5.3 Lags When Cold

Z71GMC · July 7, 2008

I have a GMC 1500 5.3 and when the engine is cold it has almost no power and some times back fires for about the first minute when driving then it stops. It is all stock except for a K&N filter. I also seem to get very poor mileage about 13-14 on the highway. What could be the problem? Thanks.

Tucson_02Silverado · July 7, 2008

If you haven't already, change the fuel filter. And add to the tank a gasoline dryer such as Berryman B-12 Chemtool or HEET.

Sort of sounds like you have a clogged filter and water in the fuel tank.

99silverado1500 · July 7, 2008

I only get 14.5 highway and im as happy as can be. My truck is the opposite of yours. When cold it runs like a bat out of hell has so much power I can roast the tires until I let off and pulls in overdrive up hills. When warmed up it runs good but wont roast the tires until I let off it will still somewhat spin them, but it downshifts like crazy on hills and runs so-so (what would benormal for the truck)

svensk · July 7, 2008

plugged cat?

ColoradoSkiCountry · July 8, 2008

Always let a cold engine warm up 30 seconds to a min before driving.

YZINGERR · July 27, 2008

Always let a cold engine warm up 30 seconds to a min before driving.

funny that you have to tell people that. I have a friend that always puts premium in the tank "to get best performance" (though I keep telling him that he is wasting his money), yet he NEVER lets his vehicle warm up!

We were in the mountains and it was about 20 degrees outside. We walk outside, jump into his vehicle and off we go! Literally about a 5 second warm up. He isnt gentle either, he'll punch it getting on to the freeway about 2 minutes later.

Oh well, not my truck!

strafingmoose · July 27, 2008

Always let a cold engine warm up 30 seconds to a min before driving.

I let it more than that in the winter, but burning hot summer as well ?

ColoradoSkiCountry · July 27, 2008

When the engine is cold as in has not been run in 4+ hours, sensors inside the engine will also be cold and until they warm up, you will not get ideal performance. New, or old. Even if it is 100+ outside.

pennzoil29 · July 27, 2008

Always let a cold engine warm up 30 seconds to a min before driving.

This is automatic for me. I'll even put it in gear, and wait a few more seconds until the rpm's drop a little before I take off. Sure does piss the ole' lady off though.

yukondan · July 27, 2008

K&N filter

Check you MAF for oil build up. Heard of similar problems from people that have over oiled their K&N filters.

Use a cleaner to clean the MAF of the oil and other collected crap.

Can you get your hands on a OBDI scanner and check for any codes that may not light up on your dash. Anyone you know have a scangauge you could borrow to check opne lop closed loop, coolant temperature, Air intake sensor temperature, O2 sensors, fuel trims etc.

fbachman · July 27, 2008

Always let a cold engine warm up 30 seconds to a min before driving.

funny that you have to tell people that. I have a friend that always puts premium in the tank "to get best performance" (though I keep telling him that he is wasting his money), yet he NEVER lets his vehicle warm up!

We were in the mountains and it was about 20 degrees outside. We walk outside, jump into his vehicle and off we go! Literally about a 5 second warm up. He isnt gentle either, he'll punch it getting on to the freeway about 2 minutes later.

Oh well, not my truck!

Don't get me wrong, I wouldn't do that either, HOWEVER,

I consulted in the dyno lab for one of the big three many moons ago... they had an engine in a dyno cell that was having refrigerated coolant cirulated thru it continuously.

They would cold soak (and i mean COLD) the engine then tiger-start it. (Tiger start meant: fire it up and go to immediate WOT). They would run it at WOT for a specified time, shut down, then do it all over again. This was initially designed as an accelerated life test. Turned out, they learned nothing. No catastrophic failures.

THis was an engine randomly chosen from an assembly line at a nearby powertrain facility.

The end result, they did NOT fail the engine after 1000s of these cycles, nor did they find significant damage on the inside. This was done during the mid-90s with a mid-90s engine.

Believe me, I warm my truck up, and recommend all others do the same.

But, that test above indicated that that engine could take it, SO LONG AS THE OIL WAS UP TO THE TASK. It was a V8 that was produced/engineered to mid-90s standards. I don't know if the new gen engines are as tough, but, believe me... that was impressive.