1992 P30 454 TBI total high end power loss

[Fwdstuck]

Hey guys, I have 1992 Fleetwood Flair 25Y with P30 chassis with the 454 TBI and 4l80 transmission that I picked up back in November. It had been in storage for about 6 years and the owner didn't much about it. Iv'e did some work on it like tuning up the engine (plug wires, plugs, rotor cap, air cleaner, fuel filter). There is one issue I can't seam to figure out. The TBI has no upper end power. It's very hard to explain. It runs great at idle and has great low end power. I have no previous experience with the GM TBI until with this motorhome. I've let this issue go until we broke down this past weekend, more on that later. Say your on the freeway and you punch it or start going uphill, it's makes that 4 barrel WHOAAAA sound but no acceleration and the speed will drop. So if you let off the petal to a sertain point will gain alittle power (hitting the low end). This very hard to explain. And the TBI will flutter between the low end power and high end no power. Looks like this has been a issue with a previous owner cause the MAP sensor has been changed and the old one was put in the box with words "no change" wrote on the box. Iv'e rebuilt the TBI cheaned the injectors and replaced the O2 sensor with no change. The breakdown happened this past weekend when we pulling a steep mountain on a 2 lane back road. It kept losing power and fluttering more on lower end of the throttle. The check engine light came on. I'm not familiar with pre 1995 ODBs. It finally died. I pulled the air cleaner off and tried to start it and there was no fuel coming from the injectors. I let it still for about 10 minutes with the key off and the check engine light went off and it started right up. I pulled the rest of the way up the mountian about 20 MPH to keep from causing anymore problems. It ran like "normal" the rest of the way home "back down the mountain".

[Fwdstuck]

I've done some research on the pre 95 ODBs and got a code 43. 43 is showing to be the Electronic Spark Control (knock sensor). Would that be causing this issue?

[c farmer]

I cant help ya sorry but nothing like a 4 barrel carb.  They just work    Maybe convert backwards?  I have a 454 carb motorhome.  Lots of power, but she likes her gas.

[AOBrodie]

Sounds like fuel pump. Replace the fuel filter and check the fuel pressure. Fuel pressure regulator might be stuck and not increasing pressure when vacuum is low.

[Eyez Open]

You are describing classic fuel starvation, compounded by high heat and demand. Orielys rents fuel pressure tools, hook it up and check for linear fuel pressure across the rpm band. If indeed your system is low on fuel it will begin to lean out,that results in detonation,that results in ignition retardation. Your knock sensors pick up sub harmonics in the coolant fluid then retard the timing. You cannot hear what they pickup.

A note here, 454 throttle body's are only flow 670 cfm, 454's using tbi are going to run out of air at about 4000 rpm. Rochester 220  is the model number I believe. A valuable tool with a tbi would be a neon light, it actually strobes the injector pulses allowing you to see there functions and seeing things the eye cannot see without a light...oops one needs to shine this neon light on the injector pods while it's functioning.

Perhaps cleaning the knock sensor contact point and connection wire might help too. They do corrode which limits communication to the ecu. I believe obd uses 5 volts to communicate.

[Fwdstuck]

Hey guys sorry for the late reply i've been busy. I seam to have some possible good news. I was thinking about the code 43 (ESC). Well some of the research i have done show that the 454s don't have a ESC. Just the ignition module going straight to the knock sensors. Well I thought I need to start simple and check the timing. These P30s have a timing tab underneth and you use the number 5 plug wire and unplug that one wire going to the distributor. Well it was showing 4 degrees. Couldn't tell if it was before or after. The tab was a little rusted. So I had to take a picture of it and then zoom in. It was after. I kept doing research on the timing of this engine for that year model. Everything shows that it needs to be 4 degrees before. So I got my wife to help me adjust it. (she turned the distributor while I was underneth with the timing light) That bolt was hard to get to, had to buy those bent wrench adapters and remove two fuel lines from the TBI to get to it. Seems to run alot better now. Doesn't have that flutter and has power on top end now too. Haven't pulled a steep mountain yet so we will see. The fuel not showing to coming from the injectors while I was broke down could of been in my head. We was inbetween two curves and my wife had to jump outside and direct traffic around us as soon as we broke down. I was panicking!!!! We will see if this timing being 8 degrees to retarded was the issue. Stay tuned.

[Oz]

Sounds good.  Keep us updated!

[udidwht]

You mean 8 degrees (ATDC) that will be an issue for sure.

That would be too retarded. Get yourself a scan tool for OBD-1 that will work on your phone and give you live data. Do that and once you set the timing with the distributor wire disconnected (4*BTDC) the the timing with the wire connected on the scan gauge should be roughly 15-16 at idle normal operating temp.

Remember that number. Because if you ever pull the distributor (or it gets moved) it will make setting the timing easy as you won't have to use the timing light. You can use the scan tool on the phone.

[Fwdstuck]

Sorry I meant to 4 degrees at the end of the last post. And I almost forgot about this post. I've been on one trip since my last post. It was in September. Drove about 300 miles and it ran alot better and I believe I have fixed that issue. The only other issue I have is when I start pulling a small incline on the freeway, it'll shift all the way down to 2nd gear if the incline is long enough and stay there until I overcome the incline. It did this before I changed the timing too. Before I changed the timing, the speed would drop dramatically. Now this could be how these engines do with the throttle body. But just wanting some info that issue

[Fwdstuck]

It has plenty of power on the low end. Like on the back roads going 45 or 55. It really prevalent on the freeway with cruise control on. Usually I set the cruise control on about 65, I go at about that speed and not slower to keep the tractors from blowing my off the road. When I start pulling a small incline, I'll turn off the cruise control and feather the pedal to keep it from shifting all the way down to 2nd.

[eXodus]

What you describe is fuel starvation. It doesn't have enough pressure to support high loads a low rpm. 
Your fuel pump is probably on it's way out.  I mean it's 30 years old so - that's normal.

Get a Vortec Type fuel pump, that can deliver double the fuel of your original and is bolt in upgrade.
https://harristuning.com/Tbi/recommended-454/

Otherwise,
It's really hard to tell what kind of terrain you are driving.
I used to have 1996 454 TBI in a 29ft Brave - that thing was underpowered. I mean the 90s 454 has what ? 230hp?

At any incline even just a highway bridge - it would downshift and it was very loud in the cab.
when you drive 65 it should downshift into 3rd (when you drive in OD)  but when you are going 45-55 - it will downshift into 2nd.  That's normal.

[Fwdstuck]

I'd expect it to downshift from OD to 3rd but not down to 2nd. And super loud in the cab. It's just a slight incline that it'll shift down to 2nd. If it's a short incline, it might stay in 3rd. I might rent a fuel pressure gauge and see where the pressure is. I might replace it anyway, cause my luck it would give up on a trip with a full tank...

[eXodus]

Your are talking about downshifting exclusive in cruise control?

That could be also something unrelated, the cruise control is using a cable pull for controlling the throttle and gearbox. Those cable brackets can be adjusted in length and need grease once in a while.  The cruise control in those years basically has only one sensor - the transmission output shaft. Which is the "speed" you are setting.

it has no idea how fast you really go or which gear you a in, just how often the driveshaft turns in minute. And the cruise control tries to match this speed signal.

So when for any particular speed it needs to pull past the kickdown point - it will downshift to 2nd. Usually the linkage is adjusted in a way that it cruise control can't reach kickdown. (My guess would be around 80% of pedal travel)  The only safety cruise control has - that after a certain time of not being able to reach the speed signal - it disengages.   

None of those things will throw a check engine light like you describe earlier, or some of the other symptoms. Get your fuel pressure measured, that's a great idea - while you drive under load. It will not show up will idling in the driveway.   An outgoing TBI pump usually has a hard time keeping up with fuel delivery while pulling up a hill.  (tank in the back - engine in the front - it's pumping up the hill)

[Fwdstuck]

Well when I start to pull a incline with the cruise control on let's say 65. The speed will start dropping dramatically and the cruise control will give it more fuel to try get the speed back up and downshift to 3rd and then 2nd but never regains 65 until the incline is overcome. I'll start with the fuel pressure check.

[eXodus]

It also depends on the incline. Some of the Rocky Mountain roads I was happy when the 454 was keeping me above 30mph.

The 1991 - 1995 TBI is not a powerful engine in stock trim. 1996 are slightly better.

Get yours tuned up - all baseline stuff corrected and then you can add a ECU tune to it.

[Eyez Open]

Ok below is a link and there is another link in that posting. How to time a tbi....I might suggest to read that old file, there is a specific method to do so.

Now since you have advanced it a picked up some power it may well be something as simple as carbon buildup causing detonation...tbi was named slobber body for a reason they ran incredibly rich and slobbered fuel.

I would go pickup some mopar combustion chamber cleaner and use it twice its actually great stuff and may very well clear up all your issues. You will have to change the oil afterwards ...it will be full of contamination.

Along those lines, you might do well to get CRC contact cleaner and thoroughly clean your tbi electrical connections...including your knock sensors...they do corrode with time to

Orielys rents fuel pressure gauges, it's a free service.

https://www.amazon.com/Genuine-Chrysler-Accessories-4318001AD-Combustion/dp/B00BV4D97K

https://www.classicwinnebagos.com/forum/index.php?topic=12099.0

[Fwdstuck]

Well I'm going to start with the fuel pressure check and go from there. Probably do that in a month due to it being winterized and in storage. We have a small weekend trip planned on April 1st and that'll be a good test. If the fuel pressure is down and the fuel pump needs replaced. What are some of y'alls other opinions on going up on the fuel pump size like what eXodus suggests?

[udidwht]

You want the cruise control off on grade pulls otherwise the engine will go 'WOT'. With the 454 TBI and grade pulls (4-8+ percent) speed is 20 - 30 or so mph. Nature of the beast. There is also no need to manually shift out of the OD on the column the trans (4L80E) will downshift appropriately. With respect to fuel pressure the 1994 and 1995 TBI years were 26-32psi. The earlier years was lower I believe 9-13 psi range. Preferably 10-13 under load. That era RV with it's gearing and 65mph....= horrid gas mileage. Once you pass 60mph the gas mileage will start dropping quickly. Your moving past the 'peak torque' point.

Do check the transmission connector on the side of the trans. Disconnect it and look on the inside with a light. There should be no sign of trans fluid. If you see trans fluid you'll need to replace the internal wire harness (not difficult) just that it will require dropping the pan. This was a known issue with the 4L80E trans. When fluid gets into the connector it will cause shifting issue/s.

[Fwdstuck]

Heys it's been super busy and haven't had the time to check out the fuel pressure until recently. Well I've decided to just replace the fuel pump with a stock one that it calls for without checking the fuel pressure first. Cause mainly I'm scared of the 30 year old pump going out on me with traveling/vacation with a full tank of fuel. It's got about half a tank in it now and I've unhooked the fuel line going into the tbi and hooked up a rubber hose into the fuel line and I've got it going down by the manifolds and out the wheel wells to fill 5 gallon gas cans. Unplugged the fuel relay and used a paper clip to short out the fuel pump to empty the tank and fill the gas cans. Been putting the fuel in my other vehicles. While I was running the fuel pump and draining the tank, I heard a loud thud sound coming from the tank! I thought that sounded like an vent issue/implosion sound. So I went to the gas cap and started unscrewing it and it started sucking alot of air and as I got the cap off it make another loud thud sound! So I've got a major vent issue!! Could be what was causing alot of my problems!!! I still wanting to change the fuel pump do to the age of the original one. I've got it ordered and it should be here in a week and by pulling the tank I'll be able to fix the vent issue easily!!! I'll let y'all know how it goes.

[Eyez Open]

Well i believe that pump is still working quite well. Id get a vented gas cap and start her back up and see the results.

[Fwdstuck]

I believe it does too, but I'm going replace it anyway due it's age and I doubt it's ever been replaced with only 30,000 miles. And if it has, it's probably aftermarket. Going with a brabd new AC Delco one. It has a vent tube that comes out right beside the gas cap under the license plate. So a vented gas cap is not needed once the tube is unclogged.

[Fwdstuck]

Sorry for the late update. I changed out the fuel pump and added a vented fuel cap. Still not alot of top end power but satisfactory. The real update is when we went on the same trip earlier this month and pulled the same mountain as last year and give it a real test. I'm now thinking that I had a vent issue when we broke down last year. It pulled the mountain great with no check engine lights or break downs. But had some transmission shifting issues. I kind of remember this from last year, but the break down overwhelmed everything. After I pulled the mountain for a while in 2nd gear at about 30 mph. It would want to shift into 3rd and stay there, even if I had the selector in 2nd. It's only done that last year while pulling that same mountain and the same this year on the same mountain. Hasn't done it any over time, shifts perfect all over times. Could that be a overheating transmission issue?

[eXodus]

Could be a number of things. When was the last time tranny's fluid change?

Change the tranny's fluid and see how it looks. If it's more black then red, yeah you got overheating. Buy if that's fine, could be electric or are valve stuck.

Changing fluid is never wrong on a hard working transmission. Just don't power flush it.

[Oz]

Changing fluid is never wrong on a hard working transmission. Just don't power flush it.

Ok, have to ask; why not to power flushing it?

[eXodus]

Power flushing introduces pressure to areas in the transmission which sometimes don't see pressure or high flow.

During a power flush the transmission is turned of, you don't know in which states all those valves are when turned off. 

It works fine when you got a nice well maintained tranny or a new one. But for one which is already old and has beginning issues. That could hasten the demise. Or dislodged dirt in large chunks instead of solving it.

I usually just du a drain and fill, when I got a tranny of unknown origin and history. Worked fine for me