wyoming9

iTrader: (1)

Seen the Bosch one back and get the Denso one.

Evan Napa sells Denso now

In any case good luck

HelpMeFixIt!!

O2 had no affect on this issue.
I can understand that one O2 might cause the truck to run better than a different one, but to have no affect at all on our issue, I'd say the O2 wasn't the cause and replacing it with a Denso isn't going to change that.

Still working to get a live data scanner to the house.
Otherwise, we're at the point of selling it as-is.

If you're in Florida or S. Ga and want it, let me know

HelpMeFixIt!!

So how many Catalytic Converters does this truck have?
I only recall seeing ONE under the passenger seat.
It has an O2 before and after it.

I'm being told some of these had as many as 4 Cats, one in each header pipe, but I dont see that on mine. Could I be missing something important here?

JasonYota

iTrader: (1)

Does it have Cali emissions?

HelpMeFixIt!!

Not sure how I'd know that.

All I know is that I had one cat under the passenger seat and just above that was a Y pipe to exhaust header.
The truck isnt at my house or I'd walk out and look again, but I seriously dont recall seeing anything in front of the Y connector.

rworegon

It's on the emissions sticker on the underside of the hood if the hood is original to the vehicle. Also, the VIN can be used to determine emission set-up.

TheDurk

The dealer can use the VIN, but if there is a way the rest of us can tell from the VIN I'd like to know what it is. I never seen a decoder that can do it. None of the parts sites can do it.

The emissions labels can be very confusing. The best way to tell is the System Codes in the top left corner under engine family:

Cali/Federal 2001+ says something like: SFI, A/F S, TWC(2), HO2S
49-state/Federal pre-2001 says something like: SFI, HO2S(2), TWC.

TWC=Three-way converter
HO2S=Heated oxygen sensor
A/F S=Air/fuel ratio sensor.

The (2) means there are two of them.

rworegon

TheDurk, I was thinking of the VIN being run by the dealer.
Could one determine Federal or Cali by looking at the ECU? Guess I need to look at some ECU pics to educate myself.

HelpMeFixIt!!

Live Data Scanner testing done - Mac Tools $4000 scanner..holy cow..
Anyways...

Cylinder 2,3,5,6 misfiring - 1,4 were not.

1-4 are shared on the same coil pack - which have been replaced, but we swapped packs between cylinders and nothing changed.
Plugs had been replaced too but swapped plugs between 1-3 as well and nothing changed. 1 and 4 continued to NOT misfire, just 2-3-5-6.

Next, we did a leak down test.

5 of the 6 measured about 25-30% leak, which I understand is normal. ALL cars experience leak, even new ones according to what I read and this range is the green/low zone of leak.

However, cylinder 3 reported a 50% leak.

We did all 6 more than once to ensure consistency and these test were very consistent.

So...we're assuming now we have a valve/seat issue in cylinder 3 that jacking everything up.

Dad is in the process today of pulling that head.

wyoming9

iTrader: (1)

What I don`t understand if I remember the Mil never tripped with all this Chaos .

HelpMeFixIt!!

This is correct.

tantacoma

This high RPM issue is puzzling to me. I have a 2.7 with AT and stock-size tires and gears. At 70mph, my RPMs are around 2400. Why would a 3.4 need such higher RPMs to go the same speed? Has the OP re-geared?

HelpMeFixIt!!

Truck is bone stock.
The couple of times I test drove it while troubeshooting this issue, its VERY easy to hit 3500rpm while accelerating, especially in 1st/2nd.
I made a mistake of pulling out into traffic and had to give it gas and happened to be in 1st gear and hit that 3500 range quick and had to back off so it would shift to 2nd then accelerate again.
I could definitely drive it in this condition, but like a grandpa while accelerating from a stop.

JasonYota

iTrader: (1)

^^ Yes the biggest issue of not being able to go over a certain RPM is from a safety standpoint. Not being able to get out of a bad situation, etc.
anything found from pulling the head?

HelpMeFixIt!!

Thats still in progress.
Its not worked on everyday.
I'll keep the thread updated for those that are interested.

HelpMeFixIt!!

Can anyone direct me to cylinder head removal instructions?

Having a terrible time getting the cam nut off and unsure of how to proceed once that nut is off. We're afraid of what is going to take place once the cams are removed and how we'll get everything back to how it needs to be for installation.
We dont have detailed enough instructions.

If we need to purchase a manual, which is best for this level of maintenance?

Thanks.

19runner99

did you ever find the problem?

HelpMeFixIt!!

Heads are off now and being rebuilt.
Residue was really bad on the valves, but waiting to hear back from the shop if they found anything else.

We just kinda put this aside since my dad and I took over a small used car business. Havent had time to mess with it.

We should know more and have it running again within the next week I think.

www.autosdirectflorida.com

HelpMeFixIt!!

Rebuilt Heads installed - Same issue - stops at 3500 and bounces like limp mode

We are at a total loss now.
Can someone direct me to any sensors, tranny or otherwise that we could check or replace?
We do have another ECU and can swap it again just in case, we already have it so cant hurt.....

Please Help!!!!!!!!!

danthemanx07

Man...

You have done a lot of work, and I am eager to see you find a solution.

I literally just discovered this problem yesterday. Same 4runner as you 1998 3.4l. My problems start at 4k though and the rpms just seem to bounce there, waffling between 3800-4000.

I have not begun to trouble shoot though. Will be subscribing here and will pass on anything I figure out from mine.