Mechanics

E150 ROUGH IDLE

1991 Ford E-Series Van

Engine Performance problem
1991 Ford E-Series Van 6 cyl Two Wheel Drive Automatic 100000 miles

91 Econoline E150 with a 4.9L straight six engine. Just purchased vehicle and found that it needed valve seals. Replaced valve seals, Motorcraft Wires, Plugs, Rotor, and Cap. Changed oil and filter.

Engine has a steady roughness more noticable in park. The roughness is enough to cause a noticable shake to the steering wheel and body. No codes or vacuum leaks were found. Vacuum gauge read a fairly steady 20psi. Please advise of the possibilities for this symptom. I'm at a loss and cannot really afford to just throw parts on it to gamble for a lucky fix.
Avatar
Justdon
September 3, 2009.




OK so have you checked the timing? How old is the fuel filter? Do you have a digital multi meter to check the coolant and air charge temp sensors? Get back to me and we will go from there.

Racefan966
Sep 3, 2009.
I'm sorry, I forgot about the timing. Yes we set the base timing to 10 degrees before TDC as the specs called for. I do have a digital meter for testing. I have not changed the fuel filter yet.

And thanks for the fast response!

UPDATE

Fuel filter has been changed. Nothing has changed.

Tiny
Justdon
Sep 3, 2009.
So when you set the timing you did disconnect the spout connector next to the distributor? Here is a pic to see what it looks like. You unplug with engine off and then start it and check timing when done turn engine off and plug it back in.


http://www.2carpros.com/forum/automotive_pictures/249564_spout_connector_1.jpg


Racefan966
Sep 4, 2009.
Yes, that's the way it was done.

Tiny
Justdon
Sep 4, 2009.
Ok lets check the tps and the idle air control valve. First the TPS with a paper clip back probe the gray wire with the white strip at the tps plug in (do not unplug it). Now hook up your meter between the paper clip and ground set on volts. Now turn key on engine off you should read about.8 to 1 volt. Now slowly lift the throttle you should see the voltage slowly and steadly increase to 4.5 to 5 volts with throttle wide open. Now it should increase voltage with no glitches or drops in voltage as yo lift the throttle. Turn key off and unhook. Now the idle air control valve this is simple just unplug it and check the ohms across the terms on the valve (not the wire harness) and let me know what the ohm's are. If this checks out then we will test the air charge temp sensor. Get back to me with what you find.

Racefan966
Sep 5, 2009.
I performed the test you requested with the following results and issues. The TPS did start at.8 and went to 4.6 at a slow full throttle.

The IAC read 9.6 ohms across the posts of the sensor.

The issues I came across was that the TPS would show the voltage even with the key OFF. The voltage would climb with the key off as well.

I found that the " check engine" light was burned out. After replacing it, I noticed that the light comes on steady when the van is started.

I also noticed that there are no warning lights being lit when the key is turned to ON.

I had a friend come by with an actron elite scanner instead of the cheap reader I have. He said that the diagnostic connector is not receiving a signal for the scanners to read.

Would any of this cause the roughness? Should I stop checking sensors and try to find this problem first?

I will add to the donation (when I figure out how) if you can continue to assist.

Thanks

Tiny
Justdon
Sep 6, 2009.
UPDATE

I have found that ALL sensors, injectors, and TFI module are being supplied with power with the key in any position. I un-plugged every sensor and injector, as well as the harness running along the rocker arm inspection cover. I still had power to every connector. I performed an ignition switch test in accordance with the Ford EVTM manual for this vehicle, which passed all tests. I then pulled the EEC computer and found that the power to the connectors stopped and two of the pins were corroded to the point of both being corroded into one blob of corrosion. I opened the EEC and found that the same white colored substance tracked past the pins and covered about five electronic parts inside the computer. This has compromised the metal pins and legs on the electronic parts.

I am searching for a replacement computer and will need to put this issue on hold for now. Maybe the new computer will correct the whole problem.

Thank you a bunch for your help!

Tiny
Justdon
Sep 7, 2009.
This will probably fix it. Let me know it don't and we will take it from there.
AD

Racefan966
Sep 7, 2009.

AD