Cleaning EGR

Hey Everyone,

I was just looking for a quick opinion prior to buying a new part. I have been getting a P0420 code (mixture too rich o2 sensor). I had a friend who thought it was my EGR, so I took a piece of a PBR can a used it to block the EGR right where the exhaust pipe bolts on to it. Turns out there was no change once I blocked it off, which was a good indication my EGR isn't functioning.

So my question is, should I attempt to clean the EGR and re-install it, or just buy a new one? This engine has about 200,000 miles on it. So i'm just curious if its even worth trying to clean, or if once they fail they are done for?

Thanks in advance!

 

Awesome thanks for the reply. Yeah you can still buy the EGR valve, which i'm assuming is just stuck. But they're about $110 on rock auto, but yeah there are a few people that make it.

I haven't tried Marvel for anything like that, but maybe ill clean it with some carb cleaner and give it a second stage bath in Marvel prior to putting it back on

Thanks!

 

Ok will do, ill let you know how it works. Hopefully be getting to it this weekend

 

Just an update here, sorry it took so long, I got sent away for a while for work. Anyways took the EGR off an cleaned it, but really didnt notice any problem with it. Valve moved freely when vacuum was applied. But cleaned it anyway and reinstalled it. I did find a stud missing on the EGR pipe on the exhaust side, so there was a small exhaust leak on the exhaust side. Got that taken care of as well, but the problem still persists...

 

I'm not sure if you have a typo on the DTC, but P0420 is: Catalyst System Efficiency Below Threshold (Bank 1). Which means the ecu believes the catalytic convertor isn't working as it should. The ecu determines this from the data it gets from the upstream AFR sensor and the downstream O2 sensor.
Might want to double check with an OBD2 reader the DTC currently shown.
It is rare that EGR valves fail. They do, just not often. If the valve moved fine with vacuum testing than it should be fine.

 

On the original dude's deal? If that was his code thrown, not sure why he went to the EGR valve. This was before you were responding to him.

 

Yeah that doesn't seem like a common type scenario. And he's in the 2.7L, just trying to help this original poster guy out by getting more input/info from him

 

It has been an intermittent code, which I have been battling for quite a while and unable to figure out. The P0420 comes and goes, meaning every 300 miles or so the code will clear itself and not pop back up. Accompanying the code is an odd idle problem. When cold starting the engine lopes at low RPM and will die if you don't give it a little bit of gas. Once it runs for a couple minutes or longer depending how cold it is it will idle around 500 RPM, and as the engine warms up the idle increases to 900-1000 RPM. A friend looked at it an thought it was the EGR, hence this post.

Currently there is no code that is being thrown. The vehicle once again cleared the code on its own prior to starting this job and disconnecting the battery.

The EGR valve did not fail, and its not the Cat or the O2 sensors, all of which I have tested.

Not sure what all the talk of a supercharged vehicle is on here, I think "1997tacomaV6" thought he was posting on another thread maybe. My truck is not supercharged...i think cruiserguy is as confused as I am...

Anyways if you're curious on more stuff I have done with the truck to see the history check these old posts out:

https://www.tacomaworld.com/threads/stuck-high-idle.509642/

https://www.tacomaworld.com/threads/high-idle-and-trouble-cold-starting.473478/#post-14321871

 

To answer your question, i've been battling this problem for a while. When a friend of mine saw the symptoms the truck was having he thought it was possibly the EGR, not solely based on the P0420 code (Which has been intermittent). He suggested I should put a piece of metal (Pop can) at the EGR valve and see if there was any change. This was where the EGR pipe bolts on to the EGR valve. I did that and there was no change, so I thought possibly that the EGR had failed, so I made this post to see if it was even worth trying to clean or just replacing. Turns out the valve was good (good insight from you), but I discovered there was an exhaust leak due to a missing stud and nut from the EGR pipe on the upstream side where it comes off the exhaust manifold. Which has not been fixed, but the problem still persists. Same symptoms described in the above reply.

Ive done a lot of digging trying to figure this out. No its not a vacuum leak. Its not an o2 sensor. Its not the cat. Its not the MAF. Its not an intake leak.

Maybe read through the high idle post I have referenced above and see what you think. Im open to any thoughts or theories.

Thanks!

 

I'll take a peek at it, thanks for being patient while we sorted out the confusion. Not saying to try anything particular, sometimes just talking/typing it out loud gets the ol gears turning in my head and then maybe we get lucky and someone who has seen this EXACT same thing chimes in and tells us what to check next

 

Im not discrediting you, i'm just confused by your post

 

Yeah I appreciate the help. This is a weird issue and a very frustrating one being that I cant figure it out.

The idle essentially behaves backwards. On start it lopes at low RPM and as it warms up the RPM gradually increases to around 900-1000. Other than that its a great truck and it runs great with no codes right now

 

That particular DTC I believe is a 2 trip logic type, meaning the ECU won't throw it on first detection but will store it as pending. And then if ECU detects the condition again, then it'll trigger the MIL. I believe most OBD2 scanners show the pending faults as well.
The symptoms you describe are generally associated with a vacuum leak. Sounds like you eliminated that possibility though.

Reading through the thread where you replaced the throttle body with a new one, it was a 'new' used one right? With the amount of light getting past that butterfly valve, yeah that was definitely affecting things.
I'd be curious to see if any DTC is pending, also just curious what do the plugs look like? Had to replace any coil packs yet?

 

You’re correct, it was a used Throttle body. I wasn’t able to find any sort of rebuild kit for them or anywhere that made a new one for a reasonable price.

I haven’t pulled the plugs, but haven’t had any issues with it running rough either. No problems with the coil packs either. But I could pull the plugs when I get home next week no problem. The engine runs great and compressions were all 150 when I did the head. The mileage is poor right now though, so it seems to be running rich.

Do you think a bad ECT sensor would have anything to do with this type of issue? Or maybe a poor connection there? I did have to wire a new connector for the ECT. I know when the ECT is not connected cold starting becomes difficult and near impossible at lower temps because the engine thinks it’s running hot. I believe the coolant line runs from the ECT on the back of the block to the IAC so maybe it’s giving some bad info. Thoughts?

 

That's a good point on the coolant sensor, that's what you're saying right?, if it tells ecu it's at temp already then the ecu would run it overly lean to start and engine would be close to dying, I think.
Runs rich at startup only? How does it run when fully warm?
Also, bear with me, what kind of gas mileage are you getting and what kind of driving(city/hwy)? You got me curious on what a spark plug is gonna look like now. I'm just looking for other things that might help us get a lil more insight, not trying to jack you around man

 

Yes essentially thats what i'm getting at with the coolant sensor. Im wondering if the sensor might be a bad part that sending faulty information to the computer for start. Essentially if the ECT is disconnected, then the computer thinks the engine is at temp. So yes, it delivers a leaner mixture which when it is cold is not sufficient for start. It doesn't have any issues with cold starting. It started it fine this morning at 29 degrees F. You just have to give it a little gas to get the RPM up above 1,000 for a couple minutes and then it idles fine once it warms up a little around 600 RPM. So this could mean its getting to lean a mixture on start. I guess the question would be where that computer is getting that information from. The ECT is one source.

When the engine is fully warm it runs great, but the RPM is high at 900-1000 RPM for idle. it definitely runs smooth though, no loping or hesitation or anything like that.

City milage is lower, around 16 mpg. I don't get on the highway much, especially through a full tank, but last time I did it was normal around 23 mpg. I think that makes sense because it runs fine at higher RPM. I think the high idle around town is likely to be blamed for the mileage.

 

That's pretty good mpg, I do the math on mine every fill up I guess, and seem to always be right close to 20-21 if hey and 17-19 city. Stock 31s. Automatic.
So I guess there won't be any clues until the MIL pops back on. Then with the scanner you can see the data from the moment that triggered it, I think on most scanners anyways

 

Yeah I usually get closer to 20 in town during the summer. This usually goes down a little in the winter with the fuel. But 16 is lower than what I typically get with stock tires

 

Yeah that's solid. So I wouldn't expect to see anything funny with the plugs or stuff like that, known what I mean? You replaced the IAC with a new OEM one I think I saw? I dunno, we need the data from when the MIL triggers.

 

You are approaching this whole thing from the wrong end. Instead of guessing why don't you plug in a live data scanner and really see what ECU is seeing.