[93celicaconv]

As you say, EGR is likely not the source of the problem. I still plan to remove and clean it so that I can rule it out as a possible issue.

I’ll look into the throttle position sensor (calibration as well) and the coolant temperature sensor. Is there any simple way to diagnose an ECU as being potentially faulty? My imagination would be that these are expensive and difficult to change; I’ll do some research.

Aside from not being able to pass emissions, is there any negative effect to continuing to drive with the deactivated EGR? Am I going to ruin my Catalytic converter by sending unburnt fuel into it?

I said the EGR doesn't appear to be the root cause of your issue. The EGR appears to be active at a state where it should not be, so the EGR is causing (in my opinion) the idle problem. But from what I can deduce without actually personally diagnosing your car is that the throttle position sensor maybe the cause of why your EGR is active when it should not be.

Your fuel tank should be under some pressure - the vapor pressure of the fuel. In winter, your gasoline will have a higher vapor pressure than in summer, as winter gasoline needs to additional volatility to ignite in cold winter temperatures. But temperature plans a major role in gasoline vapor pressure. The vapor pressure of gasoline drops as the temperature drops. I don't know where you are located, so unless you live in a relatively warm winter area, you really shouldn't be noticing significant fuel tank vapor pressure. Your EVAP shouldn't be considered faulty if your fuel tank has a high pressure - EVAP is not meant to control fuel tank pressure.

If your coolant temperature sensor is faulty, your car should remain at cold idle speeds well after the engine has warmed up. Does it? Is your coolant temperature gauge in the normal location after the engine has fully warmed up? Also, if the coolant temperature sensor is faulty and reading too cold (keeping you engine idle speed higher - but still steady), your EGR should not be active as the engine doesn't think the coolant temperature is above 140 deg F. By how you previously described your engine's operation, there wasn't anything there indicating a coolant temperature problem.

Unfortuantely, an ECU doesn't know when it has a faulty capacitor. Toyota's built in the era of yours are notorious for having ECU capacitor failures. Sometimes when taking an ECU apart, a faulty capacitor can be identified (it has leaked and also the corrosive leak may have permanently damaged your circuit board too) or the capacity may have swelled a little. Often though, a capacitor has no visual signs of failure. It is difficult to test capacitors for failure when they are installed on a circuit board. They are easy to diagnose if removed from a circuit board. But most folks are not up to going that deep into an ECU.

 

[Elle_Rav4]

Splieslife,

-- Can you confirm that the Check Engine Lamp (CEL) lights when the key is in the ON position (but engine not running)?

-- Have you checked for codes?

-- I agree with new echo owner that the EGR vacuum modulator is suspect here. Have you taken the EGR vacuum modulator top off and inspected the filter, for one thing? Though if the EGR vacuum modulator was acting up, I would expect a code to be thrown.

-- I attach the 5SFE service manual section that discusses troubleshooting for improper idle. Per this service manual section, I would also be checking the MAP sensor.

-- Here's a discussion of a 1998 2.2L Camry where the EGR valve was testing fine, yet replacement of the EGR valve fixed the problem: Stall erratic low idle at stop, after longer drive...

 

[Splieslife]

Hello all,

Thank you for your patience waiting for my reply; I’ve been busy in the shop.

I have solved the issue, the idle is completely normal now. It ended up being the EGR modulator (and possibly replacing the EGR VSV contributed to the fix as well). The EGR modulator is one of the only parts available from Toyota, so I figured I’d throw a new one in. It set me back $110 (I’m not normally a throw new parts in guy) but thankfully the gamble paid off.
The car runs great. I really appreciate all the input and contributions from everyone. No doubt that some of the other suggestions will be helpful to others who don’t have my exact fix.

To summarize my symptoms and the fix;

Idle was erratic once the car was warmed up and had been driven for 10-15 minutes. It fired up fine and ran smooth prior to this. Once the idle became erratic, I would have to apply throttle to keep the car from dying at stoplights.

The route fix was;
-Replaced the EGR modulator with OEM factory Toyota part
-(may also have contributed to the fix) replaced the EGR VSV with a unit made by Aisin (makes parts for Toyota)

Other things I did that could have contributed to the fix;
-used contact cleaner and then applied dialectic grease to all connections relating to emissions, fuel/air, throttle, ect
-replaced as many vacuum lines as was practical (almost all relating to the EGR system)
-replaced coolant with new HOAT coolant
-replaced spark plugs with laser Iridium
-replaced radiator hoses
-changed oil
-replaced PCV valve
-IAC valve was previously replaced
-Cleaned throttle body
-new air intake filter
-applied dialectric grease to the battery terminals
-ran red line fuel cleaner through the fuel

That about sums it up.

I’m not in the process of;
-replacing all struts
-replacing all cv axles
-replacing all brakes and rotors, swapping rear drum for disc
-replacing numerous broken handles

The car only has 165k miles, wish me many hood driving years, cheers!

 

[Splieslife]

I’m am in the process of replacing those last items (not was a typo)

cheers!

 

[Splieslife]

Hello there,

So I’ve got bad news. After a couple hundred miles of smooth sailing, the idle problem has returned, though thankfully, it seems very infrequent.
It started again after I was testing the ECT function which delays transmission shifting and allows the engine to rev higher. I hopped on the freeway with the ECT engaged, hit 4,000 rpm getting onto the freeway, and then almost immediately noticed a subtle irregular feeling. I took the next exit and found that the problem had returned.
This seems to happen once per long drive. I’ve discovered that if I pull over and turn the vehicle off for ten seconds, the problem goes away.
In an effort to address this I replaced my coolant temperature sensor with an OEM one from the Toyota dealership.
I’ve also replaced the following:
-thermostat with OEM
-both accessory belts

I still need to;
-clean the EGR
-test the TPS to make sure it’s within the correct voltages
-replace the two vacuum lines that run from my EGR system, under the engine, to the upper coolant port
-I also want to investigate the port that these connect to make sure it’s sound/not compromised
-I need to double check all the coolant lines running to and from the IAC valve

 

[new echo owner]

Sounds like a sticky EGR valve condition, not closing completely! Usually happens after extended high speed drives. Just a guess!

 

[Splieslife]

Hey,

Yes, I actually read the other linked thread about the sticking EGR. I just ordered a new EGR valve from Napa. Gunna throw that thing on when it comes on Friday.

Overall though, my MPG has improved from 22.5 to 28mpg. Hopefully this EGR seals the deal, because the car otherwise is doing great!

 

[new echo owner]

Nah, would try cleaning it first, would be sufficient most of the time, at least won't hurt trying before spending more money!

 

[Splieslife]

Hey,

I work in cinema so I have very little time once work picks up. I gotta just get this thing buttoned up ASAP.

 

[new echo owner]

Got it! Just a suggestion; nevertheless, keep the old one around as a spare!

 

[Elle_Rav4]

-replace the two vacuum lines that run from my EGR system, under the engine, to the upper coolant port

Consider replacing all vacuum lines with high temperature resistant silicone hose, as described here:
www.rav4world.com/threads/vacuum-line-replacement-with-high-temp-silicone-lines.255961/
I bought my silicone hose (various diameters, per guidance from the thread and trial-and-error) from eBay and replaced all hoses over a few days, a few hours total a few years ago. I took a propane torch to this hose recently, for a different project. The torch did not even leave a mark on the hose.

 

[Splieslife]

Hello all,

New EGR from Napa has solved the problem once and for all. As some of you mentioned, I may have been able to clean the stock EGR but I’m short on time and wanted to do a one time fix. The part from Napa was $250 but will be worth it if I don’t need to work on the system further. Thanks for all your help, I may invest in silicon hoses in the future.