'86 e-check problems - Any help appreciated

Well, this is kind of interesting. With a vacuum gage teed into the vacuum line to the EGR I observe the following:

At 2000 and 3000 rpm it's getting 4 to 5 inches at the EGR valve (which is enough for full activation of the valve) steady during normal acceleration and intermittently at steady speed.

However, when I try to simulate the dyno by applying some brake and gas at the same time while holding a steady rpm I get the following:

At 2000 rpm the EGR vacuum is 4 to 5 inches as I increase the load and then, suddenly as the load continues to increase slowly, goes to zero vacuum and stays there with further increasing load. When the load decreases through this point, the vacuum jumps back up.

The same happens at 3000 rpm although the switch to zero isn't as sudden, i.e., there is a narrow range of loads where the EGR vacuum shows values between 4 inches and zero.

So as the load increases at constant rpm it gets to a point (requiring only moderate braking) where the computer suddenly cuts off the EGR valve.

I'm guessing that at the 25 mph/2950 rpm test the load isn't enough to reach the point where the EGR cuts out, but at the 15 mph/1900 rpm test it reaches that point and fails. I don't really have a way to watch this as the actual test is being done.

I'm going to repeat my tests with the dwell meter hooked up too.

EDIT: The dwell stays at zero degrees with the engine under load, whether the EGR valve is getting vacuum or not. The O2 sensor is pretty much near zero Volts unless decelerating in which case it goes to about 0.8 Volts which is the idle output. With a constant load that is high enough to stop actuating the EGR valve the O2 Voltage is about 0.03 Volts - i.e., pretty near zero.

I have a "good" (passed e-test) EGR valve and connector.Yours for postage to try.If it doesnt pass and u decide not to keep on truck,return it to me.If truck does pass,pay me what u think its worth to u.BJ

Nice offer hocbj23. PM sent.

PM returned.BJ

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With engine idling and not touching either post, dwell stays around zero degrees until it decides to go to 27 degrees.

If I touch the negative post nothing changes. Idle stays smooth and rpm stays at 800. Touching the negative seems the same as touching neither.

If I touch the positive post the dwell starts climbing at a degree or two per second. If I remove my finger from the post the dwell starts dropping at the same rate. Touch and it goes up. Release and it goes down. If I let it climb above 40 or 50 it switches to 27 degree state. No change in idle rpm or quality detected.

If it is in 27 degree state, touching the positive post will always take it out without reving the engine. I can walk it up and down by holding and releasing the positive post and it never goes into 27 degree state if I don't let the dwell get over 40. But if I hold steady onto either the negative or the positive it will eventually go into the 27 degree state. The idle was smooth and rpm didn't change through all of this.

BTW, I went to court a couple of days ago and the judge gave me a continuance on this so I have a little more time.

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Good day MT. Here are the next set of measurements. Incidentally, I'm not sure I mentioned this, but when I started to pull the head (which I cancelled doing) I looked at the thermostat. It was a 195 degree unit. I replaced it with a 180 degree thermostat to see if that made a difference. That is what's in there now.


No, but I sure have checked the routing several times against the diagrams that I have. And yes, it is easy to get them crossed up.