Slight miss/stumble at lower RPM'S

[32ValveSymphony]

I just noticed this happening last night while cruising around with some friends. I was in 2nd gear going about 20 and I noticed the car had a slight miss or stumble. My guess is either my plugs need to be regapped, or maybe I am running rich after my pulley and chip? I won't be able to get her on a dyno until the 12th of July. The chip was supposed to be a "very safe" tune because of the 91 octane. Any ideas? Mods in sig.

 

[Shadowgray03]

I noticed mine doing it after the KB install. Then a couple weeks later it started throwing P0153 DTC's, I would clear it and in a week it would come back. I finally started to try and track it down, checked for vacuum/inlet leaks and couldnt discern any(use MAAP gas). Then moved to the exhaust and had a leak on drivers side cat between the O2 sensors. I tried my best to crank it down but couldnt plug leak. I logged voltage to the sensors and bank 3 sensor 1 still seemed a bit slow to respond and hung at higher voltages than bank 1 sensor. I put in some warmer plugs than I had (had IT24's) and went back to motorcraft agsf12's. This improved stumble slightly but it was still there. I got some dynomax 3" wide strap clamps and sealed the exhaust up nice and tight, and the stumble subsided even more but want quite gone. Then the damn P0153 popped up again so I bought a new O2 and tossed it in, cleared DTC and logged some more O2 voltages. Data was almost identicle with both bank 1 and 2 sensors responding in unison and with the same amplitude. Stumble is gone, exhaust leak is gone, plugs are one step colder than what came in my car and bottom end power is much improved.

 

[NastyWS6]

It could be a lot of different things, your just going to have to check each one. I would start by re-gapping the plus and see if that takes care of your problem.

 

[32ValveSymphony]

Does a stumble at low RPM's mean I should try a bigger or smaller gap?

 

[Shadowgray03]

The leaner the A/F the harder it is for the spark to jump the gap. The more pressure the harder it is for the spark to jump the gap. Since thses things run so lean under no load I would say smaller gap. I have my agsf12's gapped at .032 and it purs like a kitten.

 

[mosconiac]

Mine does this and I'm totally stock, exhaust wise.

The first change I made was new spark plugs. Perfect drivability resulted, but the stumble returned in about 5-7 days.

Next, I unplugged the DPFE sensor (with the fouling plugs) and 90% of this stumble cleared up. It threw a code, so I plugged the DPFE sensor back in and the stumble returned.



Now I have no idea what to think.

 

[32ValveSymphony]

Mine stumbles from about 1500 to a little less than 2500. I just need to know whether or not to try a smaller or larger gap. I'm no mechanic. What can I say.

 

[32ValveSymphony]

I'm going to check the plug wires for now and see if anything is amiss there.

 

[trey193]

Mine also stumbles as well, with the hood up try manually revving the motor with the throttle body where you can actually almost hover over the motor, holding it steady from 1500 - 2000 - 2500 my motor has the shake and a slight miss as well and the same driving it. I talked with Rick @ Amazon about it and he said they all do it not to worry about it as long as their is no miss at WOT and my doesnt. Not sure if at low speeds these 4 cam motors are just rough or what but they all seem to do it ???

 

[2thman]

Originally posted by 32ValveSymphony
I'm going to check the plug wires for now and see if anything is amiss there.

I changed my plugs and tried different gaps, it does not help. Something else is causing it.:shrug:

jason

 

[Poisonous Mods]

As Shawdowgray said 1st of all, Check for an Exhaust LEAK.

My Cat Back was losser then i had ever seen them so tighten them up & the bottom end is pretty good & the Miss / stumble isnt so noticable. Bad thing for me is that my EGT Sender is most likely the biggest section that is leaking.

Yes i did the crazy....Gapping on my NGK TR6 from .037 - .040, put back the Stock Plugs, bought the OBD II Scanner, Let my TUNER read it with his Scanner & check it out...all failed. Mines def. the Exhaust Leak.

 

[wuplash]

unplug your electrical connector on the dpfe sensor and see if that fixes it.that sensor is prone to condensation buildup and when taken off and turned upside down some water will come out and it does not take much to foul the sensor.i had the same issue as you and it turned out to be my dpfe sensor.

 

[32ValveSymphony]

What and where is the dpfe sensor?

 

[wuplash]

Originally posted by 32ValveSymphony
What and where is the dpfe sensor?

it is located on the driver side at the rear of the blower the sensor has 2 hoses connected to it and a electrical plug the sensor is mounted to a bracket with 2 screws holding it on.also this sensor is egr related

 

[32ValveSymphony]

Originally posted by wuplash
it is located on the driver side at the rear of the blower the sensor has 2 hoses connected to it and a electrical plug the sensor is mounted to a bracket with 2 screws holding it on.also this sensor is egr related

Thank you, I'll check it out tomorrow and check back in.

 

[broke7]

Mine did the same exact thing, threw the code. I reset it 2 times and took it in.

They changed the DPFE sensor, something to do with EGR related components.

Check out this link below it will let you know what your code is


http://24.118.217.131/F150/obdII_codes.htmook up your code.

 

[32ValveSymphony]

It just seems weird that it only started after my chip, pulley, and plugs. It also only seems to do it when the motor is warm. :nonono:

 

[Rick@Amazon]

Now that you are flowing more air past the maf the bends in the CAI become more of a problem. More air flow and volumn the stronger the turbulance. Try your stock filter as a test and see if it goes away. ;-)

Rick

 

[32ValveSymphony]

Originally posted by AmazonRacing
Now that you are flowing more air past the maf the bends in the CAI become more of a problem. More air flow and volumn the stronger the turbulance. Try your stock filter as a test and see if it goes away. ;-)

Rick

Does going to an underhood filter as opposed to a fenderwell help the stumble any or is this just the nature of any CAI on these cars? I would be willing to try a different setup if you have found one that eliminates this problem. (other than stock) :xpl:

 

[mosconiac]

I have something to add to the mix.

I reported above that new plugs and/or unplugging the DPFE sensor temporarily solved the stumble.

Here's a new twist...last night I reset the EEC and the stumble was gone when I started up the Cobra. No throttle tip-in pause, no bucking at 1500-2000 rpms...smooth. Within a few miles of grocery running, it was back. WTF?

BTW, the only engine related mod I have is a K&N on JDM adapter, no other changes.