2.7L auto weak with error code p0402 "EGR EXCESSIVE FLOW"

My '99 PreRunner has been weak for a long time and the gas mileage has always sucked. The CEL recently came on and the P0402 code comes up on the code scanner. What would cause this? Could the converter be partially plugged or even the muffler causing too much back pressure? If so how can I check the back pressure?
My truck has 165,000 on it and is a 2.7L with an auto. I also wonder how much effect the 31/10.50's have on it's power with stock gearing. It's always been weak since I bought it with 114,000 and the 31's were already on it.
What gears should be in it stock and what ratio could be installed to theoretically put it back to stock with the 31's? I like the look of the 31's but it know that they make it weaker.
My truck blows some black smoke occasionally on start-up as if an injector is going bad and leaking into the cylinder. This could be some of the problem. What lb/hr are the injectors?

Any info from ya'll will be greatly appreciated. I'm new to the site and I've been reading a lot of good info posted on here.

Thanks in advance Marshall

 

prolly something the dealer is gonna have to fix for you...could be a bad egr valve or something

 

sounds like you have a bad pcv system for the black smoke problem
and for the egr code
the egr is probably stuck either open or closed
if its open then your getting a shitty idle
if its stuck closed then you get shitty mpg
but all in all
either clean the egr
or clean the egr lines
thats one of the main reasons it does that cause of to much carbon build up or the exhaust being backed up into it
just read the topic again ahah its excessive flow
so its stuck open
so clean it out and you should be fine
run seafoam through your system to clean our the injectors and clean out the throttle body
seems like you need a tune up =]

 

Idles fine and I put a vacuum hose on the EGR and sucked on it while idling and it started running rough when the EGR valve opened. I feel like it might be more of a back pressure issue with either the cat or muffler but I'm going to take the EGR off and clean it anyway this weekend.

I've put some BG brand injector cleaner in the tank and I think I'll get some Sea Foam and try it too. Wires and plugs have been recently replaced, I need to put a new fuel filter in for good measure.

I think the 31's are dragging it down some, espaecially with it being an automatic.

 

i suppose
usually something is keeping it open since it says excessive flow
so maybe while your driving and it opens it stays stuck for a little while and then finally snaps back into place
just check the lines and try to clean out the egr and that might fix it
good luck

 

Did you ever figure out what was causing the P0402 excessive flow?

I've tested and cleaned the EGR valve and everything is fine with it. Also replaced the PCV which was bad. Check engine light for 402 keeps coming back on. Seems to come on when the engine is cold: less than a block from my house usually in the morning after sitting overnight. if code cleared and truck warm it doesn't come on; at least not yet.

I plan to test the temp sensor for the EGR, but I'm thinking if not that maybe the EGR Vacuum Modulator Valve may be bad. Any suggestion?

I'm on the forums because I'm not willing to take to dealer yet. Haynes manual is pretty much useless since it covers so many years and tends to ignore the 2.7l 4 cyl engines.

 

egr isn't supposed to be on at all until your car is warmed up iirc. so any flow would be excessive. so whatever tells the egr when to turn on may be at fault.

 

Thanks 98tacoma27, that was my next thing, but I can't find where it is located on my truck using any of the illustrations I've seen. Do you know where I might find that on the 2.7l w/4wd? Is it one three sensors attached to the charcoal canisters on the drivers fender?

I tested the egr temp sensor tonight and it is within expected range for the temp of my intake manifold. Within spec at 125 degrees F so I'm confident it can't be that. I'll check it again in the morning when completely cool, but I'd be surprised if it were off but dead on at 125 deg. Just isn't typical for a simple circuit like that.

I also applied vac to the EGR Vac Modulator valve and checked for flow changes and that device also appears to be OK. I guess I'm on to the VSV if I can locate it.

 

located the VSV for EGR deep inside the intake manifold. Not the kind of job to do when the engine is even a tiny bit warm. tested it according to specs and the first time the Ohms tested OK, as did air flow. when applying power to the VSV it worked right the first time but then tried again and it didn't open/close. checked Ohms again and it failed. called first dealer, they were out of stock but could order for 83, they told me another dealer had it in stock; went there and they wanted nearly 120 for it and had to talk them down. learned two valuable lessons; don't try to change the VSV when engine is warm, and comparison shop each Toyota dealer when buying OEM parts. 0402 code hasn't come back on, but it has only been two days. hopefully that took care of it.

 

Steve, With the 0402 code showing excessive flow cause a power loss? What if I block off the EGR completely?

 

I didn't notice a huge difference in power but mine was intermittent and my wife drives the truck more often than me. She said it didn't feel as strong. Since the mileage in city driving dropped to 15.5 MPG which is about 1 mpg worse than running in 4WD that tells me it did loose power. Much more fuel used for the same amount of work/distance.

I personally would not block off the egr or the vsv for egr. That would just cause it to throw different codes. Plus with the increased fuel consumption I would expect the converters and possibly O2 sensors to fail sooner from the excess carbon and and higher exhaust temps.

 

Did either of you ever solve your P0402 code problems?

I just popped the same code, and it was when the truck was cold as well.

 

yes, it ended up being that VSV for EGR vacuum switch. it has been months and the light hasn't come back on and it passed state smog inspection.

 

I have the same code for my 3.4L. Where is the EGR valve located and how do I clean it? Can I use manifold intake cleaner spray or MAF cleaner?

Thanks.

 

I keep getting a pending P0402 code from my Ultra Gauge. I ignore it as no engine lights comes on, however I thought it might have to do with this... What else could it be?

 

On a 3.4l? I'm not sure - I know that on the 2.4l that code indicates "Exhaust Gas Recirculation Flow Excessive Detected (Only for 3RZ–FE)" according to the shop manual. Shop manual goes on to say that it could be the following likely causes:
- Short in EGR gas temp. sensor circuit

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EGR gas temp. sensor
- Open in VSV circuit for EGR​

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- VSV for EGR​

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- EGR valve stuck open
- ECM

I tested each but, not in the order they list because I couldn't see the VSV. When I found the VSV I tested it several times and found that sometimes it passed and sometimes it didn't.

If it is a pending code I wouldn't worry about it until it actually makes the check engine light come on and stay on. If I understand the computer system correctly it has to read the fault code twice before activating the check engine light. IMHO it is too time consuming to find an intermittent problem unless you it is acting up when I'm testing. ​

 

i have a 99 toyota prerunner with 31s b/f goodrich tires.and there are no problems at all with that size tire.anything bigger would be.my erg just went out,and my engine does not run as smooth,and smells a little burnt.128.000miles and never had any major problems.its moost likely your erg valve.you will get more knock and more smoke.