Evo

Hello all,

First I'll point out Ive spent weeks searching the vast internet for these posted symptoms & diagnosis, Ive scanned the truck & replaced maint related parts that would surely have triggered my symptoms. Now I'm stumped.

1999 4Runner SR5 V6 4x4 Cali Spec (Just found this out yesterday & confirmed w/ Dealer) I'm on the East Coast. Truck has 192k Miles.

Symptoms:

When truck is Cold (Temp gauge cold) Initial start-up is good, Idles fine, Apply throttle it breaks up under 2k & will not accelerate. it back fires thru the TB. As engine temp increases, you can gradually apply throttle and it will climb in engine RPM but only while in Park, NOT while driving w/ a load on the engine. When engine reaches Temp (Center of gauge & have not checked while on scanner the actually Temp reading), The truck will drive like normal.

What Ive done so far:

I recently purchased this truck w/ Rear End damage from a collision (Rear Diff assembly was totaled).
Replaced the Rear, new shocks, brakes throughout, Fuel filter, Air filter, NGK Sparkplug wires, NGK Spark plugs, Engine Coolant Temp sensor (ECT for ECU Not gauge) & the ridiculous expensive Wideband Post Cat (up-stream) O2 Sensor. Lastly I cleaned the MAF.
Ive cleaned the Battery terminals, had an intermittent starting issue, Old worn key, got a new one cut by Dealer off VIN, no longer comes out while in run position. However, did not fix starter issue, So I put a starter in it & all good, Starter was tested & Failed LOAD Test, Contacts worn I suppose.

After the O2 Sensor installed I thought for sure that was it. Nope. I had done the ECT previously & it did not rectify the problem. The MIL (Chk Engine Lamp) does not work, Either bulb blown or pulled by previous owner. When time allows, I'll pull the Instrument Panel & replace the Bulb. Ill scan again this evening & check any codes. The previous code was a Closed Loop Malfunction (Indicating ECT or Post O2 Sensor). I have good, HOT exhaust flow, so I'm assuming the Cats are OK, It does not choke under load at Highway speeds.
I'm beginning to believe I installed a BAD ECT sensor?

The symptoms are ONLY when COLD, no other time in any driving conditions. So that narrows down the possibilities. But im stumped & too busy at this time to spend hours under the hood doing resistance tests... I was curious if this was a Cali spec programing in the ECU? so that way the truck will only be driven when @ optimum operating temp for cleaner emissions? Sounds plausible in thought, but rationally I believe its something else.

Next is T-Belt & WP, service Trans & Im done w/ it for awhile I hope.

Thanks for looking.

Evo

50+ Views & not a single reply?... Bueller...Bueller....

ToyoTech559

Did you buy the correct parts? Calif spec o2 sensor. Have you checked ignition timing? Pulled the upper timing over and checked correct if the timing belt timing is correct

ToyoTech559

Oh and what codes do you have? I would fix the codes before anything else tho.

Evo

I appreciate your input, however, I replaced all needed maint related parts, with quality "known-good" & acceptable to OEM replacement parts. If you re-read my exclamation about the expensive "wide-band" Post Cat O2 sensor ($151+Tax) , as the Federal trucks have 2 very basic O2 sensors ($65+Tax). this will answer your query.
Also, the symptom w/ cold start is just that, ONLY when cold. If Cam timing were off, a Tooth or 2, by an improper previous install, Id guess the symptom would be permanent not Coolant temp based. As far as codes go, it was a PO125 I believe is what I had previously. As stated its a closed Loop malfunction (Post Cat "Upstream" O2 sensor & ECT will effect this) Ive replaced both. Still have the symptom. My wife took truck to work this am, Her VW now has an issue.... Anyhow, when she gets home, I'll scan the truck, re-set & wait to scan truck & monitor w/ Freeze frame when its cold, see if I can pinpoint the issue. Truck is due for a T-belt & WP which I will do very soon, But would like to fix this last Gremlin before I do that. I need to test Fuel Pressure also, but that would be a consistent problem. I really think its electrical based off the coolant temp directly being the basis for the problem.... This is why I came here to ask & save me some headaches.

wyoming9

iTrader: (1)

You don`t say if it idles up on start up .

You say it idles fine .

Lots of California emissions trucks shipped to the east coast.

Mine goes into fast idle and stays there to coolant temp comes to where it should. It does this winter or summer though in the Winter far longer.

Sounds like that might be your problem

vital22re

iTrader: (2)

Didn't see if you check the tps. May be the next thing to do

ToyoTech559

Hmm during cold start the ecu fuel trim is preset. It doesn't adjust using various sensors till its at operating temp. Gonna have to ask around

Evo

Have not checked TPS, didn't think symptoms could be related, as I stated only a cold start issue. Idles well & yes it has correct fast idle function on initial start-up. Warms up withen a few minutes, but prior to optimum temp, would buck, sputter, WOT would just Bog, but never stall.
My wife just got home & said, the symptom was not present when she left work. wtf?
Anyway, Ill scan shortly & see what if any codes are present.
- Thanks for the incite.

Evo

OK, about to go scan & bring up to speed. For starters, Truck ran perfect last night, even at cold start, no symptoms. Almost as if the ECU had to re-learn? I was unaware Toyota ECU had that type of capacity, I know German Cars do, as I work on them & some Domestics. Anyway, off to scan. Truck also been sitting all nite, not just several hours.

Evo

Sorry for delays, Been busy. Wanted to update. Scanned truck, had a Lean condition code, re-set, No lights. The lean condition I think was from the Fuel Filter change and the air pocket in the system. Either that or my MAF needs to be replaced, has been cleaned twice in 2 weeks. Other than that, Truck runs perfect, even w/ Huge retarded 22" wheels, Pulled my 18' Seadoo Jetboat like it was nothing, Have no complaints. Hope this can help someone else if symptoms are similar.
- Cheers