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hsbaker

Workhorse 8.1 Hesitation & Loss Power

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I have a 2004 Winnebago Suncruiser with 42k miles.  This motorhome has run with no issues until two months ago.  I live in rural Tennessee use the motorhome as my work apartment in the city I drive the motorhome on average 160 miles per week.  I drive mountainous roads and started noticing hesitation and loss of power on inclines.  I first thought a tune-up was in order and so to the motorhome dealer we went for a tune-up.  We replaced wiring and spark plugs.  At first the motorhome ran like a champ quick response no hesitation we thought bravo--but no.  A few weeks after it started hesitating on inclines with a loss of power--back to the dealer--no fault codes.  The thought process was the catalytic converters needed to be replaced.  I took the motorhome to a muffler shop I chose only by online reviews with a 4.5 star rating with over 200 reviews.  I could have fallen over when they told me they could install new catalytic converters but they would not solve my problems.  The muffler shop suggested I go to a mechanic they thought could help me--who suggested adding Chevron Techron fuel additive to the fuel.  Bravo!! Ran like a champ for about 75 miles---Then no Bravo!  Same situation.  Dealer suggested running the fuel to empty and then adding the fuel additive with 93 Octane fuel and see if that would fix the problem.  The first 50 miles were rough, I thought all this for nothing and then as if magic the engine started running smoothly, great acceleration, no hesitation, she was running like a champ.  I even called the dealer and said problem solved--but NO.  Today (the next day) I started on my voyage to work and I do believe the champ is hung over and is running worse than it ever has. 

I am determined not discouraged--but I have to figure out the issue and get it fixed.  When I search the internet this problem is apparently common and the message boards and forums go for a while but then stop without ever concluding what fixed the issue.  I promise to finish this thread to the end with the solution to my hesitation and loss of power to maybe help my fellow RV'er.  The dealer has suggested before this to replace the coils which would cost around $1k but they are not sure this will fix my problem.  I would gladly pay that if I knew my hesitation and loss of power would be gone for ever.  However, they agree it is a gamble.  I am all about starting with the cheaper solutions and working toward the granddaddy of expenses when we are shooting in the dark.  I think we have ruled out the fuel or bad gas theory.  Here are my thoughts and trust me I am not a mechanic and I am looking for--no actually begging for a deeper understanding and suggestions than mine.

First I am thinking lets change the fuel filter just incase debris and or sludge made its way to the filter.  Cheap enough easy enough.

2) Check fuel pressure

3) Check and clean HAF sensor

4) Purchase a OBDii scanner to see if there are codes during operation that might lead me to a solution

Sorry for the length of this post if you are still reading you are either really bored or you have been in my situation and know my frustration.

Thank you in advance for your input.

 

SB

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SB, Welcome to the FMCA Forum!

Very well versed on the issue you are describing. 

The problem is often loose connection / clamp location at the air input point on the intake manifold. That is the first point to check. along the same line, check the air feed line for any restrictions. dirty air cleaner. The 8.1 is a heavy breather, the other item could be the MAP sensor. Not that common though. 

Have well over 150,000 miles on the one in our 3/4 ton Suburban. There is definitely a reason they call them Texas Cadillac's. The only thing they will not pass is a gas station.

Your coach 8.1L engine should have up graded cam position and crank shaft sensors. The original ones where pron to failure. Send me a PM if you wish.

One more thought, do your self a favor and remove the spark plugs, check each one and add some good anti seize to the threads. They can be difficult to remove if not checked and your plugs are now about 15 years old. unless you have changed them.

Keep the group in the loop as to what you find.

Rich.

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There may be more than one fuel filter. Check closely along the frame rails all the way from the tank to the injectors. For some reason they like to hide the filters.

Was the distributor cap checked when they changed the plug wires? Roter to. 

Herman

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habaker, 

Welcome to the FMCA Forums! 

As mentioned, start with the fuel filter, any idea how old/miles are on it? That is by fr the cheapest check, I am surprised the shop didn't recommend that when they replaced the spark plugs.

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Joe, he mentioned  42,000 miles on the coach. 

Herman, the 8.1 L engine is an all electronic system. No points or rotor on the engine, but there is a large in line fuel filter, but checking the fuel pressure is one of the first tests to run.

Hope that the OP comes back to read our thoughts and fill in a few gapes. 

The coils on my 8.1 L are still OEM.  Replaced the plugs at 100,000 miles , from his discretion - the problem could be heat related, but need more information an a detailed description of just how the lose of power feels while driving. Like a skip or does the engine start and run fine at times and run rough at startup other times .

Rich.

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39 minutes ago, DickandLois said:

Joe, he mentioned  42,000 miles on the coach. 

Rich, I meant how many miles on the fuel filter, not the chassis.

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13 minutes ago, jleamont said:

Rich, I meant how many miles on the fuel filter, not the chassis.

Joe, just got a PM and it was replaced 12K ago.

Rich.

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Fuel filter is still a good place to start-- not expensive or labor intensive.  There is NO average life for a fuel filter-- feed it one tank of contaminated fuel and it could be clogged.  Only clean fuel and it can go many tens of thousands of miles.

Could it be something else like one or more coils breaking down-- sure.  But before spending the $$$ to either pay a tech to put it on a machine or start throwing parts at it, the fuel filter is a reasonable place to start.

 

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I have heard that chassis mfg. will pit more than one fuel filter on.

Also there is also a small screen sock on the fuel pump in the tank. I have seen them with trash in them. Draining the tank and looking for trash may be a thought. 

Grasping at thoughts 

 

Herman 

 

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12K on a gas engine fuel filter, depending on what quality or blend of fuel is the best place to start. If that doesn't fix it time to dig deeper. 

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hsbaker,

By some chance did you put in E-85 Ethanol fuel in your coach? If so that will cause a loss of power, run poorly and suck up fuel like crazy.

Also now may be the time for a heavy dose of fuel/injector cleaner.

Herman

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The injectors in the 8.1 may be getting clogged.  I have an OTC setup where you disconnect the fuel pump and run 16 oz of highly detergent fuel under air pressure.  That will clean the injectors, intake valves and combustion chamber.  That will put new life into it.  

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Thank all of you for your valued feedback!!

I reviewed my service records and do not see that the fuel filter was changed in the last 10k miles anyway.  I am going to have them change the filter and check the fuel pressure tomorrow to see if that will fix the issue since I will be in the neighborhood tomorrow.  Would have done today but had to order the fuel filter and have it shipped overnight.

Spark plugs and wires were replaced on 12/5/2019 (IGN Wire Set Part # 9645  / AC Delco Spark Plug Platinum Part # 41-805).  For the life of me I thought we had changed the fuel filter but my records nor the dealer have a record of it being changed.... I can pray that is the issue but I am not so sure.  I am interested in HuffyPuffy's suggestion?  Not exactly sure how that would work but sounds like a great idea.

I will keep you posted on the progress

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25 minutes ago, hsbaker said:

Thank all of you for your valued feedback!!

I reviewed my service records and do not see that the fuel filter was changed in the last 10k miles anyway.  I am going to have them change the filter and check the fuel pressure tomorrow to see if that will fix the issue since I will be in the neighborhood tomorrow.  Would have done today but had to order the fuel filter and have it shipped overnight.

Spark plugs and wires were replaced on 12/5/2019 (IGN Wire Set Part # 9645  / AC Delco Spark Plug Platinum Part # 41-805).  For the life of me I thought we had changed the fuel filter but my records nor the dealer have a record of it being changed.... I can pray that is the issue but I am not so sure.  I am interested in HuffyPuffy's suggestion?  Not exactly sure how that would work but sounds like a great idea.

I will keep you posted on the progress

The process I mention is done by professional with profession equipment and cleaner.  I never had a customer regret having it done.   

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The problem with the 8.1 engine in a motor home is the 25 foot fuel line running right above the exhaust on the left side. You have a sealed floor right above the frame rails. When driving slow or lots of stopping at lights the fuel will boil in the line causing loss of fuel pressure. It can get 180 degrees under where the fuel line is. Best fix is the Banks headers with single exhaust on the right side of the frame. That fixed all the problems on my 2006 Winnebago 38J Workhorse W24 8.1 and Allison 6 Speed transmission, 35,000 miles on coach.

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3 hours ago, DougJames65 said:

The problem with the 8.1 engine in a motor home is the 25 foot fuel line running right above the exhaust on the left side. You have a sealed floor right above the frame rails. When driving slow or lots of stopping at lights the fuel will boil in the line causing loss of fuel pressure. It can get 180 degrees under where the fuel line is. Best fix is the Banks headers with single exhaust on the right side of the frame. That fixed all the problems on my 2006 Winnebago 38J Workhorse W24 8.1 and Allison 6 Speed transmission, 35,000 miles on coach.

Doug, Thanks for your feedback. Had Vapor lock  issues with a 88 series P-30 with a 454. Installed a electric fuel pump in the fuel line close to the fuel tank ,the added pressure and fuel pressure regulator at the engine did solve the problem. The coach used an aspirated Rochester Quad Carburetor. 

Never heard of an issue with the electric fuel pump pressure and fuel injectors, But high heat and fuel temperatures can do strange things.

Rich. 

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The OP, after reading his first post again, said that he loses power on the hills, not the flat land or anything about stop/go traffic or lights.  I doubt, even on a hot summer day, it get's much above 80 ambient temp in those hills/mountains/mostly one lane roads, boiling fuel in line? IMHO, no!  If that was the case, it would have shown itself right after purchase, not 42,000 miles later. 

I would not go back to the same mechanic.  I would do as Herman, Joe and Ray (Huffy Puff) advised.

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The vapor lock theory could be true after 42,000 miles, the heat over the many miles has probably caused a breakdown in several components which may have finally come to a head. So yes, this probably has solved the problem.

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Those 8.1 Workhorse chassis were famous for throttle control failure. The potentiometer would wear and give erratic signals. 
The throttle control sends a signal from the gas pedal to the throttle body.

Richard

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