Running rough at light load/partial throttle..

T

Trav4011

Active member
Took the truck out today with a revamped tune to fix some tip in enrichment issues, and lean partial throttle issues. Fixed those, but, WOT was still around 13 to 13.4:1. So, I got out of it after a quick pull in 3rd gear. I noticed afterwards on the drive back, that I was having a little bit of hesitation/bucking at light throttle/cruise in closed loop. A/F is around 14.3-15.5:1 while cruising. But, it wasn't doing this before I made the last pull. I loaded the old tune back in just to be sure, and it's still there.

I datalogged on the trip, and noticed that my MAF voltage was reading "invalid".. Other than that, nothing out of the ordinary. Voltage was good.. and I can't really think of anything else that would cause hesitation at light throttle, except for a busted up plug, or a bad COP. What do you guys think? I pulled a few of the passenger side plugs, and they looked brand new, so, I definitely think that it's lean. I'm running IT24's and stock COPs.

Travis
 
It almost feels like a vacuum leak, but, I went over all of the hoses/connections and couldn't find anything out of the ordinary..

Travis
 
I have a 2.6 with JLP's sheet metal intake.. So, the EGR is gone.

It didn't start doing this until the last pull that I made. It's gotta be a vacuum leak, bad plug, or bad COP.. Not sure what else it could be.

Travis
 
if all else fails, Patrick @ PSI in Houston is a great L tuner. I'm sure he can get you a solid dyno tune if you don't end up figuring it out. just my .02
 
Johnny and I are hacking away at it.. I really didn't stay in it for very long, but, I guess at this horsepower level, it doesn't take very long to damage stuff.

If I take it to anyone in the south, it would probably be Tim at Modular Powerhouse.. Those guys are awesome mod tuners. I just don't know SCT that well.. I'm more of a standalone kinda guy.. ;)

Travis
 
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Well.. I got the plugs pulled..

Looks like the first 2 cylinders on the passenger side had some detonation, as the porcelin was cracked on both of them. The rest of the plugs look slightly lean, but, nothing wrong with them at all. No peppering, or aluminum specks, so, the motor is fine. Curious, though.. as to why just the first 2 plugs were damaged, and none of the others were. Even cylinder number 8, which typically runs hotter than the others, looked just fine.

Rebuild100.jpg


Oh well.. I'm going to get 2 new plugs, and put it all back together.. I'm guessing that the broken porcelin would cause some rough running issues.. The ground strap/electrodes were intact, still.. but, who knows.

I also found a loose plug on COP number 7.. It wasn't fully snapped in.. and came off when I pulled on the harness. This may have been causing some issues as well. The number 4 COP has a cracked connector.. so, I'll be replacing it as well.

Any other suggestions/tips?

Travis
 
Any input as to why the front 2 cylinders on the passenger side appear to be running a lot leaner than the others?
 
Trav4011 said:
Any input as to why the front 2 cylinders on the passenger side appear to be running a lot leaner than the others?
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Not sure, but on my truck when I burned a plug at Atco back in April from starving for fuel with the stock feed/return lines with big rails and 80's, it was the #2 cylinder (2nd from the front passenger side) that burnt.

I can't quite recall on the stock rail setup, but on my setup the #1 cylinder is the furthest on the loop for the fuel from the Y-block off the feed line. I'm feeding from the rear of the rails and returning via the fronts of the rails to the regulator. I know they're not all firing at once, but maybe once you're really cranking down the numbers and big 80 injectors it starts to need some more attention to fuel mods?
 
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I've got aeromotive rails, twin -8 feed lines, twin 255lph pumps and a single -10 feed from the tank. I'm using a Fore Precision Works fuel hat as well..

I should have plenty of fuel..

Travis
 
your replacing just 2 plugs. im not saying its a bad idea. like u said the other plugs dont look to bad. but for the cost of it might as well get a whole new set of plugs. TR6 plugs are cheap off of LFP
 
Glad to hear she's not wounded! Keep us posted on what you find for the two cylinders that show lean! The plugs probably weren't helping but I'd bet the COP's were giving you the hic-ups! I'm very interseted in the lean issue as I prepare to do my fuel system!
 
Trav4011, I am having some similar issues with sputter. The only difference is that my truck is not running lean at WOT. I keep throwing Bank 1,2 too rich code P0172, P0175. Here are my issues.

1. I start the truck when it is cold. I try to crack the throttle a bit and the truck sputters. Once it gets warm (about a minute or so) I can squeeze the throttle down and she is nice and smooth.

2. When I stop at a light, the truck runs a little rough and almost sounds like it wants to stall.

3. When I roll into the throttle when crusing at about 30 to 40 MPH, the truck sputters and then goes away. It always seems to happen right after I just went heavy pedal or WOT.

I am going to check my plugs real good this weekend. Fuel filter is fairly new, I took off the Weapon-x coils and installed the stockers and that did not help, O2 sensors are brand new. For me the only thing remaining would be the plugs, dropping resistor, FPR, or vacume leak.

Man these trucks are more sensative than women !!!
 
Mine is more of a miss at light throttle/cruising.. In other words.. at 55mph, I get a slight miss/hesitation that's very intermitent.. I've got new plugs going in, and I'm bringing my coils to Ford tomorrow to test them on the machine.

Travis
 
Trav4011 said:
The plugs are brand new.. Only 200 miles on them.. There's no need to replace the rest of them.
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You may be better served swapping those Denso plugs out for some copper NGKs for tuning. Until you get the AF dialed in they are more durable and much cheaper.
I have nothing to add at this time to help you sort out the issues, but I am staying tuned. Good luck and be careful.

Jim
 
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