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Ford E150 Van Is Running Too Rich

Q. Vincent, I have a 1994 Ford E150 conversion van with the 5.0 liter, 302, V-8 and automatic transmission with overdrive. I can normally figure out anything about cars but lack the total testing equipment and a guy at the garage said I did not need to run the codes since I did not have the light in the dash on. Is that one true? It does not seem right to me.

Ford E150 Van Is Running Too Rich

I do know the MAF controls the voltage to the injectors but it would have to really be giving me a lot of voltage to cause the RICH condition I have. Even though it idles and does not choke out it idles real rough, van makes real good power when rpms rise to burn the extra gas.

The problem; It idles really rough and bucks and acts like a car when you have a burnt valve or something or wiped a cam lobe. Compression is great. It will smooth out at higher rpms and pulls strong if you stay in the upper ranges of rpms. It has a strong smell of fuel that is going out the exhaust because my Catalytic converter turns red-hot after barely 10 to 15 minutes of running. Very dangerous, and I just had a new one put on.

There are no leaks anywhere and the van ran great when put away for the winter but sat for four months and now runs like this. I read on the site about the Mass Air Flow problem Fords have and used some good electrical cleaner to spray in that area and let it dry. No change at all. Most articles I read said this would cause a lean Condition anyway. I have a rich condition. I changed the MAP sensor and it made no change at all. It even ran with it unplugged when I changed it back to the old one and forgot to plug it back in and made no difference.

I unplugged the MAF sensor for the Limp Home Type test, but that had no bearing on it at all. It is just getting way to much gas, but starts good and the more you rev it up the better it runs as it can burn all of that extra fuel. Then it will take and run just great for about 30 seconds and then goes back to rough.

Is it maybe the TPS switch and how would I test it??? That's my last guess. Plug wires all good. New spark plugs, MAF cleaned - I don't know? It has the old style that sets on the side of the intake instead of the flow through type. Is there a way to test this??? Filter clean, starts real easy and quick. It will idle but rough. Runs better at high rpms but still turns the catalytic converter red hot fast.

It has to be more than one cylinder. I thought maybe an injector stuck open?? But it would have to be more than one. Something is just telling it to run super rich or telling it to keep the injectors open way to far or to long. Please help me on this as it even has a regular shop down the street stumped.

I am going to run it up the street to check the codes but I bet you know just what it is. I'll try to set up a call if I can get the codes run and get one, but I don't have a Check Engine Light on. Is there any truth to that needing to be on to run a code check?

Long winded. I'm stumped,


You can pull the trouble codes yourself. You don't need any special equipment. Here's how to do it.


  • Ignition key MUST be cycled "OFF" for 10 seconds prior to the start of any KOEO or KOER self-test. If the key is not cycled off the system will not reset and the next test will not initiate correctly.
  • Correct results of the quick tests are dependent on the proper operation of related non-EEC-IV components.
  • Minor deviations from this procedure or the Flow of Diagnosis may cause false codes to be output.


  1. Start engine and bring to normal operating temperature. If engine will not start or stalls after starting, proceed with next step.
  2. Turn the key "OFF", then wait ten seconds.
Ford E150 Van Is Running Too Rich
Data Link Connector (DLC)

Ford E150 Van Is Running Too Rich
Analog Voltmeter Connection
  1. Activate the self test by grounding the Self-Test Input (STI) connector.
  2. Turn the ignition key "ON".
Ford E150 Van Is Running Too Rich
Key On Engine OFF (KOEO) Diagnostic Trouble Code Format
  1. Record all codes received.
  2. Turn ignition "OFF".

You can get a list of trouble codes and what they mean here, Diagnostic Trouble Codes.

The Mass Air Flow (MAF) sensor does not control the voltage to the injectors. Rather it is an input to the Powertrain Control Module (PCM) which controls the time the injectors open.

The first thing to do is check the PCM for codes. The codes will be stored even though the Check Engine Light is off. If there are codes that will give us a good starting place to troubleshoot.

If there are no codes the first thing to do is to check the fuel pressure. If it is too high, it will cause the engine to run rich. You may have a bad fuel pressure regulator.

The Throttle Position Sensor (TPS) could be causing the problem as well. There is a procedure for testing the TPS, but it is rather lengthy. If you go to the Public Library, you can get the MOTORS Manual for your vehicle in the reference section. That will have the test procedure.

Another possibility is a bad Coolant Temperature Sensor (CTS). This is a common problem.

We, also, can not discount the possibility of a bad PCM as well.

Additional Information provided courtesy of AllDATA

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