TPS

[85lebaront2]

First, a Haynes manual is not that accurate, second the EGR valve as it opens pushes the plunger into the sensor. If the plunger is too long the computer will see a signal that is too high and will set the code. If you want to find the amount to trim off, just loosen the sensor until the code goes away, then file that much off the plunger.

[vjsimone]

Filing the plunger allows it to extend further down the internal resistor when installed against the EGR-Valve plunger, increasing the resistance which lowers the voltage signal going back to the ECA/Computer. You should prove this before you start hacking away at the plunger.

This code usually is set when the voltage at Closed EGR-Valve is to high.  But it can also mean that the EGR-Valve is not closing all the way ((which will lean out the Idle and give you a 41 code) and may cause a rough idle)

As Bill states, the newer/aftermarket plungers are sometimes too long.

Measure the EVP resistance installed, across the Signal & Signal-Return wires as a baseline.

I would tap down on the EGR pintle first, then re-install EVP and re-check the resistance.

You can also shim the EVP up a little to test as well.

With an old EGR-Valve & old EVP, I would suspect the Valve first.  Take it off, clean it, beat it with a hammer, check to see if it is closing all the way.

[vjsimone]

Yes, the KOER send a signal (grounds the EGR-Control Vacuum Solenoid) to apply vacuum to open the EGR-Valve.  When you hear the Idle rev up, one of those revs test the EGR-Valve.

[vjsimone]

mp470 wrote

 I tested the EVP and it gets 5V and the resistance is around 4000 ohms at rest and 500 with the sensor solenoid(?) fully pressed in (I removed the EVP from the valve for this test).  It fluctuates smoothly.  Haynes manual says 5000 at rest and 100 with 20inHg of vacuum.  

In another manual, I have read a EVP range of 5500 - 100.  Yours does not meet either manuals spec, so this could be an issue.  At 4000 ohms for closed EGR Valve, the voltage output may be to high as well.

[mp470]

Well I didn't feel like paying $80 for a new EGR valve.  Took it off and gave it a good cleaning, it was carboned up pretty severely. Code went away, no issues since.

[Gary Lewis]

Cool!  

Isn't it amazing how gunked up the EGR valve can get?  That's some pretty ugly stuff passing through there.

[85lebaront2]

I had a 1987 F150 of a good friend for a while to solve a number of running issues. One of the things I did was run it up till the EGR opened, then tap on the body of the valve with it partially open, got all kinds of strange noises and reactions as the crap in it broke loose. After that I did a thorough throttle body and IAC cleaning. Truck ran like a new one after that.