Bizarre Engine Behaviour

[DANSLEX]

I've noticed something bizarre with my engine. Very rarely when the car comes to a complete stop, the engine revs become very erratic, going past 1000 rpm for a small moment, then back down to 400rpm and about to stall, then back up again and so on, for maybe two seconds, then settles back to normal idle. Very random too, it might occur twice or three times in one week, and at other times it might be three weeks before it reoccurs again. I spoke to the dealer and they know about this issue but have no solution for it. Apparently Lexus techs has been looking at it for a long period of time, and aren't sure what causes it etc. Very hard to diagnose as well, due to the randomness of it all. Was told it isn't detrimental to the enigne, thankfully.

Just wondering, do any of you get that as well?

[LEX51S]

I've noticed something bizarre with my engine. Very rarely when the car comes to a complete stop, the engine revs become very erratic, going past 1000 rpm for a small moment, then back down to 400rpm and about to stall, then back up again and so on, for maybe two seconds, then settles back to normal idle. Very random too, it might occur twice or three times in one week, and at other times it might be three weeks before it reoccurs again. I spoke to the dealer and they know about this issue but have no solution for it. Apparently Lexus techs has been looking at it for a long period of time, and aren't sure what causes it etc. Very hard to diagnose as well, due to the randomness of it all. Was told it isn't detrimental to the enigne, thankfully.

Just wondering, do any of you get that as well?

my car doesnt do this I dont mean to sound like a know it all or anything cos imagine the lexus techs are pretty switched on. but it sounds exactly like a failing or several failing spark plugs thats the exact diagnosis for that as well.

how many kms is it due for spark plug change?

[Poisson]

My Benz does this sometimes. It's the auto transmission changing down through the gears as you come to a halt. Can't say I've noticed it on my Lexus though.

[DANSLEX]

Hmmm, would have to go through the service history coz can't remember if plugs were changed. It's got 66K kays on the clock, due for a service in about 4K kays. I wouldn't want to sound like a know it all either, but often those techs overlook the basics. My uncle took his 5 series bmw once to get a problem fixed. Can't remember what it did exactly, but they even flew in people from germany to take a look and couldn't figure out, they were examining the ecu and so on. Then an apprentice simply changed the coilpacks and it was fine. So yeah, maybe it is something simple they are overlooking.

I just want to gauge how common it is among you guys, as apparently most IS250's suffer this problem, according to the dealer. Only that it is so rare you only notice it after a while. Had the car for over a year and it only came to my serious attention a couple of months ago. Sometimes nothing happens for two weeks, I also do a lot of kays too (over 25K per year)...

I might set my display to show gears and see where it's at when it happens. I don't think it's gears though, the car is stopped.

[LEX51S]

Hmmm, would have to go through the service history coz can't remember if plugs were changed. It's got 66K kays on the clock, due for a service in about 4K kays. I wouldn't want to sound like a know it all either, but often those techs overlook the basics. My uncle took his 5 series bmw once to get a problem fixed. Can't remember what it did exactly, but they even flew in people from germany to take a look and couldn't figure out, they were examining the ecu and so on. Then an apprentice simply changed the coilpacks and it was fine. So yeah, maybe it is something simple they are overlooking.

I just want to gauge how common it is among you guys, as apparently most IS250's suffer this problem, according to the dealer. Only that it is so rare you only notice it after a while. Had the car for over a year and it only came to my serious attention a couple of months ago. Sometimes nothing happens for two weeks, I also do a lot of kays too (over 25K per year)...

I might set my display to show gears and see where it's at when it happens. I don't think it's gears though, the car is stopped.

According to lexus log book servicing (every 15 000km) spark plugs are replaced at 90k service. other then that they are not even inspected (acording to log book). but as for helping gauge this problem i have 54k on the clock and nothing like that.

[DANSLEX]

Ok, will check the sparkplugs myself then. It runs fine otherwise so yeah, kind of doubt that is it, but hey, might as well check.

[Sapphire Cam]

The only thing with respect to varying idle speed I've heard from the technicians is if the A/C is on and you're idling (whether in traffic, at the lights or pulling up to stop), and the RPM might drop down to about 500, but then the computer gives it a little kick start. This is nothing unusual I've heard - however your issue sounds a little more exaggerated. Get it looked at.

[DANSLEX]

Nah, happened a few times without aircon... hmmm...

[aintfunni]

hmmm... I've experienced this last weekend & probably about another 2 times over the last yr of mine when I had my A/C on... My didn't sound as erratic as DANSLEX's experience, but I did notice the idling change.

I was going to mention this at my next service that is due in May.

[IronFist]

It's random but it doesn't just happen with the A/C on also without.

I think it's more of engine management thing, the guys in the US say during idling the engine sometimes goes lean to save fuel and the ECU detects this and adjusts accordingly at times can be abrupt.

There's been no known solutions to this apparently. It's a bit annoying at times when you think you accidentally slip off the brake pedal but you didn't :P

[DANSLEX]

Yeah, it is probably ECU related. Dealer told me Lexus technicians have driven these cars with IT equipment plugged in for two months trying to figure out what causes it. It's not detrimetnal to the engine so that's good, however it can be annoying!

[illusivedreams]

Yeah, it is probably ECU related. Dealer told me Lexus technicians have driven these cars with IT equipment plugged in for two months trying to figure out what causes it. It's not detrimetnal to the engine so that's good, however it can be annoying!

PLugs will not cause descibed issue.

I think it is your TPS.... or such, I would get the techs to bench test most of the sensors in the car Maf ,O2,TPS and give the connections a clean while theya re there..

Gear box should not casue revs to drop at isdle as it should already be in 1st at stop/

Good Luck buddy

[shark111]

My is250se auto does almost the same thing! depending on the manner of braking .as im coming to a stop and the gears are dropping the revs drop quite low causing a slight vibration thinking your car is going to stall before shifting into neutral..no idea what causes it,but when the car goes to lexus in south africa i will enquire..

[dis-lex-sic]

Yeah, it is probably ECU related. Dealer told me Lexus technicians have driven these cars with IT equipment plugged in for two months trying to figure out what causes it. It's not detrimetnal to the engine so that's good, however it can be annoying!

PLugs will not cause descibed issue.

I think it is your TPS.... or such, I would get the techs to bench test most of the sensors in the car Maf ,O2,TPS and give the connections a clean while theya re there..

Gear box should not casue revs to drop at isdle as it should already be in 1st at stop/

Good Luck buddy

Yep O2 sensor was the first thing that bounced around in my head.

[D1 Pete]

tps or even something simple as a vacume leak maybe..

[ldc]

Sometimes when you run over a crack/bank on the road (in parellel), the wheel gets caught up in it, hence u get the feeling the car is pulling to the sides. Hope you have eliminated this?

[dis-lex-sic]

Maybe ask the dealer to hook it up to the IT in the workshop and clear any "codes" it might have.

[last1]

I get this "almost stall" thing happening once in a blue moon. Kind of scary when it's happening - feels as if the car is about to stall, then quickly back to normal, as if nothing happened.

Good to see I wasn't the only one.

I'm not 100% sure, but I think it's more likely to happen when I'm accelerating hard at one moment, and quickly coming to a stop the next. Problem is I've never been able to replicate it when trying to bring it on. It just happens on occasion, and out of the blue.

[Howiefied]

You might want to have a look at your air flow sensor, give it a quick spray with electrical cleaning fluid. Shouldn't take more than a few minutes to do.. at least you'll be able to rule that out quickly.

[aintfunni]

I was calling Lexus dealers in Sydney for a 30K service quote today & mentioned that my car feels like it wants to stall when idling at times... I was describing this issue and the first thing he asked was what fuel I was using??!

This car has only ever had V-Power & done 22K

Then he goes that if you use E10 it will go away! All the cars they have there are all fueled up with E10 & don't have this problem.

I was thinking to myself WTF??

What do you guys reckon?

[IronFist]

The dealer probably thinking your using low octane fuel. I've only stuck with 95+ octane fuel which isn't E10.

It's a common set back which no one knows what causes it. I get it like once a like 3-4 months - I've just learnt to live with it.

If it's occurring often then it's an issue and hopefully you can replicate it to the dealer

[Howiefied]

I was calling Lexus dealers in Sydney for a 30K service quote today & mentioned that my car feels like it wants to stall when idling at times... I was describing this issue and the first thing he asked was what fuel I was using??!

This car has only ever had V-Power & done 22K

Then he goes that if you use E10 it will go away! All the cars they have there are all fueled up with E10 & don't have this problem.

I was thinking to myself WTF??

What do you guys reckon?

I reckon he's sniffing a bit too much of E10. Seriously doubt by downgrading your fuel will your problems go away.

[Aircon]

I was calling Lexus dealers in Sydney for a 30K service quote today & mentioned that my car feels like it wants to stall when idling at times... I was describing this issue and the first thing he asked was what fuel I was using??!

This car has only ever had V-Power & done 22K

Then he goes that if you use E10 it will go away! All the cars they have there are all fueled up with E10 & don't have this problem.

I was thinking to myself WTF??

What do you guys reckon?

try it...it can't hurt