Rough Idle

[b_driver]

Hi,

Here is the problem: the engine on my 2000 camry 4 cylinder 5SFE runs rough at idle, especially when A/C is on and on stop lights. Otherwise no problems at all, no check engine light.
I replaced spark plugs twice, first I tried NGK then Bosch.
Cleaned throttle body.
Cleaned fuel injectors at toyota dealership.
Tried new plug wireset.
Replaced throttle position sensor (TPS)
Replaced PCV.
Cleaned EGR valve.
No results, the same rough idle like a missfire.
The sparkplugs I replace had no smell, no oil on them, no gas.
Also I noticed strange sound from the exhaustpipe like 'pa-pa-pa....'.
Today I disconnected the oxygen sensor in the engine compartment, no changes at all, I drove awhile and no check engine light.
Could it be the oxygen sensor causing the rough idle? And why there are no error codes?

Thank you.

[JvR]

I had exactly the same problem.
The valve space was not oke

[Eye8Pussies]

it's possible

but have you checked for vacuum leaks? a tell-tale sign of a vacuum leak is a bad idle, and unless you have a MASSIVE leak, it won't show under load/throttle

[b_driver]

Originally Posted by JvR

I had exactly the same problem.
The valve space was not oke

So do you think I need to adjust the valves? Is it possible to do it myself? Or is it better to go to the dealer?

[b_driver]

Originally Posted by Eye8Pussies

it's possible

but have you checked for vacuum leaks? a tell-tale sign of a vacuum leak is a bad idle, and unless you have a MASSIVE leak, it won't show under load/throttle

Actually I checked every sigle hose and couldn't find any leak. I also replaced some of the hoses even if they were ok.

[marc780]

Is it a high mileage car? This is an important factor in such a diagnosis.
-Spray carb cleaner at every possible location for a vacuum leak - hoses, hose connections, gaskets. If idle changes at any point, you've got a vacuum leak
-throttle butterfly or aluminum throttle intake on which it touches is worn out and allowing too much air at idle. (do you own a stick shift? Its not uncommon on these cars).
-timing may be way off
-timing belt may be worn or worn out, and maybe missing a tooth or two and has jumped time
-low engine compression due to a bad valve or two (the exhaust valves are the usual culprits) or worn rings
-bad egr valve or clogged egr line

None of these conditions would necesarily cause a code or the CEL to blink on.

[b_driver]

Absolutely forgot to mention that the mileage is 111000 miles and it is auto transmission.
Timing belt was changed 2000 miles ago, no changes, the same rough idle.
It seems to me that some valves causing low engine compression. I believe that it is a regular maintenance on camrys to adjust valves, right?
The exhaust pipe makes 'shooting' sounds and when you close the pipe with a hand the air fluctuations make the hand shake. Sorry for the bad explanation.

[JvR]

'pa-pa-pa....' (plopping) sounds like, fuel that is not burning in the engine but in the exhaust.
So i think, the valves are not closing enough.

I have never seen that a mechanic adjust the valves without an order from the customer. I have always asked the mechanic when my car has more then 100.000km on it.
(Chilton Camry repair manual advice every 60.000 miles to check the valves...)

You can do it your self, but i advice not. I must not be expansive, it is easy todo because it is a 4 cyl. (V6 is very expansive, because the mainfold must be taken off....many hours)

vacuum leaks are of course also possible. (read this, a way to find the leak: http://www.toyotanation.com/forum/t207192.html)
I am not a mechanic and not a expert. So don't blame me when i am wrong.



(sorry for my bad english)

[b_driver]

Why when I disconnect the oxygen sensor and drive nothing happens? The same rough idle, no check engine light?

[b_driver]

Today I tried a bottle of Seafoam. Actually 1/3 of a bottle ,
No effect at all, probably my engine is clean enough. By the way there was a little smoke, not a cloud of smoke like others have.
One more thing I tried today is I opened throttle valve a little bit and fixed it with regulation bolt. The RPM rised from 550-600 to 700-750. So the engine works smooth now. However I don't think it is right because the throttle plate valve should be closed at idle, right? Idle speed valve should correct the RPM. I assume that this idle control valve is stucked, clogged or not working at all.
Any suggestions?
Also I noticed that when I turn on A/C the idle remains the same or even drops to 500-600rpm.

[nuchieboy]

not to thread jack but how do u raise the idle...i wanna raise mine 2 like 850-900 rpms at idle

[b_driver]

Originally Posted by nuchieboy

not to thread jack but how do u raise the idle...i wanna raise mine 2 like 850-900 rpms at idle

That's easy, but not right actually. When you look at throttle body you can see round thing with two cables attached to it: throttle cable and cable that goes to transmission. That thing (i don't know what is it probably trottle plate regulator) can be adjusted by bolt marked with yellow paint. Just try to attach something between this bolt and throttle regulator in order to keep factory default in case you want to return to previous rpms.
Hope I explained it well.

[JvR]

maybe this will help you:

To the Knowledgeable: Post-Boost Stalling Problems

(read the post from Tony the Tiger)