'96 Limited - intermittent/random idle problem

[not2tired]

HI, Great forum - searched for a similar problem and mine seems unique:

1996 Limited, V6 Auto

1. idles and runs great most of the time
2. idle will surge up btw. 1500 and 2500 rpm for no reason, while driving or while idling.
3. will eventually return to normal on its own, or
4. if you shut off the engine, it will take a 20 seconds or so to start, when it does, it will idle normally.
5. This happens on a daily basis, sometimes the check engine light will not come on, though normally it will light up.
6. The check engine light will only go out by disconnecting the battery.

Any ideas? there have been many sensors replaced by the previous owner, including the computer, (Toyota serviced) and I have to sift through the receipts to see what has been replaced.

Thanks in advance!

 

[004Gunner]

Post up the code you're getting and don't reset anything until the code has been read. Also, the wrong sensors are notorious for causing problems. The wrong brand, or the right brand with the wrong part number can both create problems. :cheers:

 

[TFJ-4runner]

How long since you changed your spark plugs

 

[not2tired]

We have owned the 4Runner for a couple of weeks, and I have the service records from the Toyota dealership.

I am looking for a code reader to get the code. Where is the plug for the code reader located?

The sensors that have been replaced are genuine Toyota, and Toyota replaced the plugs 10 months ago, (6000 miles), so they should be fine.

Previously, (10 months ago) it had a stalling issue that gave rise to replacing the computer and some of the sensors, fuel pump, filter etc.

Finally, they had removed the throttle body and the IAC valve which was dirty which remedied the stalling.

Though I do not have receipt for it, it seems that there is a new sensor close to the air box, in the rubber intake - it shows no signs of age on the outside - nice and shiny.

I am quite mechanical, and have had a number of older Toyota's, but this is the first one I have had with fuel injection, let alone having it so computer controlled, so I am not up on the abbreviations for the sensors.

Will post the code when I get it, and thanks for the speedy help so far.

 

[TheDurk]

Just to comment I love when the dealer decides they have to change the ECM and five other things when the problem was resolved by cleaning the IAC and TB, which is usually our first recommendation for idle issues around here. Cheap fix first is not in the dealer playbook.

We definitely need the code to help here, since so much has been recently messed with.

 

[TFJ-4runner]

You need to go to your local auto parts store and have them pull the code for you.

 

[not2tired]

Just borrowed a reader - will plug in soon!

 

[not2tired]

Fault Code:

I read the code, erased it and then drove it until it faulted again. Both results are below:

P0115 - Engine Coolant Temp Circuit

Catalyst and EVAP monitors had not run

Note that I am in Canada, so the temp readings are in degrees celsius, not Fahrenheit - I can change the units of measure to change the temperature units if necessary

Freeze Frame Data:
Fuel System 1: Open Loop
Calc. Load: 20%
ECT: -40 degrees Celsius
STFT B1: 0.0%
LTFT B1: -2.3%
RPM: 663
Speed: 0
IAT: 15 degrees C

This fault obviously occurred at idle while parked

AFTER RESET same fault code

Catalyst, EVAP and Oxygen sensor monitors had not yet run

Freeze Frame Data

Fuel System 1: Closed Loop
Calc. Load: 10.2%
ECT: -40 degrees Celsius
STFT B1: -1.6%
LTFT B1: -3.1%
RPM: 1391
Speed: 56km/h (34.5 mph)
IAT: 1 degrees C

Any ideas would be great - I do not have a factory service manual yet.

Cheers!

 

[theizzardking]

i'm not the best at these but it looks as if your o2 sensors are going bad or not sending a signal at all, that could def. cuase some idle problems, also listen to the durk, clean the iac and tb just to be sure.....

that said

here's the fsm for free
Toyota Tacoma/ 4Runner/ Tundra/ FJ Cruiser Factory Service Manual Page

scroll down and d/l it

 

[not2tired]

Thanks for the link -

It seems the issue could be the ECT (engine coolant temp sensor) as it is showing the temp @ -40deg.

The FSM says that reading indicates an open circuit - I am going to test the wiring harness and ECM which should narrow it to the ETC sensor. Fortunately the dealership has 1 in stock, though it is a bit pricey.

 

[not2tired]

Resolved - It was the ECT sensor - though it tested fine, it followed the resistance curve nicely, and the ECM and harness were also good, I had to wait until it was acting up and then stop and check the resistance of the sensor to catch it in a failure state.

Thanks for the input!