Kolton5543

So I've been trying to track down my power problem. I've found its been compounded by a few things mainly, too large of an intake tube and a bad crank sensor. For the most part its been all taken care of except for just a little bit of hesitation and sluggishness except for the the first couple minutes of a cold start. It runs great on a cold start. Watching data I've found that as soon as it hits closed loop the fuel trims drop about -25ish and swing erratically in the negatives. At the same time power drops out. While in the negatives like that the O2 swings pretty normal. If I unplug the O2 to force open loop it will just run balls to the wall all the time. Not a lick of power issues.

After digging through a few other things I've come to the conclusion that the O2 is what might be causing the problem. Thing is its a brand new Denso listed for a 98 4runner which is what my donor is. Coming from a southern Arizona wrecking yard I assumed it was a federal emission runner so that's the sensor I bought. I'm thinking I might have bought the wrong one. Is there a way to tell if I have a fed or cali donor? I can't seem to find my notes with the donor vin written down nor does my scan tool tell me. The exhaust on the truck was cut off from the crossover back so I don't know if it had more than one converter. It doesn't have an EGR valve if that makes a difference. Are there other tell tale signs I could look for to tell me?

Kolton5543

Bump.

millball

Is the ECU part number the same for FED and CALI???

Kolton5543

That's a good question. I for some reason didn't think aboutthe ecu part numbers. If Cali and fed use different sensors then I'd imagine the ecus would have to be different. I'll start looking into different numbers.

Ride4Fun

According to Cliff at ToyOnlySwaps there is a definately a difference in Fed and Cali
I just had a harness built for my sway and it turns out that i had a Fed wiring harness and a Cali ECM
Still haven't gotten it going, got to call Cliff and see what is going on with mine.

jsabowabo

Starting in the 99 model year Cali 4Runners got their own specific ECM. Prior to 99 the ECM was the same for Federal and Cali.

wonkainc

In my CA 1997 ECU the front O2 sensor has a different voltage range than federal. Not sure if the ECU part number is different. But It did cause a host of performance issues until I swapped the catalytic converter with the correct CA emissions one. You should be able to track down the model and year of your ECU by looking at the sticker and snagging the part number on it. (might take a bit of interweb digging, but I know you can find it. pretty sure I cross-referenced eBay ECU sellers to figure out mine)

Make sure your ECU, MAF, upstream 02, downstream 02, & catalytic converter all match model year and CA vs. Federal. Otherwise, you may get dissent in the emissions committee and it whacks everything out. Which sounds like your issue. I just had a very similar thing happen to my 1995 3.0 to 3.4 4runner.

Bigger description of all of my issues if you're curious to crossreference, though I had some vacuum leaks that made the emissions committee even more upset. (https://www.yotatech.com/forums/f160...-4-m-t-311188/)

jsabowabo

Thanks for sharing. I'm a bit surprised to hear about the front O2 being different as Denso doesn't list a specific sensor for the CA 4Runner until 07/1998, which is when the 4Runner got a CAL specific ECU. I'll check out your thread and see what I can glean from it.

wonkainc

I should clarify, the CA ECU looks for a different voltage out of the 02 sensors than a Fed ECU. The O2 sensors are more or less the same to my knowledge.

The longer explanation as I understand is as follows:
MAF reads air intake volume, air and fuel combine to make combustion. Then the combustion exshaust causes voltage in the upstream O2 sensor via heat, which has a causal relationship to the amount of O2 in the exhaust. Then the exhaust goes through the catalytic converter, and the downstream O2 sensor registers a voltage reading as well. The ECU then takes the data from all 3 of those sensors and adjusts the fuel trim accordingly to maintain that pollutant minimum stoichiometric air to fuel ratio. The logic here is that the 3 sensors should always agree with each other about what is happening. Because CA has stricter laws regarding emissions the catalytic converters out here are literally bigger with more catalyst in them which changes the downstream O2 voltage. So the CA ECU runs the engine just a little different to ensure the larger catalyst is being 100% efficient. What this means for your truck, fuel trim, and power, is that if those 3 sensors aren't reading what the ECU thinks they ought to be then it starts wiggling fuel trim all over the place trying to get emissions under control. I found that I would periodically lose almost all power for no clear or discernable reason because I was running a federal cat on a CA truck. It seemed to get very moody when I would idle on a steep hill. To further convolute the situation; in my experience, it takes several trips or an ECU reset to get the fuel trim logic to go back to something resembling normal. When I finally replaced the cat, my truck actually refused to drive up a hill at any speed and it took turning it off and back on again to get it to barely get up the hill. Then I got it into my garage turned it off and double-checked all of my electrical connections which involved disconnecting my battery. Everything seemed fine. Didn't drive it until the next day, and sure enough, everything has been perfect for almost 1000 miles now. idles like a champ and everything. My best guess is that the truck had learned a certain fuel trim logic with the wrong cat and when I replaced it, the old logic no longer applied and it freaked out.

A quick test you could try is to disconnect your battery to reset the ECU and see if that temporarily sorts your problem. It'll teach itself the bad habits again pretty quick, but for a short bit, you should have something closer to your open loop on 02 sensor test.

jsabowabo

The only issue I see is that the 4Runner didn't get a CA specific ECM until July 1998. The prior ECM's were 50 state. I think what made the difference for you was the new Catalytic converter.

Here's my resource:
https://toyota-usa.epc-data.com/4run...ne/8404/89661/

wonkainc

Thank you for the correction and source. I went back and checked my FSM and realized I was referencing voltage specs out of a 2002:
Heated oxygen sensor output voltage: Alternates from 0.45 V*1/0.4 V*2 or less to 0.60 V*1/0.5 V*2 or more. *1: California Spec. *2: Except California Spec.

You are definitely correct that the new cat fixed my issue, but the old cat wasn't 'bad'. I even verified with the exhaust shop after they pulled it, cause I was convinced that I had burned it out, not that it was just a mismatched model issue. Toyota did not create different model numbers for CA and Fed as you said, but I will be maintaining my suspicion that CA Toyotas are just a little different because that's been my experience. I've got some old OBDII data on my phone from pre-CA cat, so I'll go drive around and collect new data just to see if there's a tangible o2 sensor difference. Will post an update after I do.

wonkainc

Update -

Pre CA Cat - Vehicle runs improperly

Post CA Cat - Vehicle runs properly


Comparing the two sets of numbers, noting nothing changed except a proper CA Cat for my CA vehicle - O2 upstream voltage is now running a healthy bit more than spec minimum. Additionally and likely more critically downstream 02 is running a much lower voltage. Whether that's unique to CA or not I'm not sure.

Likely what was happening prior to the correct Cat was the ECM believed the car was running much hotter and richer due to the rear 02 sensor, and much cooler and leaner due to the upstream o2 sensor, and the ECM couldn't figure out why one was so "low" and the other so "high" and kept occasionally throwing fits of unpredictable fuel trim causing very noticeable power loss.

I feel compelled to admit, I sell whiskey for a living, not fix Toyotas (unless you count my own). Most of my ideas are more aptly put as a hypothesis, and not a fact.