MadCityRich

I'm about to get serious chasing down an EVAP related series of CELs.

Rather than get into the code issues, I was hoping to get some feedback on my symptoms and see if that points in a direction. Here's what I've observed:

CEL first came on last summer. I replaced the gas cap with a new dealership cap. CEL went away and came back very soon after. I periodically cleared the codes. Then in early fall the CEL stopped showing up. Until October, for a few days. Then it was gone all winter. Now it's back.

What I've observed is the CEL is triggered when air temps are in the mid-70s or warmer. The summer was obvious. The October CEL occurred during a brief hot spell. Just this week we had temps in the 70s and the CEL popped right on schedule.

Chasing down the EVAP system is doable, but I'm looking for target areas. The system is a network, so symptoms in one area may be from issues in other areas. I'd like to avoid the "replace parts 'til it's fixed" shotgun approach. Any pointers related to the temperature trigger or similar experience is much appreciated!

MadCityRich

BigBallsMcFalls

too vague
tell us

a) the exact codes and when they happened

b) pending codes (on deck but not yet lighting the MIL)

c) emissions check (drive cycle) 'ready' or 'not ready' state


evap can be thrown for any combination of these or more

Faulty gas cap
Fuel system malfunction
Malfunctioning air injection system
Misrouted vacuum lines
Faulty positive crankcase ventilation (PCV) system or exhaust gas re-circulation (EGR) system

MadCityRich

I know it was vague. I'm really just wondering if the temperature based symptom may trigger some insight.

I need to re-pull the code as the last time was in the fall.

This weekend I'll be pulling the codes and checking all the lines that go to the system. After that will be checking the vsv and other bits.

MadCityRich
2002 4Runner Ltd

FogRunner

As someone who recently dealt with a EVAP code on a 4runner I can tell ya it will drive ya nuts trying to find the leak.

Summer time and hot temps can make the evap system throw codes for a variety of reasons. One being hot fuel "boils off" more vapors than cool fuel. Another being the engine has to be up to temp for a certain duration along with other circumstances for the EVAP system to cycle enough to throw a code.

The most common code on a 4runner for EVAP is P0442 OR P0456 Small EVAP leak which is going to be the hardest to fine or P0455 which is a large leak most likely a gas cap or such. Which when dealing with a emissions system problem ALWAYS try a new gas cap first they a like $15 from Toyota.

But if you think you have found the culprit like the cracked hose I had on the charcoal canister you can drive it around a couple hundred miles and try to the EVAP system to cycle and test it

OR

Do like I did and give it the specific conditions it wants and it will run the EVAP test in less than 20 minutes and either pass the EVAP I/M monitor or throw a code.

1. have between 1/2 to 3/4 a tank NO more no less
2. let your 4runner sit over night to where the engine and the air are the same temp. If the engine coolant and are are more than 12 degrees F. apart it won't work.
3. Start the engine with no A/C or other loads on and let it IDLE till it warms up fully
4. Once warmed up, rev engine to 3,000 RPM and hold for 15 seconds
5. Now let engine idle with A/C on for 30 minutes.

After the 30 minutes of idling the system will have completed a full EVAP system check and you will either have a pass or a check engine light with a code.

I did this the other day because I couldn't get the EVAP and Catalyst I/M monitors to complete so I could take it in for inspection and it worked great.

dntsdad

http://home.comcast.net/~dntsdad//TS..._(revised).pdf

BigBallsMcFalls

smoke machine and a bright LED flashlight...go leak hunting

FogRunner

What I used is a can of CANNED AIR, which is nothing but R-134A, Yes a can of CANNED AIR sold with the purpose of being vented to the air. (so you rabid environmentalists can stop the flame right there)

I used a refrigerant can tap and clamped it on the CANNED AIR and with a low pressure regulator flowed it though the emissions system and went around with a leak sniffer and found the leak PDQ.

I had tried the smoke system but the leak was so small I couldn't find it. But when I used the leak sniffer it found it really quick.

Just be sure to use a good low pressure regulator and don't exceed 1/2psi.

MadCityRich

Pulled the codes today. Here's what I've got:
P0441 Evaporative Emission System Incorrect
Purge Flow
P0446 Evaporative Emission System Vent
Control Circuit

I still need to inspect the evap system hoses and such.

MadCityRich
2002 4Runner Ltd

FogRunner

http://www.ncttora.com/fsm/1996/SIL/...e/cip0441p.pdf

Right from the FSM on what to check

DRCOFFEE

For what it's worth I had this issue on my old MDX and what I found out it topping off the gas tank is bad for the evap system. When the pump clicks off, stop. The liquid fuel gets in the return line and causes problems. I also went to all the evap vacuum hoses and zip tied them all onto the ports to stop any possible leaks. After about a week I cleared the codes and it never came back. I figured there had to be some truth to the theory. The cel was on for about a year before that.

MadCityRich

So after contemplating the diagnostic procedures and diagrams, I decided to just spend $26 on Amazon and get a new VSV for the charcoal canister. I figured that if I was going to have to go digging into the system, I may as well get something out of it while I'm in there.

Buttoned things up this morning. That canister system is a bugger to get off. Midwest winters caused one bolt head to snap off. The vsv would only come off with dremel assistance as the screw holding it on the canister was seized up. I rigged a system of a rubber pad (tire patch piece) and zip ties to make up for the bolt I snapped. I wasn't ready to drill and retap for a replacement bolt.

I cleared the CEL and went for a drive. No obvious issues. It's too soon to tell if the CEL will come back or not. If it comes back, I'll get into actual diagnostics.

Thanks for the guidance and insight so far. I'll update this thread for the record.

MadCityRich
2002 4Runner Ltd.