Brief hesitation under hard acceleration, 97 T4R

[ThorInc]

1997 4runner SR5 V6 5 speed, 245k kilometers

I Googled this issue a few times and I keep coming up with the crank position sensor in most of my searches as the only thing I have not addressed. Also possibly a partially blocked cat.

Here is the symptom:

On all grades of gas but more noticeable with premium 91 octane, under hard acceleration there seems to be a brief hesitation most noticeable in 3rd gear around the torque to hp curves.
No codes, seemed to have started after I replaces the rocker cover gaskets but did not replace the plenum gaskets.
Timing has been done 15k ago, denso plugs replaced, plug wire replaced twice, NGK and one other brand, maf cleaned and swapped in a donor maf, same symptoms, no intake leaks, injectors are original, fuel filter was changed less than 6 months ago and throttle body cleaned twice in the last year. All replacement parts are OEM brands or genuine Toyota.

Exhaust system: magnaflow high flow cat forward and JBA cat back, both O2 sensors replaced with genuine Toyota sensors less than a year old each.

Accelerator cable has little play but maybe I am missing something in that area?

Being a wee bit OCD, I would like to solve this, any opinions?

EDIT: zero idling issues and it idles at 700....

 

[Frank12]

Are your sparkplug cables good or still factory? I had the similar problem with my 2000 SR5 and found out half of my sparkplug cables were like over used, and thus at times it would not fully work, like they would refuse to fire then fire then nto fire causing some sort of lag in acceleration and sometimes even "chocking"

remplacing all of the cables fixed my issue, idk if its the same for you.

 

[ThorInc]

Ngk plug wires, 2 1/2 months old. Tried a different set, same issue.

 

[ThorInc]

Medication for the mild OCD? :loco: :thumb:

 

[Sukirman]

Hesitation

PCV valve?

 

[LittleCaesar]

Plugs? Coils original? Grounds all tight?

 

[etc.]

Use 87 octane. There's no need for the higher octane and your just wasting money.

 

[etc.]

Maybe a try fuel system cleaner. I am currently using Red Line SL1 after reading numerous success stories on BITOG. Since starting the treatment, my idle has smoothed out and throttle response has increased. I originally looked into new or cleaned injectors, but they are very costly.

My suggestion will probably have it's naysayers claiming it's a snake oil, so I suggest reading for yourself on Techron and PEA - coming up with your own conclusions.

 

[ThorInc]

All brand new OEM coils (one did hit the ground in the Toyota box dropped by the dealer but it did not appear damaged, marked that on when I installed JIC) and all three were installed and worked fine before this "issue", PVC leads to a catch can but I did change the valve outabout 2 years ago now. One other thing that grounds are mentioned, the plastic injector wire loom covers did disintegrate to some degree on R & R, maybe I need to pull the upper and lower intake plenum and have a look see at the wires and harness again.

Also ran two half full tanks back to back with two bottles of Techron about 4-6 weeks ago. It seems to show up when the engine is at operation temp.

 

[stir_fry_boy]

Techron doesn't do anything. Get some BG 44k and run through it.

I run 91 octane, I've done many tests with low grade, medium grade and his grade fuel. Mine runs best with 91 and I get better mpg. I also have all original oxygen sensors at 205k. Higher octane burns cleaner, therefore will produce less wear on exhaust sensors and catalytic converter.

I wonder if you have a TPS that is starting to go bad.

 

[LittleCaesar]

What RPM range are you hitting when you feel the power loss in 3rd? I take it at the same RPM in the other gears this problem doesn't occur.

If the plenum gaskets were original and there was a tear or the like (or a vacuum leak period) you feel it in all gears.

It wouldn't hurt to take the cover off and make sure all the timing marks are lined up.

Possibly the knock sensor(s) is going south or the wiring for them is bad.

Maybe TPS?

 

[ThorInc]

most noticible in 3rd at around 2800-3300 rpm, same general range all gears. TPS is OEM and brand new. I am thinking as you suggest, checking the timing next. Will post back results as soon as I can get a warm spell.

 

[stir_fry_boy]

A question, maybe [MENTION=69868]LittleCaesar[/MENTION] knows: would a cam angle sensor cause this?

 

[ThorInc]

Update

An update: the brief hesitation issue now is 99.8% gone & I still have not changed my camshaft position sensor. I think it maybe related to winter gasoline but not 100% sure. I did run some Rislone Water Remover Fuel Dryer through two tanks of gas as well as changed my dry AFE air filter back to the TRD wet air filter. The MAF was clean running both for the most part. I still don't know the cause but for the last month it has slowly disappeared or improved to the point that I can not notice the hesitation.

My gut tells me it is the winter gas, I will update this thread if the symptom returns or is 100% gone. BTW, I generally by Shell gasoline.

 

[ThorInc]

UPDATE:
Symptom is still there on occasion but quite less noticeable. It seems to be related to air mass or air temp IMO. Have not changed the crank position sensor yet but did change the MAF and I am certain it is not the MAF. Will update if and when I have it solved 100%.

 

[ASilhouetteLie]

I had similar symptoms with my 5vz 5spd. It would hesitate right at 3K rpm all the way to redline but only at full throttle and at operating temps. If I eased on the accelerator it it would be fine. Turned out to be my coil pack boots. You got new coils though so probably not that but thought I'd share as I was getting pretty frustrated with it trying to figure it out.

1986 Toyota Supra
1987 Toyota 4Runner
1996 Toyota 4Runner

 

[ThorInc]

I had similar symptoms with my 5vz 5spd. It would hesitate right at 3K rpm all the way to redline but only at full throttle and at operating temps. If I eased on the accelerator it it would be fine. Turned out to be my coil pack boots. You got new coils though so probably not that but thought I'd share as I was getting pretty frustrated with it trying to figure it out.

1986 Toyota Supra
1987 Toyota 4Runner
1996 Toyota 4Runner

Humm, interesting. The parts guy at the Yota dealership did drop one still in the box on the ground. I marked it(JIC) when I installed it but I will pull it and swap it with another good one that I have lying around. I am going to assume that you had no CEL?

 

[ASilhouetteLie]

Humm, interesting. The parts guy at the Yota dealership did drop one still in the box on the ground. I marked it(JIC) when I installed it but I will pull it and swap it with another good one that I have lying around. I am going to assume that you had no CEL?

Yea there wasn't a check engine light or anything. I ran it hard too just to see if I could make one come on but it never did. Went through a couple cans of seafoam, techron etc. I replaced the coil boots one at a time and it gradually got better each time until I replaced the last one and it went away 100%.

1986 Toyota Supra
1987 Toyota 4Runner
1996 Toyota 4Runner