Idle Problems

[DaveinTX]

Hi all, I'm kind of new to these forums. Looks like a great place to get advice so I'll give it a try. I have a 98 es300, 105k miles. I perform all maint. myself, the only problem this car has ever had was a o2 sensor heater error, replaced the sensor and all was well.

Recently a new problem has come up. If I only drive the car for 10 or 20 min. it does fine. But when I drive it for over about 40 min and it gets hot, the car idle is not steady, it's like it cuts out about every 2 sec., sounds like it's going to stall, then revs to about 1k, it will just sit there and cycle like that, rpm going back and forth from about 500 to 1000. If I turn the car off for a min. and restart it still does it. If I give it gas it will rev up and smooths out about 3k but anything under it still has a small cycle in the engine rpms. I also took the gas cap off for a sec. in case there was a vacuum in tank but no change.The other strange thing was the exhaust seemed to have kind of a sulfer smell. No warning lights come on on dash.

If I let the car cool for about 20min. it runs fine again. I have run some lucas fuel treatment in about the last 5 tanks but no help. the car has clean air filter, almost new spark plugs, I need to check my maint. notes to see if I have changed the fuel filter I'm not sure.

I plan on checking how old the fuel filter is, I have also read on here about a idle control valve and am kind of wondering if that could be the problem. I don't mind trying to clean parts but I can't afford to just start changing parts, I may end up biting the bullet on this one and just take it to the dealer but I'll be very upset with myself it it turns out to be something simple.

Any suggestions would be very much appreciated. Thanks-Dave

[camlex]

open TB, clean plate and spray lot of cleaner in IACV hole.

Thanks,

[DaveinTX]

Thanks I'll give it a try. -Dave

[RS1013]

Thanks I'll give it a try. -Dave

On my 97 ES300, my mechanic replaced the mass air flow sensor (new dealer part) and the car's idle has been fine. Total cost of parts and labor including dignosing $325.

[Lucky13]

Could be air flow sensor.. fuel pump.. wireing for the fuel pump. Prob not the fuel filter though, not if it started happening all of a sudden.

[DaveinTX]

Thanks for the replys guys. I was thinking about the fuel pump, but whatever it is the engine temp seems to be a factor, it has only done it to me about 5 times but every time the car was very hot. I doesn't seem like the fuel pump would be sensitive to heat back there in the gas tank, but i guess it could. I was thinking maybe the idle control valve has some build-up in it that gets sticky when hot and is making the valve stick, when it breaks loose it overcompensates and goes too far , causing the "cycling" idle. when it's cool maybe the build-up is just not sticky enough to cause the valve to stick.

Thanks again for all the ideas, they are all on my list to check. I have too many other issues going on in my life right now so it's going to be a week or two before I have time to dig into this, but I will definitly update the post when I do, thanks again guys for the suggestions, any more would be welcome. This car is being handed down to my daughter very soon (I'm using for a spare on my days off right now) and I want to make sure it's good to go before letting her have it. Thanks -Dave

[Matej]

Hi all, I'm kind of new to these forums. Looks like a great place to get advice so I'll give it a try. I have a 98 es300, 105k miles. I perform all maint. myself, the only problem this car has ever had was a o2 sensor heater error, replaced the sensor and all was well.

Recently a new problem has come up. If I only drive the car for 10 or 20 min. it does fine. But when I drive it for over about 40 min and it gets hot, the car idle is not steady, it's like it cuts out about every 2 sec., sounds like it's going to stall, then revs to about 1k, it will just sit there and cycle like that, rpm going back and forth from about 500 to 1000. If I turn the car off for a min. and restart it still does it. If I give it gas it will rev up and smooths out about 3k but anything under it still has a small cycle in the engine rpms. I also took the gas cap off for a sec. in case there was a vacuum in tank but no change.The other strange thing was the exhaust seemed to have kind of a sulfer smell. No warning lights come on on dash.

If I let the car cool for about 20min. it runs fine again. I have run some lucas fuel treatment in about the last 5 tanks but no help. the car has clean air filter, almost new spark plugs, I need to check my maint. notes to see if I have changed the fuel filter I'm not sure.

I plan on checking how old the fuel filter is, I have also read on here about a idle control valve and am kind of wondering if that could be the problem. I don't mind trying to clean parts but I can't afford to just start changing parts, I may end up biting the bullet on this one and just take it to the dealer but I'll be very upset with myself it it turns out to be something simple.

Any suggestions would be very much appreciated. Thanks-Dave

Faulty TPS, change it before it goes wrong. It is cheap part. If it's adjustable, don't mess with it, let your car mechanic adjust it.

[DaveinTX]

Well guys, I started with the idle control valve and it looks like that was the problem. I didn't remove the valve but I did remove the connector and then the electronic portion. It looks like the shaft to turn valve has a magnetic cylinder on the end. When I first turned it it was sticky, after spraying inside valve with t.b. cleaner it loosened right up. the electronics portion where the connector plugs in is just layered plates with a hole in the middle for the magnet cylinder, looks like a voltage is applied to plates to turn the magnet (shaft on valve). So since there are not any gears or belts turning it just a magnetic field (like a brushless elec. motor) I'm not surprized that it starts getting stuck when dirty. I also noticed on the elec. part, the magnet had been rubbing the upper part of the plates, they were polished and slightly worn where it had been rubbing, so when i re-installed I pushed up a little to try and stop that.

As soon as I drove the car I noticed the difference, I think I may have been wrong about it being fine when cold, because now it runs (idles) a little higher and much smoother. To all that replyed thank you very much for the help all, It took all of 20min. and I'm sure saved me a couple hundred from the dealer.