STFTs at idle

CamTom12 · Jan 4, 2012

Ok, I wasn't sure if this should go into tech or aftermarket, but here it goes.

When I cranked this morning my truck sounded like my old 7.3 and ran rough for 2-3 seconds, then smoothed out to the normal, quiet 6.4 idle. It was -30*F but I was plugged in for ~3-4 hours prior. EOT/ECT both read around 40-50*F when I turned her over. I'm going to get a video of it tomorrow, should be around the same temps.

Having never cranked my truck in weather that cold, I wasn't sure if that was normal or not so I went to talk to my buddy. He hooked a computer up and we checked my short term fuel trims at idle and most cylinders where near 0 except cyl1 reading between +3 to +4, cyl2 reading between +6 to +8 and cylinder 7 reading somewhere around -2 to -4. EOT/ECT was near 150*F #it's hard to hold EOT/ECT in -30, even in high idle#. I put it in D and once the idle settled back down with the load the trims on all the cylinders kind of leveled out to much closer to 0. I'm going to try to swing by there again tomorrow after I get EOT/ECT at 180 and check before the temps fall and see what we read there.

I know all those are within limits, but could this be indicative of anything?

Mods as follows:

EGR Delete w/ WG; KEM 345 on DashDaq; Intake and DPF delete; Engine oil pan heater + block heater

O2ShootTheJ · Jan 4, 2012

I'm not sure what a lot of that means, but it probably wouldn't hurt to drop down to the 210 tune in those conditions.

forcefed6.4ford · Jan 4, 2012

my 310 and 275 used to start a little rough when it was bitterly cold out as well. With those ambient temps that you see throughout the winter it might be worthwhile to invest in a circulating block heater. At least youll be with in 50deg of normal operating temps every time you start up the truck.

Ipkyss · Jan 4, 2012

I would run the block heater longer if not all night if you are going to drive it everyday when its that cold. I would not expect it to start and run smooth at those temps. Thats cold.

CamTom12 · Jan 4, 2012

Since the EGR delete the lowest tune I can go into is my 275. It drives a lot more 'peaky' which is no bueno for slick roads.

I looked at the Webasto circulating heaters but I'm a transient resident and can't really justify the money for the amount of time it'll likely be used. I do love the idea though. Plus it'd be much warmer than the block heater/oil pan heaters are doing.

If the hard start is just a tune related issue in the cold, no biggie. I'll talk to Mike and see if he can help me out. I'm really more curious if the STFTs are an indication of anything.

O2ShootTheJ · Jan 4, 2012

call KEM, i have a 210, it was like $50

CamTom12 · Jan 5, 2012

Back to the STFTs... Anyone know if this is indicating a potential issue??

Dzchey21 · Jan 5, 2012

not really, pretty much ever truck will run some odd stft, as long as your not throwing any codes it should be fine, these things are super sensitive so if there is any issues it will throw a code for contribution.

I does however look like one cylinder is lower than the rest, it might be worth monitoring to make sure it doesnt get worse, but like i said it will self test all the time.

That being said i noticed some rough starts when cold and plugged in and im positive its because your showing coolant temperature but the air temp is still really cold, so the fueling isnt quiet right for the temperature, i noticed that my truck actually started smoother without a block heater, but that doesnt mean its good to start with that cold of oil.

CamTom12 · Jan 5, 2012

Ah, makes sense. I hadn't thought of it like that. I cranked in -38 once not plugged in (didn't have access to an outlet), but I couldn't remember how long it took to smooth out. It was almost a year ago. I'll video the crank tomorrow. It's not crazy or anything, just not what I'm used to. Thanks, man!

And my EBP tube finally came in so I can fix that tomorrow.

Big Angry Hillbilly · Jan 5, 2012

Spec on STFT variation is +/- 10 percent, yours looks ok.

My truck is kind of particular till it warms up with the big file in it.

Make sure you've got a winter front on, too!

CamTom12 · Jan 5, 2012

So I went to record the crank this morning (well, afternoon, haha) and no dice. The hard crank yesterday was most likely the cold weather. It's a balmy -22 at the house today and she started smooth like butter. Not even margarine - straight butter.

So it looks like that and my STFTs are all fine, thanks for the help guys!