Hey Guys,
In all my googling and searching I always seem to end up on Ford Truck Forums for what I'm looking for. Seems like a huge group of Ford gurus, and a plethora of diy write-ups and trouble shooting guides, why not join right?
So here's why Im here, I recently purchased an 88' F350 with a 5.8l c6 auto. Its a cab and chassis 2wd truck. Story when I bought it was it had been parked for several years untouched.
They got it running by replacing the rotted out side fuel tank, sender and in tank pump, bypassing the stuck tank selector valve, new fuel filter, air filter (eaten by mice), plugs (autolite platinum), wires (balden standards) cap and rotor (guessing parts store brand).
After all this the truck started and ran and everything appeared to work fine, but there was a pretty major "missfire" or "skip". The next thing that was replaced was the Throttle position sensor, no change so all 8 injectors were replaced with ford reman's. still no change. This is where they threw in the towel.

I confirmed that everything he said had been done and seemed like honest enough guy so I purchased it with hopes of it being something fixable.

Now once I got it home I noticed it was running very rich, eye burning rich. But it started, moved under its own power and stopped. The idle is always very high with no load (in park or neutral)
I pulled the plugs to check for fouling and check compression and found plugs 2,4,6,8 black and wet, while plugs 1,3,5,7 were nice and tan to white. (yes Im using fords cylinder numbering not GM/Chrysler) Compression was 120-150 in no order at all.This is when I noticed that they were platinum plugs and read on here at that can cause running issue, so i threw in a new set of copper plugs, and re-routed the wires from neat and tidy to well spaced out.
This made a very small change in power but there was still something holding this engine back. (skip, or misfire?)
During that, I found the EGR has been tampered with, maybe a vac leak causing high idle? So I deleted the egr by plugging all the manifold ports, crimping off the egr tube leaving the egr valve free to open and move as it wants but not take in any air. There were vac lines missing on all of the solenoids near the Coil, installing vac caps to all the open or broken vac lines brought the idle to normal. Now with a normal idle speed (no tach, and didn't check with the timing light, when I verified 10* with spout disconnected) there is still a skip or misfire, and running rich.
Fuel pressure tested at 38psi and 45 with the vac line disconnected.

At this point there was an intermittent CEL, I assumed from having so many things apart, but I pulled codes KOEO
67 and 82 nothing else.
Shift position switch and ?? unknown?
Here's some other observations,
Engine shuts off when the AIC is disconnected,
Engine smooths out slightly when the MAP is disconnected, ( installed a know good one off a running truck, no change)
Coolant temp sensor for ecu ( 2 wire) tests the same hot and cold as a new napa part, replaced because it was out, but tested good,
replaced o2 sensor, the one in the truck was dented and pretty mangled looking, it also rattled when you shake it, NTK brand installed
Here's my last observation. The start wire on the starter solenoid ( the only small wire on the S terminal ) has 5v constantly with the key on, it gets battery voltage when cranking, but only goes to 0v when the key is off.
if this is unhooked with the engine running the engine rpm drops not a lot but its very noticeable, and picks up when reconnected?
The truck is reeally numb at low rpm driving around, and burns an ungodly amount of gas.
The skip/misfire to me sounds like an exhaust manifold leak but its on both sides and I cannot locate any leaks with a stethoscope, heater hose or my hand. no sign of black soot leaking out between any joints either...

Sorry for the novel, poor grammar and spelling. I'm not the really the computer type...I understand that all the backstory I can provide may help someone out with where im at so far, and what to try next... I have a haynes manual. But dont know where to go next?

 

Welcome to FTE. I'm not familiar with the earlier pre-92 as other & hope they will chime in.

The AIR injection vac lines can be capped, but the solenoids need to remain connected to their wiring to get rid of the 82 code.

The 67 can either be wiring, adjustment, or water intrusion through the top of the connector into the switch. Updated models have it on the side.

I'd test the new TPS to see if it "sweeps" smoothly with increase/decreases the resistance.

EGR is best left connected & the port on the side between it & manifold capped with metal plate & gasket, but vac line & sensor left connected. The pipe from the manifold is best capped with a pipe plug

That way the ECU can command it to "move" & then "see" it move. Also, EGR does not activate at any time other than a steady state cruise so you won't get a code or problem at idle.

For a leak at the EGR valve, you can open it up & inspect diaphragm/gasket & test it with a hand vac pump.

For the 4 wet, 4 dry plugs I would recommend Ohm-ing out the wires with a DVOM meter, even if new. The EFI in this type is "batch" fire of injectors 4 on & 4 off a cycle, but I don't know if the numbers you list are in the order of what you're seeing.

Do set the base timing with a timing light & SPOUT out.

Also, my favorite, no cost thing to eliminate possible rough running is remove shutter wheel under rotor & clean magnet on PIP sensor of any carbon, metal or debris that cling to it with brush, compressed air & electrical contact cleaner.

All ignition, injection & fuel pump operation is based off this sensor.

FYI Rebuilt distributors rarely have this sensor replaced if you go that way. Replace PIP with Motorcraft part if you change it.

Don't know about the 5 volts on the start terminal in run. Would recommend looking at the switch at the base of the steering column as it sometimes splits in half & causes all sorts of strange issues.

Hope this helps & good luck.

 

Fuel pressure at idle should be 30-32 PSI. 38 is way too high. Highly suggest you get a new fuel pressure regulator, then retest.

 

I don't know about the 5.8, but someone on here a while back had a similar issue on a 4.9, and it turned out one of the injector ground wires had melted against something (probably the EGR). The injectors were ground-switched, so this meant those three injectors were spraying constantly, causing the same wet plugs, poor running, and pig-rich mixture you're dealing with. Inspect your injector harness for pinched or damaged wires, especially if it looks like someone's been in there.

 

Scndsin,

Good to know that the air injection system can be capped off and still "operate" if left plugged in electrically. I never though of it until you said that the egr doesn't come into play until cruising conditions, but the vac line attached to the Egr is pulling a vacuum constantly? Should the vac only be applied under conditions to open erg are met? maybe vac lines have been re-arranged or there is an issue with one of the air injection components? The port between the egr and intake was closed off with a sheet metal plate and custom cut gasket, so no air is getting through.
The tube from the manifold was split in two so I capped off the manifold and crimped the short bit left of the Egr to keep bugs and debris from making its way into the valve.

Another thing I really haven't thought of was the shift position sensor must also be the "neutral safety" sensor, so this could play into constant 5v at the start signal wire? I'll study some schematics!

Good idea on the shutter wheel, I just search for this specifically and came up with quite a bit, best part is its free to try.

rla2005,

I got the pressures listed using an OEM Tools brand loaner kit from the parts store. It looked like a brand new kit but I cannot confirm that these readings were calibrated. The pressure did increase when the vac line was unhooked at idle, so I took that as things were as they should be.
Do you really think that an extra few psi could cause issues like this?

TooManyMIce,
I've still not ruled this out, so I'll keep my eyes pealed as crawl around the engine bay, but I have cut back most of the loom and wire tape to inspect the wiring. Along with this i've cleaned up grounds as I find them.

Thanks for the fast responses guys, Hopefully I can find a few minutes sooner than later to go through a few of the suggestions, Ill update asap

 

Absolutely can cause a rich condition.