masitaly17

Hi, got a weird one here hoping someone has experienced something similar and determined the root cause.. I will try and make it brief but informative.

2006 GS430, 175K miles.. Never had any real engine or emissions control issues... Post CAT EGO sensor replaced about 5,000 miles ago...

My issue is the engine will lose power on a mildly loaded acceleration (i.e. passing a car, on-ramp, or going from a 5mph speed to acceleration of 25-30 MPH). It has happened 4 times in the past 4 weeks while driving. When trying to accelerate I feel the loss of power, engine RPM goes from 1500-1600 rpm range down to 1,000ish, when pressing the gas pedal at that same moment the RPM will then drop to 500 or less, or die completly (3 times).. Each time it dies I pulled over to the shoulder, key off and key on, and it starts back up with zero issue or hesitation. There is no CEL on during this time or ever... The only four times this occurred it was after a longer drive (45-60 minutes in rush hour traffic). In my mind i was thinking ignition coil issue in which the coil was breaking down after the longer drive and heat build up...

I brought it to my repair shop, he was able to reproduce the issue while monitoring with the scan tool... There is a pending MISFIRE fault on all 8 cylinders and ECU is retarding ignition timing, indicating it is clearly trying to compensate for the misfire on all 8 cylinders.. They were not able to identify a root cause and suspect I had some bad fuel in the tank which was causing this misfire on all 8 cylinders.. I didn't really 100% agree with them but understand this could be plausible... So I filled up the 1/2 empty tank with 93 octane from Mobil.. And have been driving it for the last 6 days with no issues, until today.. Same issue after about 45 minutes of the rush hour drive...

Soooooo, anyone have heard or seen this before? My biggest concern is the fact all 8 cylinders are in a misfire condition, that pretty much eliminates injectors and coils as they are not likely failing intermittently all at the same moment in time.. Possible throttle body creating issues but I would think there would be a DTC (pending or active) indicating the throttle blade is not in the desired position.. Carbon buildup should not impact it intermittently like this (in my opinion).. I have always had concerns about the electrical on this car, I am almost certain there is some type of leak allowing water to get into the inside (maybe plugged sunroof drains).. 4 weeks ago I had my car parked outside while on vacation for 6 days, when i came back my electric power steering motor had shorted and fried the controller for the motor ($2,000 repair bill for that, So the fact my electric power steering motor shorted out by just sitting OUTSIDE leads me to be concerned about electrical and moisture issues in the car.. Plus when it sits for a few days I can come back and it smells a little musty... Water ingress inside car..

sorry for the length, trying to be as descriptive as possible in hopes that someone, anyone has had a similar issue with a "that's it" moment.. If i don't get this sorted out quickly i am going to have to get rid of my Lexus, which I really don't want to do but I need a reliable car to drive in the 1 hour Chicago rush hour traffic.......

SILENTM

What are your long term fuel trim readings

sha4000

iTrader: (1)

Does the car idle low?

ibidu1

iTrader: (1)

Almost sounds like a fuel issue to me, you can borrow for free tools from auto parts stores. Try and see if they have fuel pressure testers. I think you may have clogged injectors, or even a worn out fuel regulator.

masitaly17

i was not in the vehicle during the test ride, I will ask the shop tomorrow what the LT Fuel trim was... Where are you going with that inquiry? Lean condition progressively getting worst until the misfire event occurs?

masitaly17

Idle is smooth and seems to be in the normal range it has always been... No issues with the cold start idle warm up schedule (i.e. RPM slightly increased during cold start)...

masitaly17

I have thought about fuel pressure dropping out b/c that is what it feels like... Loss of fuel pressure during the loss of power situation.. The shop thought it was bad fuel causing a vapor lock which is why i filled up wtih 93 octane Mobil gasoline.. I was not in the vehicle during the test drive but I assume there is a fuel pressure sensor on these vehicles to monitor on the scan tool?

Can anyone confirm if fuel pressure can be monitored on the scan tool and can anyone confirm if there are DTC's that will set during a low fuel pressure event? If so, do you know the setting criteria?

Thanks for the initial feedback, made it home today with no issues.. Everyday is a nerve racking experience, not cool to have a car die in rush hour Chicago traffic..

ibidu1

iTrader: (1)

But first of all have you kept up with good maintance? Plugs, air filter, cleaned the throttle body, cleaned the maf, did a top engine clean/seafoam in the intake?

masitaly17

I would say probably not as good as recommended.. I am about 60-70K on the spark plugs now.. I am thinking about changing them next weekend.. Will do the top engine clean/seafoam at that time. Do these V8's have any known issues with top end crud buildup? I have been using Mobil 1 full synthetic since I purchase the car (60K miles when purchased).. Changed ever 5,000 miles (sometimes 5,500 miles..

Maintenance is a good thing and definitely required, I am not convinced these items would cause the intermittent misfire on all 8 cylinders.

masitaly17

I borrowed a scanner and monitored it during my drive tonight... ..

Long Term FT Is around +8% during 2,000 RPM and around +3 at idle (600 rpm)
Short Term FT is around +4% during high 2,000 RPM and around -1 at idle (600 rpm).

Fuel trims never really got over 10% during any period of acceleration, hard throttle, deceleration, etc.. Bank 1 and 2 are about the same side to side...

SILENTM

Ok so looks like your ecu is compensating for a lean condition and is slowly adding more fuel. You will not see the LTFT increase on a single test drive ( it is a progressive thing unless major issues ). Since both side are the same you can trace it back to common component that feeds both sides i.e. for example fuel pump is getting weak or fuel pressure regulator. Since your vehicle is over 10 years old and coming up to 200k i would recommend both, but as ibidu1 recommended try and get fuel pressure reading first to verify or go ahead and replace them as preventive maintenance if they haven't been done before.

masitaly17

ibidu1

iTrader: (1)

Nice congrats on the new car! Did you consider the 2019 lexus ES350?

masitaly17

I didn’t consider the ES but I did consider a Certified Pre-Owned IS.. The price difference between the BMW and IS for a CPO was about $6K - $7,000 so that was the driving factor in getting the BMW. Of course once I test drove the BMW my decision was made, it makes for an easy sale since they ride and drive so nice.