2003 Tundra - check engine light on - smell something "burning"

Purchased new - great condition - no rust, 5-speed. Check engine light has come on several times... 1st time - changed filler tube and gas cap - problem solved! 2nd time - gasket on top of gas tank was attacked by mouse, chipmunk, squirrel ??? - replaced it - problem solved! Now again, but there is a burning smell within a few minutes of driving. Two "P" codes show up - my mechanic will go from there first, but the burning smell doesn't make sense! Help!

 

Smell like sulphur? Could be the catalytic converters.

 

Not Sulphur - had catalytic converter changed - mechanic said it wasn't the converter.
He was thinking an oil leak, but it doesn't smell like oil and it isn't losing/leaking oil -
smells like burning leather or cloth???
He can't get it in the shop until October

 

Really need to know the P codes.

Also need to know if V6 or V8. If V8, rodents love to nest on top of the engine, under the intake, and the P codes could support that.

 

V6

 

I had a "million-mile" filter in it and last time they took it out so I could clean it, there was a mouse nest in there... I haven't thought about that until you just mentioned it... Thank you - I will check tomorrow.

 

Definitely check the filters.

Meanwhile, curious ... where are you smelling the burning, and can you explain what it smells like?

Like, it looks like you've got one of the sought-after 5spd manual V6 trucks. Clutch burning up smells almost like a mix of mechanical burning with rubber burning. Almost like someone ground up rubber tire and a bunch of coconut hull, and smoked it.

Or, if you have a stuck caliper piston, your brakes can overheat and that smells similarly depending on your pad composition.

Knowing what it smells like, and where you smell it would help.

Knowing what P codes you threw may also help us understand what that problem is and if it could be related.

 

Yes, that's my truck... I had a new kitchen put in and the guy said he would do it and take my truck as payment. I said "no thanks"! I have had other offers - I bought it new and I have taken care of it, so I know how it drives and when something is wrong.
The smell could be rubber - I will check the engine and filter in the morning. The smell is not inside the truck.
They did find one of the hoses was loose - fixed it, but that wasn't the problem.

 

Checked engine - no critters!
PO171 and PO174 is what the mechanic wrote down
They reset the "check engine light" - it stayed off for about 2 days, then came back on

 

Those codes are lean condition. Check for vacuum leak at intake manifold. I’ve heard the PS vacuum switch can do that too.

 

If rodents were an issue, and there's a lean condition, it's possible the rodents chewed thru intake stuff. Or the last person who had the intake off re-used old gaskets.

But it could also be a dying/bad fuel pump. Or some dumbass changed the fuel filter with aftermarket, and now it's clogged as the aftermarket fuel filters tend to get.

I don't see a correlation between the codes and the smell though. I suspect OP has a corpse or a nest somewhere, unless the clutch is burning up. Sadly we still can't smell shit thru the internet. Which is probably for the better.

 

The rodents were an issue many (over 12) years ago - hopefully they (Toyota garage) used new gaskets (I always tell them Toyota parts only, but that don't mean they listen!)
Ahhh - fuel filter??? Maybe?
No clutch issues - shifts like a dream - Actually no problems until this "check engine light" popped up (knock on wood)
I am writing all this down for my mechanic... I lived in PA and had a great mechanic. Now living in NY and the Toyota dealers are all rip-offs! My mechanic is a retired race car driver - I will forward all your thoughts to him! Thank you (all) so much!!!
I will let you know what happens!

 

Update: Code P0107: Possible fuel pump/line issue. Could not inspect it as long as the check engine lite was on - asked me to drop it off for a couple days, but before I left one of the guys removed the gas cap, cleaned it off, sprayed silicone on the gasket and applied grease on the threads. Told me to drive it. The check engine light has not come back on.

 

Interesting. Typically a bad gas cap will throw P0442 or similar P044x EVAP code. EVAP codes in the P044x range usually happen if your fuel line and/or tank vent and/or vacuum line was chewed thru by rodents, or cracked fuel filler neck, or cracked/loose vacuum hose, cracked EVAP canister, or bad gas cap.

P0170 is typically fuel/air mixture related. Like you have a bad intake gasket, inadequate vacuum, or your upstream O2 (air/fuel ratio) sensor is going bad on the side the code references (P0170 is drive side, IIRC). Or of it's on both sides, potential MAF issue.

 

You are correct on the code (air/fuel ratio) - exactly what the mechanic told me! I can't explain it and the light may return - until then no light and it will pass inspection.

 

This is the most important part! Every 4th or 5th year of my life, check engine light tends to creep up within 90 days of inspection. Good luck!

 

LOL!!! Thanks, will keep it in mind! I know I am pushing my luck, but I love driving my 5-speed and want to keep it "alive" as long as I can! I don't mind putting money in it - the mechanics seem to say, "it's a chore and may be a temporary fix because so many other things could be the problem!"

 

I'm back and so is the check engine light... It was off for about a week - checked the gas cap and it was loose (?), also a dead battery. Went back to my mechanic and 2 codes showed up. After trying another gas cap; resetting light, replacing battery, a different code showed up - PO171. They replaced the Mass Airflow Sensor and we passed inspection (oh, they also found a disconnected hose, which they replaced). Can't complain - this vehicle owes me nothing after 22 years of faithful and trustworthy driving! (They also were surprised not to find any rust underneath - When I bought it, I had it undercoated, then again a year later). I also have a Highlander to add to my Toyota family and my daughter has a Tacoma! Happy driving!

 

Breaking that down a bit....

The new P0170 and P0171 are likely related. Both codes suggest a problem with fuel/air mixture in one of the groups of 3 of your V6. Bascially the 3.4L in your truck has 3 cylinders opposite each other in a V format. 3 cylinders per "side" (aka each "bank") of the engine as shown below.

Your on-board computer is telling you you're getting too much air OR not enough fuel to 3 cylinders on one side ("bank 1") of your engine, but the other side ("bank 2") is all good.

I'm not as familiar with the V6/3.4L in these trucks, but if it was a MAF sensor issue, the Mass Air Flow sensor reads ALL air coming into both heads (both sides) of the engine as one single number, so all 6 cylinders should have the exact same amount of air coming in from outside. It would take something specific for the air/fuel ratio to be that far off. Like...

• Fuel pressure is lower on one side of the engine than the other
• You're getting outside air seeping in on one side of the engine (like, the gasket on the intake manifold for that side is leaking, or you have a cracked/loose/leaking vacuum hose)
• The air/fuel ratio sensor ("upstream O2 sensor") for one side of the engine is reporting bogus info, *IF* your engine has dedicated upstream sensors, one per bank (I don't remember how your engine is laid out)
• There are probably others also, but the above are what I'd expect

Not sure if this really helps you or not, but hopefully it's a little clearer what the problem is, and possible solutions?

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