[SOLVED] P0420 lurching/hesitating/surging/searching - fuel pump

Anyone know what this could be? When climbing hill/mountain roads my truck seems to "shift" up and down constantly until I crest the hill or give it more gas to actually shift. I use the quotes around shift the first time because the rpms don't move during the "shifting". It feels like I'm feathering the gas pedal. I believe it to be the Torque converter locking and unlocking. Why would it do this?
2006 4x4 auto sr5, 120k miles, no cel codes.

Edit: got P0420/p0430 cat efficiency codes at some point during testing. Replaced Exhaust manifolds (upper catalytic converter) and had a window of success but it come back. Fuel trims were high. In the end the Fuel pump fixed my issues.

 

has this guy been driving your truck?


~Black Pipe

 

bump for an actual answer/suggestion?

 

Hey sandman, as long as everything else acts normal don't get too concerned, yet. It's probably your converter locking in and out as you said. Its lockup is directly related to engine torque. Poor quality winter BLENDS of gas and air density affect torque. I can't tell more without a test drive but, again, if everything else seems normal, and your fluid levels are good, try a different brand of gas and go from there. Hope this helps.

 

It's been going on for a while (months). It's not just once or twice it's pretty continuous (starts to feel like you're in a rocking chair) as long as I'm going up a grade or hard throttle. I can get out of the hesitation if "drop it to passing gear" or downshift on my own. It was pretty bad driving through the mountains in Virginia. The whole weekend trip (shoecreek) I was running Super Unleaded.

I'll be changing the trans fluid and adding a tranny cooler sometime soon. We'll see if the new fluid changes anything.

 

Damn, I was hoping that wasn't the case. A trans flush might help. It could be a solenoid problem. Its a pressure switch that's in the valve body(the valves that control the shift) that locks the converter. Most modern autos semi lock or lock the converter in several gears. Do you notice any shifting changes in any other gear?

 

Yea. I've noticed it in 4 and D. If the fresh fluid doesn't help I'm afraid it might be clogged cats. Another member had this same issue and that was his solution, after he changed every part on his truck (first gen).

 

That sure could be with it locking in and out in more than one gear. I'd look for a loss in HP or torque. If your trans fluid looks good(the right color) and doesn't smell, (like burned pork chops), your trans probably isn't the problem. If you can access a trans pressure guage, you could check your fluid pressure. Drag cars have them on their guage pack. That would be another sign it's the trans. I think a HP issue is more probable though. Hope this helps.

 

I'm very interested with your findings on this. I've been battling this on my 2005 for a while myself. I've tried everything from plugs, air filters and even ran a can or two of sea foam through it to clean out the intake system and I think that has clogged up the cats good now as I am getting the P0420 code off and on and some very big vibrations at low speed, low RPM, and low throttle. At this point I'm about read to just change out stock manifolds for some long tubes(which I've found is cheaper than OEM replacements) and deleting those first two CATs.

 

Changing the Trans fluid did not help. It was needed anyways but I still have the same symptoms.
In your case receiving the codes I would look first at the cats. Remember they are under warranty until 80,000 miles. If you are in warranty but would rather have long tunes I would like to get the warranty replacement cats from you.

 

I'm sitting at a little over 187,000 miles. So no warranty work for me.

 

Bummer. Just changed out my passenger manifold 121k miles, changed the driver side around 98k miles. It's too early to tell if anything is different. I'll let you know.

 

I pulled secondary filters and reset ecu on 06 4.0L with very noticeable improvement in response and acceleration from 50 mph and up. You will read a lot of people who pulled secondary filters with no noticeable change. It worked surprisingly well for me. With that being said; torque conv., solenoid, cats, and 1001 other issues could be the problem.

 

Changing out the passenger side manifold. Trying to rid myself of this surging. 121781 miles


Edit: Pretty sure the surging is gone. I haven't driven to far out of town but around town I don't feel it.

 

Wow, I forgot about this thread. After a lot more searching I tested the fuel pressure and it was very low! I'm almost surprised it was still running. Anyways I replaced the fuel pump with a walbro255 from URD and pressure is back up, codes are gone, and she runs beautifully.

 

Hey sandman looked every were for this same problem surging lurching feel . no codes or anything, any way found your post. thanks, how did you check fuel pressure I couldn't find pressure port on my 06 Tacoma 4.0

 

There is no port on our trucks but you can add one easy enough. I have used this

$14 Dorman 800-177 Quick Connector 5/16 In. Steel TEE to 6mm with O-ring, 2 Pack

Dorman Tee but it puts the fuel line at an odd angle. I just ordered this

$61 Nitrous Express 16190 5/16-8 mm Late Model Billet Fuel Line Adapter

Nitro Express (16190 5/16-8 mm) fuel line adapter and will be putting the pressure port in it.

$14 Dorman 800-177 Quick Connector 5/16 In. Steel TEE to 6mm with O-ring, 2 Pack

http://amazon.com/dp/B00CMB4I62

$61 Nitrous Express 16190 5/16-8 mm Late Model Billet Fuel Line Adapter

http://amazon.com/gp/product/B003BBFOZQ

 

@Mach375

 

Already replaced my tank pump (prefilter was stuffed) with a 255Lph AEM, moved the filter out of the tank. I'll get pics eventually...maybe.

 

More reference steps from my build thread that I never Copied here. Freeze data with real numbers