Motorhome Engine Problems

[Wizard29]

My fiancee and I just purchased a '97 Bounder with the Chevy 454 and are having some problems with it.
The test drive went fine and we were satisfied with how it ran at the time. However, we have since found out that when it gets put under a significant load like climbing the Cajon pass or towing our enclosed trailer, it starts to shudder and completely loses power. I can floor it and force it into a lower gear and then the engine will pick up and spin it's ass off, but when it shifts into the next gear, it sputters and loses power again. This tells me that it is not making power in the lower part of the RPM range for some reason. The stutter is accompanied by an occasional backfire. As it is right now, the motorhome is only able to climb the Cajon pass at about 25MPH without the trailer.
The funny thing is that the problem continues even after the load has been removed. After climbing the pass, it continues to completely run like crap all the way to our house in Oak Hills - no acceleration and completely unable to handle any sort of uphill grade. Start it up the next morning and it runs totally fine until it sees a load again.
Had the computer checked by the mechanic. Showing 8 different codes, two of which are for the transmission. The other 6 are for the O2 sensors reporting lean on both banks. The mechanic said the transmission codes are related to the engine running poorly and having to floor it to get it to go anywhere. He suggested the exhaust may be plugged and/or too restricted. I uncorked it at the collector before the cats and ran it on the pass today. Same result, so it isn't the exhaust.
So what the hell could the problem be? It just seems like it misses pretty badly under a load and then after it has been under a load until it has a chance to rest for a while.
Bad knock sensor retarding the timing?
Jacked up computer?
Something else affected by the extra stress of a load (that apparently can return to normal after a while)?
Anyone who has any suggestions, please help me out....

[HP350SC]

I would start with a fuel filter....

[upsman105]

What about the clutch plates? Torque converter?

[YeLLowBoaT]

I would start with a fuel filter....
that and the fuel pump would be a good place to start.... many chevy/gmc trucks from that time had fuel pump probs.

[djunkie]

complete tune up, cap, rotor, plugs, fuel filter.
Fuel pump is a definant possibility as Chevy's have a problem with them.

[H20 Toie]

that sounds like mine when the cat got plugged ran fine down the road but if you hit a hill no way it could hardly pull itself. but i would change the fuel filter first.

[mike37]

If your geting O2 sensor codes chang the O2 sensors the O2 sensors are only good for 60k miles
and check the cats

[JetBoatRich]

when you are done with finding the problem and it seems to running good :cool:
Remember take it easy on the hills and cruise :rolleyes: it is a motorhome the gasser's do not like hills :yuk: just take it easy :cool:

[Rexone]

Could be any combination of the above mentioned ignition / fuel problems. I've experienced similar in Suburban...
Also once the fuel filter gets plugged it usually ruins the fuel pump output overworking it. Change fuel filter often is cheap preventative maintenance.
One independent shop that will diagnose and FIX is Engine Dynamics in Baldwin Park, John Avery, Neil. Good luck... :)

[Moneypitt]

First, do you have the code book and the dianostic jumper plug? Those items may save you alot of grief down the road. Second, there are "default" settings that take over in the event of a "'sensor" failure. This could explain the continuing problem after the load failure. There are so many things that depend on sensor signals for proper performance. Third, as a test, create the problem. As you continue on with the sluggish running, pull off the road and disconect the battery for about a minute. This will, or should, erase the default settings that are temporalily stored in the computer, simular to leaving it sit overnight when it somehow corrects it's self. When it was checked by someone reading the codes it was probably running OK and the code history was all that was found. Those codes are in the memory, the hard codes as I believe they're called, whereas the default value, the part that is going bonkers while under load, would have disappeared once it is re set by the sensor working properly again. This is simular to a low fuel pressure code while low on fuel, once the fuel level has been corrected the history of low fuel wouldn't show at the next code reading. You didn't mention if it is carbed or injected. Either way, there should be a throttle posistion sensor that dictates all sorts of critical data to the computer. The O2 sensor as well is an important player in how the fuel is delivered and since it has stored a "code" that means it has had a problem. Try the battery disconnect during the problem, this erases the recent "soft" codes and allows the computer to "re set". One more thing, rather than floor it for the downshift, just pull it down a gear so you don't have to rev it so hard to keep it pulling up the grade. If the battery deal works then you have a little more info towards narrowing it down to which sensors will reset, and which ones won't based on the hard and soft codes. The book and the dio. plug are not exensive and would allow code readings on the side of the road while it is acting up. Beware that those systems require a constant GOOD ground, and although pulling a grade shouldn't change your ground connection, stranger things than that have happened. A fuel filter problem should correct its self after the heavy load requirement disappears, unless the O2 goes into default because it is marginal. Again, try the battery deal while it is happening.....MP

[havasu5150]

My Pace Arrow with a 454 had similar symptoms, started coughing and sputtering on the way home from Glamis, would barely get out of it's own way. Had to get off of the freeway and milk it in on Solome Hwy Turned out to be a burnt plug wire. Did a turn up on it, purrs like a kitten. No problems since

[v-drive]

Doesn't GM have a problem in the electronic ign? I think when the coil on top of the distributer gets hot it starts operating poorly. This is just something I have heard....v-drive

[Wizard29]

Thanks for the information everybody. The motorhome is fuel injected, by the way. I should have said that in the beginning.
Today I replaced the coil, all four O2 sensors, and the fuel filter. The performance has improved, but only marginally. I can now climb Cajon Pass at 40 MPH, which is an improvement, but still far from good enough when it isn't pulling anything.
Ran fine before climbing the pass. Climbed the pass while seeing the problem still (albeit less) and then the problem existed all the way back to the house. Got in in the driveway and I can rev it up just fine in neutral. However, when I put it in drive and step on the gas, it sputters and does not apply the solid power to the transmission that it should.
The fuel pump crosses my mind as the possible problem, but that does not explain why it would run fine until seeing a load and then run like crap during a load and still like crap after the load has been removed. One would think that if the pump was bad, it would give crappy performance all the time....

[JETEATER]

I have a 96 Flair with a 460 and it did the same thing.
It was the fuel pressure regulator.

[Wizard29]

I have a 96 Flair with a 460 and it did the same thing.
It was the fuel pressure regulator.
It ran fine until it saw a load and the ran like crap for the remainder of the time it was running with a load or not?
Where is that regulator and how much was it?

[Moneypitt]

Did you try to re set them computer by stopping in a safe area and pulling a battery cable off for a minute or so, and then re connect and see if it still runs bad on the flat highway?? .......Try it.......MP

[Jordy]

One would think that if the pump was bad, it would give crappy performance all the time....
Not necessarily. If you're running without a load the demand for fuel is more easily kept up with, even with a bad pump, versus a run under load.
For example, and it's the same ballpark, although somewhat unrelated, I had the same problem a while back with one of my generators, granted it was fuel filters. Ran great with minimal to no load, however, start loading it up and it would start running out of fuel, drop frequency and then trip the breaker. Or, basically pull the hill at 25 mph. ;)
If the fuel supply is lacking, performance is going to suffer. I'd check the fuel pump. What did the plugs look like when you pulled them out? Really clean and lean looking???

[meaniam]

Katchina26 works for a gm dealership as a tech. he is knowledgable and may tell you whats common and what steps to take to narrow this down.. dont go out spending a bunch of money with out narrowing the problems down. otherwise your just spinning your wheels.....
if it is your fuel pump acting up it proably wont be long before it fails and leaves you stranded. if this happens place your ear by the fuel tank and have someone turn the key to the on postion. you will hear it hum. if not hit the tank with your palm a few times. that may get it going enough to get to help.
invest in aaa membership and cover the R.V. it will pay for itself

[Just Tool'n]

Computer control vehicles are all cause & effect.
Look at your fuel pressures, under load, do a current ramping of the draw of the pump, these 2 will be a true indicator of fuel system delivery to the motor.
Also when starting up, from dead cold, does it crank right up, or take awhile to start. if it cranks awhile before stating, the check valve in the pump is bad, also with a fuel gauge it should show pressure first thing in the AM, if not then check valve is bad.
Putting a scan tool on it running it under load, looking at the paramters for fuel delivery will be important.
Have you looked at the missfire monitors for the cylinder's & which on it is, this will tell you if one is missing, plus if you are getting a miss, that unburnt fuel goes out the exhust & the O2 sensor will show a momentary rich condition on that bank of cylinders.
See what I mean by cause & effect
O2 voltage tells the computer to command the Short term fuel trim to lean out fuel, over a long time, computer tells it to lean out long term fuel trim.
Or just the opposit if it is getting a long term lean condition, computer tells it to enrich the fuel mixture, short term trim, then over a period of time a long term fuel mixture.
All of these parameters are available in a good scan tool.
Your cheapo code readers only give you codes. your next level give OBDII data only which are the 16 parameters the goverment mandated for emissions, all vehicles sold from 1996 on have to meet this standard.
Next are your scanners that give you all functions, Generic OBDII, plus mfg specific data, this is what the mechanic need to diagnose vehicles today.
Remember imformation is very valuable. A scanner will not allways tell you whats wrong, but it will give you inside info of what the vehicle is doing, and what area to posssibly look into deeper.
Remeber it is all cause & effect, or a an electricall short might effect the running of your motor home up the cajon pass.
Good luck too you.

[NorCal Gameshow]

when it comes to filters and fuel pumps on fuel injection you can have more then one of each.
everytime I've had problems under a load it's been on the electrical side (plug wires or module)
Don't rule out something floating around in the exhaust system plugging it.
is your e-brake off? J/K
the money you'll save in gas by not having to keep test driving it on the pass, might pay for a trip to the shop :D

[Wizard29]

Lots of good information here, that's why I love these boards.
MP, I haven't tried the battery thing yet. I've only run a test one time since making some other changes.
The fuel pump idea makes sense, but it would make more sense if the engine performed poorly only under a load. In this situation, it runs fine until it sees a load, craps out, and then continues to crap out even while going downhill (load completely removed).
It's back at the mechanic now. He's going to run a fuel pressure test as well as a full diagnostic on it. I hope he finds something. This problem is driving me nuts...

[Beer-30]

How long is it?
If it is over 25 to 26 feet, I would not expect to go much more over 40 uphill. If it is a 30-33 footer, I would say that is great performance. Lack of aerodynamics and all that weight means a 454 is flat working its butt off.
I guarantee you the exh manifolds are cherry-red going up hill. Had the same motor in my first dually and after cresting a hill, you could jump out and open the hood to see the red manifolds cooling down. Not too lean, just a lot of heat. Anything over 26 feet should be diesel - in my opinion.

[Wizard29]

B30, it is 35 feet long.
I would think that not pulling a trailer, it should do better than that on a hill. If it were pulling my trailer, then I would say that 40 is about what one might expect.
In any case though, it definitely has a problem because it sputters and backfires all the way. Even after climbing the hill and getting back to the level, it still sputters and backfires. I can step on the gas and it just doesn't do anything.
When I get it parked, I can put it in drive, step on the brake, hit the gas and not see the engine give the solid torque to the transmission that it should. It just shudders and won't rev....

[brazosriver]

wiz..my motorhome is also fuel injected..I was having problems and it turned out that the four throttle body bolts were loose. I tightened them up and it ran great..Just one more thing to check and it only takes about 5 min. good luck. glen

[Sleek-Jet]

You should be able to pull 45 - 50 in second gear no problem... unless it's one steep ass hill.
I've driven a 454 powered 34' class A, pulling a 'vette on a car trailer out of Bullhead headed for Kingman at 50 mph. And that wasn't really whipping it. The only mod to the rig was a better exhuast (no headers).
Hopefully your mechanic can pin point the problem... but I'm with everyone else in saying it has something to do with the fuel delivery.

[RiverRatMike]

My fiancee and I just purchased a '97 Bounder with the Chevy 454 and are having some problems with it.
The test drive went fine and we were satisfied with how it ran at the time. However, we have since found out that when it gets put under a significant load like climbing the Cajon pass or towing our enclosed trailer, it starts to shudder and completely loses power. I can floor it and force it into a lower gear and then the engine will pick up and spin it's ass off, but when it shifts into the next gear, it sputters and loses power again. This tells me that it is not making power in the lower part of the RPM range for some reason. The stutter is accompanied by an occasional backfire. As it is right now, the motorhome is only able to climb the Cajon pass at about 25MPH without the trailer.
The funny thing is that the problem continues even after the load has been removed. After climbing the pass, it continues to completely run like crap all the way to our house in Oak Hills - no acceleration and completely unable to handle any sort of uphill grade. Start it up the next morning and it runs totally fine until it sees a load again.
Had the computer checked by the mechanic. Showing 8 different codes, two of which are for the transmission. The other 6 are for the O2 sensors reporting lean on both banks. The mechanic said the transmission codes are related to the engine running poorly and having to floor it to get it to go anywhere. He suggested the exhaust may be plugged and/or too restricted. I uncorked it at the collector before the cats and ran it on the pass today. Same result, so it isn't the exhaust.
So what the hell could the problem be? It just seems like it misses pretty badly under a load and then after it has been under a load until it has a chance to rest for a while.
Bad knock sensor retarding the timing?
Jacked up computer?
Something else affected by the extra stress of a load (that apparently can return to normal after a while)?
Anyone who has any suggestions, please help me out....
Check your ignition module in the distrubutor. I've had the same problem before. You can remove it and take it to Autozone and they will test it for free. Just something to try if you haven't tackled that one yet.

[Beer-30]

I would throw valvesprings into the ring, but I would think that would more be a sputter at the higher rpm.
Since the backfire and sputter is during heavy load (lower rpm) I would try coil or ignition module.
If it was fuel, I wouldn't think it would wind up when he downshifts it. :idea:

[TCHB]

It could be a plug wire when under heavy loads.

[Beer-30]

That too.

[Beer-30]

What ever came about of it????

[MBlaster]

I'd say time for a new spider and injectors+ a major tune.

[NorCal Gameshow]

What ever came about of it????
HERE YA' GO
Last week some of you may recall I was having troubles with a motorhome I purchased. It would crap out under a load and even after the load had been taken away. Up until the load though, it would run fine.
I had many useful suggestions from some of the members here. Most suggestions had to do with fuel delivery. Due to those suggestions, I had the mechanic examine the fuel system and we discovered a fuel pump delivering only half the pressure it was supposed to. The pump has since been replaced and the problem is solved.
Thanks to all of those who took the time to help me out!

[Flying Tiger]

Even the new GM fuel pumps still have the problem.
It's a faulty check valve.
Someone makes an aftermarket fuel pump that is Da Kine, far superior to the Delco.
This is why Toyota is beating the crap outta them.

[Beer-30]

Cool. Thanks NORCAL.
Wow, half the pressure. Anyone want to guess exh temps during the hill pulls with super-lean condition? Yikes.