Surging at idle & on throttle 04

First Post

2001 4runner same 5VZ-FE engine 2000-2002 had the same throttle body i think with the IAC built in.

I did a head gasket replacement, originally replaced for misfire in cylinder 4 and a cylinder pressure leak into the coolant passage, ended up needing both heads fully replaced (cracks between valves seats) and a valve adjustment.

Now it seems to run great at start up but once it is warm,1 min or so, it surges on idle and acceleration, like 1 mild surge per second or two. Just strong enough to not want to drive it. It bounces 150-300 rpm no matter what rpm range I'm in.

one new coil (for cylinders 1&4), new spark plug wires, new spark plugs, No electrical power surge from the generator, No CEL codes!
Got 2 different Denso O2 sensors 89467-35011 (Bank1, sensor1, before cats)

If I unplug the sensor it stops surging but runs a little high (1000rpm instead of 750idle) leads me to suspect one of the fallowing:

Fuel injectors, MAF, IAC, Vacuum leak, cats blocked (CA model), TPS - i don't think this goes bad or needs cleaning in a way that will cause a surge but correct me if i am wrong.

CATs are my lead suspect - back pressure causing a bad reading, the new good O2 sensor causing the computer to lean the gas until it stumbles around 500rpm and the IAC steps in to kick it back up then the cycle repeats.

Same Idea with the Fuel injectors (2nd guess) - sending too much fuel or one staying open and pooling extra fuel into a cylinder so on start up the computer sets the engine too lean.

SalemCBR or Mtnbkeguy any solutions?

 

I just recently got my truck up and running. I had the battery off for over a week. The first two days of driving it I stalled multiple times sitting in traffic. It seemed to lose the base idle rpm and drop to 250ish.

But on day 3 it didn't stall, and hasn't since. It needs to relearn the mapping a little so maybe drive it for a bit?

 

defiantly worth a try I only went around the block two different times.

 

I had a surge problem all did was replace the Idle control valve. After cleaning the throttle body very thoroughly. Good luck.

 

actually, since you are on '01 you might want to pull the TB and clean out the IAC and TB to make sure, didn't notice at first in your description.

 

I have an 02 tacoma that was doing the same thing I removed the catalytic converter welded up a pipe and got an o2 sensor bypass and fixed everything. But that was after 1300 dollars on parts trying to fix the surging problems

 

for areas that require the CAT for inspection or emissions, that probably won't fly

 

A TPS will go bad and do exactly what ur truck is doing. U have to test it with aohms meter while it's plugged up on the truck. U can take it off and test it, but easier while its on. As per in the FSM. And not all the time will they throw a code. My first one threw a code, then I replaced it with a dorman one from auto parts store (don't waste money, cause they only last a couple months) .. Then I replaced that one with a Toyota one from eBay. It didn't really plug in right. (should have known better) . But it did last a couple weeks until I got it wet from flushing my heater core. Then my idle got off and my truck started surgeing a little. So I got one from the Toyota dealership and presto, it's back to idleing just fine. My first replacement went bad after or during me doing my valve cover gaskets, so I thought it was my IAC valve that I took off and cleaned. But after a month of running down the problem, ( cause I had just replaced it two months ago) it was the TPS. Now after I replaced it each time, I had to reset the ECU and let it relearn. But then I figured out to just pull the EFI fuse and it would reset also. But I don't see how cleaning one could help it. But I know from experience that they can go bad and that u need to get an OEM one from a reliable place, and that they do cause alot of problems pertaining to how ur engine runs. So when you've done the basics , plugs and wires and filters- start with those dang sensors, cause they don't always throw a code. Mainly the TPS and MAF sensors. I see this thread is old, but I thought this info needed to be attached to it,since he didn't say if he got it fixed or what it was. And someone might read it like I did, looking for answers. Also they can work, but not right. I put a meter on one of mine and got a reading that was a little low but was consistent with the FSM, just a little lower , so I thought it was ok. That's one reason why I messed with it for a month also. But when I replaced it , and drove it for a little while, I knew that a low reading meant a bad reading!! They don't put that stuff in there for nothing, and my truck is no exception to the info.

 

New member here. Im having the same issue with my 2004 Tacoma with the v6. Got a P0171 code . My upstream 02 sensor was bad. Looking at possible causes I cleaned the MAF sensor then replaced it using an OEM part. I had no issues for about a week then popped the same code. So i removed the upstream 02 sensor, cleaned it with carb cleaner(temporary attempt) and reinstalled it while I ordered a sensor on ebay. I bought one if the generic sensors and after I installed it, the truck surges like crazy on acceleration. It doesnt stall but steadly surges. Im soaking the old sensor in lacquer thinner as I write this and am going to reinstall as a check. If that solves the problem then Im pulling the throttle body for a good cleaning since this is a new to me truck. I had no driveability issues other than the code. Does anybody have experience with failures with the genaric sensors (chinese)? I know Denso and OEM Toyota are the best now it s time to order one of those.

 

YO
Other seasoned members will say
1-don’t bump a 2019 thread
Start your own!
2-hit or miss with AM sensors
Especially fuel/air related
3-welcome!!!

p0171 has many possible causes
Looks like you attacked 2of them



That surge u speak of….is a clue
What exact sensor did you RR after the front O2 ?
Cheers

 

This was the exact topic I was looking for so I added my question to it. I checked for air leaks, scanned for any other codes. I ended up cleaning the original and reinstalling it. The surging went away. Shows me stay away from the generic unbranded parts ebay is selling and go with OEM.

 

I for one like the bumped threads. So there’s a richer history of information in it.

Can you clarify “I ended up cleaning the original and reinstalling it. The surging went away.”

Which part? The 02 sensor?

thanks.

 

Yes the upstream 02 sensor