Check with O'Reilly's or other parts stores.
Many can "read the codes" stored that might help with DIY diagnosis.
(if the folks are competent)

Do what is "free" first, and see what they say. Maybe take it to more than one place that does the free scans and compare.

Post what you find, and maybe you can save some money, rather than spending time and money having a shop looking, first.


My Ex and both daughters had Toyotas and had several issues with the "check gas cap" and other CEL with fuel issues.

Evap filter and cat converter was two of the issues.
Another was a failing crank/cam sensor that tossed those codes, and then ended up not with failure to start and stalled/stuck once on side of road.
Got it to run and I was able to get it read for the code, and saw the sensor code, so changed both sensors and it was happy for years after.

You have an older vehicle with high mileage and that can often lead to causes of failure related to low mileage and long time of some components.

Catalytic converters, sensors, filters, hoses and things failing due to age, and items that normally cause such faults are items with high mileage wear (normal failures) when not changed per time/miles, as most are "miles" that determine the interval to change them.

(One of the worst things for machines, is they are not operated, or operated to infrequently and things fail that otherwise would not in frequent/daily operation)

Thanks, Sigmonkey. I will take it back to my mechanic for a free diagnostic if the light comes on again.

It's actually an older vehicle with low mileage. 1993 4Runner with only 43k original miles. It was the last vehicle my Dad ever owned, but he didn't drive much in his later years.

Checking in with AI yields possible clues...

quote:

A check engine light that comes on at a full tank and goes off around half-full often points to a problem with the Evaporative Emissions (EVAP) System, particularly issues with the gas cap seal, a purge valve, or the fuel tank pressure sensor, because the system runs self-tests when the fuel level is in a specific range (15-85%). The light turns off when the condition (like a leak or sensor issue) temporarily resolves as fuel levels drop or conditions change. The fix usually involves replacing the gas cap or diagnosing EVAP system components like the purge valve or canister.

ETA: the gas cap does look a little funky. Also, no little "burp" when I unscrewed it, indicating pressure loss. Will try replacing it first.

This message has been edited. Last edited by: kkina,

quote:

Originally posted by tatortodd:

quote:

Originally posted by lyman:

quote:

Originally posted by nhracecraft:
^^ What about the Fuel Filters? Serious question...

To my knowledge all Fuel Pumps (Gas and Diesel) have filters. Do they not filter adequately? I'd think any sediment in the underground tanks/fuel would be large enough to be caught in the filter(s), no? Water is a different issue entirely though.

I'm been leaning towards this 'don't fill when the fuel delivery truck is there' is a leftover from days long past and basically a non-issue in the modern era, but I've NEVER had a 'bad gas' issue either. I also only fuel up at 'top tier stations' so there's that.

I can only say for Kroger, and it has been 10+ yrs since I worked for them, but filters (for sediment etc) were replaced yearly,

I think,


water was not an issue , see my post about Veeder Root and the paste used on the sticks used to verify

I don't know Kroger's practices. Were y'all using absolute filters (i.e. the filter's micron rating in 3-dimensions) or the less expensive 2-dimension micron rating filter? Did y'all have a differential pressure gauge or alarm across the filter to determine if it was clogged before the yearly changeout?

I suspect we have an apples and oranges comparison going on here on the water. The question is about truck stirring up the tank and causing problems. Am I correct that the water sample was pulled at the time of day/week/month the accountants specified rather than immediately after the truck offloaded (i.e. stirred up the tank)?

no idea on the filter type, they screwed in the pump like an oil filter or fuel filter on a car or truck so guessing just a standard sediment filter,

we the water, we pulled a veeder root report several times daily, and for every delivery (unless a delivery was overnight, )
drivers had keys to the lock,
we had to check regularly to make sure they were locked (again, been gone from them a bit, do not recall if that was the daily/weekly/monthy check list, but thinking daily)


re the water, and the manual check, that was done by the drivers, they had the long stick, think about a yard stick 20 foot or so long, and the paste to see what kind of water,


wanna say the pickups were a foot or 18inches from the bottom as well


ETA, we did not shut down to receive deliveries, as in people could buy gas, while the tanker was there and dumping a load, and never had an issue with bad gas

and of course, we are talking relatively new fiberglass type tanks, (the oldest kroger fuel center is probably 25yrs old now, if that) not old as dirt steel tanks that have been in the ground since Fred Flinstone was driving,

I only add ‘Top Tier’ gas to my vehicle. Both take 91 octane. I don’t ever fill up elsewhere.

Replaced the gas cap. After driving about a half mile, the CEL self-extinguishes, and has not come on again. Engine running nice and smooth.

All this drama for such a minor thing.

Well, the CEL came back again, so not the gas cap. The final verdict: a leaking intake hose damaged the oxygen sensor. $560.

Thank you all anyway for the input.

That diagnosis is not possible.

A leaking intake hose can affect the mass air flow sensor reading, and at times can affect the cleanliness of the sensor element and heaters.

An oxygen sensor is fitted to the exhaust manifold, nowhere near the intake manifold. There are upstream and downstream oxygen sensors, on either side of the catalytic converter.

Someone either misinformed you, or confused you with terminology.

I may have indeed misunderstood the explanation, language barrier thing.

At any rate, the CEL is back on again. It's back to the shop tomorrow.

Yeah if I eat Taco Bell

^Followup question: ever read the OP?

quote:

Originally posted by kkina:
^Followup question: ever read the OP?

I went through this with a 2003 Land Cruiser. Replaced the gas cap, cleaned the mass air flow sensor and throttle body. Ended up the charcoal canister was the culprit. Good Luck

You can get bad gas.
Here is a recent case in Colorado where diesel fuel was added into the underground gasoline storage tanks.
This will cost somebody big money as the incident was well documented.
https://www.9news.com/article/...e4-9ede-3167d7237f92

quote:

Originally posted by kkina:
Thanks, Sigmonkey. I will take it back to my mechanic for a free diagnostic if the light comes on again.

It's actually an older vehicle with low mileage. 1993 4Runner with only 43k original miles. It was the last vehicle my Dad ever owned, but he didn't drive much in his later years.

This is why vehicle year, make, engine is so important.
First off, that is a damn good truck.
However, It is pre OBD2 (uses flash codes), does not use a MAF (uses a VAF, vane airflow sensor).
But what the hell, you can fix anything on the internet, all vehicles are the same, just throw parts at it until it gets better.

quote:

does not use a MAF (uses a VAF, vane airflow sensor).

Are you sure about that? My mechanic (and AI) says the 3VZ-E engine uses a MAF.

You are right about it being a damn good truck (as long as that pesky head gasket doesn't blow).

Grok indicates a Vane Airflow Sensor for this.

https://grok.com/share/bGVnYWN...b8-9eca-39b7ba9ca1db

And images for this vehicle sure look like a VAF sensor.

Weird. Maybe either were used on that engine. At any rate I don't care what it is, as long as it's fixed.

Well, that escalated quickly.

The tl;dr version is that a small problem cascaded into a big problem across multiple systems. Bottom line, I'm looking at a $5,000 repair.

I knew it was going to be bad when the mechanic called and said I should come down, we need to talk.

Followup question: ever read the OP?
^^^^^^^^^^^^^
Yes I thought you would like the joke. Lighten up Francis.