Running Lean

[thegreengoblin]

Hi I have a 2001 explorer xls and my check engine light came on so I took it to get scanned and its saying both banks are running lean. I think I have a vacuum leak but not sure. Does anyone know of any hoses that are notorious for having problems or anything that would help me find the problem?

 

[1998Exp]

Hi I have a 2001 explorer xls and my check engine light came on so I took it to get scanned and its saying both banks are running lean. I think I have a vacuum leak but not sure. Does anyone know of any hoses that are notorious for having problems or anything that would help me find the problem?

You may not be aware of the fact that the XLS designation is just for the trim. Whether you have shiny wheels or leather seats doesn't help anyone advise on an engine issue. What's important is which of the three available engines is in your Explorer. If you can't figure it out, just post the eighth characteer of your VIN.
Afterthought: they probably did not offer the 5.0L V8 with the XLS (lowest) trim, so most likely yours is either the SOHC V6 or the OHV V6.

 

[nathan mayden]

I had this issue with the 4.0 sohc and it was my intake oring seals

 

[XLTrunner]

Yep...pretty good bet it's the intake manifold gaskets. There's all kinds of past threads on this issue.

 

[thegreengoblin]

I am acutally about to replace that today I will let you know if that solved the problem

 

[J_C]

On a vehicle that age, any of the vac hoses may have popped off somewhere, or the rubber ones dry rotted. You can even introduce new cracks or accidentally pop some off just fiddling with them. Intake gaskets are definitely another likely source of a leak.

A dirty MAF sensor can also cause it to run lean. If you haven't cleaned the MAF in the last 10,000 mi. or more, I would try that before the intake gasket(s) since it's cheap and easy to do and can't "hurt" to do anyway so long as you use a spray only, nothing mechanical/abrasive, do not touch the MAF sensor element itself with anything.

Is it running rough? That can make it easier, to plug suspect vac line ports at the intake, spray starting fluid around the gaskets to see if the engine responds by running smoother.

 

[D. Cione]

I have the V6 OHV and have been putting my girl together for 6 months - the last two months have been all about the lean codes - I have changed almost everything and if I could do it again - I would say first check the line/hose under your throttle body, do a fuel pressure test, do a vaccuum test, forget the spray carb cleaner around the engine and wait for the engine to sputter, its a waste of time because it seldom seems to work. From your fuel test, and vaccuum test results, you should know if its your manifold gaskets - which at the end of the day, its a 2001, they havent been changed, just change them. And whatever you do , if you do the work yourself, don't forget that they have to relearn how to idle and how to drive.

 

[96eb96]

I have the V6 OHV and have been putting my girl together for 6 months - the last two months have been all about the lean codes - I have changed almost everything and if I could do it again - I would say first check the line/hose under your throttle body, do a fuel pressure test, do a vaccuum test, forget the spray carb cleaner around the engine and wait for the engine to sputter, its a waste of time because it seldom seems to work. From your fuel test, and vaccuum test results, you should know if its your manifold gaskets - which at the end of the day, its a 2001, they havent been changed, just change them. And whatever you do , if you do the work yourself, don't forget that they have to relearn how to idle and how to drive.

The EGRs also leak thru the pintle. Propane or carb cleaner under the egr makes the trims (or idle) go crazy. I also found leaks in the vacuum harness connectors - not to set a code but not optimal either. You need a bit of air to set a code, usually intake gaskets or a massive leak.

Best way is a smoke machine. The other way is to watch fuel trims as you gas it or spray carb cleaner. Without a smoke machine though you may not be able to pinpoint it.

 

[J_C]

I have the V6 OHV and have been putting my girl together for 6 months - the last two months have been all about the lean codes - I have changed almost everything and if I could do it again - I would say first check the line/hose under your throttle body, do a fuel pressure test, do a vaccuum test, forget the spray carb cleaner around the engine and wait for the engine to sputter, its a waste of time because it seldom seems to work. From your fuel test, and vaccuum test results, you should know if its your manifold gaskets - which at the end of the day, its a 2001, they havent been changed, just change them. And whatever you do , if you do the work yourself, don't forget that they have to relearn how to idle and how to drive.

Doing a fuel and vac test does not tell you if it's the manifold gasket(s) vs any other vac leak. Maybe if the reading was bad enough it's a sign but that will tend to make the engine run poorly too and usually that's a primary complaint instead of the check engine light.

Sure you could just do the more laborious repair attempt because that engine has never had it done before, but that seems like near the last resort rather than the first. You can systematically check everything else first, then do the upper & lower gaskets only if the cause is still elusive. It could even be a simple case of loose bolts and they need tightened.

 

[scrivyscriv]

A quick way to verify a vacuum leak.. hook up a scan tool and watch the fuel trims. With an intake leak you'll have high short and long term fuel trims (STFT & LTFT) at idle, and they will quickly drop down to around zero when you get around half throttle. "High" to me is anything over 10 or 15, on up to 25. I believe 25 or more on the fuel trim will set a check engine light.

Then.. if you have confirmed an intake leak.. isolate it. MAKE a smoke machine - it is easy, quick, and cheap.. there are numerous tutorial videos on how to make them.

To give you an idea of what you're looking for.. when I smoked my intake leaks out I found leaks from the upper and lower intake manifolds at the gaskets/o-rings, vent tube at the oil filler neck, IAC breather cap, and underneath the EGR valve.

 

[96eb96]

This is the procedure to find leaks. You can get a smoke machine on ebay for around $60, make one yourself for 30ish. A place will do it for an hour of labor too, then you can repair.

Read below to understand what could leak. Something like an EGR valve may show some smoke, but a professional knows how much. Then you can verify the leak with fuel trims.

http://www.thedieselstop.com/faq/9497faq/tsb/tsb/files/012005.pdf

Propane and brake cleaner is another option, but sometimes the gas may not reach the problem area. For something obvious it is a good idea.

Also, don't neglect crankcase leaks, like scrivy said above things like your oil cap or valve covers could leak. PCV is a vacuum leak that is taken for granted by the PCM, but if extra air is pulled in you can have issues.

Also, check LTFT /STFT at idle, 1500, and 2500 RPM.

If you are above the high single digits at idle, and it drops to near zero at 1500, you have a vac leak.

If it stays high you may have issues with the injectors.

A dirty MAF could also cause high fuel trims because air is being underestimated.

Even new cars may hover around 0-5% trim. That is normal,

 

[thegreengoblin]

so I took it to a shop to get a diagnosis and they told me that my brake booster went out. I though it would have to do with a vacuum hose leaking. im not good with anything to do with the vacuum lines. would the brake booster going out make my car run lean?

 

[J_C]

Yes, a leaking booster can cause a vac leak because there's a vac line going to it. That vac leak is unmetered air the computer doesn't know about so to whatever extent it is leaking, it will run that much leaner.

On the other hand, it could just be a dishonest shop that saw a vac line loose somewhere but wants to profit from replacing something that doesn't need it. I could just be paranoid, but I've seen shops pull stunts before, being far less than honest to maximize their profit.

Did the brakes seem to need more effort to apply recently? A booster will provide less assist the worse it's leaking. You can pull the vac line off of it, plug the end, and see if that makes the engine run better, but before driving it somewhere, remember that you now have manual brakes and the braking effort that goes along with that.

Then again, BRAKES! Kind of important to have, might not want to risk second guessing their diagnosis.

 

[96eb96]

so I took it to a shop to get a diagnosis and they told me that my brake booster went out. I though it would have to do with a vacuum hose leaking. im not good with anything to do with the vacuum lines. would the brake booster going out make my car run lean?

Very likely.

 

[thegreengoblin]

thank you for the responses you've helped me more than you know

 

[thegreengoblin]

honestly I don't know about the brakes. I've had this truck for 2 years and its always had the check engine light on. I have always bin easy on it because I didn't have theif I money to replace it.but now I have full time job. I think I am going to le them replace the booster and if it doesn't help it then I will go back. thank you for your imput

 

[thegreengoblin]

Update: I got the brake booster replaced. I can tell a major difference in the brakes and acceleration. after I got that fixed I was driving home and my check engine light came back on. took it in and it is still running lean. the dude at the shop told me that my fuel pump was going out and that is why it is running lean. could this be the case I honestly don't know much about the fuel system

 

[nathan mayden]

Rent a fuel pressure tester from AutoZone and check it fuel pump failure is pretty common with age and high mileage

 

[J_C]

It might help if you had the OBDII trouble code.

That is a very suspect diagnosis. They cannot determine a fuel pump is going out on an engine that is still running, without ruling out a clogged fuel filter by changing it, and just being lean, they could measure vac to see if it's what it should be, as well as fuel pressure.

Suppose they did (and you can also) use a gauge to check low fuel pressure. It could be the fuel filter, or the pressure regulator which IIRC on a '99 SOHC would be on the sending unit in the tank, or the pump itself. They might intend to have you (pay for and) replace both the sender unit/pressure regulator AND the pump, though depending on what they are charging for parts, that's not necessarily a bad idea, to replace both while they're at it.

On the other hand if you haven't replaced your fuel filter in recent years or might have put some bad gas in it (or tank is just starting to rust out inside), I would think about replacing the fuel filter first, and then see if the problem persists, or you could ask them how they "know" it's the pump as the answer to that could be interesting.

Generally speaking, having it run lean is a lot more likely an intake manifold leak than the fuel pump itself still running but not providing enough pressure, unless it's due to it being the pressure regulator or clogged filter instead of the pump.

Having written that, there may be some advanced diagnostic methods which can be employed to determine the pump has low RPM or a bad winding, by measuring the power ripple on the leads going to it. A multimeter with a frequency setting, an oscilloscope, or some specialty diagnostic tool might be able to do this, but it is not a common thing for an automotive tech to do, for one because I don't think there is published data about what the fuel pump RPM is supposed to be, and because using a scope then, you'd look for a missed motor winding, a blank space in an otherwise regular current pulse which isn't the sort of thing I've ever seen a tech mention.