Hesitation under acceleration from stop
 

Edit: I’ve narrowed it down a little, it only happens between 1st-2nd gear shift (roughly 1500 rpm) when coming out of a stop. If I put the auto shifter into L (1st gear) it will not do the hesitation. Kind of leaning toward this being something with my ECU or throttle body/throttle position sensor or the wiring for them. It’s pretty consistent and repeatable. Thinking about taking it to the dealer for diagnostic but I know that can be questionable.

This has been plaguing me for a while. When I do a rolling stop/stop very shortly and accelerate i get a slight hesitation. It revs for a split second then it seems like it dies a little then picks right back up. If I do a full stop and wait a second it won’t do it. Ive done quite a bit of maintenance on this thing so I have a decent head start on narrowing this down hopefully.. i try to stick with oem toyota parts where I can.

Any suggestions/recommendations would be helpful!

2000 limited 5vzfe 184k miles no CEL and drives 100% fine except for this issue.

Here’s the relevant things I’ve done so far:
Replaced:
-plugs/wires
-fuel filter
-air filter
-timing belt (eBay kit Tim recommended)
-valve cover gaskets/pcv
-automatic transmission solenoids (all 3)
-throttle position sensor (got a CEL to replace this)

Cleaned/rebuilt/tested:
-cleaned/rebuilt injectors (eBay kit)
-cleaned/swapped/tested MAF
-cleaned/tested IAC
-cleaned throttle body/intake manifold
-coil packs tested per FSM
-cleaned electrical connections on TB/MAF/TPS
-over drive/ect have no effect on this problem

How far does the RPM drop? A friend of mine had something similar and it turned out to be low tranny fluid. Turn out a line busted and from a stop the damn thing could barely get up on the rhino ramps it was so low

MAF's can be bad even when they are within spec.

Good to know, might get one just to rule it out..

I don’t think it’s that. It’s been happening for a while and it drives 100% completely fine other than this. I’ll take a peek at the fluid level though just to rule it out.

I’ll try to get a little video of it happening tomorrow..

Have you tried cleaning your IAC?

Oh yes I did try that and I tested it as well, thank you Ill add that to the list.

You don't mention the IAC...oh wait, you did. Nevermind that then.

You've been around for awhile, so likely know about the very hard to see wires on the maf sensor, but since I've seen many a post that turned out they were only cleaning the bulb and not the tiny delicate wires I'll throw that in the mix.

I did clean the small wire inside too, I basically used a whole can of MAF cleaner lol. However the first time I cleaned it I noticed a decent amount of caked on dirt over the “bulb” part of the MAF and I cleaned it off with a q tip as it wouldn’t come off with the MAF cleaner. I didn’t touch the small wires inside though. Not sure if I ruined the MAF when I did that or not as I know your not supposed to touch it..?

I've had the same issue since I bought mine 5 years ago.

If I come to an abrupt stop and then immediately give it gas it stumbles for a moment and then catches.

Don't have a solution, just thought I'd share!

I know it doesn't help you, but mine does it too.

My checklist looks very similar to yours

My 99' does this since I got it, if it's idling at 700-750RPM warmed up and I quick blip the throttle 1/2-WOT in neutral or Drive, especially noticeable if I actuate the throttle from under the hood(a quick miss than throttle up), the only thing I haven't checked is valve clearance, front O2(FED) or another ECU which isn't easy to do on an immobilizer system. Done OEM MAF, TPS, Wires, Plugs, cleaned IAC & TB, compression test 195, fuel trims are normal now, new ATF and OE filter, checked timing marks, checked Crank rotor and crank pulley bolt, ran a ton of premium and Lucas fuel conditioner cleaner, Scoped cylinders-carbon minimal?, I have to induce it with an abrupt throttle blip ON/OFF. My 97 with double the miles and only used as a plow truck, doesn't do this but it has a different MAF and injectors, I began to wonder if this is a 99+ Thing it doesn't effect the way it drives just a weird hesitation/throttle cut if your goofing around, I'm considering swapping TB's incase that throttle stepper just isn't set up right.

Interesting, I wonder how difficult it would be to swap to an older MAF/throttle body. I have a feeling there are some differences though. It does sort of seem like it’s a 99-00 issue, everyone saying they have the same problem so far has a 2000 and you have a 99..

I was thinking 96-98 injectors since our 99+ are prone to failure anyways and offer no mpg or performance improvement that is measurable. My truck is a 99 model built in Oct 98, and the 96-2000 use the same TB, IAC, TPS, I don't think the average person would notice this unless they blipped the throttle from under the hood while its warmed up idling at 700-750rpm, I cannot recreate this hesitation when my idle is 850+ rpms

Hmm well this happens for me wether it’s warmed up or not. I haven’t really payed attention to the rpms, when I make the video I’ll try to get the rpms too. I’ll have to take a look at 96-98 injectors..

I think I have to take back what I said about wether it’s warmed up or not. Now that I’ve been really trying to recreate the problem it does seem like it only happens when warmed up and it also seems to only happen around 1500 rpms as I’m accelerating. I just cleaned all the electrical connectors with contact cleaner and swapped MAFs with my buddy.. Nothing changed, going to try and go for another test drive in a bit and see if overdrive or etc makes a difference. I usually drive with etc on and overdrive on.

Edit: over drive/etc being off or on has no effect