Running Rough & EEC Codes

[Mhfco6]

Starting a new thread since all the other issues have been resolved, thanks again guys. Can anyone help me investigate these further?

I’ve checked all grounds and they are intact, may have a bit corrosion. Battery to core support wire grounds are good and battery to frame to engine 4a are good. Found a ground strap on driver side from firewall to engine in good shape, but strap on passenger side from fender to hood is in bad shape.

KOEO
11 - all clear

KOER
13
72
73

 

[RonD]

Always good to post the code definitions you are using

13 (R) Idle Speed Control(IAC) motor or Air Bypass not controlling idle properly (generally idle too high)

72 (R) No MAP or MAF change in “goose” test – retest, check for frequency or voltage change – MAP MAF

73 (O) Rerun test, if 73 is still output replace TPS
(R) No Throttle Position Sensor (TPS) change in “goose” test. Must get at least 25% throttle rotation

72 and 73 are set if you didn't complete the test mode, "goose test" is when you press down on gas pedal during test procedure

Google: 1984-1994 Ford Self Diagnostics Test - KOER

Watch that video is shows test procedure and when to:
Turn left turn right
press brake
press gas pedal


13 would be if idle is too high, is it?
If so then after engine is warmed up unplug the 2 wires on IAC Valve and see if RPMs drop, they should, engine may even stall, either is good

If RPMs do not drop then either IAC Valve is stuck open or you have a vacuum leak

 

[Mhfco6]

Always good to post the code definitions you are using

13 (R) Idle Speed Control(IAC) motor or Air Bypass not controlling idle properly (generally idle too high)

72 (R) No MAP or MAF change in “goose” test – retest, check for frequency or voltage change – MAP MAF

73 (O) Rerun test, if 73 is still output replace TPS
(R) No Throttle Position Sensor (TPS) change in “goose” test. Must get at least 25% throttle rotation

72 and 73 are set if you didn't complete the test mode, "goose test" is when you press down on gas pedal during test procedure

Google: 1984-1994 Ford Self Diagnostics Test - KOER

Watch that video is shows test procedure and when to:
Turn left turn right
press brake
press gas pedal


13 would be if idle is too high, is it?
If so then after engine is warmed up unplug the 2 wires on IAC Valve and see if RPMs drop, they should, engine may even stall, either is good

If RPMs do not drop then either IAC Valve is stuck open or you have a vacuum leak

Alright, engine warmed back up. After the 1 flash I turned left/right, stabbed the brake and floored the gas. No codes = 11 system pass while engine running.

Idle is around 900-1,000

Unplugged IAC and idle dropped a little bit and dipped down low a few times but did not stall.

 

[RonD]

Good work

Not sure why its running rough now......................

 

[Mhfco6]

Good work

Not sure why its running rough now......................

Me either, may just need to blow the cob webs out of it. Hopefully.

 

[Mhfco6]

What should the fuel pressure be? When I checked it was around 30, when throttle cracked it would jump to around 40 then stabilize back to 30.

 

[RonD]

30-40psi is spec on 1997 and earlier EFI Rangers, 35psi average, so seems OK

FPR(fuel pressure regulator) is on the fuel rail's Return fuel line
It is a spring valve set for 43psi, so spring is pushed open a bit at 44psi
It also has a vacuum hose direct to intake
At idle vacuum is high so it pulls the FPR open a bit to get the 30-35psi
When you "step on the gas"(open throttle) vacuum drops so pressure should go up BUT..........
If you were driving(not idling) the computer would also be opening the injectors way more, under a load, so fuel pressure wouldn't spike up as much as 40psi, it might go to 35psi if it was at 30psi

If you take off the vacuum hose it should show 43psi, approx.

Electric EFI Fuel pumps are capable of 80+psi, just FYI

 

[Mhfco6]

30-40psi is spec on 1997 and earlier EFI Rangers, 35psi average, so seems OK

FPR(fuel pressure regulator) is on the fuel rail's Return fuel line
It is a spring valve set for 43psi, so spring is pushed open a bit at 44psi
It also has a vacuum hose direct to intake
At idle vacuum is high so it pulls the FPR open a bit to get the 30-35psi
When you "step on the gas"(open throttle) vacuum drops so pressure should go up BUT..........
If you were driving(not idling) the computer would also be opening the injectors way more, under a load, so fuel pressure wouldn't spike up as much as 40psi, it might go to 35psi if it was at 30psi

If you take off the vacuum hose it should show 43psi, approx.

Electric EFI Fuel pumps are capable of 80+psi, just FYI

Fuel pressure idles around 29-30. It will move up towards 40 when revved but not for long. RonD you are right, with the FPR vacuum line removed is reads 40 psi on the dot.

I removed tank yesterday and emptied it if any old fuel. I replaced the sending unit and put a new screen on the fuel pump while I was in there. Also replaced the fuel filter on the rail and replaced the suspect ground strap from fender to hood on passenger side.

I swapped back to the OE ignition coil and did not appear to hesitate so I took it down the road. It seemed to hesitate under load more now. I’m off to get 10 gallons of fuel.

Wondering if the frame reservoir being removed and bypassed is causing issues. My 1987 4.9 will spit and sputter under 1/4 tank since I deleted the tank selector valve.

UPDATE: fuel level is 1/2 and hesitation misfire is still evident.

The misfire is confirmed after the coil, but before the distributor. Both old coil and new coil show misfiring via spark tester, although the old coil shuts engine after revving. Swapped coil from my 1987 F150 with the 4.9 and same misfire symptoms on the Bronco but the 4.9 still runs like butter with the same coil that was acting up on the Bronco ii.

 

[Mhfco6]

New distributor did the trick. 25 miles today and no issues.