1997 Es300 Erratic Engine Rpm

[dayaln]

Hi All:

I have 1997 ES300 with around 110,000 miles on it and I love the car! Around last year, I noticed a strange problem. I noticed that the engine was rather rough while I am on the freeway, once I stopped, the engine RPM was all over the place... Let me explain, it does not idle properly, it will drop to around 200 rpm or so and then suddenly jump back to just below the normal idle speed of 750 (for my car). Basically jumps between rpms and shakes the car as it is going to stall (it does not actually stall).

This problem happens only once in a while, many days I am fine. Once the engine cools down for a few minutes, everything is ok again... Almost all long trips on a freeway cause the problem.

I think this is what I noticed - if you are coasting a down-hill and then push on the accelerator momentarily and then let go - then this problem comes up... Some times, this happens with in a few minutes of drive from home. Most times, I can drive my 20 miles to work without any problems.

I can not consistently repeat the problem... I do not like to go on fishing expeditions trying to fix this problem with my money while the repair guys experiment trying to guess what is broken...

Engine has been tuned after this problem came up and I had an injector clean up service - did not help...

Could anyone help? Did anyone else have similar problems.

Thanks all!

Dayal

[supreme300]

is it stik or auto??

[steviej]

three possible problems that are very common to Toyota/Lexus engines that cause what you describe.

1. your idle air control valve is dirty, most likely with carbon build up. Easily cleaned, moderately expensive to replace. Do a search on this as it has been discussed many times and several members have successfully cleaned there own.

2. the accordian like air tube that goes from the air box to the throttle body has a hole or a crack in it. Cheap and easy to replace. If it has a hole or crack, more air is getting in to the throttle body than the ECU thinks is. This will cause rough running conditions especially at idle.

3. your throttle body is dirty. same solution as #1.

steveij

[SKperformance]

iacv ,carbon ,throttle body

[SW03ES]

is it stik or auto??

All ES' after 93 are auto ;)

[dayaln]

Thanks all for the suggestions, I will try them and report back...

Dayal

[amf1932]

Does the engine burn any oil? I was thinking that the back pressure from decelerating causes oil to get into the combustion chamber which could foul the spark plug(s) temporarily. Check your PCV valve.

[steviej]

excellent point amf1932, another possibility and a cheap fix at that.

steviej

[dayaln]

amf1932:

"Does the engine burn any oil?" - Hmmmm, I do not know how I can find that. I noticed that the exhaust smells bad lately, almost smells like you smell unburnt gasoline. The fuel efficiency i.e miles per gallon has not changed though, at least from what I can tell. May be you are on to something. I wil ask the repair guy to check the pcv valve as well.

Thanks!

Dayal

[amf1932]

"Does the engine burn any oil?" - Hmmmm, I do not know how I can find that.

Do you have to add any oil during change intervals and if so how much?