Code and symptom interpretation....please

[blackcurrant]

While cruising down the road in my 94 MTX with 99k miles my car behaved as if it was running out of gas. The tach continued to measured speed. i feathered the throttle and it ran a little further at certain throttle positions before it finally wouldn't go any further. i drifted off the road. i restarted the car and it fired right up....drove a little farther and it started'running out of gas' again. keeping the throttle at a certain position...around 1/4 throttle...kept the engine running but as i headed into town that became impossible. i coasted off the road and restarted and drove...each time the car running less and less until finally it wouldn't start. i'm ashamed to admit whether i remember the fuel pump priming or not. called AAA and had it towed home. once it was off the hook she fired right up...pulled into garage and ran codes....

KOEO
121 TPS out of range
173 rear o2 sensor
528 voltage at pin 10 or 30 (AC was off!)
542 fuel pump open, bad ground or always on

KOER codes were normal

Grateful there were no 211s!!!

car starts and runs...i hear the fuel pump prime and run at startup.

went ahead and checked DIS connections...cleaned connection to manifold and ground connections which were corroded.

Finally..the question i have... where are the fuel pump connections and grounds?

Thanks

Mike

 

[projectSHO89]

You can test your fuel pressure using a tester that is available from AutoZone for around $40. Then you will know if it is a fuel delivery problem.

If testing reveals that there is no fuel delivery problem, I would start with a new TPS (Throttle Position Sensor). Best buy is a Windstar recall kit # F19Z-9B989-BA for around $15 from a Ford dealer.

You will probably need a new rear O2 sensor to correct the 173.

The 528 relates to the clutch switch.

The 542 is due to the stalling engine.

Steve

 

[Markus]

The 542 is due to the stalling engine.

Steve [/QB]

Not necessarilly. 542 (and 543) is often triggered by a bad oxygen sensor.

 

[Mike Kopstain]

What's the condition of the secondary ignition ( Plug wires, plugs)?

This sounds like a spark issue.

 

[projectSHO89]

Symptom is consistent with a bad TPS or a fuel delivery problem. Read his symptoms carefully and note that the engine tried to run at different throttle positions, then failed to. Since the PCM has already errored out on the TPS, it would be foolish to ignore it anyway. If in doubt, it can easily be tested with a meter anyway.

The input to the PCM that is tested for the fuel pump secondary circuit is the output of the FP relay in the relay box. Inconceivable as to how a bad O2 sensor would cause this sense line or the PCM to cause a 542 or 543.

Steve

 

[blackcurrant]

Oil in the plug wells...yessir! cleaned it out. it was just getting up to the wire/plug connection. Why would the car restart, idle and run for a while if this was the cause?

Any other ideas? Is it possible the fuel pump wiring has a bad ground somewhere?

 

[blackcurrant]

projectSHO89:
Symptom is consistent with a bad TPS or a fuel delivery problem. Read his symptoms carefully and note that the engine tried to run at different throttle positions, then failed to. Since the PCM has already errored out on the TPS, it would be foolish to ignore it anyway. If in doubt, it can easily be tested with a meter anyway.

The input to the PCM that is tested for the fuel pump secondary circuit is the output of the FP relay in the relay box. Inconceivable as to how a bad O2 sensor would cause this sense line or the PCM to cause a 542 or 543.

Steve

Steve, i'll check the TPS...the car has seen alot of highway miles..maybe wore a section on it.

Thanks for all the help, fellas! I'll keep yous posted.

 

[Markus]

projectSHO89:
Inconceivable as to how a bad O2 sensor would cause this sense line or the PCM to cause a 542 or 543.

Steve

From the Ford manuals:

Diagnostic Trouble Code (DTC) 543/524 indicates a fuel pump secondary circuit failure between the B(+) supply and the Fuel Pump Monitor (FPM) connection to the power-to-pump circuit.

Possible causes:
• No Starts:
• Open circuit between the B(+) supply and the FPM connection to the power-to-pump circuit.
• Fuel pump relay contacts always open.

• Engine Starts:
• Left/Front Heated Oxygen Sensor (HO2S) short to power
• Damaged Powertrain Control Module (PCM).

<small>[ May 02, 2003, 03:00 PM: Message edited by: Markus ]</small>

 

[projectSHO89]

• Left/Front Heated Oxygen Sensor (HO2S) short to power

Well, sumbeech!. I would never see that just from looking at the schematic. I guess there must be adjacent wires in the harness...

Steve

<small>[ May 02, 2003, 03:45 PM: Message edited by: projectSHO89 ]</small>

 

[Markus]

projectSHO89:

• Left/Front Heated Oxygen Sensor (HO2S) short to power

Well, sumbeech!. I would never see that just from looking at the schematic. Iguess there must be adjacent wires in the harnes...

Steve

I don't think there has to actually be a short to power to trigger the 542/543. Last summer I tried an experiment. I checked the car for codes and found none. I disconnected one of the 2 O2 sensors and drove around. Sure enough the CEL came on. I ran the codes when I returned home to find the 543 code along with the O2 code. And I did not stall the car.

I wonder what Ford was thinking when they designed the system this way shrug

 

[blackcurrant]

Mark,

that would support the 173 code as well...

Can a bad o2 sensor cause drivability problems this severe? The last i knew it would just have a detrimental effect on MPG.

Thanks for the excellent insights. I shudder to think what the ford service dept would have done with this!

Mike

<small>[ May 02, 2003, 04:20 PM: Message edited by: blackcurrant ]</small>

 

[Markus]

blackcurrant:
Mark,

that would support the 173 code as well...

Can a bad o2 sensor cause drivability problems this severe? The last i knew it would just have a detrimental effect on MPG.

Thanks for the excellent insights. I shudder to think what the ford service dept would have done with this!

Mike

I've never come across the drivability issues you have when just an O2 sensor is bad. Perhaps this sensor in conjunction with the TPS is the problem?

 

[ant-live]

Now i've been running into some issues myself with the 542 code. I'm also getting a 511. The car starts, but i keep getting a whinning noise noise and power surger while driving, i replace the fuel pump over a year ago. But i also, have Ted's LPM and wondering if it has some to do with it. Any ideas, chip or HO2S?

 

[blackcurrant]

Markus:

blackcurrant:
Mark,

that would support the 173 code as well...

Can a bad o2 sensor cause drivability problems this severe? The last i knew it would just have a detrimental effect on MPG.

Thanks for the excellent insights. I shudder to think what the ford service dept would have done with this!

Mike

I've never come across the drivability issues you have when just an O2 sensor is bad. Perhaps this sensor in conjunction with the TPS is the problem?

AND in conjunction with the oil in the plug wells and the corrosion on the braided head ground and the corrosion behind the DIS ....

I haven't tested out the TPS yet...i want to drive it around abit first with the corrected ignition issues.

Thanks again for all your help!

Mike