Gas tank building excessive pressure & fuel smell. Dangerous for sure! Why does this happen?

[krispykritter]

IMHO all 06-up, all makes and models. Need action taken w/S.A.I. or they kill the CATs and more.

S.A.I. Filter Modification, in VVT engines. To prevent its failure! Alert Alert!

We've a $2.00 part in the S.A.I. (secondary air injection) system of the VVT engine, that is taking-out ~$7,000.00 $15,000 $25,000 (inflation) in parts. WOW! I've a very easy and cheap WORK AROUND. You are going to love this ;) This thread is dedicated to the 4.7L 2UZ-fe VVT engine, in the...

forum.ih8mud.com

I have actually fully disabled that system, fortunately. I've read your theories and diagnoses of that issue! Always appreciated

 

[augustwest]

What year and miles?
I'll guess 06-07 150k to 250K miles!

05 173k

 

[2001LC]

I've been getting the P0420 and P0430 codes for a while now, and have been resetting them via the Torque app. On Saturday, I finally got around to running a bottle of cat-a-clean through it, and then this morning the dash lights up and I'm getting P0420 and P0430 again. The dash typically lights up 1-2x per day, so the 3 days I got out of it was longer than usual. Should I run some more cat-a-clean through it? Check the O2 sensors? Would really hate to have to spring for new cats.

05 173k

You can try 2 cans 44k in full tank. Sea-foam foger. Than Chevron techron, next tank. Yes even more CAT-a-clean (last best IMHO).
But very unusual for a CAT, even more so for both to go bad on 98-05 even at 1 million miles. You must find and correct upstream issue first. Or you'll keep killing CATS.

Once I'm sure no excessive fuel or oil being dumped into CAT. I do a high RPM run on HWY. About 4,500 RPM at ~60 MPH, gets CAT temps to max. But if suspect fuel or oil, built up in CAT. I use cleaners first. Since they (CAT) with "fuels", can ignite and burn up.

Watching fuel trims and ECT can yield valuable clues.
Upstream:
MAF sensor. (I've seen only 2 bad CAT both BK 1., in 98-05. Each had a bad MAF. One replaced with aftermarket (AM) MAF. The AM MAF killed a CAT. The other, factory MAF went bad. It had poor air filtration.
Poor air filtration.
Engine coolant temp (ECT).
Compression
Vacuum leaks
Poorly tuned.
Exhaust air leak(s).

Any fluid loose, where no leaks found. i.e coolant, PS fluid or engine oil.?

Exception to upstream issues:
Impact to CAT (both)
Flood waters.
A clog in exhaust. Such as rodent nest in tail pipe/muffler.

 

[augustwest]

You can try 2 cans 44k in full tank. Sea-foam foger. Than Chevron techron, next tank. Yes even more CAT-a-clean (last best IMHO).
But very unusual for a CAT, even more so for both to go bad on 98-05 even at 1 million miles. You must find and correct upstream issue first. Or you'll keep killing CATS.

Once I'm sure no excessive fuel or oil being dumped into CAT. I do a high RPM run on HWY. About 4,500 RPM at ~60 MPH, gets CAT temps to max. But if suspect fuel or oil, built up in CAT. I use cleaners first. Since they CAT with "fuels", can ignite and burn up.

Watching fuel trims and ECT can yield valuable clues.
Upstream:
MAF sensor. (I've seen only 2 bad CAT both BK 1., in 98-05. Each had a bad MAF. One replaced with aftermarket (AM) MAF. The AM MAF killed a CAT. The other, factory MAF went bad. It had poor air filtration.
Poor air filtration.
Engine coolant temp (ECT).
Compression
Vacuum leaks
Poorly tuned.
Exhaust air leak(s).

Any fluid loose, where no leaks found. i.e coolant, PS fluid or engine oil.?

Exception to upstream issues:
Impact to CAT (both)
Flood waters.
A clog in exhaust. Such as rodent nest in tail pipe/muffler.

I can’t thank you enough for this. Honestly, so much of this is over my head. If it’s alright with you, I’ll shoot you a DM to see what my options are. If you can fit me in, I’d be happy to become one of your customers.

 

[2001LC]

I can’t thank you enough for this. Honestly, so much of this is over my head. If it’s alright with you, I’ll shoot you a DM to see what my options are. If you can fit me in, I’d be happy to become one of your customers.

Sure, shoot me a DM with contact info. You can stop by, and will look over together.

 

[Coin]

FYI, I used to get repeated P0420 codes. I replaced the rear O2 sensors in the exhaust and haven't had an issue since. Very easy fix

 

[rock climber]

FYI, I used to get repeated P0420 codes. I replaced the rear O2 sensors in the exhaust and haven't had an issue since. Very easy fix

Same for me. Use denso O2 sensors, same os OEM, but much cheaper.

 

[jerryb]

god forbid someone actually check the device that reports the error.
wasn't this the fuel temp thread?

 

[Patassa]

It was clear 104f was parks OAT on dash gauge.

I was asking: What was your ECT (Engine coolant temp)?
I ask; because very often correcting a high ECT, eliminates fuel boiling.

What's the best/easiest way to get a reliable ECT reading?

 

[DTC72]

What's the best/easiest way to get a reliable ECT reading?

Fancy way is Scan Guage. Easy/cheaper way is a $100 OBDII code reader that either has an included dashboard or download a 3rd Party dashboard. A very simple one is BlueDriver.

 

[AFei]

What's the best/easiest way to get a reliable ECT reading?

One of the cheapest way to read the coolant temperature is this type of $1x device: Amazon product ASIN B011NSX27AIt works well, along with Torque on Android, for my 04 LX.

 

[Hugh Heifer]

One of the cheapest way to read the coolant temperature is this type of $1x device: Amazon product ASIN B011NSX27AIt works well, along with Torque on Android, for my 04 LX.

Don't leave it plugged in to the OBD receptacle. Most of those cheap dongles do not sleep.

I highly reccomend a Scangauge II since it is programmable and really not THAT expensive. It also sleeps. I set mine to read my XMSN temp.

BTW, I may have mentioned this above. I had been suffering from some of the usual issues with fuel smells, etc and replaced my gas cap which is often the first step. The new one has been on several months and my issues seem to have subsided.

 

[Eyedaho]

Don't leave it plugged in to the OBD receptacle. Most of rhose cheap dnagles do not sleep.

I highly reccomend a Scangauge II since it is programmable and really not THAT expensive. It also sleeps. I set mine to read my XMSN temp.

BTW, I may have mentioned this above. I had been suffering from some of the usual issues with fuel smells, etc and replaced my gas cap which is often the first step. The new one has been on several months and my issues seem to have subsided.

I also seem to have alleviated my fuel smell issue by replacing the gas cap, even though there was nothing visually wrong with it.

 

[AFei]

Don't leave it plugged in to the OBD receptacle. Most of rhose cheap dnagles do not sleep

You are correct that it doesn't sleep which I can confirm, and technically will contribute to drain the battery. However, our LX/LC does suffer slow battery drain regardless of the OBD scanner, and the contribution from the OBD scanner is very minimum, like <xx mA.... For a new battery, it seems not an issue, and I have left it attached and sit for several weeks. However, it's always a good practice to unplug the OBD scanner if plan to leave the LX/LC parked for extensive length of time...

 

[Hugh Heifer]

You are correct that it doesn't sleep which I can confirm, and technically will contribute to drain the battery. However, our LX/LC does suffer slow battery drain regardless of the OBD scanner, and the contribution from the OBD scanner is very minimum, like <xx mA.... For a new battery, it seems not an issue, and I have left it attached and sit for several weeks. However, it's always a good practice to unplug the OBD scanner if plan to leave the LX/LC parked for extensive length of time...

I had a cheap one that would kill my battery in 48 hours. Mileage may vary.

 

[Reshala]

This issue came up for me yesterday and was pretty alarming. I used the LC to move some of my wife's recently deceased grandmother's items. OAT of upper 80's, LC loaded with stuff, AC blasting full the whole time because the rear hatch was open. I stopped and put a full tank in, drove about 40 miles, dropped some items, drove another 40 miles, and when I stopped I heard the gas tank glugging as if it were pouring liquid out of an unvented container. I also heard the pressure hiss. I mistakenly (I hope) believed that this was the result of a blocked fuel vent or evap canister line. When I unscrewed the gas cap in an attempt to quickly equalize the pressure however the hiss and glug continued. Tellingly though instead of sucking air to equalize what I thought was negative pressure I got a huge cloud of gas vapors. That was concerning particularly because I was planning on using this car for our vacation which requires driving from Central Kentucky to Hilton Head in August/July. I started reading here and this thread gave a lot of good insight and I'm pretty sure the heat is the issue.

Mine is a 2003 with 282k on it. A few months ago I was driving and heard metal against pavement. It turned out to be a heat shield above the muffler. The muffler was rough but intact at the time. I removed the heat shield and kept going. There has been exhaust noise for a while and I thought it was nearer the front from the way it sounded. After I read on here that heat was a likely culprit I looked under it while it was hot yesterday and wow, I mean wow. The amount of heat lingering under there is a huge problem. The heat ping was the worst I've ever heard and you can see it throughout. Today while cool I got under to do a good inspection of the exhaust and the muffler is toast. A baseball sized hole and a golf ball sized hole and finger pressure pokes through. To my pleasant surprise everything else was in crazy good condition from the muffler connections forward to header/manifold. The muffler itself seems to be a very easy install although the connection is definitely a 20 year old exhaust connection. I'll start PB blastin' now.

Here are my concerns:

1. I want to replace the heat shield that was previously removed but so far have not tracked down the part or part number. Alternatively I could do a heat wrap on it. Heat wrap could be cheaper and easier. See issue 2 for my concerns here.

2. It's pretty likely that the major heat culprit right now is the hot exhaust gas getting dumped directly under the truck and separated from the fuel tank only by the prop shaft. That said, the cat to muffler routing passes right in front of the tank. I'm inclined to wrap this as well to keep the heat in until it exits out back or at least to minimize heat in this direct area. I'm pretty concerned about making changes to heat management that's not consistent with OEM because I'm not an engineer. I don't want to crispy any sensors upstream or even potentially dump heat back into the bay or onto the block even though it's a pretty good distance downstream.

Basically, new muffler plus keeping heat in the system and hoping that it dissipates correctly and not upstream to more sensitive or critical components. Sorry for the long post and thanks in advance for any insight.

 

[2001LC]

Driving with holes in muffler is a very bad idea. Wherever a hole, hot gasses are directed out it. This can be onto wiring, fuel tank, etc., rather than out tail pipe. We're seeing a number of issues, from melting wire sheathing and or wire housing blocks. Also, these holes often result in exhaust fumes entering cabin, through rust holes or open window or bad door seals. Make sure to check the resonator (last muffler) also, for holes.

Your fuel boiled. Which 90% chance in 03-up, pushed raw fuel into charcoal canister flooding it. Which if so, is likely toast.

It's also very likely your engine is running hot. It would be a very good idea to monitor ECT (engine coolant temp) through tech stream, as you drive in 80F plus OAT temps with AC, to determine of so. If you find ECT gets over 200F, you're running hot. Which needs address first thing.

I'm unclear on how heat shield fell off. But all factory heat shields are necessary.

 

[Reshala]

Driving with holes in muffler is a very bad idea. Wherever a hole, hot gasses are directed out it. This can be onto wiring, fuel tank, etc., rather than out tail pipe. We're seeing a number of issues, from melting wire sheathing and or wire housing blocks. Also, these holes often result in exhaust fumes entering cabin, through rust holes or open window or bad door seals. Make sure to check the resonator (last muffler) also, for holes.

Your fuel boiled. Which 90% chance in 03-up, pushed raw fuel into charcoal canister flooding it. Which if so, is likely toast.

It's also very likely your engine is running hot. It would be a very good idea to monitor ECT (engine coolant temp) through tech stream, as you drive in 80F plus OAT temps with AC, to determine of so. If you find ECT gets over 200F, you're running hot. Which needs address first thing.

I'm unclear on how heat shield fell off. But all factory heat shields are necessary.

Thank you so much for the insight. Replacement final muffler arrives today and install this week or weekend. Coolant was almost .75 gallon low which gave me real pause. The dash gauge always showed under half but I understand that that is more of a binary response rather than accurate representation of real temp and is also placed high in the block. Follow up questions:

1. Would you feel comfortable heat wrapping the new muffler as well as the pipes from front resonator back?
2. Regarding evap canister, will its destruction result in codes or simply cause performance issues? The truck continues to run really great with no symptoms of fueling issues that I'd expect to encounter. I have a client who owes me and is going to check it but I'd love to spend that money on a winch mount rather than evap canister if it can be done responsibly.
3. There are MVIC cables in the $50 range advertised as coming with Techstream. I think it might be Techstream light though. There's also places on the internet where I've seen downloads for it. The other option is Bluedriver which seems popular but doesn't seem to be much more than a really good reader. Which direction would you go?


Thank you very much for the insight. I apologize for the large number of questions.

 

[2001LC]

Thank you so much for the insight. Replacement final muffler arrives today and install this week or weekend. Coolant was almost .75 gallon low which gave me real pause. The dash gauge always showed under half but I understand that that is more of a binary response rather than accurate representation of real temp and is also placed high in the block. Follow up questions:

1. Would you feel comfortable heat wrapping the new muffler as well as the pipes from front resonator back?
2. Regarding evap canister, will its destruction result in codes or simply cause performance issues? The truck continues to run really great with no symptoms of fueling issues that I'd expect to encounter. I have a client who owes me and is going to check it but I'd love to spend that money on a winch mount rather than evap canister if it can be done responsibly.
3. There are MVIC cables in the $50 range advertised as coming with Techstream. I think it might be Techstream light though. There's also places on the internet where I've seen downloads for it. The other option is Bluedriver which seems popular but doesn't seem to be much more than a really good reader. Which direction would you go?


Thank you very much for the insight. I apologize for the large number of questions.

Very likely you were overheating. I always look at why was coolant low, a leak or something else:
One or any combination other than leak:
a) Coolant system not properly filled.
b) Reservoir, not working as it should. No coolant in it. It's hose hung-up on shelf, curled upward sucking air. Reservoir hose and or it's cap clogged.
c) Bad radiator cap.
d) Bad thermostat.
f) Fuel mixture to lean.
g) Radiator fins clogged, resulting in overheating. Which is so common.

Radiator fins need cleaning! Alert Alert Alert

I've a 06LC w/192K I just bought. In reading history I found PO complained of engine temp raising when both front and rear AC on. Toyota Dealership diagnosed with clogged radiator fins. Recommended new OEM radiator, $600 for the US spec Radaitor plus coolant and labor. They should have added...

forum.ih8mud.com

Overheating for any reason. Can expand coolant to point it exceeds capacity of system. It may then, blow out reservoir cap relief hole.

1) I'd not heat wrap, directly on the anything. Air gap the barrier, gives best results. This may help understand why "air gap". Personally, I've never used anything but factory heat shield. Exception is aftermarket CAT.


2) A bad CC often times, does not give a DTC (CEL). It's part of EVAP system and can result in excessive fuel pressure build up.

I like to get all up-stream issue corrected first. If I then still get fuel boil issues, I replace the CC as last step. Also worth a note: The 03-07 owner's manual warns to stop fill gas tank, at first auto-shut-off of fueling pump handle. Overfill may result, wherein CC floods and is damage.

3) I have blue driver for iphone which is close software. It's easy to use. But limited on what (PIDs) it can be read.

I also have the OBDIImx for iPhone, which uses most any open software app. The OBDIImx, allows me to see more. Like AHC pressures, Transmission fluid temps, the list is endless depending on which app downloaded. They both log the data.

 

[Reshala]

Very likely you were overheating. I always look at why was coolant low, a leak or something else:
One or any combination other than leak:
a) Coolant system not properly filled.
b) Reservoir, not working as it should. No coolant in it. It's hose hung-up on shelf, curled upward sucking air. Reservoir hose and or it's cap clogged.
c) Bad radiator cap.
d) Bad thermostat.
f) Fuel mixture to lean.
g) Radiator fins clogged, resulting in overheating. Which is so common.

Radiator fins need cleaning! Alert Alert Alert

I've a 06LC w/192K I just bought. In reading history I found PO complained of engine temp raising when both front and rear AC on. Toyota Dealership diagnosed with clogged radiator fins. Recommended new OEM radiator, $600 for the US spec Radaitor plus coolant and labor. They should have added...

forum.ih8mud.com

Overheating for any reason. Can expand coolant to point it exceeds capacity of system. It may then, blow out reservoir cap relief hole.

1) I'd not heat wrap, directly on the anything. Air gap the barrier, gives best results. This may help understand why "air gap". Personally, I've never used anything but factory heat shield. Exception is aftermarket CAT.


2) A bad CC often times, does not give a DTC (CEL). It's part of EVAP system and can result in excessive fuel pressure build up.

I like to get all up-stream issue corrected first. If I then still get fuel boil issues, I replace the CC as last step. Also worth a note: The 03-07 owner's manual warns to stop fill gas tank, at first auto-shut-off of fueling pump handle. Overfill may result, wherein CC floods and is damage.

3) I have blue driver for iphone which is close software. It's easy to use. But limited on what (PIDs) it can be read.

I also have the OBDIImx for iPhone, which uses most any open software app. The OBDIImx, allows me to see more. Like AHC pressures, Transmission fluid temps, the list is endless depending on which app downloaded. They both log the data.

Thanks so much. Rad overflow was dry when coolant was added. There's about an inch in the bottom now. No obvious leaks and hoses in good shape. Coolant is super clean and clear with no obvious contamination from scary fluids. Heater Ts were done about four months ago so I'm going to monitor closely and hope that it wasn't adequately refilled after. Will follow up with more accurate temp monitoring. Thanks a bunch for all of the great input.