Hi , my 4cyl. 95 camry was running perfect and all of the sudden it does not idle right. It normally idles around 1000 rpm, but it now drops down to 600 and back to 1000 rpm every second, at one second intervals and it does this over and over again. I cant for the life of me figure out what is causing this problem. I thought it might be an air leak in the air intake hose, so I removed it and it still does it with it taken off the throttle body. There doesnt seem to be any hesitation at all when I step on the gas or floor it. The only other thing I noticed is my fuel economy seems to be suffering badly, I havent tracked it yet for MPG but I find the needle falling fast. Any ideas would be greatly appreciated. Thanks alot.

 

IAC valve controls idle speed. Could be varying fuel pressure (bad regulator), MAP sensor or hose going to it, throttle position sensor.

The AutoZone website has some info on testing these items the sites vehicle repair guide section.

 

experience - might be the same here?

. have had two hi mile Hondas (180K, 205K) and both did it.
mechanic told me it's a sticking hi idle control valve which is (on Hondas) far in the back of the engine
and takes a lot of labor to remove the tubes and hoses to get access to it.
He figured well over $500 in labor. He suggested to just let it be, which I did.

One of the cars it went away after 1 minute of warm-up; the other it developed into a permanent situation but never influenced driving -
once you got above idle pressure on the gas pedal, the hi-idle control valve was irrelevant. So when driving, it worked well.

hopes this helps.

 

ouch!$500 that hurts a lot!!!

 

Thanks for the suggestions, I didnt have any check engine light, but I pinned the diagnostic connector with a paper clip as suggested and I came up with error codes 22 which is coolant temp sensor and another code 71 which is EGR valve. I guess i will try a temp sensor first because this is the cheapest option. Strange though I had a temp sensor go bad in this car before, and it didnt exhibit the same symptoms, They were different. The car didnt idle up and down like its doing now, but it just idled really low all the time like it was going to stall, and it was flooding out which was essentially what was happening I think because the sensor was telling the ECU that the engine was cold and it was dumping excess fuel to the engine. Im hoping it is the sensor because I cant do the EGR myself because I dont want to get in the whole mess of taking the whole throttle body off to access it, or I dont have a lift to attempt to access it from underneath! ill keep you all updated, thanks

 

Tried a new temp sensor today, and unfortunately that didnt fix the problem. So now the only thing left is the egr. I did read somewhere that it could be the crankshaft position sensor which is behind the distributor cap. Im at a loss now because I cant do the egr itself. The only other symtom it does is that when I am moving down the road when i let off the gas, the car bucks sometimes, only with no gas, then as soon as I give it gas, its fine and stops bucking. But the idling up and down is driving me crazy. And I did take a reading on my MPG, I filled up with 8 gallons and reset the trip and I only got 100 miles which is 12 MPG, ridiculous for a 4 cyl camry!

 

Which coolant sensor did you replace, the one with two wires on the water outlet manifold?

Any change in idle engine cold or hot?

EGR system is supposed to be off when:
Coolant below 140F.
Throttle closed.
Light engine load.
Rpm over 4400.

The code is tripped if:

The EGR temp sensor measures EGR gas temp at or below 158F for 50 seconds when engine coolant temp is 176F or greater and conditions are set that allow its operation (meaning the conditions previously stated have not turned the EGR system off).

Might clear the codes then try this.

With engine warm let idle for 3 minutes. Drive at 55-60 mph for 4 minutes or less. If the issue is code 71, the CEL should come on.

Might be a stuck EGR valve.

 

Finally found out what the problem was. i was running out of time and I couldnt take it anymore and decided to turn in to the toyota dealership. I exhaused every option trying to diagnose it myself but turns out it was a broken vaccum line rubber tube that ran to the manifold absolute pressure sensor. I thought I had checked every vaccum line but I overlooked this hose because I thought it was an electrical wire because there is some plastic coiling around it, never thought it was a vaccum line. I was hearing a hissing sound coming from the area but couldnt pinpoint it, it sounded like it was coming from the throttle body which makes sense because that little black box that is the map sensor is located only within a few inches of the throttle body. Boy am I glad to have this fixed, i was getting 8mpg and with the price of gas it was taking a toll on me financially. The map sensor was running too lean and it was dumping too much fuel into the engine to compensate for the lean condition.