Weird problem
06-06-17, 10:34 PM
#1
Driver School Candidate
Thread Starter
Weird problem
Hi All
Recently I picked up 07 gx470 with 170k miles. I Have done following services till now.
Recently I picked up 07 gx470 with 170k miles. I Have done following services till now.
At mechanic shop: timing belt water pump and drive belt with all pulleys and thermostat, spark plugs, rear OEM shocks, differential oils, tx case oil, brake fluid flush, PS flush, engine oil.At dealer: transmission fluid exchange. Not drain and refill.
Here are the symptoms I'm seeing.
1) when cold in morning and first time I put it in reverse I hear belt clicking sound for about a minute but it goes away after that 2) when engine is cold it drives fine and accelerate OK but when hot it struggles to move. It moves but after pressing accelerator a lot. RPM barely moves so does speed. If I press accelerator further it down shifts to lower gear and rpm jumps. 3) checked output of alternator on 2500 rpm load as 13.4v. battery without load at 12.8v
4) battery is year old and passed test. So it looks good.
5) transmission feels like skipping a bit of I accelerate without doing full stop.
6) mileage is very bad 12-13 mpg.
Any ideas what can be wrong and what to look for? Does it sound like issue with timing belt or serpentine belt job?
Thanks Bulletguy
Here are the symptoms I'm seeing.
1) when cold in morning and first time I put it in reverse I hear belt clicking sound for about a minute but it goes away after that 2) when engine is cold it drives fine and accelerate OK but when hot it struggles to move. It moves but after pressing accelerator a lot. RPM barely moves so does speed. If I press accelerator further it down shifts to lower gear and rpm jumps. 3) checked output of alternator on 2500 rpm load as 13.4v. battery without load at 12.8v
4) battery is year old and passed test. So it looks good.
5) transmission feels like skipping a bit of I accelerate without doing full stop.
6) mileage is very bad 12-13 mpg.
Any ideas what can be wrong and what to look for? Does it sound like issue with timing belt or serpentine belt job?
Thanks Bulletguy
Last edited by bulletguy; 06-06-17 at 10:35 PM. Reason: Append
06-07-17, 04:44 AM
#2
on the gas milage issue, i read somewhere that O2 sensors have a limited life even if they have not totally failed to the point of check engine code, changing them out may improve performance? just a thought.
06-07-17, 06:19 AM
#3
Pole Position
I get 12-13 mpg (click the banner in my signature) in city driving, as I spend a lot of time idling (thanks, City of Austin, for not building any new roads for the last 20 years)
So it's not unusual.
Chip H.
So it's not unusual.
Chip H.
06-07-17, 07:42 AM
#4
Pole Position
You say that when hot the RPM barely moves. If you put it in park or neutral, does the engine rev normally, or is it the same problem? Need to figure out if this is an engine issue or a transmission issue first off.
06-07-17, 08:25 AM
#5
Driver School Candidate
Thread Starter
Thanks ChipH.
I feel your pain. That's problem across USA. Infra spending is at lowest level.
Thanks Alan
I'll try replacing O2 sensors. Do you know where are upstream sensors located? I couldn't locate in my car. I found 2 downstream sensors under the car on exhaust pipe.
I feel your pain. That's problem across USA. Infra spending is at lowest level.
Thanks Alan
I'll try replacing O2 sensors. Do you know where are upstream sensors located? I couldn't locate in my car. I found 2 downstream sensors under the car on exhaust pipe.
I assume there are 4 sensors in this car 2 upstream and 2 downstream. Please confirm and help locate them.
06-07-17, 12:46 PM
#7
Driver School Candidate
Thread Starter
Trending Topics
06-07-17, 01:46 PM
#8
Not sure where they are..but like a said, they are not functioning at 100 % efficiency even though they have not failed, i.e. No codes. I have read on this board that replacing them and old plugs make the truck drive like new.
Oxygen sensors are one of the most often replaced sensors. Inputs from the O2 sensors are used by the engine management system to adjust the fuel mixture. This is critical for maintaining low emissions and good fuel economy. If an O2 sensor gets “lazy” because of old age or contamination, the computer may not be able to adjust the fuel mixture quickly enough as the engine’s operating conditions change. O2 sensors that are failing tend to read lean, which causes the fuel system to run overly rich to compensate. The result is increased emissions and fuel consumption.
Oxygen sensors are one of the most often replaced sensors. Inputs from the O2 sensors are used by the engine management system to adjust the fuel mixture. This is critical for maintaining low emissions and good fuel economy. If an O2 sensor gets “lazy” because of old age or contamination, the computer may not be able to adjust the fuel mixture quickly enough as the engine’s operating conditions change. O2 sensors that are failing tend to read lean, which causes the fuel system to run overly rich to compensate. The result is increased emissions and fuel consumption.
Last edited by ALAN553; 06-07-17 at 01:52 PM.
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bulletguy (06-10-17)
06-08-17, 06:14 AM
#9
Pole Position
Agree. Bad O2 sensors will tell the ECU to run rich. You can sometimes see a build-up of soot on the exhaust pipe and back bumper when this happens.
The front O2 sensors are at the bend right after the manifold joint, before the catalyst. You can see the fitting on this diagram.
http://www.lexussouthatlantaparts.co...rimLevel=19100
Note that early models only have the one catalyst, with the join from the other cylinder bank coming ahead of it. They're rare - I think only the few 2003's have it like that. Yours is almost certainly like the lower part of the diagram.
Chip H.
The front O2 sensors are at the bend right after the manifold joint, before the catalyst. You can see the fitting on this diagram.
http://www.lexussouthatlantaparts.co...rimLevel=19100
Note that early models only have the one catalyst, with the join from the other cylinder bank coming ahead of it. They're rare - I think only the few 2003's have it like that. Yours is almost certainly like the lower part of the diagram.
Chip H.
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bulletguy (06-10-17)
06-08-17, 07:33 AM
#10
Pole Position
You never did clarify exactly what's happening per my original post, but I got thinking further...if the engine struggles to rev when hot, you could have a plugged cat convertor. When it struggles to rev, poke your head under and see if the cat(s) is glowing (obvious fail), and measure it with an infrared thermometer at the welds for the inlet and outlets. Inlet temp should be 300-500F, outlet should be about 150F hotter than the inlet.
06-09-17, 11:59 PM
#11
Driver School Candidate
Thread Starter
You never did clarify exactly what's happening per my original post, but I got thinking further...if the engine struggles to rev when hot, you could have a plugged cat convertor. When it struggles to rev, poke your head under and see if the cat(s) is glowing (obvious fail), and measure it with an infrared thermometer at the welds for the inlet and outlets. Inlet temp should be 300-500F, outlet should be about 150F hotter than the inlet.
In park, idle rpm is around 700. And it revs amazing and smooth till 4000 rpm.
In drive, idle rpm drops to 500.
From 0 to 50mph it accelerates fine when cold. Immediately after start. Once driving for some time it starts this behaviour. I have to press gas pedal twice hard for car to move. And many a times it feels that even to reach normal speed of 30-40mph engine roars a lot but speed increases very slowly and rpm barely moves. I cleaned throttle body (flap) and it felt like car was driving normal as expected but issue returned again after few miles.
I'll report the cat observation tomorrow, but do you expect issue with plugged cat if I'm able to rev fine in neutral?
In drive, idle rpm drops to 500.
From 0 to 50mph it accelerates fine when cold. Immediately after start. Once driving for some time it starts this behaviour. I have to press gas pedal twice hard for car to move. And many a times it feels that even to reach normal speed of 30-40mph engine roars a lot but speed increases very slowly and rpm barely moves. I cleaned throttle body (flap) and it felt like car was driving normal as expected but issue returned again after few miles.
I'll report the cat observation tomorrow, but do you expect issue with plugged cat if I'm able to rev fine in neutral?
Last edited by bulletguy; 06-10-17 at 12:03 AM.
06-10-17, 06:26 AM
#12
Pole Position
Sorry Ian I missed your post.
In park, idle rpm is around 700. And it revs amazing and smooth till 4000 rpm.
In drive, idle rpm drops to 500.
From 0 to 50mph it accelerates fine when cold. Immediately after start. Once driving for some time it starts this behaviour. I have to press gas pedal twice hard for car to move. And many a times it feels that even to reach normal speed of 30-40mph engine roars a lot but speed increases very slowly and rpm barely moves. I cleaned throttle body (flap) and it felt like car was driving normal as expected but issue returned again after few miles.
I'll report the cat observation tomorrow, but do you expect issue with plugged cat if I'm able to rev fine in neutral?
In drive, idle rpm drops to 500.
From 0 to 50mph it accelerates fine when cold. Immediately after start. Once driving for some time it starts this behaviour. I have to press gas pedal twice hard for car to move. And many a times it feels that even to reach normal speed of 30-40mph engine roars a lot but speed increases very slowly and rpm barely moves. I cleaned throttle body (flap) and it felt like car was driving normal as expected but issue returned again after few miles.
I'll report the cat observation tomorrow, but do you expect issue with plugged cat if I'm able to rev fine in neutral?
06-11-17, 09:54 AM
#13
Lots of random ideas being thrown around, but the one that is correct is that your catalytic converter(s) are plugged. Every symptom you describe points to it.
The easiest way to test this is to unscrew the upstream (first) O2 sensors and just let them hang safely out of the way. This provides a path for backpressure to escape, and the GX will accelerate fairly normal when warm. It will be loud and your check engine light will be on, but it will run better.
To diagnose whether it's one side or both, you can screw one sensor in at a time and see if the problem returns. Most shops have a backpressure tester that can verify cat failure.
The easiest way to test this is to unscrew the upstream (first) O2 sensors and just let them hang safely out of the way. This provides a path for backpressure to escape, and the GX will accelerate fairly normal when warm. It will be loud and your check engine light will be on, but it will run better.
To diagnose whether it's one side or both, you can screw one sensor in at a time and see if the problem returns. Most shops have a backpressure tester that can verify cat failure.
06-29-17, 08:34 AM
#14
Driver School Candidate
Thread Starter
Replacing MAF sensor and O2 sensors seems to have fixed the issue.
Will watch for few weeks if it appears again I'll try cat diagnosis as suggested in here.
Thanks everyone who provided their valuable suggestions.
Thanks everyone who provided their valuable suggestions.
06-29-17, 09:27 AM
#15
Do you part # of all 3 items you replaced? And where did you get it from? Are they easy/safe to replace for someone not mechanically inclined?