High Mileage Fuel Injectors - Fuel Trim Correction - 2003 Toyota 1ZZ-FE

Scott Owner/Technician Claremont, California Posted   Latest   Edited  
Case Study
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2003 Toyota Corolla LE 1.8L (1ZZ-FE) 4-spd
P0171 - System Too Lean Bank 1

A +35% total fuel trim correction = P0171 on this Toyota. Ultrasonic cleaning produced a dramatic flow rate increase. However, the injectors still require replacement because of the huge variance between them. (Jim Linder would have likely made that call out of the gate. ;) ) One would likely not know unless they were flow tested as shown. For testing purposes, these injectors were reinstalled and after extensive road testing, TFT =~5% across various loads.

Now, this is a vehicle produced before OBD Air Fuel Ratio Imbalance Monitoring which would have flagged the imbalance.

Initial Injector flow test (Automatic Mode x2) 

Post Injector flow test (Automatic Mode x2)

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Geoff Diagnostician
Lahaina, Hawaii
Geoff Default
 

Fancy stuff! I've never seen it out here, but thanks to iatn​.​net I know that dirty injectors seems to be the "secret answer" in many cases on older Toyota. I even have the OTC buzz-box but have never used it. I also learned from extensive reading that many, many, folks flat-out never consider the simple FACT that a lean DTC can be a fuel problem. Too many Identifix hits for MAF…

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Pj Technician
Pleasant Hills, Pennsylvania
Pj Default
 

Yeah, we see the injectors causing lean codes on those pretty regularly. Measuring the flow like Scott did is easily a more accurate diagnosis. But like you, I use a WPS to measure fuel pressure while activating the injectors with an injector pulse tool. Using the pressure transducer for me has been a huge help, because I’ve seen injectors flowing less than a single PSI difference cause issues…

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Scott Owner/Technician
Claremont, California
Scott Default
 

Fortunately this application took about 10 mins to have the injectors out and on the flow bench. Testing across multiple PW’s/RPM’s brings out the truth. I have tested the way you described in the past and have had mixed results.

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Gary Owner/Technician
Buena Vista, Colorado
Gary Default
   

I still have my old OTC injector tester but rarely use it. Climbing 10,000-foot high high mountain passes at WOT, most of fuel injectors I see clean themselves unless the owner has a preference for cheap gas. Only when I get a vehicle from the metro Denver area do I ever see these problems. OTOH, most of the vehicles I work on might fail an injector flow test at lower altitudes...

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Martin Instructor
Burnaby, British Columbia
Martin Default
 

Hi Scott. We got plenty of use out of our Lucas ASNU system in the program and it is a great visual opportunity to demonstrate spray pattern issues and volume imbalances. Your photos appear to be the standard run the test twice for best effect. We also would run injectors in the ultrasonic cleaning bath through a few cycles and re-test. Here is a photo of ultrasonic cleaning and the junk that…

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Scott Owner/Technician
Claremont, California
Scott Default
 

This Asnu is the “New Digital” unit circa 2004. The automatic flow test runs the injectors through various duty cycles, RPM/PW and is usually pretty effective at identifying non-linearities. I’ve replaced hundreds of those Multecs and gave up on trying to clean them. Too often I’d see these flake out at specific DC’s which was a big eye-opener. I would just pull them, flush and test to expose…

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Martin Instructor
Burnaby, British Columbia
Martin Default
 

Our machine is older than yours by a good few years Scott. It has been updated somewhat, but still serves well enough for the getting the message across. I had a stash of the Multecs from 3.1L and 3.4L engines and a mix of others, all good to demonstrate the effects, but not good candidates for re-use. Those and Nissan injectors of the time were poor candidates for cleaning. The Bosch…

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Geoff Diagnostician
Lahaina, Hawaii
Geoff Default
 

Does that Kent-Moore Fuel Displacement Gauge measure the volume sprayed instead of a pressure drop? I can't read what the measurements are. Happy New Year Martin

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Martin Instructor
Burnaby, British Columbia
Martin Default
 

Exactly that Geoff. It relates to the volume of the fuel that displaces the diaphragm in the gauge, resulting in dial indicator needled travel The volume comparison is the difference in needle deflection of the dial indicator for each injector and it is more accurate than just observing the pressure drop on a gauge. The gauge is a standard 2" diameter dial indicator with 0.100" travel in…

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Dennis Owner/Technician
Salt Lake City, Utah
Dennis Default
 

We run 9 ASNU machines and clean injectors for a lot of shops, we have found as little as 3 % total variance from one engine bank to the other will set lean codes especially on the Ford V6 engines. As for Piezo injectors since the adaptor is so expensive we are looking at a unit that can fire the Piezo injectors on a diesel engine and incorporate it into our GDI machines for only about $200 per…

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Scott Owner/Technician
Claremont, California
Scott Default
 

Hi Dennis, Wow, thats a lot of equipment! Please let me know what you come up with as a solution if you don't mind sharing. Also, are you seeing a lot of fuel trim imbalance codes?

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Dennis Owner/Technician
Salt Lake City, Utah
Dennis Default
 

Yes we are seeing a lot of fuel trim codes , especially on vehicles that will sit for extended periods. The Ethanol in the fuel is really causing problems. We also do a lot of marine injectors and they become really bad after sitting thru the winter. I will let you know how this new Piezo trigger works

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Hollis Technician
Boulder, Colorado
Hollis Default
 

Hi Scott, In the image showing spray pattern prior to cleaning, it has them listed as good, I've always assumed that restricted injectors would have irregular spray patterns resulting in poor fuel atomization, causing poor performance. The few high mile injectors (250K+) that I've experienced caused rough idle and fuel trims were high, IIRC, they were slowly leaking causing fuel…

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Scott Owner/Technician
Claremont, California
Scott Default
 

Hi Hollis, Fair observation, and the spray pattern didn’t show anything out of the ordinary and the vehicle has about 150k. The vehicle actually ran smooth without any complaints other than the MIL being on.

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Hollis Technician
Boulder, Colorado
Hollis Default
 

Good to know, thanks!

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Randy Diagnostician
Glendora, California
Randy Default
 

This area of injectors were junk . Donot year range butt early 2000 and up lean code inspect injectors. Fuel pressure good under load . Bad injectors. Have replaced a shit load for this problem

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Sean Technician
Cincinnati, Ohio
Sean Default
 

I have yet to, but I thought about using an arduino and building an injector flow tester. I feel you could program the arduino in multiple test runs say 5 5mspulses 5 10ms pulses and so fourth. with aftermarket fuel rails, a second controller to operate a common fuel pump that can be easily swapped out to or even use the same arduino if possible to keep psi where you need it. I think cost wise…

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Scott Owner/Technician
Claremont, California
Scott Default
 

Hi Sean, Absolutely, I think that would be a pretty cool project and a lot of work! Let us know if you make this happen.

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