear on cold mornings.

I currently have my entire dash apart for this RS3200 keyless entry install, so I will be testing all those ideas once everything is back together. Thank you again.

 

[ATL Cruiser]

Update on this for anyone interested. My automatic transmission was slipping ever so slightly. Not enough slippage to really notice but enough to notice on hills during cold mornings for a few minutes.

The A440F finally failed a couple months ago. I converted over to a manual H55F. I now have zero issues whatsoever. Plenty of power in cold or hot weather.

 

[FJ73Texas]

Welcome to the manual club @ATL Cruiser

 

[Gun Runner 5]

Sluggish Acceleration…..
I just assumed this was a general discussion about owning a diesel powered 70 Series.

 

[ATL Cruiser]

Sluggish Acceleration…..
I just assumed this was a general discussion about owning a diesel powered 70 Series.

*correction - "more sluggish than normal"