rpm cycling

[mr2kx]

The rpm on the car after driving it for awhile will sometimes hover up and down between 500 and 1000 only while at a complete stop (does not stall). I recently changed the IAC valve thinking for sure that was the issue but it did not fix it. Now I think it could be a vacuum hose check valve that may not be open/closing properly? Or a sensor of some sort but probably not since no cel. any thoughts?

[dc_98_cam]

Year? engine? miles? Camry?

Sometimes the engine coolant temperature sensor can go out .... Do you have a multimeter to check resistance ... and maybe a thermometer?

Seems to be temperature related ...

Your air filter ok?

[LostSouthernStar]

Is your A/C on when this occurs? Sometimes when my engine is under load when idling and the A/C is on, my RPMs will hover around the 700-1000 RPM range...this is normal in MOST cases, though I can't say the same for your case because I do not know the full aspects of your vehicle, but it is a good place to start.



Also, is your Overdrive engaged? When it is not turned on, the engine revs much higher then it normally when you have O/D switched on.



If neither of these cases are true for you, then I would recommend having a professionally trained mechanic investigate.


Use a ScanGuageII or UltraGuage to check out your OBDII to see if any trouble codes show up, this may answer some of your questions.



Hope this helps! God bless!


-LSS

[mr2kx]

Sorry I did not mention, The car is a 95 toyota camry, 4cyl. I think the car has a abnormaly high idle (1100 in park, 1000 in drive; even higher with a/c but thats normal)

I had the coolant temp sender replaced last yr with a aftermarket part.

It cycles when the a/c is on or off, does not matter. Overdrive is not engaged.

Would the engine have a code stored without a CEL? I didnt think to check for codes with no light.

[hill8570]

Originally Posted by mr2kx

Sorry I did not mention, The car is a 95 toyota camry, 4cyl. I think the car has a abnormaly high idle (1100 in park, 1000 in drive; even higher with a/c but thats normal)

I had the coolant temp sender replaced last yr with a aftermarket part.

It cycles when the a/c is on or off, does not matter. Overdrive is not engaged.

Would the engine have a code stored without a CEL? I didnt think to check for codes with no light.

Probably should address the high idle first. May or may not be related to the hunting.

Most likely cause of a high idle is a vacuum leak -- one of the hoses connected to the throttle body is disconnected, cracked / holed, or fits too loosely at the connections. Check the vacuum diagram on the underside of your hood against your physical hookup, and make sure everything is correct and in good physical shape. If you suspect that a connection is leaking vacuum, spray some sort of fuel (I tend to have throttle body cleaner in my cabinet, so I use that) at the suspected leak point -- if the engine stumbles then you have confirmation.

A lesser possibility is the throttle positioner is broken, and always sticking out. The positioner is right beneath the large throttle wheel (where the throttle cables connect). At idle, disconnect the vacuum hose from it (plug the hose with your thumb to keep the vacuum from leaking) -- the positioner should stick all the way out. Reconnect the hose, and it should suck back in.

Did this high idle predate the temp sensor replacement? A sensor reading too cold can give a high idle since the ECU thinks it should be running richer than it really should. Not super likely, but it can happen. Easy enough to test with a voltmeter. If you don't have the procedure, let me know and I can forward it on via PM.

[mr2kx]

Ok, I did some investigating to find some interesting results. first off, I managed to bring the idle from 1000 to normal 800 rpm by trying to tighten a sensor plug. I noticed the sensor is somewhat loose and when messed with it (I kinda hit it and pushed it in hard) The rpms dropped significantly. I don't know what this part is, mayb a throttle position sensor. Heres the pic:

A lesser possibility is the throttle positioner is broken, and always sticking out. The positioner is right beneath the large throttle wheel (where the throttle cables connect). At idle, disconnect the vacuum hose from it (plug the hose with your thumb to keep the vacuum from leaking) -- the positioner should stick all the way out. Reconnect the hose, and it should suck back in.

I did this and it seemed to work fine. When disconnected, the thing came out and the idle went way high then i plugged it back it and it returned to normal.

Most likely cause of a high idle is a vacuum leak -- one of the hoses connected to the throttle body is disconnected, cracked / holed, or fits too loosely at the connections. Check the vacuum diagram on the underside of your hood against your physical hookup, and make sure everything is correct and in good physical shape. If you suspect that a connection is leaking vacuum, spray some sort of fuel (I tend to have throttle body cleaner in my cabinet, so I use that) at the suspected leak point -- if the engine stumbles then you have confirmation.

I sprayed throttle body cleaner on most the vacuum hoses I could find and the engine was not stumbling at all.

I also disconnected these 3 vacuum lines while the engine was running and none of them had any vacuum and the engine seemed fine w/o them being connected:



however those 3 vac lines did seem a bit frayed just at the tip from when i used pliers to remove them a while back. I know that was dumb but it doesn't have a leak there because i sprayed that whole area with the cleaner and the car did not hesitate.


Unfortunatly there is no vacuum diagram under my hood. =(

[mr2kx]

Yup it is the TPS. I am going to try and clean the connectors before buying a new one. Ill let you know if the rpms still are hunting after. I found this part for 60-80$ on ebay. At the very least I may have solved the high rpm.

[mr2kx]

Ok TPS only solved the high idle. I brought it to the stealership and they dont know whats wrong with it but are guessing to start with replacing the CTS. is the CTS different from the I4 and V6 engines? I see lots of CTS for 30$ on ebay but no listings on the I4 engine. anyone know a cheap place to buy it? (30-50$ mayb?)

[dc_98_cam]

Originally Posted by mr2kx

Ok TPS only solved the high idle. I brought it to the stealership and they dont know whats wrong with it but are guessing to start with replacing the CTS. is the CTS different from the I4 and V6 engines? I see lots of CTS for 30$ on ebay but no listings on the I4 engine. anyone know a cheap place to buy it? (30-50$ mayb?)

I think you mean Engine Coolant Temperature sensor ... ECTS .... right?

I read that you had replaced the ECTS in an earlier post ... not OEM part.

[mr2kx]

I think you mean Engine Coolant Temperature sensor ... ECTS .... right?

I read that you had replaced the ECTS in an earlier post ... not OEM part.

If there are 2 coolant temp sensors in the car (i assume there is) then I do not know which one was replaced the 2 yrs ago. (the cts or the ects) The temp gauge stays working during its hunting idle.

here is a search i looked up for cheap parts... looks good right?

http://motors.shop.ebay.com/i.html?_...506.m270.l1313

one of these should be fine you think?

Edit:
none of the parts on ebay say it will fit a 4cyl.. are the 6cyl ECTS the same thing?

[dc_98_cam]

... Looking at the wiring diagram for '94 5s-fe. There is only one ECTS ... described as "Engine Temperature Coolant Sensor (EFI Water Temperature Sensor)".
It would have one light green wire going to it, and also one brown wire.

There is a separate part called a 'Water Temp Sender' ... This is what you replaced earlier ...

The ECTS looks like it would be worth a try replacing it ... seems to be associated with the EFI ... electronic fuel injection system.

You would want to be certain that you get the correct part for your car.

The parts diagram shows that the ECTS is located at the right end of the cylinder head .... if you are standing in front of the car.
It should be a few inches below the valve cover ... at the extreme right.

[hill8570]

Before you spend $$$ on a coolant temp sensor, just disconnect yours after the engine is warmed up. That causes the ECU to default to "engine warmed up" (it'll also turn your CEL on, but it'll go away again once you reconnect). If the problem goes away, have at replacement. FWIW, I don't think I've ever seen a duff ECT cause hunting, but I guess there's always a first time.

BTW, the part number is 89422‑20010 . Most of the cheaper online dealerships sell it for $50. Town & Country Toyota over in North Carolina is doing free shipping for August, so that's one option. http://www.trademotion.com/partlocat...&siteid=215498 or 704-972-3840 .

[dc_98_cam]

^ +1 on what hill8570 said. Try that and see what happens.

[fenixus]

you should always use OEM sensors around the engine, especially those being a primary feed to ECU (unmonitored) ... it would save you lots of troubleshooting ... and grief ...

disconnected ECT for EFI sensor will default to 180F if I remember well, so do it after car is fully warmed up.

you can also plug a resistor into the ECT for EFI plug to cheat the ECU on temperature reading and see if it helps. refer to graph below for resistance values for certain temp ranges.



I usually replace ECT for EFI sensors as part of major tune up... did it on both cars.

[mr2kx]

I just ordered a new CTS, checking the resistance wont do because of how it is a intermittent issue. I will replace once I get it and let you know.

In the case it does not fix it I will probably junk the car although I dont want to.