D21 Suddenly runs rough after freezing

[Duct Tape and Bubble Gum]

My 1996 D21 was running, well, fine until I went to start it after a very cold (below zero) night recently. Extremely rough idle and then died after 20 seconds. Ran the scanner, no codes. Fluids all look fine. Yes it has gas in it.



When I parked it two days ago, it was running smooth. It has always started, even in below zero (F) weather. Now it cranks, starts and immediately dies unless the block heater has been plugged in for a while, it which case it will start but run rough, even when engine begins to warm up.


Any ideas? The combo of no DTCs and the fact that it was running fine a couple days earlier is confusing.

[Deerhurst]

It's there any RPM change when pushing in the clutch? I've been cold enough that my tranny fluid get thick enough to stall the truck in neutral.

[89'HBV6]

Water in the gas... frozen water in the lines, does not take much. Hope you try to keep the tank full, up there. Condensation is bad in cold climates. Use that block heater, it's needed where you live. I had one in Colorado on a different vehicle, I needed it also.

[jp2code]

I don't live in a cold climate and I never have. What happens if the oil gets too cold? I'd imagine the hydraulic lifters stop working.

[Duct Tape and Bubble Gum]

Yes, there is an RPM change when depressing the clutch, but I don't think it's just the cold tranny fluid this time. That's a normal thing where on below-zero days I have to coax the clutch down gradually a couple times so it doesn't kill the engine, but then it's usually fine after a minute. The difference this time is that it runs very rough even with the clutch depressed.

[Duct Tape and Bubble Gum]

Update, I went for the low-hanging fruit and replaced the plugs/wires since they were due anyway. No change. All the old plugs smelled like fuel except the third one back, so I suspect maybe a clogged/frozen injector on that cylinder? I can't get it to stay running long enough to pull the wire on that one while it's running and see if it changes. Any ideas on getting ice out of the lines without a heated garage?

[LugNut1990]

Cheap/old gas?


If E85 is sold there, put in one gallon.

[Duct Tape and Bubble Gum]

Solved! Thanks for the input folks. After leaving the block heater on for a few hours finally got it to fire and stay running (rough) on its own. Pulled the wire off the spark plug on the suspect cylinder and there was no change at all in the rough idle, so I'm guessing it wasn't getting fuel. Added a bottle of HEET with injector cleaner and let it keep chugging along for about a half hour, then it smoothed out and seems to be running fine now. Hard to know if it was the HEET or the increased temp under the hood that cleared out the blockage, but either way I think I'll be adding the stuff in the colder months and using the block heater when I can.

[89'HBV6]

Originally Posted by Duct Tape and Bubble Gum

Any ideas on getting ice out of the lines without a heated garage?

Toluene is very volatile and usually sold by the gal @ paint stores.. it is what's used in fuel additives. I use it, one oz/gal of non-eth, it can help... See if you can find any of this, up there.

Also, here are a few reads for you...

https://www.goldeagle.com/tips-tools...nd-how-fix-it/

https://mechanicbase.com/cars/water-...tank-symptoms/

https://sg.news.yahoo.com/contaminat...090035087.html

https://cartreatments.com/water-in-gas-tank/

[89'HBV6]

Originally Posted by Duct Tape and Bubble Gum

Hard to know if it was the HEET or the increased temp under the hood that cleared out the blockage, but either way I think I'll be adding the stuff in the colder months and using the block heater when I can.

I still think you have water problems. Frozen water can block the injectors, until it melts.

Look for the product I pointed to, above. Lots cheaper than buying HEET, espically when you get it by the gal. I suspect you're need a gal for a whole season.