Etoo, have u solved your problem? I annoyingly unfollowed this thread until someone liked my post. It's always good to give the "and they lived happily ever after" side of the story.

Yes my brother, the issue has been resolved

chukel:
Etoo, have u solved your problem? I annoyingly unfollowed this thread until someone liked my post. It's always good to give the "and they lived happily ever after" side of the story.

Etoo, please how did resolve the issue.
I am having the same problem. Changed sensors, MAF and the likes. Thanks

joobreel:
Etoo, please how did resolve the issue.
I am having the same problem. Changed sensors, MAF and the likes. Thanks

I had similar RX300 issue about 3 months ago.

It started on a morning. Under normal circumstances when started, the RPM first rises to between 2x and 2.5x, stays there for about 5 secs to 7 secs then gradually begin to come down to the expected less than 1x rpm. But with the onset of the problem, it starts and cranks quite well, but the RPM now starts at just a little above 1x RPM and soon rapidly approaches zero that the engine will wanna stall unless I slightly put my foot on the accelerator pedal to keep the engine running. Once I'm able to keep it running for about two minutes, I can finally lift my foot off the gas pedal and then things get on normally. The second week I noticed jerky movements develop after it's been driven for about 40 miles especially on hot afternoons. The problem stops once I top up with petrol, so I assumed it may be a bad fuel pump. I had it replaced (the whole unit actually for around 15k) with marginal improvement but I wasn't yet satisfied.

The third week I noticed that the fuel gauge indicator drops faster than I am used to and noticed I had to spend little more on fuel. Sadly for the five years I'd owned it, I always kept the mileage info on the "instant mileage option", but now I would require to know the premorbid "average mileage" and the new average MPG" to tell a difference. I decided on a workaround. I also own a RX330, and a close colleague also owns a RX300. So I decided to do a comparison.

My findings: My RX330 averaged at 17.2MPG, colleagues RX300 averaged at 16.5MPG while the problematic RX300 averaged at 14.1 MPG. I don't even think a V8 SUV performs at that abysmally poor 14.1MPG (I stand to be corrected though). Also for the first time since the trouble started, I had someone hit the gas pedal while I went to the back to check the exhaust. You need to see the soot that covered the floor nearest to the exhaust.

So I visited a mecho and narrated my findings. A scan came back with many errors (of course the check engine light has been on for more than a year). After clearing some errors, two errors kept popping up among which is, according to the mecho, 2 sensors located in the front and rear if the exhaust. Each was to cost 12k for replacement excluding workmanship. Within 2 days it was fixed and repeat scan came back with no errors.

MY EXPERIENCE: I decided to take it on a trip to Ilorin and had a mileage of 18.9MPG. Okay, that's impressive considering that even happened to be better than my supposedly non-problematic RX330. The check engine light came back on the third day. However everything continued fine for about 3 weeks thereafter. About a month ago, I started the car, heard a click and all the light went off. I knew it was battery contact issue and the mecho had not taken the extra care to tighten the battery terminal nut. So I did that and everything was alright for about two days.

Since about a month till now that I'm typing this, the mileage has dropped to a constant 15.3 MPG. Of course no soot from the exhaust (or maybe I assume so), but I can tell the marginal increase in fuel purchase than when I was doing 18.9 MPG and the premorbid period

I know I need to get the ride re-assessed with this repeat episode of poor performance vis-a-vis gas mileage but time is a luxury. I need to have enough time to stay with any mechanic that'll work on it. For lack of trust in most car mechanics, I make it a point of duty to always hang around when work is done on my ride.

Pardon the epistle, but I tried to be this detailed for your sake. Hope you can pick one or two things from my experience to help address the issue with your RX300.

I've had same problem with my RX 300 since I bought it. I have changed O2 sensors, air flow meter, welded everything on the exhaust, scanned severally but all to no avail. My vehicle does 10.4MPG presently. One mechanic has asked me to change the full exhaust pipe from the engine to the back. Although in my own case the dealer removed my exhaust pot the one under the vehicle. I have replaced it but my motor still dey consume fuel die. I go just sell am las las sha. Because I don tire, mechanic go don use me buy land by now sef.

Macheteros1:
I've had same problem with my RX 300 since I bought it. I have changed O2 sensors, air flow meter, welded everything on the exhaust, scanned severally but all to no avail. My vehicle does 10.4MPG presently. One mechanic has asked me to change the full exhaust pipe from the engine to the back. Although in my own case the dealer removed my exhaust pot the one under the vehicle. I have replaced it but my motor still dey consume fuel die. I go just sell am las las sha. Because I don tire, mechanic go don use me buy land by now sef.

did you buy brand new o2 Sensors?? and waht was ur scan results?

joobreel:
Etoo, please how did resolve the issue.
I am having the same problem. Changed sensors, MAF and the likes. Thanks

Did U scan ur car?

Macheteros1:
I've had same problem with my RX 300 since I bought it. I have changed O2 sensors, air flow meter, welded everything on the exhaust, scanned severally but all to no avail. My vehicle does 10.4MPG presently. One mechanic has asked me to change the full exhaust pipe from the engine to the back. Although in my own case the dealer removed my exhaust pot the one under the vehicle. I have replaced it but my motor still dey consume fuel die. I go just sell am las las sha. Because I don tire, mechanic go don use me buy land by now sef.

Woah! 10.4mpg is really bad. The impact on fuel money becamwe apparent at 15.2mpg. 10.4mpg will definitely be a killer.

ceaser:


Woah! 10.4mpg is really bad. The impact on fuel money becamwe apparent at 15.2mpg. 10.4mpg will definitely be a killer.

I had to plan my movement around my car o. No unnecessary movement. Until I'm able to fix it.

erico2k2:

Did U scan ur car?

Scan is the first thing. I scan all the time.

ceaser:


Woah! 10.4mpg is really bad. The impact on fuel money becamwe apparent at 15.2mpg. 10.4mpg will definitely be a killer.

how do you guys calculate this mpg thing??

captainking:
how do you guys calculate this mpg thing??

It's always part of the cruise information displays of cars. On the RX330 occasionally, and the RX300 specifically, it is displayed on the centre console screen and you can get it out by pressing on the "INFO" button on the console. The info then changes from "Instant MPG" to "Average MPG" to "Average MPH (miles travelled per hour)" to "Elapsed time of travel (in hours)" to "Expected time of arrival (the time in hours on the remaining fuel in your tank)" and then back to "miles per hour". The cycle repeats each time you press the button.

On other vehicles without centre console screen, this info is most likely available on the driver instrument cluster panel. In this case, you can retrieve the info by repeatedly pressing one of the two long buttons projecting outside the glass covering the instrument cluster, but in this case, the "time" may also be displayed as part of the info cycle. This applies, based on my use, to '14 corolla, '09 corolla, '07 ES330 (No nav), 07 IS250 (No nav) '03 Benz E230, '02 Peugeot 206 (this has only one button on the cluster) and '99 Nissan primera. The last two display in Kilometer per litre cos they are from Europe.

Attached is the picture I took of the MPG on the good RX when I begun to suspect the other one was faulty (that's the point I confirmed that the other one doing a 14.2mpg was a serious misnomer). I took the picture as evidence for the mecho that handled the defective RX. I don't have pictures of the other vehicles outlined handy.

Etoo:
Yes my brother, the issue has been resolved

Pls how did you eventually resolved it

Etoo:
Yes my brother, the issue has been resolved

Though it’s an old thred, kindly respond how did you eventually solve this issue pls

Bad spark plugs, oxygen sensor, bad fuel and a host other things can cause the black smoke.

@etoo,you didn't detail the house how you resolved the issue,it will help others with similar issues,patience is needed when fixing issues with cars,do not allow kazeems destroy your vehicle. Follow instructions from professionals when being guided,do not throw parts at the issue, e get why.

Check the catalytic converter conditions if present and also the entire exhaust sytem for blockages caused by the use of wire mesh to muffle the drone of the engine when the cats have been removed. This wire mesh blockage can send wrong signals from the Oxygen Sensors to the ECU thereby initiating a higher volume of fuel being dumped into the engine. Check the catalytic converter conditions if present and also the entire exhaust sytem for blockages caused by the use of wire mesh to muffle the drone of the engine when the cats have been removed. This wire mesh blockage can send wrong signals from the Oxygen Sensors to the ECU thereby initiating a higher volume of fuel being dumped into the engine.

MAKE SURE YOU SCAN THE ENGINE FOR FAULT CODES. (Check light may also be hotwired with Alternator or Battery lamps on the dashboard to stay ON on ignition and disappear after the engine is started) Have that checked too.

vacettetommy:

Though it’s an old thred, kindly respond how did you eventually solve this issue pls

In my own case at that time, it was a bad sensor along the exhaust. I also noticed that the fuel consumption increased significantly as the on board MPG display went down from the usual 15mpg to about 9mpg

It was scanned. Two sensors, one in front and one at the back of the exhaust were changed and things went back to normal.

On a second RX vehicle, the problem was not with the sensors, but a particular mechanism along the left side of the engine just visible when you remove the plastic engine cover. It looks like a lever that has a thin rubber pipe at one end. The pipe had inadvertently pulled out from the nozzle, exposing the nozzle tip and making the lever to pull back. The mechanic simply plugged in the pipe back into the nozzle and I could see the lever moved back to its required position which made the soot from the pipe to stop.

I don't know much about this second issue, but the mechanic revealed to me that is a trade secret and a minor issue that they can charge quite a bit for.

ceaser:


In my own case at that time, it was a bad sensor along the exhaust. I also noticed that the fuel consumption increased significantly as the on board MPG display went down from the usual 15mpg to about 9mpg

It was scanned. Two sensors, one in front and one at the back of the exhaust were changed and things went back to normal.

On a second RX vehicle, the problem was not with the sensors, but a particular mechanism along the left side of the engine just visible when you remove the plastic engine cover. It looks like a lever that has a thin rubber pipe at one end. The pipe had inadvertently pulled out from the nozzle, exposing the nozzle tip and making the lever to pull back. The mechanic simply plugged in the pipe back into the nozzle and I could see the lever moved back to its required position which made the soot from the pipe to stop.

I don't know much about this second issue, but the mechanic revealed to me that is a trade secret and a minor issue that they can charge quite a bit for.

Thanks man, I’ve eventually resolved the issue as well

vacettetommy:


Thanks man, I’ve eventually resolved the issue as well

Care to share the processes and how it was addressed?

ceaser:


Care to share the processes and how it was addressed?

In my Own case some hoes/pipes are bad, which were replaced, maf sensor and cold start sensor we’re also replaced….. but we start with scanning with OBD2 scanner before doing anything