Possible causes of consistent surging/hesitation?

Looking for suggestions as I haven’t tracked it down. 2003 4x4 v6 manual trans. I have owned since new and well taken care of. I have consistent hesitation/surging in 4th and 5th gear at moderate acceleration between 2200 and 2900 rpms. Here is recent work.

maf is good
Tps is good
Throttle body is clean as a whistle
New double plugs, wires and coils
New cats and 02s due to theft
New pcv
No intake leaks
Newer driveshaft

was thinking a dead spot on a sensor that I would skip over quick/not notice in first through third gear. Also the hesitation seems to stop if I stomp it to the floor during acceleration. Any ideas?

 

What are double plugs? You should only be using Denso p/n 90919-01166. Not sure if that’s your issue, just something that caught my eye. What parts are OEM and what is aftermarket?

 

Yes oem. Double electrode.

 

OEM plugs are not double. What other parts that have been replaced are aftermarket? What did you use?

 

There is an actual sticker still on my engine to only use double electrode plugs.

 

OK, forget about the plugs for a minute. You said you have a bunch of other stuff that is new. What brands / part numbers did you replace them with?

 

I always use oem except for the cats as they were 8-12 months out. Hesitation did not come at the same time as the cats though.

 

Understood. So this hesitation between 2200 to 2900 RPMs only occurs while in 4 and 5th gears and not any other gears?

 

4th and 5th only. But other gears tend to work through that rpm range pretty quickly

 

Fuel filter.

How many miles?

You have any way to monitor fuel pressure while at those RPM ranges?

Last person I recall with similar, it was a bad coil pack. And they weren't throwing codes for it.

 

You led into what I was about to ask if the answer was yes

 

^^^THIS GUY^^^

 

Forgot to mention, I changed the fuel filter. 240,000 miles. Monitoring fuel pressure is on my mind, but wouldn’t that effect gears 1-3?

 

No cel, no codes

 

Changed coils wires and plugs after it started. It was due, no effect on hesitation though

 

Hesitation, then a surge?

 

Over the next few days, drive at a slower speed through that range of RPMs in the lower gears to see if you can replicate it. It Hass to be engine related and not transmission or speed related.

 

If you're not hitting those RPMs in those gears, maybe?

If it were me, I've be checking fuel pressure/delivery with my MX+ at those RPMs and compare to similar in lower gears. But let's be honest. It sounds like you're implying it's something from the transmission (well, torque converter) back. And the symptoms could match a torque converter shitting the bed. Transmission shop should be able to tell you.

 

If this ^^ I'd expect something vacuum related.

 

I’ve tried . Won’t due it. Weird as hell. Its like a am bucking a heavy wind. Accelerates then slows then accelerates then slows, unless I stomp on it, then it just accelerates through. Once above 3000 rpm, no problems.

 

Manual trans. Plan to look into fuel delivery.

 

It is time for every petroleum based vacuum hose to need replacing

 

Whoosh, totally forgot that point from up at the start.

 

I'd almost be tempted just to proactively replace the fuel pump, but I'm a glutton for painful jobs. At 240k miles, the shit has lived a very full life.

 

Injectors?

i cleaned the injectors on my jeep with a 9v battery & spray can of carb cleaner.

 

Hesitation / surge sounds air management related. MAF, TPS, throttle body, vacuum hoses etc.

 

this is where I have been with this. Haven’t found a vaccum leak as of yet but will probably start replacing all the hoses tomorrow.