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Open Roads Forum  >  Class C Motorhomes  >  Class C

 > Check Engine Light...Going on 5 years & 20,000 miles...

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T-Rex

Carlsbad, CA

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Posted: 01/27/21 12:35pm Link  |  Quote  |  Print  |  Notify Moderator

klutchdust wrote:

Try posting the issue on BAT auto and a Ford truck forum. Your issue is the fuel/air mixture on a cold start. Post what you wrote on BAT, they have helped me in the past with real brain teasers.
This has to be dealt with methodically. As mentioned, contact cleaner ,not brake clean ,can really help.

Also once codes are cleared remove battery power to engine, it has an effect on the computer systems to reset. Kind of like what you do to your desktop.


Sounds like a good tip to try. Will do. Thanks.


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T-Rex

Carlsbad, CA

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Posted: 01/27/21 12:39pm Link  |  Quote  |  Print  |  Notify Moderator

Krusty wrote:

You likely have an air leak or a vacuum leak. Inspect hoses and ducts carefully. Starting with your air filter housing. Make sure the two halves are locked together all the way around (NOTE: this is very difficult with a K&N air filter unless you take the housing out and assemble it on a bench). Any gap between the two halves will result in rough running, and Check engine Lamp. Also check the rubber grommet where the MAF sensor wiring comes out of the air filter housing. Make sure it is seated fully. If you have any rubber elbows or couplings in your PCV tube, make sure they are not deteriorated and loose.


Thanks for the specific suggestions. Much appreciated.
I don't know what the PCV tube looks like, but I'll do some Google searching so that I know what I'm looking for. For now, I'm only familiar with the Air Intake Hose and housing for the air filter. After that, I'm in new territory...

Krusty

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Posted: 01/27/21 12:50pm Link  |  Quote  |  Print  |  Notify Moderator

PCV system typically has one tube that goes from the intake manifold to one valve cover, and another tube that goes from the air intake duct to the opposite valve cover. Just check any of these tubes for soft spots, holes or leaks. They are usually fairly obvious.


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BurbMan

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Posted: 01/27/21 01:42pm Link  |  Quote  |  Print  |  Notify Moderator

T-Rex wrote:

When you say that I should spray the contacts, are you referring to spraying the electrical connection that I disconnect in order to clean or replace the sensors (eg. MAF sensor)?


Not exactly...

The Mass Air Flow (MAF) sensor sits in the air intake between the air filter and the throttle body. It looks like a piece of screen with very fine wires criss-crossing across the opening. These wires vibrate to measure the volume of air entering the engine, and the Powertrain Control Module (PCM) uses this info to tell the fuel injectors how much fuel to add.

A typical sensor looks like this:

[image]

The wires can get dirty and send a bad reading to the PCM. The wires are VERY fragile so you need to be careful removing teh sensor and use ONLY cleaning fluid specified for MAF.

This is the correct cleaner:

[image]

Here is a You Tube Video on how to remove and clean a MAF. Your set up will be slightly different, but you'll be able to identify the parts and remove them after you watch the video.


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carringb

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Posted: 01/27/21 07:34pm Link  |  Quote  |  Print  |  Notify Moderator

It’s not likely the MAF is the culprit in this case. A dirty MAF will cause a lean condition all the time, to the point it will cause pining, before it ever causes cold-start symptoms.

Vacuum leak is very likely. I even had the PCV valve pop out of the valve cover once, when I let it go about 100k too long and it plugged.


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Posted: 01/27/21 07:36pm Link  |  Quote  |  Print  |  Notify Moderator

T-Rex wrote:

I can (and have) changed the oil. I've also recently changed (actually, reconditioned, the K&N air filter).
K&N filters are known to cause problems with MAF sensors. As mentioned, clean it !

rjstractor

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Posted: 01/27/21 07:37pm Link  |  Quote  |  Print  |  Notify Moderator

T-Rex wrote:

I can (and have) changed the oil. I've also recently changed (actually, reconditioned, the K&N air filter). This is pretty much the extent of anything I've ever done on an engine; however, with detailed instructions, I'm ready and willing to expand my meager experience.


The K&N filter might have something to do with your issues. From what I understand, even slightly over-oiling the filter can lead to a fouled MAF sensor, which sounds like it may be one of the things contributing to your CEL codes.

T-Rex

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Posted: 01/27/21 09:35pm Link  |  Quote  |  Print  |  Notify Moderator

rjstractor wrote:

T-Rex wrote:

I can (and have) changed the oil. I've also recently changed (actually, reconditioned, the K&N air filter). This is pretty much the extent of anything I've ever done on an engine; however, with detailed instructions, I'm ready and willing to expand my meager experience.


The K&N filter might have something to do with your issues. From what I understand, even slightly over-oiling the filter can lead to a fouled MAF sensor, which sounds like it may be one of the things contributing to your CEL codes.


Thanks for your comment!

When I bought this 2007 RV in 2015, it was 8 years old, but had only 9,000 miles on it. With so few miles at the time, my guess is that the prior owner never cleaned the K&N filter, and therefore, over-oiling of the filter isn't causing MAF sensor problems. Nevertheless, I will be cleaning the MAF sensor in case it's gotten dirty for any reason.

T-Rex

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Posted: 01/27/21 09:36pm Link  |  Quote  |  Print  |  Notify Moderator

rjstractor wrote:

T-Rex wrote:

I can (and have) changed the oil. I've also recently changed (actually, reconditioned, the K&N air filter). This is pretty much the extent of anything I've ever done on an engine; however, with detailed instructions, I'm ready and willing to expand my meager experience.


The K&N filter might have something to do with your issues. From what I understand, even slightly over-oiling the filter can lead to a fouled MAF sensor, which sounds like it may be one of the things contributing to your CEL codes.


Thanks for your comment. I actually did clean it, but the CEL light continues to show it's ugly head.

T-Rex

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Posted: 01/27/21 09:56pm Link  |  Quote  |  Print  |  Notify Moderator

BurbMan wrote:

Apply logic here: The MAF measures incoming air and the then PCM pulses the fuel injectors to dispense the right amount of fuel. If the O2 sensor says the mixture is always too lean, that means too little fuel or too much air. If too much air, then either the MAF is sending the wrong reading, or air is getting in somewhere after the MAF.

The lean code is also the symptom, fix the rough idle and the code will go away. Since the O2 sensor was already changed it's likely not that.

1. Get some MAF cleaner from the auto parts store and clean the MAF. DO NOT use any other chemical to clean the MAF.
2. Replace the air filter.
3. Check all vacuum lines for leaks, the V-10 has the known issue Grit Dog mentioned, the hove from the PCV melting.
4. Check for air leaks, be sure all bolts are tight to throttle body and intake manifold.
5. Check air intake tube after the MAF for cracks, etc.

A lean condition can also be caused by too little fuel, so it's possible one or more injectors on bank 1 are clogged or defective, but this is much less likely at this mileage that an air leak.


I'm with you on the "Apply logic here" advice. I'm going to clean the MAF sensor, but as others have mentioned, it seems that this would cause the CEL all the time, and I can definitely drive the RV a few hundred miles with stops along the way and not see the CEL. I don't even have it come on every cold start. It's just an occasional thing.
So, I don't think the MAF sensor will turn out to be the culprit.

Since the CEL only appears after some cold starts (and mild rough idling), I'm wondering if a small vacuum leak would have such a symptom. Does a cold engine require more of a vacuum draw than a warmed-up engine for some reason?

Alternatively, would a cold engine do something to the fuel injectors (or something else in the fuel system) that would occasionally cause an insufficient quantity of fuel? I do know that if I press the gas pedal slightly, I prevent the rough idle and the CEL.

Thanks everyone. Hopefully, I'll have a chance to visit the RV this weekend and check things out!

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