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AlvinC
AlvinC, Ford Technician
Category: Ford
Satisfied Customers: 1241
Experience:  With Ford 20+years as Dealership Technician Ford Senior Master Technician Gas and Diesel
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1994 F150 xlt: driving down..distributor, cap..fuel filter

Customer Question

1994 F150 XLT 5.0 Truck starts & runs, but surges. Surging gets worse driving down the road & also bucks. Seems as long as it is getting throttle it is ok, but at idle or when you let off the gas it surges pretty bad.
Have replaced Throttle position switch, coolant sensor, distributor, cap, rotor button , plugs, wires & fuel filter. problem still persists.
Submitted: 2 years ago.
Category: Ford
Expert:  Canadafix replied 2 years ago.
Hello.
Welcome to Just Answer.

My name is XXXXX XXXXX I will assist you with your surging question.

I have a couple questions before we begin.

Is the check engine light on? If so, what codes are stored?
How many miles on your F150?
Have you checked out the EGR valve operation?

Thank you.
Bernie.
Customer: replied 2 years ago.
Check engine light not on, truck has 210000 miles on it. we cleaned the egr when we did the throttle body & upper intake. Only scode stored was MAF sensor , we changed it, cleared codes, it continued to surge
Not sure how to check the egr valve operation
Expert:  Canadafix replied 2 years ago.
Hello.
Sometimes a vacuum supply to the EGR valve can be an issue or the EGR position sensor is erratic, but not enough to set a service code.
When you had the EGR valve off did you check to see if the port was sealed on the bottom?

Disconnect the vacuum supply to the EGR valve and drive it to see if it smooths the engine. This may make the check engine light come on.

Let me know if it makes a difference.
Thank you.
Bernie.
Customer: replied 2 years ago.
Ok, unhooked egr vacume line & blocked it off. Drove truck about 10 miles. Still surges & bucks. Stopped at O' Rileys had codes scanned again. Here is what it is currently showing:
DTC172
HEGO (Oxygen Sensor Fault / Lean)
DTC213
SPOUT Circuit open ( Not even sure what that is)
DTC332
Insuficient EGR Flow ) Vacume line was still off & blocked)
DTC538
Insuficient RPM change during KOER
DTC632
Overdrive Trans Cancel Switch

When driving, truck sputters, surges, bucks. Surges at idle, almost stalls or does stall at stop when in gear. Chugs when giving throttle to accelerate. Check engine light did come on when EGR hose was off. We cleared the codes. Also, air bag light keeps flashing, pretty sure not related, but thought I would mention it as it was doing it.
Expert:  Canadafix replied 2 years ago.
Hello.
Thank you for your reply.
The O2 sensor lean code is indicating oxygen in the exhaust.
This code can be set for many reasons...not enough fuel, a vacuum leak, misfire, bad O2 sensor.

What struck me though is the open spout connection.
The spout is a connector that is unplugged to set base ignition timing. This takes the computed timing out of the loop.
Once the timing is set, the connector needs to be plugged back in to allow computed timing.
If the plug is missing or the circuit open it will certainly make the truck run poorly.
This is what the connector looks like.
graphic

The spout connector should be over near the ignition module mounted on the inner left rear fender near the hood hinge.
graphic

You will need to verify the circuit is intact. Once repaired, you will need to set base timing.

INITIAL TIMING

  1. Place transmission in NEUTRAL (M/T) or PARK (A/T) with A/C and heater in OFF position.
  2. Connect an inductive timing light.
  3. Disconnect the single wire in-line Spark Output (SPOUT) connector or remove the shorting bar from the double wire SPOUT connector.
  4. Start engine and allow to reach operating temperature. With engine at timing rpm, check or adjust initial timing to specification. NOTE: To set timing correctly, a remote starter should not be used. Use the ignition key only to start the vehicle. Disconnecting the start wire at the starter relay will cause Ignition Control Module (ICM) to revert to start mode timing after the vehicle is started. Reconnecting the start wire after the vehicle is running will not correct the timing.
  5. Reconnect single wire in-line spout connector or reinstall the shorting bar on the double wire spout connector. Check timing advance to verify distributor is advancing beyond the initial setting.
  6. Remove test instruments.
Check that out and let me know what you find.
Thank you.
Bernie.
Customer: replied 2 years ago.
Tested timing as descibed above. Removed SPOUT shorting bar from wire harness, let engine get to operating temp. Hooked up timing light, started engine. Timing is set at 10BTC but rocks back & forth a degree or two due to engine surging at idle.
Replaced shorting bar on SPOUT wire harness.
Expert:  Canadafix replied 2 years ago.
Hello.
When you disconnect the shorting bar with it running does the timing revert back to base and change the way it runs?
Customer: replied 2 years ago.
no change, still surges & timing stayed at 10btc
Customer: replied 2 years ago.
Relist: Other.
Answers and suggestion were fine, just need them faster. Have to have this diagnosed by tomorrow as needed to use for work tuesday
Expert:  AlvinC replied 2 years ago.
Hi this is Al, I have seen your issue many times and it can be easily overlooked because you can not see the concern. The gasket between the upper and lower intakes have very thin runners and will get sucked in and cause an internal vacuum leak creating your concern. I would replace the upper intake gasket and when installing it glue it to the lower intake with weatherstrip and trim adhesive to prevent further issues. I hope this helps, if not let me know, Al
Customer: replied 2 years ago.
Have also seen that before on the 5.0 . We changed the gaskets out when we cleaned the throttlebody ( we took the entire upper intake off ) I actualy found the problem about 30 minutes ago, & will explain how. It was a fluke & got very lucky finding it.

I re-tested the timing as I remembered I didnt check it after replacing the SPOUT bar.
Timing was still 10btc but went nuts when I would rev engine up to check spark advance.
a wild thought hit us , use timing light to check all the plug wires to see if any cylinder was not firing correct. Sure enough #2 & #6 were firing intermitedly. knowing the module was just tested & checked good, decided to pull the cap off the new distributor & look at the pick up coil. From the factory, it was bent just slightly. using a flat head screwdriver, bent it to were it was no longer rubbing the shaft & pickup. put it all together, fired her up, purrs like a cat. no miss, no surge, runs like new.

Greatly apreciate everyones help on this one!! good suggestions & idea's for sure.
Just got extremely lucky finding the issue on this. Also will NEVER buy another distributor made in China!!!

Expert:  AlvinC replied 2 years ago.
Glad to here of your success, let us know if we can help in the future, Al

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