surging at lower RPMs

[JonnyG]

Hello all, I am new here and this is my first post.
Was hoping for some guidance, I just acquired a 1994 Winnebago Warrior WCD23RC Chevy P30 Chassis 454 TBI with 40K miles. It idles fairly well but at lower RPM it seems to shutter a bit. WOT seems to really go but I don't have much point of reference since this is my first big block and I didn't really know how it should sound or react. its a bit lumpy at lower rpms where the cruise control keeps it on the highway, not sure how else to describe it. Just replaced the cap and rotor, the air filter is clean. plug wires look to be in good shape. will be changing the fuel filter when I get back home in a few days. From what I could tell the vacuum lines all seem to be in good condition still, a lot of what I read suggested replacing them all based on its age. Pulled the intake off and it all seems clean and in running order.

At the risk of making some of you repeat yourself could I ask for some help? I've called around a lot of the local shops in Edmonton don't even want to touch it, the local chev dealer said to call back if im desperate and could "maybe" help though it won't fit on their lift. 15 years ago my VW broke down on my honeymoon and ruined it, not sure if I'll ever live that down so making sure this is reliable before taking it too far. Just took it for a short trip(100KM) a couple weeks ago and it was overall OK but the surging is concerning to me. The previous owner admitted to me that it stalled out on a steep hill not too long ago but started back up and kept going? I have yet to confirm this but could see it going that way if I push it too hard, ive been pretty gentle on it so far.

Where should I start? Im guessing I'll be on my own here because of its age and have to just figure this all out. The cap and rotor kind of looked like crap and was glad I swapped it out, ran better after but didn't fix the surging. Apparently a mechanic maintained this unit but talk is cheap, until I can verify. Can anyone recommend a vacuum replacement kit or am I on my own figuring out what hoses and fittings I need? The dash says its about 195 steady but the dog house feels hot and kind of warms  up a fair bit. is this normal? Any help is appreciated

[eXodus]

Hello and Welcome,

I used to have a 1995 Brave - with the same engine and chassis as you have now.

Nr 1.  Change all fluids and filters, and I mean all - brakes, oil, coolant, hydraulic, transmission, differential, bearings.
Nr 2. Get new plugs and wires,   

For instance the former previous put the wrong kind of plugs in my engine, a few threads short.

- get the correct parts for your engine code - don't remove a part and go shopping with this.
Do not ever assume that anything was done correctly on an old RV when you are not the original owner..

Ask here and get the factory manuals.

It sounds like you got vacuum leak.  I just got a 50ft roll of vacuum hoses and replaced them all. 
PCV valve is another good source of vacuum leaks.

At higher RPM the O2 sensors controlled TBI is able to overcome the leak you got - not so much a low rpm. 

The doghouse is terrible to non insulated from the factory whatsoever and so makes a great coffee warmer.
There are multiple products available to insulate the cover - makes it less warm and also cuts down the noise.

But heads up - it's all really simple technology - nothing you can't learn - with a decent toolkit you rebuild almost everything in your driveway.

Let us know what you find out.

[JonnyG]

Thank you for the reply, this is sound advice. I just discovered a leak in the roof which wasnt supposed to be there...

I was wondering about plugs and wires, although the plugs were "changed" just a few thousand miles ago and the wires look to be in good condition. I really need to take things apart and verify they are correct. Any recommendations or just get what the auto parts store sells? Im assuming there are some favourites around here.

I just picked up a smoke machine to test for vacuum leaks, apparently this is the way some folks prefer to do it? Makes sense to me, I dont have a great place to work on this unit at the moment so trying to spend the least amount of time on the ground. Is there a specific vacuum hose i should pick up? I assumed it was different sizes, maybe its just all 1/4"? Im learning as I go here so bear with me, maybe i should have prefaced this by saying my time working on older engines is limited so not a lot of experience there.

Are there factory manuals for a 94 P30 around on here? wasnt aware people were sharing

I shook the PCV pretty good and some chunks of black stuff fell out and cleaned things up a bit.

I was more worried that it might be running hotter than it should, if this is normal i will move on from this.

circling back to the fluid changes, brakes is often overlooked so will for sure do that. hydraulic as in power steering fluid? bearings? do they need to be re greased? or?
ive been on the hunt for more info and its been a bit more challenging than expected, the local Winnebago dealership wasnt overly useful.

It idles along at 10MPH, does that seem normal?

[eXodus]

Sure happy to help,   Roof leaks happen in any age of RV (even the 2 year old leak) just a matter of maintaining the gunk (dicor) on top

For parts,  many around here like Rock Auto,  or local Napa/ O'reilly stores (preferred with those with older employees). I for myself are hardly in a hurry and order many things on Amazon or Ebay. But be aware for those two - can be very much hit and miss.  Their parts catalogs are not always correct to a P30 chassis.  So a bunch of things I have to send back.

I usually search for the Chevy Van of a few years before the RV  A 1990 Chevy G30 van with 454 shares many parts with the P30.
With my later P30 I'm looking for 1996 Chevy Express parts. 
Finding parts is a bit like scavenger hut - I like it.

I don't know about a smoke machine,  I'm a computer guy and that's old school tech,  I hook up the OBD reader and watch the O2 Sensor voltages for vacuum leak.
Further when looking at the fuel trims, I can see at which bank of the engine the leak is.
But my 1995 already had OBD2... so no idea if you can do this on 1994.

There are factory manuals for the chassis somewhere shared in this forum.

the PCV rubber elbow it's disintegrating from the inside out - that is usually the issue,  you can get a replacement kit at most stores for less then $10. Dorman help or so.

No idea about the vacuum hose size, was a long time ago.  Most of them are metric now. Pick something close.

Depending on the year the 454 is running with a 195 or 210 thermostat.  It's a massive very inefficient engine and will produce a lot of heat.

Hydraulic is powersteering - correct - and a leveling system if you got one.
Front bearings need to be "packed" or greased.

Places which do stepvans - light commercial vehicles - have more experience with the P30 then the RV dealerships.
A Chevy commercial shop is another way to go.

10mph idle seems normal, depends on the rear gears (4.10 or 4.56)

[JonnyG]

Thanks for the reply, currently working on spark plug swap and they are such a pain in the butt. I have 3 sockets and they all get stuck in the hole just as I'm snuggling them up, stupid heat shields. Been trying to find a thin walled socket but doesn't seem to be anything local. Am I doing something wrong or is this just one of those things?

Was able to get some decent 8mm MSD spark plug wires eventually, very little stock around here. . It has OBD1 from what I read. Have yet to find the port... it's a real pain to get under there.

[JonnyG]

Im used to being able to just remove spark plugs and not have to be screw around with removing things in the way, maybe I need to be more reasonable here? Clearly the cooling panel? on the right side and exhaust shields need to be unbolted before I can proceed, right? ive been reading that people unbolt everything thats in the way and then get behind the wheels and have pretty direct access. stupid me was trying to do it all above, this may have been more obvious to others but ive always had to do them from the top and it seemed doable, never encountered those heat shields though. Really worried im going to snap those bolts trying to remove them. Worst part is the plugs look just fine, they have factory clearance and brown colouring one them. I think the culprit really was the wires, but won't know for sure until I get the plugs done and things bolted back up. Kinda cutting things to the wire here, supposed to be on the road with the Mrs by 5pm at the latest tomorrow...

Maybe I can do with out those shields? ive been reading that people tend to like heat socks that go over the cables instead? Looks like the previous cables were belden and have a lifetime warranty? will have to get those replaced so I have a set ready to go if I burn up the ones im about to put in. Also not sure how much these MSD street-fire wires can handle, maybe I shouldn't push my luck>

[Oz]

Although I had older, dodge chassis rigs, my opinuon is that having heat shields is a good thing.  A pain when needind to do service work, but better than having wires or lines melted in the middle of a trip.
I used adjustible angle plug boot wires from MSD. 8mm Super Conductor series.

Heat socks are a plus.

[JonnyG]

Thanks for the reply Oz, I think you are right. As annoying as they are I should leave them be. I've decided that since the plugs aren't bad looking to just run them and hold onto the new ones until I have a better plan and some patience. Getting the socket wedged in there on the last turn was maddening.

Replacing the plug wires as per eXodus's initial recommendation seemed to do the trick, many thanks for that. The wires on cylinder 6 and 8 were cooked and likely the culprit. Should be heading onto the highway soon so I'll be able to test further but from the short test drive it was far smoother, almost like I was down a cylinder.

[eXodus]

Glad I could help. 

Plugs and wires are cheap, and you get annoyed about yourself if you try to change them last.  Plug development came a long way - an when you put in modern plug, iridium core from a good brand - those should last for 100.000 miles.  So probably the last plugs you put in the RV.

I've changed my sparkplugs through the doghouse sitting on my knees, when you go through the wheel wells -it's more confined and the heat shields are in the way.  From above - with a mirror wasn't that big of a deal, didn't need to move the shields.  But I'm tall and have long arms.  So not an option for everyone.

Get the fluids change one after another, so you have clean state where you have a lot of know instead of unknown variables.

[JonnyG]

It's incredible how much of a change just a few plug wires can make, after 2.5hrs on the highway this is a whole new experience. It runs as smooth I could expect it to and far more power. I'm able to climb hills pass slow vehicles with ease, was a struggle before.

I had a closer look at the fluids and they all look clean and recently changed. Tranny fluid is clear light red, motor oil is clear light brown. Coolant looks ok, might flush the system though. I've been reading this transmission can get a bit hot and the cooling has since been updated, any thoughts on that? Coolant temp was at 200-210 the whole time which seems fine?

So am I crazy here? Has nobody else had issues with the spark plug socket binding? I would prefer to do it up top, a mirror is a good idea. I should try and get a better look at what I'm dealing with here, the shields could just be bent or something.

[Eyez Open]

A few things to high idle speed and a ancient P32

1. Fuel pressure must be a constant 9/13 lbs at all engine speeds, Orielys rents the gauges.
2. The TPS controls the idle speed and much more, for peace of mind one can hook up a voltage gauge,move the TPS  and watch the voltage move. If it jumps around a new tsp is in order, the line voltage runs from 1 to 5 volts.
3. Next is the coolant temp unit, it to can be measured  for consistency and again the voltage is from 1to 5 volts. Take note here the coolant temp sender is also a choke of sorts, cold engines get more of a injector pulse...not good when your engine is warm.
4. Grounds Ground and Grounds, it would be very wise to clean every contact you can find on the tbi. CRC contact cleaner is very good stuff...and of course you also have the main chassis ground and the battery...lol time to shake hands with your new found friend, TBI is incredibly simple once you get to know it..

One last thing, timing on those old tbi units needs to be exactly on mfg specs, they are very fickle and do not tolerate changes at all

Just had a thought, a trip to a well schooled GM dealer with your VIN code in hand. In 1994 GM went with 30 lb fuel pressure on some of there trucks. Only a VIN code at a GM parts dealer would have that info

[Max]

From my own experience i can tell dont use cheap wires. On my 81 Brave with the Chevy 454 most of the heatshields were missing or broken. First time i used a wire set for roundabout 40$ and after a 300mile trip the engine starts misfiring due a burned boot. Now i use a heavy duty set with camic boots from rockauto. It is pricy (100+$) but since then i have no trouble with them. And i also use the chinese heat protecting socks instead the metall shields. This engine produce a lot of heat in a motorhome. No problems since 6000mls.
The sparks i use are the ngk iridium due the lpg conversion, thats the only way o drive a us gas motorhome here in germay

[JonnyG]

Thats interesting, i didnt realize LPG was still viable. i know many years ago people ran it because it was cheap, is there a specific reason you run it? cleaner burning?

From all the reading ive done the general consensus seems to be that the AC Delco stock copper core plugs are the way to go, didnt see much advantage to the nicer ones other than changing them less. i dont exactly plan on putting a ton of miles on this rig.

I did read about those ceramic boot plugs AFTER i had mine prepaid on order, I have a sneaking suspicion I might need to order some before the next trip. On the way back she wasnt running as smooth as she was on the way there. Not as bad as before but something seemed a little off, kind of afraid to take off that dog house and look at this point. I dont think these wires were rated for any especially high heat, although they were cut for the 454 so you'd think they would be fine, 8mm MSD street-fire wires arent junk are they?

I did clean up some of the grounds but will go through all that i can find. The main ground strap looked kind of ugly, was one of the first things i cleaned. Will have a look for CRC contact cleaner, was under the impression that some sandpaper was the way to go?

Still holding off on sending her into a mechanic, was wanting to tackle as much on my own as i can so i can be more comfortable messing with it if it breaks down. maybe its time

Thanks for all the helpful suggestions, its given me a lot to ponder on and saved me some time. Ive got a plan to get it running in tip top shape by next spring hopefully, not much of the season left here in Alberta

[Oz]

Sorry, I forgot... look in the member area.  There's a table of available P30 manuals, and a TON of other manuals there for you.

[Max]

I am from Germany where the fuel is up to 6$ a gallon (the cheapest fuel with 10% of ethanol is up to 1.64€ per litre). So it is like a financial suizide to run a motorhome on gasoline. Using lpg is the cheapest way to drive american cars (lpg is now 75cent a litre).
It burns cleaner and the exhaust fumes does not smell that bad like a non catalytic gasoline engine. But the main reason is the cost savings .
You loose some horsepowers but its a rv and not a race car and a 22feet motorhome with the 454 is still good powered.
Due the higher octane of lpg you need a very good ignition system. If the engine runs fine on gasoline and poor on lpg then mostly the ignition system needs some attention. Thats why the iriduim sparks. This works well.

[eXodus]

It's incredible how much of a change just a few plug wires can make, after 2.5hrs on the highway this is a whole new experience. It runs as smooth I could expect it to and far more power. I'm able to climb hills pass slow vehicles with ease, was a struggle before.

I had a closer look at the fluids and they all look clean and recently changed. Tranny fluid is clear light red, motor oil is clear light brown. Coolant looks ok, might flush the system though. I've been reading this transmission can get a bit hot and the cooling has since been updated, any thoughts on that? Coolant temp was at 200-210 the whole time which seems fine?

So am I crazy here? Has nobody else had issues with the spark plug socket binding? I would prefer to do it up top, a mirror is a good idea. I should try and get a better look at what I'm dealing with here, the shields could just be bent or something.

Even when it looks good - could be 10 years old. When it wasn't driven since the last change - still you got a degraded fluid.

It's up to you.  I like to get a known baseline and change all the fluids when I get a new old vehicle.   

Engine oil change - with a good synthetic fluid  when you DIY is like ?  $30-50?

Transmission if it's still nice smelling and red - you can just do a drain and refill - leave the pan on and the filter -   
Drain whatever comes out - refill the same amount.     
Drive 50-100 miles - repeat.    Drive 50-100 miles - repeat.
Then you got 80% new fluid in there for a very low cost.

I got regular JEGs 8mm performance wire on my V8.  Installed them 5 years ago - didn't melt yet even while heavy towing.
Only the regular heat shields on the manifolds.

Changing the spark plugs with a Metric socket and a 3/8 drive was no issue - I can imagine that a 1/2 drive will not fit.

[cadillac_al]

I plan to change my plugs next week.  I'll look into that tight fit socket issue.  I was told to change my plugs through the front tire well.  It looks pretty easy from there.  I gave up on AC plugs years ago. I could barely get 2 years out of them.

[JonnyG]

Thanks for that cadillac_al. The "internet" said to use stock plugs and that the fancier ones were a waste of money, how many miles would you say you get on the AC's? Do the better plugs add anything other than longevity? If i tightened the plugs then backed off 1/4 turn i could pull the socket out 1/2" and then snug it. was tedious but worked, i tested 4 sockets(all 3/8" metric) total and they all did the same thing. a mirror showed the shields off center a bit.

As usual eXodus you have some great logical advice. even though the transmission seems to be shifting fine that peace of mind has some value, how often are you changing trans fluid?
The guy i got this off of drove it multiple times per year for the last 5, its before that that it sat a while. His brother is a mechanic and helped him take care of it and for the most part that seems to hold up which is why I didn't hurry and do that first. its on the list though!

I read somewhere that folks dont like synthetic in their 454s and that it tends to find leaks where there were none before. I run it in my other vehicles and prefer it but didnt want to have to deal with leaks. I bet it helps it run smoother and cooler? speaking of which, is the stock cooling sufficient or are there some aftermarket mods you all like?

[eXodus]

The fancier plugs - don't give you any more power, just are more consistent and long lived - since you just experienced - the pain of changing them - I'd rather spend $10 more and don't have to do this every 2-3 years.  They should last 10+ years.  I'm not planning on touching them before 100.000 miles. (got about 50k on them now - took a look lately and they still work excellent)

Fluid: It's combination of years and miles.

I'm doing a drain and refill every other year - no matter the miles - but when hit 30.000 miles the tranny gets a full pan down change.  I drive the RV about 5-10k a year - so every 4th year.  Walmart carries the GM tranny fluid for really cheap.  You need about 2-3 Gallons for a drain and refill (Valvoline or Mobile  Dexron) -  check which spec your tranny needs.

Engine Oil:
There is the possibility that an old engine already leaks and that only the crud of the old oil is keeping it sealed. Any oil change might open that. Even when you change dino (conventional) brand that could happen.   
The cause of this is not the fluid - it's the already existing leak, which would been discovered at some point anyhow.  Even with the old oil it will leak at the same spot eventually (just takes longer)

But you don't need to switch synthetic -  regular oil changes are far more important then what you put in.   I've just standardized my vehicles - everything gets 5W30 Synthethic.

[JonnyG]

Does yours take 5W30? 10W30 is recommended for mine, i read you should never go lighter than whats in there only heavier. Id love to use 5W30 as my truck uses it and i have lots of it on hand.

[eXodus]

read your manual don't trust a random guy on the internet. Every year of the engine might be different.

My understanding is that the number after the W is the weight of the oil. And the number before W - is the additive packages which makes is flow easier during cold starts.

So   W20  W30 W40  is the thickness.  So when you speaking about a heavier oil - usually you refer to the second number.   

Yes you are right - you shouldn't put in a XXW20 - that would be lighter -  but when your engine is worn - a W40 might give it a few more years and reduce excessive oil consumption.
How many miles to you got?

[JonnyG]

I did see that chart in the manual and from what i recall it said 10W30 is the correct oil, even the filler cap says that. You are right about not trusting a random guy on the internet, although some of you have been rather helpful 

Pulled this from https://www.valvoline.com/about-us/faq/oil-types-weights-and-viscosity-faq
What does the "w" in a grade of motor oil stand for?

The "w" in motor oil stands for winter. The first number in the oil classification refers to a cold weather viscosity. The lower this number is, the less viscous your oil will be at low temperatures. For example, a 5W- motor oil will flow better at lower temperatures than a 15W- motor oil. The higher number, following the "w" refers to hot weather viscosity, or how fluid your oil is at hot temperatures. The higher the number, the thicker the oil at a specified temperature.

the bit about the additives im a bit foggy on but i to recall a old friend telling me that new oils exceed the needs of older engines so that part is less important now?

I am at 40,500mi

[eXodus]

the bit about the additives im a bit foggy on but i to recall a old friend telling me that new oils exceed the needs of older engines so that part is less important now?

I am at 40,500mi

In my opinion:
A modern Full synthetic is better at every part of the temperature spectrum then a (dino) conventional oil. There are like a hundred more parameters to oil then only viscosity.  How good it adheres to surfaces, pressure stability, heat stability, added metals to reduce wear etc. 

Most parts of the world you can't even buy conventional oil anymore.  US is an exception to this.
You can probably run a engine with "wrong weight" synthetic a longer and healthier life then with the correct conventional.

As long as the oil temperature spectrum is matching with the ambient of your surround. I'm usually running 5w30 - it's the cheapest brand full synthetic around here. I got one Dodge and one Chevy truck north of 200.000 miles on that oil - and using only a little between the 7500 and 10000 mile interval.

My RV I do usually on a 5000-7500 mile cycle, since it's working harder. Once a year usually.

[JonnyG]

That's pretty impressive, you are in a nicer climate than I and can get away with that. We change our oil more frequently up here because the winters can be really harsh(~-30C/-22F). The MH will be parked for that time though doesnt matter as much i guess.

Are you saying that you ran 5W30 in your 95 Brave? The coolest i will likely ever start this thing is maybe 20F and max maybe 100F, will for sure be parked during the colder times. Not trying to start an oil debate here as i know they can get out of hand in a hurry, just unsure what i can get away with. 10W30 synthetic isnt as easy to find around here i noticed when shopping around today. I also saw in 96? that the 454 started using 5W30, I wonder if anything really changed in that year? Being that the mileage is so low you'd think it would be tight enough still to be able to handle the thinner oil? I read claims that the older engines like a thicker oil because its not as precise but im not sure how much that actually holds up. Some claim it needs higher levels of zinc or ZDDP? Ive read some around here like the 15W40 diesel oils because of the higher zinc content but i assumed that was because they have higher mileage? Id hate to bugger up what I assume is an engine with lots of life left in it.

Odd question, how would you go about cleaning off the intake manifold? I cant just take a pressure washer to it, can i? the splash back inside would be too much id think. i vacuumed up as much as i could but id like it to be cleaner. degreaser and scrub brush?

[eXodus]

I don't remember what my 454 called for from the factory.

Maybe something to do with Oil history,  10W30 was before 5W30 - maybe it got common around that time.  Who knows.
My 454 was at 60.000 miles when I sold the RV and didn't need significant oil between changes.

I got a 350 in a truck at 200.000 miles which slowly starts using a bit of oil and leaking. Going to add a 10W40 to that one probably soon. 15W40 - doesn't go down in temperature that far that I would be comfortable using this in a cold climate, where you might be sitting.

I like to have my trucks stupid proof.   W%   So when I happen to drive it to cold place and don't think about - it won't mess with anything.
That's why I got all the same oil, I don't need to worry that I used the wrong oil on any of them them.

No idea about the intake - Is the 454 iron? Plastic?- I only did the aluminum one of 350 once, put that in a tub of degreaser, let it sit overnight and then lots of scrubbing.