Toyota suggests testing the EGR valve by pulling a vacuum on it and seeing if it holds. But how long should it hold? Is 2 minutes ok? Should it hold indefinately, say 10 minutes? I would appreciate hearing from anyone with knowledge or experience on this subject. The car is a 96 Camry with 112K miles.
For any EGR valve, if it holds 20 psi vacuum for 30 seconds, I consider it OK. I don't think the Toyota one is any different.
The more important thing is the Toyota EGR pipe plugs up with carbon. So besides checking the vacuum, you should remove and clean the ports and pipe if you suspect EGR valve is not working. Also check your PCV and IAC valves are not plugged the same.
fbrustman wrote:
Johngd, thank you for your reply. I'll guess my EGR valve is ok. I cleaned the EGR pipe and the IAC valve so that isn't it. I will try cleaning out the EGR valve and seat next. Over looked that when I had it off. Is the filter in the vacuum modulator critical, i.e. must it be clean as a whistle? Besides my lungs I don't have a ready means of blowing it clear.
BTW, what was the problem that caused you to look at the EGR valve? Did you get OBD codes?
The modulator mangnifies the vacuum to a point strong enough to operate the EGR valve. The filter is just like an air filter no need to be "sparkling clean".
Before you take the EGR valve off again,if you have a vacuum pump operate the EGR valve and see if the engine stalls or runs rough. If so, you don't need to clean the valve as it obviously works. Now whether there is vacuum to operate it is another matter. For instance, the vacuum switching valve not closing, modulator not working and other problems.
What symptoms are you see> Johngd, thank you for your reply. I'll guess my EGR valve is ok. I cleaned
johngd, Thanks again for replying to my questions. I'll try pulling a vacuum on the EGR valve next and see if the engine stumbles. How did I get into this? For several months the car had a cold stalling problem in the AM. At my brothers prompting I started searching the web for clues. That lead me to the IAC valve. I cleaned it once, sort of, without removing it from the throttle body. That helped so later on I got the IAC valve off and cleaned inside it. That did the trick very well for the cold stalling. But, a week, or so, after I cleaned the IAC valve the check engine light came on. I couldn't get it to flash codes. The engine seems to be transitional between OBD-I and -II. Took the car to a parts store. Their OBD-II scanner didn't fit the under dash connector. A mechanic I trust checked it and told me the vacuum proportioning valve was the likely source. He replaced it, but the check engine light came on again after a few trips around town. I don't want to spend a lot of $ chasing possible sources of the code(s), so I started checking out the other parts of the EGR system. Since then the Check engine light has come on after a couple of trips around town, but on other occaisions I've done 70 mile trips at highway speed without the light coming on (a relatively cool day). I wonder if hot weather has anything to do with what is happening. Thanks again. Fred B
If that's how you started getting problems I would start by checking all vacuum hoses are connected and are not cracked after working near them. It's very easy to leave one loose behind the manifold and air intake housing where you can't see it or thought it was connected.
*ALL* 96 model year cars use OBD-II even those built in 95. Your local parts store should have the correct reader for borrowing free as most do these days. This is the easiest way to tell where the problem is.You said "vacuum proportioning valve" I take it a "vacuum switching valve"? It opens and closes a vacuum line via a 12v electrical signal. If so this is also a common problem with Toyotas on the air cleaner housing for evap purge. But this doesn't appear to the problem as you found out.
There are too many two-cycle codes to know where the problem is (idle control, fuel, egr, evap, coolant temp, emssions, etc). But if you can't find a parts store with free OBD-II reader, Pep Boys I think does it for $20.
If the problem showed up after you removed and cleaned the IAC I think vacuum leak/hoses is the most likely source of problems.
Hi Johngd, Thanks again for more clues. I'll look over the hoses around the throttle body. When I had them off they looked in good shape, but you never know. You mention hoses out of site not getting reconnected as a potential cause. About 6 weeks ago the timing belt, water pump, etc. was replaced. Is there likely to be a vac hose(s) in that area I should seek out? Fred B
In addition to Haynes repair manuals, the following web site has many good technical articles check it out:
I assume you have one vacuum pump with a gauge on it and maybe a short vacuum hose if needed to bypass the EGR VSV between the EGR valve and the modulator.
I would do the following:
-- Make sure your port P of the EGR Modulator connects to the port E on the throttle body and port R to port R (see page 3 of the EGR article).
-- make sure the wire to the engine coolant sensor near the IAC is ok
-- Connect your vacuum gauge to the Evap port on the throttle body to see how much vacuum your engine is pulling while running. This has the larger hose connected to the VSV on the air cleaner housing.
Q1: Do you see low vacuum of 3 in/Hg? This is what the modulator should pull on the EGR valve. (page 7)
Q2: Does the engine run rough? (page 7)
You should answer yes to both questions. If not you can repeat the above with a direct hose connection between the EGR valve and the modulator's port Q this bypasses the VSV. If this works, then the two hoses going down to the EGR VSV and/or the VSV may be suspect. Make sure the vacuum hoses are connect to the right ports on the VSV behind the manifold (You said you had this VSV changed out?)
"" wrote: > BTW, what was the problem that caused you to look at the EGR > valve? Did > you get OBD codes? > > The modulator mangnifies the vacuum to a point strong enough > to operate > the EGR valve. The filter is just like an air filter no need > to be > "sparkling clean". > > Before you take the EGR valve off again,if you have a vacuum > pump > operate the EGR valve and see if the engine stalls or runs > rough. If > so, you don't need to clean the valve as it obviously works. > Now > whether there is vacuum to operate it is another matter. For > instance, > the vacuum switching valve not closing, modulator not working > and other > problems. > > What symptoms are you seeing? > > fbrustman wrote: > > Johngd, thank you for your reply. I'll guess my EGR valve is > ok. I cleaned > > the EGR pipe and the IAC valve so that isn't it. I will try > cleaning out > > the EGR valve and seat next. Over looked that when I had it > off. > > Is the filter in the vacuum modulator critical, i.e. must > it be clean as > > a whistle? Besides my lungs I don't have a ready means of > blowing it > > clear.
I agree with comment about carbon build up - I have had ?96s & ?99s with the exact same problem - just clean the build-up out. My rule of thumb on the vacuum test is to operate the valve manually (when removed from the engine) and block the vacuum line with my finger. In this way you can see if the diaphram is leaking. The usual symptoms are for the engine to idle very badly as the EGR sticks in the OPEN position.
"JMerr10385" wrote: > I agree with comment about carbon build up - I have had '96s > & '99s with the exact same problem - just clean the build-up > out. My rule of thumb on the vacuum test is to operate the > valve manually (when removed from the engine) and block the > vacuum line with my finger. In this way you can see if the > diaphram is leaking. The usual symptoms are for the engine to > idle very badly as the EGR sticks in the OPEN position.
What I have seen work is apply vacuum to it, then rev the engine up for about 30 seconds, off and on the throttle. This can help blow out the "pellets" that form from carbon.
The answer to all the problems with "insufficient EGR flow" (MIL code PO 401)was plugged vacuum ports in the throttle body. When I cleaned the IAC valve I saw all the sludge that had accumulated in the throttle body. So I decided to clean it too. Using a rag I wipped it all out. But, in doing so I unknowingly smeared sluddge into two of the three vacuum ports. Cleaning them solved the problem. My thanks to JohnGDoyle for his help and guidance. I wouldn't have figured it out otherwise.
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