I've been getting rich codes P0172 and P0175 and have been checking it out. (You can see what I've been up to on various posts relating to MAFS, fuel trims, etc.)

Earlier today I was checking for excessive Fuel Pressure, it's spot on spec.

Now I'm checking for leaking injectors.

I connected my fuel pressure gauge and it initially registered 43 psi. Leaving the Key ON and Engine OFF the fuel rail slowly lost pressure over the next 45 minutes. It reached 25 psi after about 15 minutes, 6 psi 15 minutes after that, finally reaching 5 psi fifteen minutes after that. Half an hour later it was at 4 psi.

My question is, What should the leak down rate be? Does my rate indicate a leaking injector?

Also, how do I go about determining which injector(s) are leaking?

Thanks!

 

While not an officer in the Politically Correct Police, I would comment that it would be easier to follow if you stayed in one thread.

You either have a bad fuel pump leaking the pressure back to the tank or one, or more, bad injectors.

I would take the injectors out and have them cleaned and tested.

 

Speaking from experience, I can tell you that a bad pump won't give you a rich mixture. My pressure leaks down to zero in about 2 seconds. Then it appears as if the fuel slowly drains back to the tank. If I wait more than an hour or two to start the car, I have to crank it for 5-10 seconds before it finally starts. If I park with the nose pointed downhill, however, that doesn't happen.

A leaky injector, however, is going to leak continuously. The 41 PSI on the line is going to be squirting fuel through the leaky injector even when the injector is supposed to be closed. That fuel will build up in the manifold and get sucked into the cylinder along with the "normal" amount of fuel when the intake valve opens. Those cylinders end up running rich and you get the codes.

 

I thought it would be better topic by topic rather than one 5 page thread ranging across a bunch of issues.

 

You are correct, failing pumps aren't associated with rich conditions.

I believe some system leakdown occurs by design, I just don't know how much. Have you replaced/tested your fuel pressure regulator?

I'm still wondering how to check injectors to see if they are leaking. Do I take them somewhere or energize the fuel rail and look?

Thanks

 

I thought I remembered a post from one of the cognoscenti giving some leakdown time numbers, but can't find it. My limited experience says that your numbers are pretty good ... if an injector is leaking, it's a slow leak. Two leaking seems unlikely, which leads to ...

How does this sound? You've got codes saying rich on both banks, right? Maybe some cause common to both banks is now more likely than a leaky injector. MAFS error maybe?

Just thinking out loud ...

 

Your are on track with the MAFS idea especially since it's common to both banks. I tested mine and it seemed to be within spec - but I may change it out anyway.

I'd sure like to find those leakdown time numbers, I'll poke around - they would be very handy.

I've never experienced a bad injector, so I thought perhaps several could be tired and leaking. But this isn't likely you say...

Thanks

 

I'm no expert on this, so grain of salt and all that. My idea was that since your leakdown is pretty slow (though I don't know exact spec') it seems unlikely that two or more bad injectors are contributing to it.

I can see that post in my head ... actual numbers like x pressure after y minutes, etc. Can't find it.

 

I was doing some homework and found this quite by accident:

Fuel Injector Testing Fuel Injector Cleaning Fuel Injector Service

Good reading. He is in Florida, so maybe some of our southern friends know about his shop...

 

A fuel pump, leaking back into the tank, would not cause the engine to set a rich code - the fuel actually has to enter the engine for that to happen.

When you first start the car does it run rough and push black smoke out the tailpipes? That would indicate a reason to suspect the injectors leaking into the engine. A bad MAF or a leaking/bad fuel pressure regulator (what type fuel system do these cars use - pressure regulator or electronically regulated fp?) can cause rich codes tobe set. A failing engine temp sensor can also do the same (not always the same sensor as the one that reports to the dash gauge.) O2 sensors can also be suspect.

Sorry, I don't know too many specifics about our cars - yet. Normally I can look at the info a scanner retrieves and determine what's going on without having to know exactly what systems are in place, just by being familiar with how various systems work.

 

Scott's MY 2000 uses traditional pressure regulation. Later models ('03+ ?) went to a returnless system with a pressure sensor.

What do you think about the leakdown rate he's seeing? My thought was that it was too slow to match up well with the idea of 2 or more (would have to be 2 or more, since both banks read rich) injectors leaking?

 

I agree. As slow as it's leaking down, there's no way a leaky injector could be letting enough fuel squeeze past to cause a rich condition.

 

It starts and idles fine - no smoke. All the things you raise are potential causes listed in the JTIS.

Fuel Pressure Regulator: It has a vacuum driven pressure FPR. I replaced the unit a year ago and the (dry) vacuum line just recently. Next week I'm going to test the FPR to see that it holds pressure just to make sure.

Fuel Pressure: JTIS says this high pressure readings (return line problems) can be a cause - mine is spot on.

Injectors: This stemmed from the fuel pressure leakdown I observed. Granted, it's a long shot in the absence of any other indications (smoke, etc.)

Engine Temp.: I checked readings for both the IAT (Intake Air Temp.) and the ECT (Engine Coolant Temp.) and they are within spec.

MAFS: This may be the wild card. Right off I checked it's readings and they are close to the spec's. I have, but I'm not sure those spec's. are absolute. Additionally, the live readings from my scanner are, of course, bouncing around a bit so it's hard to get a solid feel. I felt mine were close enough, and I'd find another cause right away. I haven't, so now I'm rethinking the MAFS as the cause.

A new (rebuilt) MAFS comes next week, maybe that was it all along...

Thanks

 

...And there would have to be at least one leaking on each side. Too much coincidence?

 

My long-term trims have rebounded dramatically after replacing my MAFs last week. Though I was in the 'lean' neighborhood, when I was getting my codes, I was over 14% of normal, now Its fallen to 6% (and continues to decrease).

You still need fuel pressures at all? I didn't provide any after reading your above posts where you were satisfied they met spec.

 

Go to the auto parts store and get a copy of HAYNES TECHBOOK OBD-II & ELECTRONIC ENGINE MANAGEMENT SYSTEMS. It will help you understand what you should be reading.

 

If you have them, it would be a good idea to have acceptable leak down rates and pressure levels attached to this thread in case someone else needs them later on.

That's encouraging news about your MAFS! I watch my LTFT and STFT figures while I drive and they really bounce around a lot (but are always negative in my case). I understand that LTFT is built from STFT, but I can't discern a relationship beteeen the two at all. (Maybe that's my trouble?) In fact, now that I think about it, my LTFT values change every few seconds. Not very Long Term is it?

I'll install my MAFS when it arrives next week.

Thanks

 

will do scott!

 

This is likely a semantic difference, but my understanding is that:

Negative trim values trip Rich fault codes P0172 and P0175. (Too little O2 is present - the engine is running rich - and fuel is being deducted to increase O2 values)

Positive trim values trip Lean fault codes P0171 and P0174. (Too much O2 is present -the enigne is running lean - and fuel is being added to decrease O2 values.)

I'm experiencing high Negative values and Rich codes so there is either not enough O2 or too much fuel. (That's why the JTIS notes a blocked air supply or leaking injectors as suspects.)

If my engine was actually suffering a Lean condition (too much O2 - either from unmetered air entering through leaks or blocked injectors), is it possible for the ECU to overshoot it's compensation consistently enough to cause it to actually trip Rich fault codes?

Thanks, much to learn.

 

Hey Spurlee. That part you are quoting I was half asleep and I deleted it shortly afterwards.

While waiting for your MAF check the stupid stuff. I've seen a lot of it down throught the years.

Get a flashlight that works. Pull out your air cleaner. Put light against one side of the air cleaner and you should see a bright spot on the other side where the light is. If not the air cleaner is bad and it will give you the rich readings. Do this even if the air cleaner is new. You may have gotten a knock-off. While it is out check the passages to and from the air cleaner box. If they have something restricting the airflow, you will run rich.

Does the car have any of those extra horsepower for $69.95 type of things?

Did anyone try adjusting the throttle position sensor? Not a good idea.

Did anyone run the JTIS tests on the MAF, IAT, AND TPS? What is the voltage that they are getting? Is it too high or too low? How is the resistence to ground?