[lgrape]

My 2003 Corolla with 270K has had the P0240 cat efficiency code in the past, and I got rid of that one with the spark plug non-fouler on the downstream trick. It then threw the dreaded P0171 code. It runs fine other than a rough idle, so I've ignored it but now need to pass county emissions testing to renew the license. Tried this so far;
Replaced intake gasket with new type orange gasket
Replaced throttle body gasket
Replaced air filter
Replaced MAF sensor with Amazon $20 cheapy
Had replaced both O2 sensors a couple years ago with Denso units.
Replaced several vac hoses that were hard and cracked.
Replaced spark plugs.

Still throws the code. Fuel trim readings are high, from what I've read it most likely is a vacuum leak.

 

[75aces]

Double check to make sure the vacuum line behind the intake manifold is installed.

Have you checked the brake booster for any leaks?

 

[zaf_uom]

Try to do a vacuum leak test. Heat some mineral oil and have a hose plugged into a glove after the MAF sensor and blow the smoke into the system. Any leak will be visible if smoke is getting out of the engine. I'd doubt the cheap MAF sensor from amazon to be honest. If you have access to an OBD2 scanner, the MAF reading should be around 5 when idling at 700RPM and around 11 when idling at 2500rpm. Give that a shot.

 

[lgrape]

Try to do a vacuum leak test. Heat some mineral oil and have a hose plugged into a glove after the MAF sensor and blow the smoke into the system. Any leak will be visible if smoke is getting out of the engine. I'd doubt the cheap MAF sensor from amazon to be honest. If you have access to an OBD2 scanner, the MAF reading should be around 5 when idling at 700RPM and around 11 when idling at 2500rpm. Give that a shot.

Do you mean the g/s MAF readings? I just got my scanner and am learning how to use it.

 

[zaf_uom]

Yes, it should be in units of g/s. Sorry, I gave you the wrong values:
Idling: A/T around 2 g/s.
2,500 rpm: around 6.5 g/s.

 

[lgrape]

I did this for a leak test. I plugged off the exhaust muffler output and the air intake tube to the throttle body. Disconnected the vac line to the EVAP and plugged it too. pulled the vac hose off the brake booster and plugged in an air line. I then hooked up my air compressor and regulator and pumped in 5 psi through the booster hose directly into the intake manifold. Then I soaked everything with soapy water. Was also looking for a leak at the exhaust manifold, I read this could be my issue. Only one leak found. Lots of bubbles at the #2 injector. I was going to build a smoke pump but figured this would be easier to try first.

Here is the weird part. I need to drive the car until the new $30 Ebay fuel injector set comes in. I know they are most likely counterfeit, but many reviews say they worked and a few said they are crap so I'll take the chance. I also ordered additional injector seals. I also read that you should disconnect the battery for an hour or more to reset the computer, so I did. After I buttoned it all up, I drove my kid to the airport and put an hour on the car. I was watching to see when the CEL would pop back on but it didn't. When I got home I plugged in the scan tool and it had the green light! No stored or pending codes, and IM says its ready status. WTF? I'm going to run it down to emissions testing in the morning and see if it holds long enough to pass. Maybe while I was pushing on the injectors I got it to seal?

 

[lgrape]

Yes, it should be in units of g/s. Sorry, I gave you the wrong values:
Idling: A/T around 2 g/s.
2,500 rpm: around 6.5 g/s.

My last g/s reading with the cheap sensor were;
Idle 2.87 ( I think the idle was like 800 rpm)
2500 RPM 6.6
Just for curiosity sake I plugged the scanner into my wifes Miata that has a 2 liter engine;
idle 2.89
2500 RPM 7.8

I'm at 1000 feet altitude at about 70 degrees temp if that makes a difference.

Unfortunately the old sensor that was in the car does not appear to be a DENSO, at least it does not have any writing on it.

 

[zaf_uom]

My last g/s reading with the cheap sensor were;
Idle 2.87 ( I think the idle was like 800 rpm)
2500 RPM 6.6
Just for curiosity sake I plugged the scanner into my wifes Miata that has a 2 liter engine;
idle 2.89
2500 RPM 7.8

I'm at 1000 feet altitude at about 70 degrees temp if that makes a difference.

Unfortunately the old sensor that was in the car does not appear to be a DENSO, at least it does not have any writing on it.

The MAF values look alright to be honest. That cannot be true as to complete the evap, the car has to be sitting for at least 8.5 hours after a soak. Is your OBD tool working properly? If you disconnected the battery and the codes have been cleared, your drive status will not be ready. You have to do some predefined driving patterns to fix that. I would be skeptical to be honest but I am not expert. I suspect that the soapy water fixed the leak but I suspect that once the water has evaporated, the leak will manifest itself.

 

[zaf_uom]

I did this for a leak test. I plugged off the exhaust muffler output and the air intake tube to the throttle body. Disconnected the vac line to the EVAP and plugged it too. pulled the vac hose off the brake booster and plugged in an air line. I then hooked up my air compressor and regulator and pumped in 5 psi through the booster hose directly into the intake manifold. Then I soaked everything with soapy water. Was also looking for a leak at the exhaust manifold, I read this could be my issue. Only one leak found. Lots of bubbles at the #2 injector. I was going to build a smoke pump but figured this would be easier to try first.

Here is the weird part. I need to drive the car until the new $30 Ebay fuel injector set comes in. I know they are most likely counterfeit, but many reviews say they worked and a few said they are crap so I'll take the chance. I also ordered additional injector seals. I also read that you should disconnect the battery for an hour or more to reset the computer, so I did. After I buttoned it all up, I drove my kid to the airport and put an hour on the car. I was watching to see when the CEL would pop back on but it didn't. When I got home I plugged in the scan tool and it had the green light! No stored or pending codes, and IM says its ready status. WTF? I'm going to run it down to emissions testing in the morning and see if it holds long enough to pass. Maybe while I was pushing on the injectors I got it to seal?

As far as the injectors are concerned, I purchased a set from amazon for $40 but ended not using them. They have the Denso markings but are 100% counterfeits. Most of the reviews said that they fail prematurely and some of them failed within a year. I ended up using genuine denso ones. I am not sure the route that you want to go but one denso injector is more expensive than a full set of 4 counterfeits.

 

[lgrape]

The MAF values look alright to be honest. That cannot be true as to complete the evap, the car has to be sitting for at least 8.5 hours after a soak. Is your OBD tool working properly? If you disconnected the battery and the codes have been cleared, your drive status will not be ready. You have to do some predefined driving patterns to fix that. I would be skeptical to be honest but I am not expert. I suspect that the soapy water fixed the leak but I suspect that once the water has evaporated, the leak will manifest itself.

The reason I thought the MAF sensor was bad is because when I Googled " what should a MAF sensor g/s reading be" it comes up with this;

"With the engine at idle, the MAF's PID value should read anywhere from 2 to 7 grams/second (g/s) at idle and rise to between 15 to 25 g/s at 2500 rpm, depending on engine size. Most manufacturers provide specifications for air flow at idle; some will provide specifications at several engine speeds"

So I thought that mine was so much lower at 2500 RPM that what they say it must be a bad sensor. They say 15 is minimum and mine is only 6. Much to my dismay the new sensor read about the same as the old one. Then I found this forum and read P0171 threads for hours. In only one post did a guy give g/s numbers for a Corolla, and they were about what I had. Thanks, Google!

My scan tool gives the green light, but now that you mention it I think there is a red X on evap readiness, all others have a green check. I did do over an hour of stop and go and freeway, and shut it off once at a stop Then more stop and go. The water should have fully dried off the head in that hour, but we shall see tomorrow.

 

[lgrape]

As far as the injectors are concerned, I purchased a set from amazon for $40 but ended not using them. They have the Denso markings but are 100% counterfeits. Most of the reviews said that they fail prematurely and some of them failed within a year. I ended up using genuine denso ones. I am not sure the route that you want to go but one denso injector is more expensive than a full set of 4 counterfeits.

I guess I'll try the counterfeits and see if they work. If they fail I'll buy DENSO or a reputable reman. Where did you buy your DENSOs to insure they are real?

I have no idea what brand or how old the current injectors are. I did hear the previous owner had them "rebuilt" by a local guy that comes to your house and does it in his van. Maybe that is just a reseal? Even so, that would have been 4-5 years ago.

 

[zaf_uom]

With so many fakes out there, it is impossible to know which is which as all the fake ones also have denso written. I would try a dealership if yours have failed. They are not cheap though so expect to pay around $70 for a new one and around $45 for a reman. My observation has been as follows: the genuine one has no sharp edges (smooth all the way) where the plastic meets and is of a darker shade of green. The fake one that I got from amazon had sharp edges on the body and the green was lighter in color. I am not sure if this is specific to one seller but give the fake one a shot and see if there is any improvement.

You will not pass inspection unless all the emission status are ready. Some states can have one not-ready and you can still pass but it is specific to states I think. Check out: EG003-02 Toyota Technical Service Bulletin titled Readiness Monitor Drive Patterns.

 

[lgrape]

Even after sitting all night the EVAP was not ready. I read on the Arizona emissions testing website that my car could have one monitor "not ready" and still pass. Real old OBDII cars can have two not ready.

Took it to the testing station and it passed! As soon as I drove out I pulled over and it was already showing a pending P0171. I will put in the new injectors this weekend and see how it works. But at least I can renew my license and drive legally while I work on it.

So the Foxwell scanner shows a green light even with that EVAP monitor not ready. I read that allowing a vehicle to pass with one "not ready" is a Federal guideline, so maybe that is built into the scanner to let you know it will pass. The scanner switches to a yellow light with the pending DTC. Not sure it would pass with a pending DTC, will have to read up. So maybe I lucked out and it didn't throw the pending code until after they tested it.

 

[zaf_uom]

I've glad to hear that it worked out for you. I think that the EVAP is the only exception for passing an inspection. P0171 is one of the hardest code to fix and it can be a lot of things in the engine. Use the monitor and put the values down at idle and at 2500RPM and someone who knows more than me can help you out.

 

[lgrape]

I've glad to hear that it worked out for you. I think that the EVAP is the only exception for passing an inspection. P0171 is one of the hardest code to fix and it can be a lot of things in the engine. Use the monitor and put the values down at idle and at 2500RPM and someone who knows more than me can help you out.

I still have to replace the leaky injector seals. I do have the cheap fake Ebay injectors coming. Would like to use the scientific method and just replace the seals first to see if that fixes it. Then even if that does fix it, install the new injectors and see if they work any better.

I read the car will pass with a pending code as long as the monitors are ready (except for the EVAP) .

 

[lgrape]

I received the cheap Ebay injectors and the extra seal kit. The kid had driven the car to work twice, and I got it back to work on it. Much to my surprise, it had not throw the P0171 code, and the Pending P0171 has cleared on its own as well. But, it had a pending P0442. The kid had filled it up with gas, so I re-seated the fuel cap and cleared the P0442 pending and it did not come back.

LT fuel trim was now 13.3 at idle, along with STFT -5. Car still idles rough. Maybe my soaking the injector seals with soapy water washed some dirt into the leaking seal and plugged it up?
I then pulled the injectors and put in the Ebay units. The original injectors seals were rock hard and cracked in pieces when I tried to slide them off the injectors. Should have just replaced the seals on the old injectors but wanted to test the ebay units to see if they even worked. Well they did work, and they worked fine. Both FTs now close to zero.
Idle still rough. Blocked off brake booster and drove around VERY carefully. No change in rough idle. Hooked booster back up.


Drove it 30 miles and the ebay injectors performed well. Decided to remove them and put the originals injectors back in with new seals and both sets of injectors performed about the same. Possibly the old injectors made the car seem quicker but very very close. No codes, no pending, all monitors reset except EVAP.

Latest readings;
fully warmed engine
850 rpm idle
STFT -3.1 bouncing around to -.08
LTFT -7.0
MAF 2.6 g/s

Still idles rough, but no codes!

 

[75aces]

Replace your intake manifold gasket with the revised orange one.

DIY 2003-2004 Corolla, Matrix, Vibe TB, IACV, and Intake...

Other DIY's exist for these tasks, but this guide explains how to replace all three gaskets and clean everything at the same time - which you might as well do if you're going to invest the time to do any one of these tasks. This guide is very detailed: it discusses cleaning and replacing the...

www.toyotanation.com

Yet another mysterious lean engine (P0171) code

Hi all - this is my first post and I was hoping to get some thoughts on my troubleshooting process (and I apologize for my long post, but I want to make sure I give as complete a picture as possible). A little over a year ago, my 2003 Corolla LE (136,000 miles at the time) check engine light...

www.toyotanation.com

 

[John Anthony]

I think the DS already replaced the intake gasket with the updated gasket. Yeah, fuel injector problems will cause P0171 for sure. Rough idle could also be motor mounts or EGR system problems.

 

[lgrape]

I think the DS already replaced the intake gasket with the updated gasket. Yeah, fuel injector problems will cause P0171 for sure. Rough idle could also be motor mounts or EGR system problems.

I don't see anything on this engine that looks like an EGR, where is it? When I look for it on Rock Auto, they don't seem to have one, unless its called something else?

 

[John Anthony]

I don't see anything on this engine that looks like an EGR, where is it? When I look for it on Rock Auto, they don't seem to have one, unless its called something else?

That's because I've been working today on a Gen 3 Camry's EGR system and had that in my brain, duh! You're correct, no EGR on our Gen 9 Corolla.