I love this truck, but here's where I am... debugging...: ideas?

Truck was fine, then over time starting running rough.

1st symptom... Used to start quickly, then had to floor the accelerator to start.

2nd symptom... Would not idle low without dying, so increased the idle speed with the throttle screw; replaced EGR valve and sensor.

3rd symptom... started missing and throwing codes... KOE: 23, 31, 67; Continuous: 33, 41, 96.

Replaced O2, AND complete Exhaust system (new pipe from manifold, new catalytics, new mufffler, pipes, WHOLE deal.)

4th symptom... black exhaust from end pipe; still runs rough... until it gets really HOT, then runs just like I always remember.... smooth, no breaks on acceleration, like a dream.

KOE are now only 63 (expected from high idle set screw), and 67, Continuous 34.

5th symptom: Running "fine" except for high idle; put truck on incline; then won't start. Push it to level, will start. Jumpered over inertia switch, no change in behavior.

Drive Truck.
6th Symptom(s) (and here's where the fun starts):
Drive truck, as expected, turn off; then won't start; hasn't started since.
Only KOE are 63, and 67, Continuous is 34.
Power Relay test: all is ok.
Jumper Fuel pump; pump runs.
Spark at coil AND incoming to Distributor.

Replaced fuel filter; pressure "seems" good, no clogs up to filter; clean fuel, but dirty filter.

Suspect EEC and/or Fuel pump.... fuel pump pressure test next....

Saw something about "if code 96 and truck starts, replace EEC", if code 96 and no start, replace fuel pump".....

"Code 96 and truck starts" seems to be root (replace EEC).


How can I be sure, as I start to continue to trouble shoot fuel pressure and ignition module?

Thoughts?

 

EEC itself is possible, but less likely than the ECC (brown) relay, or FP relay (green).

Or ground circuits for both.

"The EEC Power Relay not only supplies battery voltage to the Fuel Injection Computer (also known as the E.E.C. Electronic Control Assembly), but also supplies power to the fuel injectors, the fuel pump relay, and a few other emissions related solenoids."

See Link: http://easyautodiagnostics.com/ford/...-relay-tests-1

 

Power relay (brown) is good.

Discovered this afternoon, on a hunch, that ONE of the things that would cause strange fuel behavior similar to what I'm seeing is a bad MAP sensor, and/or a leaking fuel pressure regulator....

Sure enough, pulled the vacuum hose off the fuel pressure regulator, and found gas in the line; lots of gas, not just a little..... fixing that as soon as the part comes in... then we'll see what's next....

 

1) NEVER touch the accelerator on an EFI during starting, unless you know for sure that it's flooded.



2) NEVER tamper with the throttle stop screw on an EFI - it has nothing to do with idle speed. The 2nd part of this diagram's caption is the Ford procedure for resetting that screw to its proper position.



3) The HEGO is not a maintenance part - it should not be replaced unless it fails diagnosis. Fault codes are NOT diagnosis; they merely indicate where to begin diagnosis. Fault codes NEVER mean to change parts without diagnosis, and the exhaust has relatively little effect on how the engine runs (with regard to the symptoms you described).



4) When you post codes, include their COMPLETE definitions; preferably from several lists. Don't pick out words or shorten the definitions. My list is in this caption:



5) "Won't start" is very vague. Exactly what does happen, and exactly what doesn't happen?

6) Buy a Haynes manual, read it cover-to-cover a few times so you're familiar with what's in it, and then use a digital multimeter to perform the ignition diagnostic procedure in Ch.5 (usually Sec.5 or 7 depending on which edition you get).



7) While you're already working on the truck, pull the EEC out and look inside.



8) While you're already working on the truck, I highly recommend changing the EEC PWR and FP relays to the newer style.



Yes, the leaking FPR could be the root cause of the original symptom.



But it might have caused some other problems that need to be fixed before the engine is damaged further.

. . .

 

Thanks Steve, very helpful.

By "No Start" I mean, cranks but no start.

HEGO was bad; very old, been on there for many years, and the exhaust was shot, so I replaced everything (front to back).

Throttle set screw... I figured, but opening it got the tach up enough to be able to use the truck. Thanks for the advice and the post on how to reset it; will do as soon as I replace the fuel regulator, and anything else I might find worn as I take the intake manifold off.

(I'm the 2nd owner on this truck...and it ain't pretty, but it usually runs so well; it sits a lot, but up to now has been very reliable when I need it).

This has probably been a creeping problem on this truck for a while, and I was too ignorant to pay attention and diagnose quickly.

Do you know of someone who sells a vacuum tube replacement kit for this truck?

 

You're still saying "no start", which is vague. Does it cough? Does it sputter? Does it smoke? What color? Does it backfire? Does it sound like it's about to run, but then stall again? The more precise & descriptive you are, the more likely we'll be able to help. So far, you've given us nothing to even guess on.

Same for the HEGO - you're still saying it was bad, without saying that it failed any test. Only that it was old, which is NOT the same as "bad". The HEGO in my Bronco is 20 years old, and has been through at least 3 severe wrecks. Its case is crumpled, but it still works right. Many new aftermarket HEGOs don't work nearly as well, and can cause problems like you're having.

You can buy hard nylon tubing on Amazon, eBay, many parts stores, and elsewhere. Many people simply use rubber hose to replace the original plastic lines, but some use silicone hose, and a few bend hard steel brake line tubing. No one sells a kit specific to that truck.