Tacoma misfire/surging

2009 Tacoma 4.0
Surging misfire with specific pre-requisite: 1000-1500RPM engine under slight load via an incline (10 degrees uphill) @ 25-03 mph and 35-40mph respectively.

Resistance on ignition coils all at 8, power at pigtails was full battery voltage....
haven't gotten to the MAF sensor and O2 sensors yet....any other thoughts fellas?

 

Sounds like a secondary ignition miss, coils, spark plug boots, and plugs is where I'd look closely at first.
Do you have an engine light on or flashing?

 

No MIL.
I pulled all coils previously...boots are good, I mean everything looks clean. I replaced sparkies with new ones.
Like I said-I had full batt voltage at power connectors for the coils. Next thought I have is maybe a dirty MAF sensor, or failing o2 sensors, which @ 130,000 miles, would make sense if one of those is failing.

 

If you think an O2 sensor might be causing a problem just disconnect it, the engine can run without it.

What kind of plugs did you use? Are you sure all the vacuum lines are connected?

Could still be a ignition coil problem that just hasn't coded yet

 

I had considered the possibility of early stages of ignition coil failure. I used Denso plugs as the replacements. pretty sure I used denso for the old ones. .042 gap. the old ones I pulled sat at .045 which means I replaced them recently and like a dumdum, failed to write it in my service log.

I supposed I can check to ensure vacuum lines are connected....EGR or PCV issues also possible? Dirty PCV....? The last tank of fuel got me 13mpg....which I made a point to look out for.

 

Do you have an auto or manual?

 

Auto

 

I'm going out to pull the o2 pigtails right now, and drive it up the hill to see.

I do have the thought that a secondary winding in the ig coil has started to fail and hasn't coded yet like you said earlier. I guess I will find out. My understanding is that code throwing can be multi-phasic in that it can throw a prelim and then a confirmatory code but depending on if it throws between present moment and last instance of key-on, then it may not throw a confirmatory code.

 

Does your tach move up and down when it does it? I'm wondering if it could be TCC shudder.

 

Start the truck in a very dark garage or something. Look for any light around ignition components. Cheap scan tool can verify o2’s.

 

Tach does not flutter.

I do not have a dark garage. I imagine you're wanting to see if I can find it arcing to ground somewhere?

I should add that this problem does not happen every time I am at 1500rpm/25-30mph. It is inconsistent in presentation.

 

I was thinking that too.

Maybe run it in 4th gear, see if it does it.

You can also tap the brake lightly while accelerating, this signals the converter to unlock.
If the vib goes away, it’s likely TQ shudder. (Keep accelerating while you tap/press the brake pedal lightly.)

I was kind of skeptical to throw it out there, as I honestly can’t remember if the truck will go to 5th at 25-30mph? I know the converter is Locked/partially/ or unlocked in 4th. But the guys that have reported shudder, often say it doesn’t do it in 4th.

 

So my understanding is that the TQ should not have issues if you, say, drive it down the road at 60mph for a minute or two in 3rd or 4th gear, which I have.

 

Drive it in 4th gear under the same condition as it had been doing it.
Low RPM with load (and on incline), if that when you were/are Hong the problem.
Try 3rd too if you want. No need to go 60 mph if that isn’t where the problem exist.

 

yeah, I will run it here in a few and get back to you.

 

OK so took awhile, but I drove it and with that shake, it did not go away when applying brakes and in that speed range

 

Center bearing in good shape?

 

Well, back to the drawing board.
Do you have access to a scan tool?
Maybe see what the grams per sec. is?

 

This could be true especially the last sentence. I had a O2 sensor take 2 months to throw the code in an old car before despite the car running like junk.

You mentioned your last tank MPG was 13..is this consistent with history, if not then how far off?

 

MAF sensor readings are really only effective to look at at idle (rule of thumb g/s should be close to engine displacement in L on a hot idle) or recording a WOT pull through first gear with a graphing scanner (record IAT, Peak RPM, and Peak MAF) and put your data into a Volumetric Efficiency calculator otherwise unless it's obviously way off or the OE gives you a value to look for at a certain RPM/Throttle range it's just a number with not much meaning.
It may be useful to look at fuel trims and O2 sensor data when it's happening but I would want to rule out a single cylinder miss first.