Issue with IS250 engine

[Chris McC]

Hey all,

I hope someone might be able to help.  Two notable issues to describe the problem I am experiencing.  It is currently sporadic, it might happen around 50% of the time from a cold start. It's an auto. Owned the car for 16 months, issue started a month or so ago.

1.  Car often idles at 1k rpm, even coming up to temp.  When releasing the brake pedal to allow the car to creep forward, car surges forward too strongly - enough that if I apply no throttle, the car has gone fast enough to change into 2nd gear once before in traffic.  Strangely,  I have had situations where the car will idle at 700rpm in neutral, but still push forward strongly when put back into gear.

2. Whilst the car is still warming (I can't say at this point whether this issue might still happen at temp, it hasn't yet), if I am in say 5th gear, just holding a very light throttle to maintain speed at 40-50mph, when I come off the gas, the revs drop down to near idle then rebounds back to the correct revs. I can feel a slight jolt through the drivetrain as expected.

My current thought would be a sensor - TPS or Air mass?

Thanks for your help, Chris.

[Beamish]

 

Have a look at these videos, may be of help.

 

 

 

[Chris McC]

Very helpful, thanks Declan, I will give this a try 

[Chris McC]

I tried the Throttle body relearn but the issues are as before.  

Any other help most welcome, thanks.

 

[H3XME]

On 1/16/2024 at 9:09 AM, Chris McC said:

I tried the Throttle body relearn but the issues are as before.  

Any other help most welcome, thanks.

 

Start from the easiest fixes. Clean the MAF. Clean the throttle body. Air filter clean? When was the last time your plugs were changed? Could be the coil pack going bad. It is cold outside. Funny idle can be caused by a few things so it's difficult to tell you exactly what you need to do.. Does the car perform okay other than the issues stated above? Do you think it hesitates when you put your foot down? 

I had something similar on my 250, but mine was manual. Say if i was doing 60mph at 2000RPM, then coming down to an island and pop it into a manual to coast down the car would sometimes stall. RPMs would drop and the car would shut off. And after restarting the car and coming to a stop, it would rev hunt. Rpm would be unsettled, idling at 500rpm. Almost like a loss of oil pressure. It all went away when i cleaned the maf. Also changed the air filter but that wouldn't have affect on this as the old one wasn't that dirty.

[Mr Vlad]

If you clean the throttle body Make Sure You Unplug The Multiplug it has. Failing to do that and you move the butterfly then you'll have issues alright.

Have you got Techstream? If not then get it. Run it's diagnostics to see if there are any hidden codes.

And as Lucas mentioned. Check the plugs and coil packs. How many miles on your car? You could have a carbon build up issue which can cause running issues. 

Do you know the cars service history?

[Chris McC]

Thanks Both - good pointers.

Lucas, air filter was recent, yes I had thought about cleaning the throttle body and MAF. Plugs were done at 60k I believe.

Vlad, thanks for the tip.  Will be putting a scanner on the car when the mechanic comes over for the live data.  Car has 77k, FSH, all the oil changes were done well ahead of schedule throughout its life, every 5k'ish miles, very lucky to have found such a good example.

Thanks again guys, will pass info on to the mechanic.

Chris.