Engine/Transmission (1998.5 - 2002) What three cylinders does engine run on when cold?

[TWilkening]

Probably a stupid question, just curious. My truck is outside doing the three cylinder idle as I type, and it got me thinking this. I am guessing it is variable? It first I thought maybe every other in firing order, but that would be only the front 3. Anybody have a clue?

 

[johncameron]

Good question, I'd like to know also.

 

[obert]

I think i've read that the engine runs on "evry other" on the firing order, and judging by the sound -- very smooth/ even -- I'd have to say thats correct. I guess it depends on the location of the engine when 3cyl command hits the pump as to wether the front or back 3 are fireing. Like a lottery- if the first skip is for cyl 2, then you'll be running on 5-6-4.

 

[JCyrbok]

I thought that I had read somewhere that it runs on 1-3-5 for a time and then 2-4-6 for a while and alternates like this to heat uniformly? Cant remember where I had seen that so it may not be correct.



J-

 

[TSRAM]

How cold does it have to be for 3 cyl. mode to kick in? Not even sure if it's "turned on" with the mad ecm as was shipped. Anyone know?

 

[TWilkening]

On mine, it will high idle around 20-25 degrees and 3 cyl in the low teens.

 

[16919]

My 3 cyl will kick on in around 10 degrees or so after sitting a good 14+ hrs

 

[Wyomingcowboy]

How can you tell?

 

[JCyrbok]

On mine, it will high idle around 20-25 degrees and 3 cyl in the low teens.

same here, but it has to sit for quite awhile. Mine does it after 8 hours sitting at work if it is really cold, but if it is just 20's it wont. over night in the low 20's will kick in the high idle.



J-

 

[JCyrbok]

How can you tell?

How can u tell what?



If u are asking how u can tell if it is running on 3 cylinders it will sound like your truck is about to blow up, very loud and rattlely running at about 1200rpm.



J-

 

[TWilkening]

How can you tell?

If it's straight piped (like mine is), it sounds like a machine gun going off.

 

[PBliss]

But you have to have a smarty or other programer for the engine to run on three cylinders right? It doesn't do it if its stock?

 

[JCyrbok]

But you have to have a smarty or other programer for the engine to run on three cylinders right? It doesn't do it if its stock?

Or you can have the dealer turn it on with a re-flash of the ecm, that sets it up that way. I got mine done for free several years ago while in for other work. I have heard that the charge is like 100 if that is all they are doing.



The trucks ship with it in the off position in the ecm for some reason. They may ship with it turned on now, but not sure.



J-

 

[obert]

I thought that I had read somewhere that it runs on 1-3-5 for a time and then 2-4-6 for a while and alternates like this to heat uniformly? Cant remember where I had seen that so it may not be correct.



J-

The beast has a mechanical rotary pump (electronicly governed). With the way the metering solenoid works, thats physicaly possible, but I'd have to say not likely. Two plungers rotate in a 3-lobe cam ring, its easy to have the solenoid to just skip evry other event. That (yours) sounds like a good theory off the top, but I'm thinkin' that the VP/ecm arnt smart enough for that. Someone else will have to comfirm/deny for shure... .

edit=== 135/246 would have a rather rough idle and certainly un even exhaust sound. Perhaps there are different versions, but mine has a very smooth exhaust sound- even ignition- I gotta stick to the "evry other" thing.

How cold does it have to be for 3 cyl. mode to kick in? Not even sure if it's "turned on" with the mad ecm as was shipped. Anyone know?

Above temps are typical. Depends on if and how much the heaters are running, and IAT condition. Software looks for 35* for 1200rpm and 15* for 3cyl. , this is supposed to be intake temp only. I cant remember the TSB # that spells all this out, but its definately on this website in a few places.

How can you tell?

How could you NOT tell??? :-laf:-laf Yeah, with the open exhaust, trust me you will know.

But you have to have a smarty or other programer for the engine to run on three cylinders right? It doesn't do it if its stock?

The smarty has "latest" software version, which not only has the hi idle option, but its also automaticly turned on. My '98 didn't even have the option untill it was updated. I luckily happend across a real nice service manager while I was out of town. I stopped in to ask about this and another "quirk" I was having. Turned out he used the quirk to file a warranty claim for ECM update (possibly under EPA warranty), solved the other prolem and just "clicked on" hi idle & 3-cyl options while he was in there.



If you know some one with a smarty, have them plug in and load a smarty program, then go back to stock ecm and you'll have the new software. Save your $$ from the steeler and buy your buddy w/ smarty a case of his favorite beverage.

 

[Moose Truck]

If you know some one with a smarty, have them plug in and load a smarty program, then go back to stock ecm and you'll have the new software.

That's how I got mine... Thanks to Warpig and AJ

 

[Highfinance97]

Tsb 18-019-01

TSB 18-019-01



Michael

 

[4xquadrod]

Ok, this is all news to me. Why have this, as opposed to having it fire up on all 6?

 

[Scrappy]

Ok, this is all news to me. Why have this, as opposed to having it fire up on all 6?

by having 3 cylinders pumping air(putting a load on the others) and the others actually firing it will make the engine develop heat and reach operating temperature while idling.

 

[JCyrbok]

by having 3 cylinders pumping air(putting a load on the others) and the others actually firing it will make the engine develop heat and reach operating temperature while idling.

If ou read the TSB for it I think it was to avoid fuel washing the cold cynliders and something about bending valve stems. The higher rpm allows more heat, better cold ignition etc.



Plus I like to wake up the people who live behind my workplace when I leave work!:-laf



J-

 

[obert]

sounds like the office....

by having 3 cylinders pumping air(putting a load on the others) and the others actually firing it will make the engine develop heat and reach operating temperature while idling.

Is that what they call a "Kaisen event"? 1/2 the people doin twice the work to get the same jod done? And at the end of the day the only result is more heat.

:-laf