1988 Ford F-350 7.5L - No power on Acceleration
 

I have been trying to fix this truck for over a year and I am running out of ideas so now I am throwing it out here for advice.

1988 Ford F-350 Vin G 460ci 7.5L V8 with manual 5 speed transmission

Symptoms:
Lacks power on Acceleration
Lacks power when hot
Slight hesitation on throttle
Timing holds @ 28 BTC and climbs to ~40 BTC on acceleration

Timing:
Initial Timing @ 10 BTC
Computer Advance @ 28 BTC

Spark plug gap:
.044

Compression:
Cyl #1 ~140 PSI
Cyl #2 ~140 PSI
Cyl #3 - 8 not tested at this time as engine runs smooth

Fuel Pressure:
32 PSI and holds pressure for long time when parked.

Codes:
KOEO = 32
KOER = 32 / 41
Continuous Memory = 22 / 32

Map Sensor:
pin 1 @ 5v
pin 2 & 156Htz no vac. / 101 htz idle vac
pin 3 @ good ground

TPS Sensor:
Tests good

EGR Valve:
Exhaust side closed.
Leak on top side at pintle beneath vacuum biscuit.

EVP Sensor:
Tests good

EGR Regulator:
Not operating correctly

Heg02 Sensor:
Tests good

Fuel Pressure Regulator:
Tests good

Catalytic Converter:
Removed from system before we got it.

Air Filter:
Needs new air filter, problems persist even without filter installed.

New Parts:
Fuel Filter
High Pressure Fuel Pump
Battery Cables
Spark plugs
Spark Plug Wires

History:
This truck has been the unfortunate victim of junkyard mechanics. The guy who owned it took it to a junkyard for all service needs and these particular guys messed up everything they have touched. I have spent the better part of a year fixing all the electronics, and wiring, and all mechanical components they screwed up.

It had old fuel in it and had the fuel pumps seized up, which I took apart, cleaned, and fixed all three sealed fuel pumps and it worked good to get it home. Unfortunately, it had set for almost a month which caused some of the valves to seize up due to the untreated fuel. It bent about half of the pushrods.

I removed the Intake Manifold from the top of the engine and replaced the pushrods from a parts engine and used a cordless drill to spin up the oil pump to get oil flowing again.

I replaced the high pressure Fuel pump and fuel filter after draining both tanks of old fuel. Replaced and flushed all fuel with fresh treated fuel.
(I had stored the old fuel in the back tank for a while which ended up getting stolen by an idiot. He showed up a couple weeks later stating the engine in his truck blew-up because of bad fuel he got. Serves him right.)

I have gone so far as to make sure the harmonic balancer is lined up with TDC, which it is.

I have not pulled the exhaust off, as it is currently a one piece welded unit since the catalytic converter was removed. The engine revs up good and does not feel or sound like it is getting too much back pressure.

I have pulled the computer and looked inside it. I could find no burned circuits, corrosion, or unexpected circuit board smells.

One thing that bugs me is the timing. I set it to 10 degrees with SPOUT removed and with the SPOUT plugged in it advances to 28 degrees and never backs off. Isn't it supposed to back off after 2 minutes? Currently it stays steady at 28 degrees at idle unless you pull the vacuum line off of the MAP sensor and only then does it drop back to 10 degrees. When giving the engine throttle the timing advances up to at least ~40 degrees and possibly a bit more.

The temperature sending unit for the gauge is working fine and the engine does not overheat.

All vacuum lines have been repaired.

The PCV valve line is blocked off from the vapor canisters after the actuator as battery acid appears to have eaten the canisters.

I have worked on and repaired practically everything on this truck, including the rear axle seals which were put in backwards by that junkyard group!

At this time, if you drive it with a load, it simply has no power when accelerating, and has trouble making it up moderate hills. My dad states that the power loss happens much worse as the engine gets hot and even coming back without a load it will have no power to climb hills.

The engine runs smooth at idle but has a slight hesitation when punching the throttle. All cylinders are firing and there is no arcing or cross spark detected in darkness.

I know the EGR regulator is not working right. I have taken it apart and cleaned it, but I think the coil inside is bad and will require replacement. Though I do not think it would cause this lack of power issue.

The EGR valve itself is leaking on the top side around the pintle below the vacuum chamber, though no one seems to know how much of a leak there is too much. It is closing off the exhaust side of the valve.

I still need to replace the speaker in the passenger door, and somehow find an upper actuator for the steering column ignition switch because $76 is insane for that tiny chunk of metal.

I think that is about all I can pack into this, so Hello, I am new here, and I need help! At this rate it will be psychiatric help if I cannot solve this soon!

Not a mechanic but can give my 2 cents
 

Your post have been there a long time without response. Is your problem solved ?

No, not solved yet. Only change so far is that I have tested the fuel pressure again which stays steady at 32psi and I am able to get near solid fuel in it with fuel in the front tank. I was concerned that the tank switch mechanism might be giving issue.

I also found and replaced the upper actuator in the steering column for a more reasonable price.

I will not know more until we have need to haul a heavy load, but any ideas would be welcome?

Hum !
 

So many possible causes. You have checked many.

Exhaust system partially clogged ? (I am now cleaning mine. Mice have built a nice home while the truck was not used in winter under the snow). The engine starts and then choke.

Fuel injection computer replaced with wrong model ? Do you have fuel injection?

Do you use high octane gaz ?

My catalytic converter busted. (you dont have one). My mechanic told me it happened because my exhaust line was too small, causing restriction and overheating the converter. Is your exhaust line big enough for the 7.5 litre engine ?

...

EGR system
 

I would put that in good order.

EGR
 

Found that here : http://www.justanswer.com/ford/2nisc...ing-pitch.html


The turbo's on the 6.0L do experience sticking turbo vanes due to coking deposits in the turbocharger. The turbo can be disassembled and cleaned (reconditioned). You can also have low power (with black exhaust smoke) due to a sticking EGR valve. With either of the above conditions you'll have a smooth running engine but lack of power. There are specific test procedures to identify sticking turbo vanes. If the EGR is sticking it will set EGR related codes. ...........

It's 460 gas engine...

I have not had a chance to go through and fix the EGR solenoid yet, or double check some other details suggested here yet. However, something struck me as very wrong while I was working on other things.

When I tested the fuel system, I received a good hold pressure for a long time, but while running, the guage would bounce wildly extremely fast with the RPM of the truck. It would bounce anywhere from 26psi to 45psi. The needle would be bouncing so fast it would simply be a gray blur.

Could the fuel injectors be bad?

At 26 psi it won't run right. It should hold steady at any rpm. In fact it should rise a little when you open the throttle. Pull the vacuum line off the pressure regulator make sure no fuel comes out, (if it does regulator is bad), you should see the pressure rise by about 5 psi. I have had them idle but not run down the road due to a bad pump. If the lift pumps in the tanks are bad it can cause this problem by not supplying enough fuel to the main pump on the frame. If you used an Airtex pump or other China made pump it may not be any good straight out of the box. LOL

The main pump I replaced is a low cost but good one that maintains steady pressure. The pumps in the tanks I have taken apart and cleaned from the old fuel that had them gummed up. They are not in that great of shape.
I have checked and verified the fuel pressure regulator is working properly, but I will double check it again as soon as I get a chance.

I won't rule out the new main pump I put on it until I check out the lift pumps again.

Two things that stand out to me are,,
The fuel pressure which should be pretty steady as long as you have a fluid filled gauge and should never drop below 32-35psi. Ever.

The timing advance which should not stay locked at any one reading for any amount of time and that suggests a bad PCM, it is possible for it to still run the motor sorta correct but not manage spark properly. Age is the enemy of electronics and these things are well past their due date.

Okay, I finally had time to run some additional tests and checks.

As for the EGR solenoid, It is working perfectly. As best I can tell the entire EGR/EVP subsytem is in good working order. For some reason the PCM still gives a code 32. I am not all that convinced the PCM even truly tests it as no change in vacuum is ever observed at the EGR valve itself even though I can manually activate the solenoid and manipulate the system just fine.

The Fuel pressure is still doing as I described before, except it does not drop off as much as I originally stated. It averages 32psi with the regulator vacuum on, then seems to jump up as much as 42psi with the vacuum removed from the regulator. The gauge needle still fluctuates wildly, and each time I check the flow I get a tiny amount of bubbles, otherwise the fuel flow is solid.
The only way I can describe this any better is to show you with this video I took with my ipod.

Back to the timing... Same thing... with the SPOUT out it sits on 10 degrees. With the SPOUT in it moves and holds at 28 degrees. With acceleration the computer advances the timing off the scale on the harmonic balancer.
This video which I would not recommend watching is a failed attempt at showing the timing. I chalked the 0, 10, and 30 as well as the mark edge of the pointer. You can see the 30 degree mark real clearly in a few parts.
Turn audio off before watching!!!

Actually this second timing video you can see the long 10 degree mark I chalked easier and this one shows the advance going past the 30 degree mark with acceleration.
Again, I recommend not having audio on!


Right now I think the main pump and tank pumps are working fine. The fuel system still holds pressure for a long time after shutoff as well.

I have already checked the three grounds to the PCM and they are good. I checked them when I first started diagnosing the timing.

So what does that leave me with?
Something bad in the fuel system?
PCM bad?
Both?

I really appreciate the input you have provided me thus far and as that blasted PCM is pretty expensive I would really like to be sure before I tell me dad he needs to buy a new one.
The PCM on it is e7tf-12a650-bt1d which I think means it needs an e7tf-btd to replace it?


UPDATE: I just read that it is not uncommon to have a fuel gauge tester bounce like what I am seeing if you have replaced the stock pump with a high volume pump. The pump I replaced the bad stock pump with is called a Precise.
http://www.rockauto.com/catalog/more...507&cc=1126437
Yes I know my fuel gauge is a cheapish non liquid filled, but I am beginning to suspect I am not having a fuel system problem at all, which tends to heavily point towards Conanski's PCM thinking.

I am very not pleased....

I installed a new PCM today and I am getting the exact same results.

Timing as described previously has not changed at all, and I am still getting a code 44 and code 32.

Perhaps the old wire to the EGR solenoid has built up a resistance. I can test that by simply bypassing the harness and going direct to the battery to the hot side of the connector.

The code 44... I'll have to recheck the entire circuit again... edit: (hmm, just noticed... this is a new code. not 41!!!! Yay! a change!!!!)

The truck actually seems more responsive though.... I cannot explain it yet, but I would feel better if I could see some kind of change.


Update: Okay, this is actually looking better. Code 41 is no longer present so I assume the computer is metering the fuel properly now, that would explain the responsiveness. Maybe, just maybe it has power now...

I will look through and check the thermactor system and see what its problem is, and figure out why the EGR solenoid circuit is still giving issue.

Due because of the video or is the timing light, its erratic hit and miss style flash actually happening?

If so that is a problem, indicating a miss fire and if so check more than a single cylinder. IE; is it all of them or only one or two, if so might simply be a problem in that wire.

Fuel gauge, mine isn't fluid filled either have never seen it react like that not even close.

Have you had a vacuum gauge connected to that motor? if so what did it look like?

steady needle?

varying needle?

If varying varying by how much, a little bit or a lot?

Any variation of the timing is the camera's fault. The timing is smooth and steady. The engine runs superbly smooth, and I detect no misfire.

The Fuel gauge jumping around I have only ever seen in a few youtube videos.

At this time I do not have a vacuum tester, but I may invest in one if this new computer does not fix it.

It will take me a bit to get to it, but as soon as I can, I should not have much trouble sorting out the code 32 and 44 with my multimeter.

My dad drove the truck today and said it feels much more responsive with no hesitations, and he believes I have fixed the problem. He will use it to haul hay via a gooseneck trailer in a few days and then I will know more.