Running Rich (on Poor Man’s Income) (1 Viewer)

[The Bishop]

My ‘97 LX450 runs perfect, sounds great , idles, and revs perfectly until it gets up to temperature (about 8 - 10 minutes). Then it bogs down, runs rough, and blows black gas rich exhaust smoke.

I replaced both O2’s yesterday. Still being a problem step child.

 

[bajaphile]

Did you try to reset the ECU by pulling a battery terminal or ECU fuse for ~10-15 mins? Long term fuel trims may still be off?

Speaking of which, good to check for fuel trims before and after the reset and see if anything changes.

 

[The Bishop]

Yep, I pulled the battery for over an hour while I ate dinner.
How do I check fuel trims?

Whatever it is, Bishop goes from running absolutely perfect to full stumble, bumble, and black smoke after 8 - 10 minutes….

 

[The Bishop]

MASS = ?able
EGR= should not cause black smoke, just rough idle, etc.
VCV = ???? thoughts

BTW - MASS sensors are hard to find right now. At least at regular auto parts stores.

 

[thatcabledude]

I always suggest swapping the engine coolant temp sensor in instances like this. ECU could be dumping fuel because it thinks the engine is still cold.

It's cheap and easy, so couldn't hurt to do it if still factory anyway.

 

[The Bishop]

I was just wondering about that.
You are right...cheap enough ...can't hurt to try.

 

[ZetheGSD]

You didn't by chance happen to buy this 80 out of springfield MO last year did you?

 

[The Bishop]

Yes
21,k miles later and this is my first mechanical issue.

 

[ZetheGSD]

Awesome to see! You beat me to that cruiser by an hour LOL. It's all good as I was able to nab a 96 triple locked for similar money with more miles, and in need of more work LOL.

I am planning on upgrading to land tank new style MAF, so if you still are in need of a stock MAF just hit me up and we can get something figured out.

 

[thabruiser]

If you haven't figured it out yet, check your Coolant temp sensor for the ECM. I have had several give the same symptoms you are describing because the ECM sees the Coolant temp being -40* F. At cold start it does fine, but loads up too much fuel aftter warm-up. Hope this helps. EDIT: Just read back through and saw @thatcabledude beat me to it. haha.

 

[The Bishop]

I just replaced that and it warmed up and idled down perfectly.
I let it run for 10 minutes and the issue appears to be gone.

Going for drive now.
=====
@30 minute drive...perfect.
Thanks
ALL Y'all for your help.

 

[The Bishop]

Nope....still messing up this AM.
Turned around and took a different car to work.

Ugg

 

[thabruiser]

Do you have access to an OBD2 scanner with live data? It would help in diagnosing this, to know what it's seeing. No CEL, right?

 

[The Bishop]

A friend is bringing his scanner over this afternoon so hopefully it helps.

 

[thabruiser]

Out of curiosity, did you replaced the Coolant Temp Sensor with a new Toyota one? Or aftermarket?

 

[thatcabledude]

Hopefully not the one for the dash gauge

 

[The Bishop]

Out of curiosity, did you replaced the Coolant Temp Sensor with a new Toyota one? Or aftermarket?

OEM

 

[The Bishop]

Hopefully not the one for the dash gauge

View attachment 2775756

Nope I made sure it was the one fir the comp.

 

[The Bishop]

Update
P0304 code misfire on 4.
Cap looks good, but I cleaned the posts and cap.
Checked all the wires...nothing looked worn or arcing.
Pulled each plug. 4 was definitely chard and wet.

Thoughts?

 

[Aloha Jen]

Mine was doing exactly this a few years back. The culprit was the wire harness that runs by the top of the engine and a super hot exhaust pipe I think. It was getting almost melted, but Rewrapped it with some fire resistant wrap and has been good ever since. It’s an easy fix, would hurt to try it.