Another rule of thumb I use regarding engine health and fuel economy is drive at a steady speed over level ground at 100 kph (60 mph) for at least one km and report what the average fuel economy is. In my car it is about 30 mpg. If your car has significantly less fuel economy it is likely due to the code popping up, your driving habits, environmental conditions, use of AC (I had a post on that, 2-3 mpg hit on AC versus no AC) or a combination of all of the above.

 

Here are the codes. What should I do. Pls guide..

 

Ok so we have p0171 &0174 lean both banks
Whatever it is affects both banks and the computer thinks it's too lean which means more air than it thinks is there about (or a fuel starvation issue but you have high fuel use so we can rule that out)

p1175 throttle motor
I haven't seen this error before. It will affect both banks evenly. Perhaps a another throttle body assembly to swap in.

p0443 - emissions valve code

1. So overall a lot of the problems are very very likely to be MAF sensor related. Check and/or replace with a new MAF from a reputable source like a lexus dealer or a denso from Rock Auto. (What ever you do don't get sucked in by the eBay "oem" sensors to save money as it will be a fake. That fake sensor is likely to throw weird and unrelated error codes and in turn drive you nuts trying to figure out what else is going on - seen this many many times. Don't fall in that trap)

2. Also what condition are your vacuum hoses in? Touch the pcv hose. Is it Hard and Brittle? Or nice and rubbery? If it is brittle replace all your vacuum hoses and pcv valve and grommet as they are all likely to all be hard and brittle and will fail sooner rather than later leaking unmetered air into the engine.

disconnect the battery for 10 minutes and see how it drives then and if any codes come back.

 

quick question:
has anything changed or work been done since your last post?

 

No brother.
I was waiting for guidance. Since you all update me above regarding codes now I will do all these jobs and let you know the result. I really appreciate your help guidence.

 

Hi brother, I done the job as you said on above. So only P1128 and p0443 codes are gone. Now only these 3 codes are remaining. I will cross check all hose pipes and connectors and will inform you again. Meanwhile if any other suggestion would be appreciated. Many thanks

 

Ok so with new MAF and new vacuum hoses / pcv valves there no vacuum hose leaks and computer still thinks its running lean..
I reread your previous post. After you check and likely replace all the vacuum tubes and pcv Valve then report back.

And to double check, what exactly did you do? New MAF? Throttle motor?

does your lexus have any modifications?

If after checking and probably needing to replacing the rubber hoses if after that you are still getting lean codes then:

1. check (or get checked) the fuel pressure? This is a manual check with special set of guages. Report back the pressure.

what model scanner are you using?

 

When Mechanic open the hood and engine cover, This sensor pipe was broken, I changed this sensor so those Codes were gone. P01128 and 443. now my next job will be to check all hose pipes and everything. I will share the details again.

 

Yep - thats a fuel vapour vacuum hose line VSV valve. They all do that. Given that valve cracked, and the visible oily coating near the PCV in the photo (the thing top left in line with the oil cap with the foam covered hose), I can guarantee all the other vacuum hoses will be hard and brittle too. And changing them will very likely get rid of the lean codes

 

This is full pic. I crop previous pic. Additionally no modification has done in the car. All stock.

 

This guy has made a nice video that shows the vacuum hoses that need changing. The nice thing is the hoses used are bright red so you can see where they are.

Don't forget the new pcv Valve and grommet.

https://m.youtube.com/watch?v=UO-En1w4HFY

 

Brother its massive change my fuel economy. I changed some of the hose pipe which needs attention. Full engine clean. And no plugs or coils changed. Check engine light goes and never pop up after 300km driven. Now my car is giving 13 to 14 L per 100km. And in slow drive its goes 16L per 100km.
Thanks a lot and I really appreciate for ur help.
By the way I am living in Dubai. Really thanks a lot brother. God bless.

 

Hey guys I got Denso MAFS from Rockauto. Do you have to disconnect the battery to install it?

 

No. The car should be switched off for best results.

Disconnecting the battery won't hurt as it will reset the computer so it will run super smooth for a little while afterwards.

 

I disconnected the negative terminal and installed the new MAFS. So far I can’t really tell a difference in the behavior of the car. But then again I had cleaned mine when I first bought the car. I’ll keep you guys posted if I notice any difference.