Bucking under acceleration

Ran into an interesting issue over the weekend. Apologies in advance for the long post, but want to provide details.

Went to help someone move on Sunday. Truck ran fine, with three stops before getting to the apartment. When I left, it acted like I was overloaded, which I was not. Would shudder on take off. After unloading, had the same issue at the way home.

I went out again later and accelerated quickly entering a highway. The tach almost redlined before I let off the gas. Same issue continued.

Last night, I went to see a buddy that is a car guy to get his thoughts. No issue on the way over. We ran an errand and the issue worsened as the truck warmed up, so it seems to be an issue only when warm.

After that, my wife and I took it to dinner and it got worse. I did notice in that drive that the same thing would occur when I let off the gas and then accelerated again. So, it doesn't seem to be a speed thing, but coming out of idle.

I can't really tell from the feeling in the cab if it is engine, transmission or something else.

The truck got a major tuneup about 7k miles ago (about a year). New timing belt, water pump, injectors. New plugs 15k miles ago (I am religious about changing every 30k). No codes. I do not see any vacuum hoses loose (could have missed something).

My plan is to take it to a dealership rather than a regular mechanic. Before I do, I wanted to see if anyone had encountered anything similar. I fear this is will be one of those, "We think its this. Well not that. Lets try this." things.

2000 Limited
253k miles

Thanks for any insight anyone can share!

 

Sounds like it's getting too much air. Check your air box and lines to make sure they are closed and sealed. Check the maf. It might be dirty or bad connection.

 

Thanks for a quick reply. I will check those today.

 

I just checked. The airbox and fittings are all tight. So is the MAF plug in. Could the MAF be bad? I think I replaced it within the last few years. Hard to recall after almost 20 years of ownership... Thanks again for the ideas!

 

Just know: It's never the fuel filter.

Meanwhile, this caught my eye: "New timing belt, water pump, injectors."

Who did that work, some mechanic, a dealership, or you?

And where'd you source the parts?

Any symptomatic reason for replacing the injectors, or just for the hell of it?

Any codes set currently (or pending, which would show w/code reader) that could give us some direction?

The crank position sensor on the front of the engine has wiring that's disturbed during the timing belt/water pump overhaul process, and it's not unusual for it to be improperly restrained, and a pulley will cut through the wire, usually just above the harmonic balancer if my orientation is about right. Here's an example. (example of how to tuck below driver's side cam cover if not routed properly)

Not saying it would cause this specific issue, but with it being so few miles from the major work, and that being touched, it's worth checking that harness.

 

It would be worthwhile to pop the MAF out and inspect, make sure nothing is sitting on the sensor, no riff-raff in there. May as well get some CRC MAF Cleaner and clean it while it's out. The process to clean is in the video at this reply. Let the MAF sit out and dry for 10-15 minutes after cleaning to let it come to room temp again BEFORE you install, it'll be cold as hell after cleaning and prone to holding condensate.

You can also test the MAF if you really wanted to. You just need a multimeter and basic knowledge. If you have both, LMK and I'll grab the FSM page on it.

 

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Work was done by our daughter under the supervision of her instructors in the best two year auto tech program in the country (IMO - Pittsburg State University, Pittsburg, KS).

Good question on the injectors. Recommended so I did it. High end injectors (not that they couldn't have an issue).

Great idea on the harness. Goes with some miles on it since the work was done. And thanks for the pic. I'll check that later today. No codes earlier Sunday, but I'll check again when I check the wiring.

Thanks again. Will post the results!

 

As long as you're not sourcing your parts off fleaBay or scAmazon, you should be alright.

But I'll say, some have reported here - and others directly posted experiences with - these trucks being picky about parts. And plenty of reports getting very authentic-looking counterfeits from the sources I just posted. Like, manufacturers confirming they never produced a part with the stamped lot# on the part, etc.

Curious for updates! Hopefully it's something simple.

FYI: If you do proactively replace the MAF, you don't necessarily need to buy Denso (OEM brand), another member did a side-by-side comparison of the OEM to the Hitachi branded MAF, and it was identical. The assumption is/was Hitachi was the original manufacturer of the MAF in these trucks. Make sure you leave the negative battery cable off for 10 minutes to force the truck to re-learn after.

 

Thanks for commenting on sourcing again. I forgot to mention that they all came from O'Reilley's.

 

Lube your driveline, inspect carrier bearing. Dry ujoints or carrier will cause vibes as you change speed .

 

Thanks! Can you share the info on how to test the MAF?

 

Attached PDF covers a couple of bases: Testing MAF, checking TB, etc. specifically for the 2000-2003 years.

Hopefully it helps.

 

Thanks, All

Trying to respond to several ideas at once.

Carrier bearing was replaced a couple of years ago. I checked it and it is still good.

Checked for wiring getting into the belt. All is good.

MAF cleaning – what a great video. I love this guy! Will pick some up and try it. And thanks on the procedure to test. Will do that first.

Will let this thread know what I find out. I’m out of town for a couple of days so may be the weekend.


Thanks again!

 

Honestly, that dude is great! Channel is full of helpful stuff, I share his vids on here for reference and sometimes w/friends&family.

Here's his channel, if your kid is getting into wrenching on Toyotas, he's a great reference and almost always does things by the book: https://www.youtube.com/@ToyotaMaintenance

 

I’ll have to use that! She had the Tundra for about three years, but I bought an F150 for her and took the Tundra back before she moved to Dallas. She’s wrenching on Cadillacs for a living at Sewell Cadillac. If she moved 8 hours away, I knew I would buy another truck, and I love the first gen Tundras. She loved the Tundra, but really loves Fords. So it worked out for all of us!

 

Thanks to all. Finally had time to clean the MAF. No change. Still no codes. Open to ideas!

 

This is a tough one because you had the fuel pump replaced recently and these symptoms are textbook what you can see with a failing fuel pump. Store brands (any aftermarket brands, really) are prone to premature, and the fuel pump is one of those things you ALWAYS want to use OEM parts for, because OEM will run for another 240k miles without blinking, and it's a painful job nobody wants to do.

That said ... if you DID use an OEM fuel pump, if I were you, the next step I'd be taking is testing the fuel resistor and consider bypassing it totally as a test (temporarily).

You'll find the resistor in one of these locations: https://www.tundras.com/threads/help-2006-stalled-and-won’t-start.117506/#post-3025323

You can test the resistor using this info: https://www.tundras.com/threads/2006-double-cab-fuel-pump-no-power.36822/#post-2962132

I'd also do a once-over and reinspect the crank position sensor harness. Very, very carefully.

But I think it's worth your while to find out exactly what brand of fuel pump was used. The only way you're really going to be able to tell if it's really the fuel pump is if you have some way to watch the fuel pressure levels while it's bucking.

And even if the fuel pressure is dropping, it doesn't mean bad fuel pump per se. It could be the power to the pump is getting cut, by the resistor, by one of the two associated relays, or by the ECU.

 

PS - here's another person saved by checking their crank position sensor wiring!

https://www.tundras.com/threads/timing-belt-replacement-proper-wire-routing-psa.119070/#post-3057503

 

Have you checked your ATF fluid level? Just to be sure?

 

Wish I had read this before taking it to the dealer! Dropped it off last night. I think I may have typed wrong The injectors were replaced but not the fuel pump. That could be it! Thanks!

 

I did check the fluid. There was some thought somewhere (maybe here) of water in the fluid. Hard to tell that.

The dealer was thinking maybe the torque converter. They are seeing that on RAV4’s with similar symptoms.

 

All -

Thanks again for the help! I gave up and dropped it at the dealer yesterday. I generally like to use small shops, but this one has me worried so I took it to the dealer. The Service Guy said it could be the torque converter. They are seeing the same thing on RAV4’s. Had not seen it on a first gen Tundra that he could remember. The good news is that mine was not the only first gen there!

Will share the results when I get them. Thanks again!

 

Yeah, that was my thought too, although I was trying to be optimistic and thinking it was just low ATF rather than actual mechanical problem.

But yes, it sounds transmission/TC related to me.

 

thx for the optimism. Crossing my fingers!

 

Pink milkshake?

 

Well then, I stand by this looking like a textbook case of what you'll see in cases of fuel pump failure. I'll be curious to see what the stealership says.

 

All - the dealership said it is the #6 ignition coil. They wanted $325 to fix. New Denso from Rock Auto arrives today. $71 with shipping. I'll fix it in the parking lot of the dealership (I have been out of town on business). I asked why it didn't throw a code and the advisor rather rudely told me he didn't know. Probably mad that I am not having them fix it. I have had coils go out before, but they always go completely out. Never had an intermittent issue. Hope this actually fixes it. Will let everyone know.

 

Well, not only that, but you should've gotten a misfire code, as you already know... Something smells funny about this ...

 

Fully agreed. That's part of why I want to fix it in their lot...of course, they will probably want to charge another diagnosis fee since they didn't fix it. Our daughter is a mechanic for a dealership and I want her to have a great career, but stuff like this makes me question the entire industry (again).

 

Best thing to do (probably) is get a couple of years under the belt, then go work for (or open) a specialty shop.

Dealerships are more about (1) Quantity over quality and (2) concatenating as many labor hours as possible on work.

I don't doubt they probably tested the vehicle. But it just seems like a weird diagnosis based on the symptoms and apparent lack of misfire codes.

I've been wrong before, though.